another bizarre audio circuit
John Larkin
I've always sort of liked the classic "GE" tape head/mic preamp
circuit:
ftp://jjlarkin.lmi.net/GEcircuit.jpg
but it occurred to me that it might also make a nice headphone amp...
ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
Audio tends to be nonsense, but at least the audio guys have fun
playing with circuits, whether they make a lot of sense or not.
John
Fred Bloggs
Bizarre??? Just a standard buffered input CE with negative feedback DC
bias to stabilize the operating point against Vbe and reverse leakage
collector current change with temperature- a textbook circuit...
Bitrex
>
>
> I've always sort of liked the classic "GE" tape head/mic preamp
> circuit:
>
> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
> but it occurred to me that it might also make a nice headphone amp...
>
> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>
Neat, like a parafeed amplifier. The choke will have to be pretty big
for audio frequencies...
I can think of a modification that would give more gain for the negative
feedback to "work" with: change the input transistor to a JFET, get rid
of the capacitor and extra resistor in the bias stabilization circuit,
and just stick a resistor in the emitter lead of the output transistor.
Then, move the load resistor of the first stage down and connect an
NPN transistor with a current limiting resistor to the output between
that load resistor and the power supply. If I've figured things out
correctly you then have a gyrator load for the first stage. The bias
should still be self-stabilizing too, because of the DC drop across the
output load inductor.
>
> Audio tends to be nonsense, but at least the audio guys have fun
> playing with circuits, whether they make a lot of sense or not.
Yup!
>
> John
>
>
>
Bitrex
> On 3/2/2011 11:40 AM, John Larkin wrote:
>>
>>
>> I've always sort of liked the classic "GE" tape head/mic preamp
>> circuit:
>>
>> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>
>> but it occurred to me that it might also make a nice headphone amp...
>>
>> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>>
>
> Neat, like a parafeed amplifier. The choke will have to be pretty big
> for audio frequencies...
>
> I can think of a modification that would give more gain for the negative
> feedback to "work" with: change the input transistor to a JFET, get rid
> of the capacitor and extra resistor in the bias stabilization circuit,
> and just stick a resistor in the emitter lead of the output transistor.
> Then, move the load resistor of the first stage down and connect an NPN
> transistor with a current limiting resistor to the output between that
> load resistor and the power supply. If I've figured things out correctly
> you then have a gyrator load for the first stage. The bias should still
> be self-stabilizing too, because of the DC drop across the output load
> inductor.
>
Nope, sorry, cancel that, it won't work. The output stage has gain and
the gyrator won't work properly.
John Larkin
<bit...@de.lete.earthlink.net> wrote:
>On 3/2/2011 11:40 AM, John Larkin wrote:
>>
>>
>> I've always sort of liked the classic "GE" tape head/mic preamp
>> circuit:
>>
>> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>
>> but it occurred to me that it might also make a nice headphone amp...
>>
>> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>>
>
>Neat, like a parafeed amplifier. The choke will have to be pretty big
>for audio frequencies...
You could just use a power resistor and tweak the drain voltage
operating point. It's just not as elegant.
John
John Larkin
Which textbook?
John
Bitrex
The circuit I'm working on now as my "exercise in simplicity" from the
thread a while back uses another transistor for the load on the output
stage, simulating an inductor. This also has the advantage in Class A
of being able to set the idle current to half of the desired maximum
output current, instead of the usual need to set the idle at the full
output current.
If I remember correctly I think if one uses a resistive load the
quiescent idle current will have to be _more_ than the maximum output
current to get the desired output current into the load when the
transistor shuts down, because of the drop across the resistor.
I think I have an unhealthy obsession with simulated inductors.
Arny Krueger
wrote in message
news:2tdtm6t4b88dsnpdl...@4ax.com
> Which textbook?
I don't know about textbooks, but it was a pretty standard circuit back in
1965 when I built a high performance RIAA preamp as an undergraduate project
as part work for my degree in engineering. if memory serves, it was in the
RCA transistor manual. I later built a number of these as standard parts of
Heathkits.
And voila, here's a schematic of a Dyna PAT-4 with essentually the same
circuit:
http://home.comcast.net/~g.e.dunn/PAT4/schem.jpg
The challenge that I had in 1965 was to build it using PNP germanium
switching transistors which weren't all that linear, were speced for beta =
20 and had no noise spec. The prof made a tactical error that he corrected
the next year - he didn't specify how many transistors or any other parts
that I was limited to use.
So, I built two amps with the circuit illustrated above, cascaded them, and
used 4 darlington pairs for the transistors, rather neatly solving the beta
problem. If memory serves the first stage was RIAA and the second was flat
with a gain of 10.
The thing ran rings around any commercial circuit that we compared it to,
whether SS or tubed both on the bench and in listening tests. In my travels
through the lab's parts bin, I also found a stash of appropriate-valued mil
spec metal film resistors, etc. As a commerical product, it might have had
to sell for $100s.
m II
"Arny Krueger" wrote in message
news:p6-dnUSFTZphXvPQ...@giganews.com...
> Which textbook?
http://home.comcast.net/~g.e.dunn/PAT4/schem.jpg
----
Jeeezzzz You must be old.
I remember cutting my teeth on my first big project in 1968 on a Heathkit
stereo amplifier. The RIAA network was a secret bunch of components
encapsulated so the user could not tell what hidden secrets were installed.
I finally through that kit out a few years ago on a move cleanup. Many
repairs taught me a few things about power transistor output circuits and
why to not increase the length of the speaker connection screws until they
hit the chassis out the back of the terminal strips. Even took a few
warranty repairs at the shop. After about 6 sets of output transistor
replacements it came back with clearance holes behind them....duh!
mike
John Larkin
wrote:
I used to design language labs and recording studios/mixers, and we
used that circuit a lot for tape heads and mic amps. It was called
"the GE circuit", don't know why.
>
>And voila, here's a schematic of a Dyna PAT-4 with essentually the same
>circuit:
>
>http://home.comcast.net/~g.e.dunn/PAT4/schem.jpg
>
>The challenge that I had in 1965 was to build it using PNP germanium
>switching transistors which weren't all that linear, were speced for beta =
>20 and had no noise spec. The prof made a tactical error that he corrected
>the next year - he didn't specify how many transistors or any other parts
>that I was limited to use.
I think I used 2N3391s, silicon NPNs, which were the black [1] GE
cylindrical epoxy transistors with the flange on the bottom and the
concave top, where they poured the epoxy in. 1968, approximately.
People here were discussing a low-parts-count headphone amp, and it
occurred to me that this configuration is a lot of bang for a few
parts, as a power amp. I thought the bipolar-mosfet thing was cute,
but then I'm easily amused.
John
[1] their early ones used brown epoxy and were photosensitive.
Fred Bartoli
As the other Fred said, it's a pretty standard circuit, from the 60's,
with its structure inherited from the toobs era.
It's nothing else than a CFB opamp which made good use of the low
available gains and FTs of that era.
--
Thanks,
Fred.
John Larkin
<bit...@de.lete.earthlink.net> wrote:
Yes, you can swing almost all the way to the rails with a
constant-current load, as opposed to a resistor, so it's more
efficient... like an inductor. The inductor allows close to 2x Vcc p-p
voltage swing, if that matters.
But the constant-current load bumps the active parts count by 50% !!!
I think you could do a nice headphone amp with one mosfet. Or go nuts
and use a GaN fet.
John
Fred Bloggs
>
> - Show quoted text -
Just about any textbook that goes into bias point sensitivity analysis
of transistor circuits- you remember the S- functions, mainly ICQ
stability. The big three were HFE, VBE, and ICBO. Then the rest of
your circuit is just ac-bypass and the shunt-series feedback for
signals. I've seen it dozens of times.
John Larkin
I bet you haven't seen the bipolar+mosfet version, with inductive
pullup, used as a power amp.
John
Vladimir Vassilevsky
John Larkin wrote:
>
> I've always sort of liked the classic "GE" tape head/mic preamp
> circuit:
>
> ftp://jjlarkin.lmi.net/GEcircuit.jpg
Here is a couple of very low noise audio circuits for the same purpose:
http://www.abvolt.com/misc/inputs_audio.jpg
I like BJT and JFET in cascode.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
John Larkin
<nos...@nowhere.com> wrote:
>
>
>John Larkin wrote:
>
>>
>> I've always sort of liked the classic "GE" tape head/mic preamp
>> circuit:
>>
>> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
>Here is a couple of very low noise audio circuits for the same purpose:
>
>http://www.abvolt.com/misc/inputs_audio.jpg
>
>I like BJT and JFET in cascode.
>
The one on the left, with the base and gate connected, is sure cute.
John
Fred Bloggs
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Wed, 2 Mar 2011 14:55:18 -0800 (PST), Fred Bloggs
>
>
>
>
>
I believe the collector inductor and/or transformer are used to
significantly increase the efficiency of the output stage, where that
consideration outweighs the additional cost.
Bitrex
I'm having a little trouble with the operation of that one. The way
it's set up, assuming the output sits at 0 volts won't the input BJT be
cut off?
John Fields
---
Even though you scorn and ridicule audio, there's nothing wrong with
anyone seeking perfection there, just as there's nothing wrong with
your search for perfection in the genre which pleases _you_ to pursue.
So, speaking of fun, why don't you do a complete design and assign
values to the circuit components and identify the semiconductors?
Or is that legwork _we're_ supposed to do in order to flesh out your
divine revelation?
---
JF
John Larkin
Jfets usually run at negative gate voltage. Assume the transistor base
is at +0.7. The jfet source will be at some more positive voltage,
+2.5 maybe. That's enough to run the transistor.
Actually, you can cascode a transistor into the source of a fet that
has a grounded gate. In that case, the source/collector voltage might
be a volt or two. You would have to look at the fet transfer curve,
and know the design operating current, to see exactly what that
voltage might be.
The problem with jfets is the huge part-to-part variation in Idss and
transfer curves. A 10:1 datasheet spread in Idss isn't unusual.
+10v
|
|
|
d
gnd---------g
s
|
|
+------> Vs
|
|
10K
|
|
|
gnd
For a typical vanilla jfet in this circuit, Vs might be +1 to +4 volts
maybe.
John
John Larkin
<jfi...@austininstruments.com> wrote:
>On Wed, 02 Mar 2011 08:40:42 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>
>>
>>I've always sort of liked the classic "GE" tape head/mic preamp
>>circuit:
>>
>>ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>
>>but it occurred to me that it might also make a nice headphone amp...
>>
>>ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>>
>>
>>Audio tends to be nonsense, but at least the audio guys have fun
>>playing with circuits, whether they make a lot of sense or not.
>>
>>John
>
>---
>Even though you scorn and ridicule audio, there's nothing wrong with
>anyone seeking perfection there, just as there's nothing wrong with
>your search for perfection in the genre which pleases _you_ to pursue.
>So, speaking of fun, why don't you do a complete design and assign
>values to the circuit components and identify the semiconductors?
>
You're not playing the game. You are sitting in the henhouse, clucking
about the people who do.
>Or is that legwork _we're_ supposed to do in order to flesh out your
>divine revelation?
>
Chickenleg work!
John
Bitrex
> On Wed, 02 Mar 2011 19:26:29 -0500, Bitrex
> <bit...@de.lete.earthlink.net> wrote:
>
>> On 3/2/2011 6:30 PM, John Larkin wrote:
>>> On Wed, 02 Mar 2011 17:21:23 -0600, Vladimir Vassilevsky
>>> <nos...@nowhere.com> wrote:
>>>
>>>>
>>>>
>>>> John Larkin wrote:
>>>>
>>>>>
>>>>> I've always sort of liked the classic "GE" tape head/mic preamp
>>>>> circuit:
>>>>>
>>>>> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>>>
>>>> Here is a couple of very low noise audio circuits for the same purpose:
>>>>
>>>> http://www.abvolt.com/misc/inputs_audio.jpg
>>>>
>>>> I like BJT and JFET in cascode.
>>>>
>>>
>>> The one on the left, with the base and gate connected, is sure cute.
>>>
>>>
>>> John
>>>
>>
>> I'm having a little trouble with the operation of that one. The way
>> it's set up, assuming the output sits at 0 volts won't the input BJT be
>> cut off?
>
> Jfets usually run at negative gate voltage. Assume the transistor base
> is at +0.7. The jfet source will be at some more positive voltage,
> +2.5 maybe. That's enough to run the transistor.
>
that circuit with the input BJT's emitter at ground if its base is at
0.7 volts the minute its base goes negative it's going to cut off.
Maybe the emitter should be connected to the negative supply?
> Actually, you can cascode a transistor into the source of a fet that
> has a grounded gate. In that case, the source/collector voltage might
> be a volt or two. You would have to look at the fet transfer curve,
> and know the design operating current, to see exactly what that
> voltage might be.
I'm foggy on how such a cascode reduces noise - improved distortion,
bandwidth, and PSRR I can understand but how does two transistors end up
less noisy than one? I know with tubes a cascode was considered a low
noise alternative since two triodes in cascode would have lower noise
than a single pentode, with similar gain.
Bill Sloman
He's not playing your game, which involves telling John Larkin how
cute his circuits are.
> >Or is that legwork _we're_ supposed to do in order to flesh out your
> >divine revelation?
>
> Chickenleg work!
It's half the story - a few component values make it a lot easier to
work out what a circuit is doing.
--
Bill Sloman, Nijmegen
John Larkin
<bit...@de.lete.earthlink.net> wrote:
That's what transistors do!
>Maybe the emitter should be connected to the negative supply?
>
>
>> Actually, you can cascode a transistor into the source of a fet that
>> has a grounded gate. In that case, the source/collector voltage might
>> be a volt or two. You would have to look at the fet transfer curve,
>> and know the design operating current, to see exactly what that
>> voltage might be.
>
>I'm foggy on how such a cascode reduces noise - improved distortion,
>bandwidth, and PSRR I can understand but how does two transistors end up
>less noisy than one? I know with tubes a cascode was considered a low
>noise alternative since two triodes in cascode would have lower noise
>than a single pentode, with similar gain.
Actually, in Vlad's circuit, the cascode probably doesn't help much.
But it sure is cute!
John
Bitrex
Right, but the gain of that stage is going to be very unsymmetrical. I
guess with so much gain and the negative feedback it doesn't matter though.
John Larkin
He's not designing circuits, which is what this newsgroup is about.
You aren't either. Both of you start to cluck and peck when people do
design circuits. No surprise.
>
>> >Or is that legwork _we're_ supposed to do in order to flesh out your
>> >divine revelation?
>>
>> Chickenleg work!
>
>It's half the story - a few component values make it a lot easier to
>work out what a circuit is doing.
You can't look at a circuit this simple and see what it's doing? OK,
no surprise.
John
John - KD5YI
Well, I thought designing a circuit included supplying component values.
No?
John Larkin
wrote:
I posted topologies. Values can be scaled to the application, but you
need a topology first. If I were actually going to build this, for
money, of course I'd have to define specs and then compute values.
That's just grunt work.
John
TheQuickBrownFox
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>You're not playing the game. You are sitting in the henhouse, clucking
>about the people who do.
You sound like one of these punks they put on TV that spews nonsense as
if it was once a colloquialism.
You know nothing about folks here, yet you constantly spout off little
particulars from the depths of YOUR brain, and attribute them to those
you attack as if they are factual.
You are worse than the poorly raised punk fucks that are all over the
streets. They have an excuse. You were supposed to remember your
upbringing, yet you thumb your nose at that and everyone around you ,
which *you* have decided belong on your personal shit list.
You are almost as immature as Terrell, and that is at a very close
second.
Hey John... Grow the fuck up.
MakeNoAttemptToAdjustYourSet
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>He's not designing circuits, which is what this newsgroup is about.
Bullshit. You do not know the facts in the first case you cite, and
you are off the mark in the second case you cite.
Electronics is far more than a mere circuit. There are several
physical disciplines involved. This group is about ALL aspects of the
science of electronics design, and that extends BEYOND only circuits.
Grow the fuck up, you mouthy little school marm wanna be bitch!
You have no clue what John does or does not do.
So you need to grow the fuck up in that respect as well, you pissy
little bitch.
John Larkin
<DoNotAttemptT...@anytime.org> wrote:
>On Wed, 02 Mar 2011 18:32:42 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>He's not designing circuits, which is what this newsgroup is about.
>
> Bullshit. You do not know the facts in the first case you cite, and
>you are off the mark in the second case you cite.
>
> Electronics is far more than a mere circuit. There are several
>physical disciplines involved. This group is about ALL aspects of the
>science of electronics design, and that extends BEYOND only circuits.
Word salad.
>
> Grow the fuck up, you mouthy little school marm wanna be bitch!
>
> You have no clue what John does or does not do.
JF? He clucks. Like you, he doesn't post circuits.
Well, maybe once in a great while. To my knowledge, you have never
posted a circuit, or shown any evidence that you know how to design
electronics.
>
> So you need to grow the fuck up in that respect as well, you pissy
>little bitch.
Show is some circuits, Big Man. How about an original headphone amp?
John
John Larkin
Hey, DimmerMan, post us a circuit.
John
John - KD5YI
Not really. I have a few circuits I could throw out and claim that they
are topologies and you would not be able to use them without values.
Granted, mine are more complex than the one being discussed, but I'm
hoping to make a point.
John (not Larkin)
John - KD5YI
>
> John
>
Good challenge, John. I expect more word salad from him since he has
never shown any technical abilities. I expect mostly a host of profanities.
John (not Larson)
TheQuickBrownFox
wrote:
> but I'm
>hoping to make a point.
Consider the target. Impossible task.
He is hard wired stupid.
John Larkin
wrote:
I think circuit topologies are fun to play with. Lots of textbooks
show, and discuss, circuits without explicit values. Once you have a
topology, then you can proceed to specs and component values.
If you think all circuits should be posted with values, post some.
John
MakeNoAttemptToAdjustYourSet
wrote:
>On 3/2/2011 10:02 PM, John Larkin wrote:
Moer proof of you utter stupidity. I have posted links several times
here to photo sites that have all of my library of photos that I feel
someone could see.
You were just your same old retarded self back then, and failed to
visit the photo bin.
You AND the Larkin John are fucking absolute idiots.
Me? I work on Satellite gear and 10G Base gateways. The gear I am
configuring is the fastest gateways on the planet surface, and it will be
part of a huge backbone quite soon. Several gateways in several cities
are already in place.
On my slow days, I perform a specific repair on military radios that no
one else in the shop does, so our boys can stay safe. This involves
placing an EMI shield so that nothing spills out. Tempest standards are
pretty tough.
One of my favorite "modern" things to do is watching a design get
printed over on the 3D printer.
Remembering waiting by the dot matrix printer for a print job to
finish, then thinking about modern laser printers and their speed and
resolution, then seeing this "part" get "printed". We actually use them
too!
You can "print" a PCB test fixture mount and even place PEMs and such
in it.
We do this now before we send the frame out to get hard hobbed. Now
THAT is a fun machine. The laser for making labels and such is cool too.
Amazing what one can do with 45 Watts worth of amplified light and a
precision x y gantry.
Yes, I do both circuits AND mechanical layouts. I also work on the
radios. No, that is not engineering, it is skill management.
k...@att.bizzzzzzzzzzzz
Don't forget DimBulb's love of poop.
John - KD5YI
You are correct, John. Now you have a topology. Please post the
component values.
Thanks,
John
John - KD5YI
Ah, yes. For some reason I don't think that much about feces like he does.
John - KD5YI
Really? I could post a photo site of anyone I choose and you would not
have any idea they were not mine. I discard that claim of your proof of
technical abilities unless you can back it up.
> You were just your same old retarded self back then, and failed to
> visit the photo bin.
>
> I am fucking absolute idiot.
>
> Me? I work on Satellite gear and 10G Base gateways.
Yes, I'm sure. They need technicians to clean them and return them to
service.
< The gear I am
> configuring is the fastest gateways on the planet surface, and it will be
> part of a huge backbone quite soon. Several gateways in several cities
> are already in place.
Configuring? Touching up the paint job, perhaps
> On my slow days, I perform a specific repair on military radios that no
> one else in the shop does, so our boys can stay safe. This involves
> placing an EMI shield so that nothing spills out. Tempest standards are
> pretty tough.
Sure. Hey, dipshit.. get of the phone and put that EMI shield in that
radio like we told you!
> One of my favorite "modern" things to do is watching a design get
> printed over on the 3D printer.
>
> Remembering waiting by the dot matrix printer for a print job to
> finish, then thinking about modern laser printers and their speed and
> resolution, then seeing this "part" get "printed". We actually use them
> too!
Good God! You and your company are still using dot matrix printers?
> Yes, I do both circuits AND mechanical layouts. I also work on the
> radios. No, that is not engineering, it is skill management.
Jesus! You are the flunky everyone here has accused you of being. You
poor piece of crap. You've probably been sweeping and mopping the floors
all along and picked up enough words to make you seem important.
You're not worth playing with anymore. Piss off.
John Larkin
wrote:
Given i/o specs, the DC analysis is simple. But there are two AC
aspects that are sort of interesting: the lf response, and loop
stability. I'm sort of disappointed that nobody has commented on
either.
As I'm disappointed in how many people want to whine and cluck about
personalities, and avoid actually discussing electronics.
John
Phil Hobbs
transconductance is so high that even with a 2.5:1 range of I_DSS, the
spread of V_GS is pretty reasonable.
They're also very quiet, go about 700 MHz, and cost 20 cents. Other
than that, they stink.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
Jeroen Belleman
> On 3/2/2011 8:06 PM, John Larkin wrote:
>> Actually, you can cascode a transistor into the source of a fet that
>> has a grounded gate. In that case, the source/collector voltage might
>> be a volt or two. You would have to look at the fet transfer curve,
>> and know the design operating current, to see exactly what that
>> voltage might be.
>
> I'm foggy on how such a cascode reduces noise - improved distortion,
> bandwidth, and PSRR I can understand but how does two transistors end up
> less noisy than one? I know with tubes a cascode was considered a low
> noise alternative since two triodes in cascode would have lower noise
> than a single pentode, with similar gain.
As far as I can see, a cascode has the same noise as its bottom
transistor, near enough. The virtue of a cascode is that it
greatly reduces the effect of the Miller capacitance, so you
get more bandwidth and less input capacitance.
Jeroen Belleman
Bill Sloman
Without the component values, it does take a moment's thought, which
is wasted on a bizarre (if simple) circuit with few potential
applications.
--
Bill Sloman, Nijmegen
Phil Hobbs
At high frequency, you get noise from the output feeding back via Miller
capacitance. Cascoding can help that.
Jeroen Belleman
> John Larkin wrote:
>>
>> The problem with jfets is the huge part-to-part variation in Idss and
>> transfer curves. A 10:1 datasheet spread in Idss isn't unusual.
>>
>>
>>
>>
>>
>> +10v
>> |
>> |
>> |
>> d
>> gnd---------g
>> s
>> |
>> |
>> +------> Vs
>> |
>> |
>> 10K
>> |
>> |
>> |
>> gnd
>>
>> For a typical vanilla jfet in this circuit, Vs might be +1 to +4 volts
>> maybe.
>>
>> John
>>
>>
>>
> BF862s are much better--cutoff to full on in half a volt or so. Their
> transconductance is so high that even with a 2.5:1 range of I_DSS, the
> spread of V_GS is pretty reasonable.
>
> They're also very quiet, go about 700 MHz, and cost 20 cents. Other
> than that, they stink.
Indeed, when I discovered their existence back in 2001, I could hardly
believe the datasheet. I'd never seen a JFET with a ratio of yfs/Cin
that high. That, and with only 0.8nV/rtHz input-referred noise. I love
it.
Jeroen Belleman
Jon Kirwan
<pcdhSpamM...@electrooptical.net> wrote:
><snip of BF862 discussion>
>They're also very quiet, go about 700 MHz, and cost 20 cents. Other
>than that, they stink.
You need to spend some hundreds of dollars in one buy in
order to get close to that price/unit, don't you?
Jon
MakeNoAttemptToAdjustYourSet
wrote:
>>
>> Moer proof of you utter stupidity. I have posted links several times
>> here to photo sites that have all of my library of photos that I feel
>> someone could see.
>
>Really?
Yes, dumbfuck.
> I could post a photo site
Yes, if your IQ wasn't that of a circus flea.
> of anyone I choose
No, you cannot. You can only post YOUR site. If you post someone
else's site you are posting THEIR site, you dumb whore for a mother
bastard.
> and you would not
>have any idea they were not mine.
Can you really be that stupid? I alter my original assessment. Your
IQ is only 15.
> I discard that
Good for you. I don't give a fat flying fuck what you retain or
discard, you pathetic, meaningless piece of shit.
> claim of your proof of
>technical abilities unless you can back it up.
The posts are already in the group, bitch. Posted way back in the
threads they were originally posted in, ya little bitch.
Your lame refutation falls short of one main ingredient. That being
credibility. My original posts, which you failed to examine, are fine
and are still there for all to see. So much for them belonging to
someone else.
Can you really be that stupid?
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Wed, 02 Mar 2011 18:36:25 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Wed, 02 Mar 2011 08:40:42 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>
>>>
>>>I've always sort of liked the classic "GE" tape head/mic preamp
>>>circuit:
>>>
>>>ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>>
>>>but it occurred to me that it might also make a nice headphone amp...
>>>
>>>ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>>>
>>>
>>>Audio tends to be nonsense, but at least the audio guys have fun
>>>playing with circuits, whether they make a lot of sense or not.
>>>
>>>John
>>
>>---
>>Even though you scorn and ridicule audio, there's nothing wrong with
>>anyone seeking perfection there, just as there's nothing wrong with
>>your search for perfection in the genre which pleases _you_ to pursue.
>>So, speaking of fun, why don't you do a complete design and assign
>>values to the circuit components and identify the semiconductors?
>>
>
>You're not playing the game. You are sitting in the henhouse, clucking
>about the people who do.
---
I'm playing, all right, just not the way you find acceptable, which is
to heap adulation on you.
But there's nothing new there, since you almost always blame the
mirror when its reflection doesn't please you.
---
>>Or is that legwork _we're_ supposed to do in order to flesh out your
>>divine revelation?
>>
>
>Chickenleg work!
>
>John
---
Methinks the chicken resides on _your_ roost, since by not doing the
legwork he avoids any criticism which could arise from errors he might
make.
---
JF
John Fields
---
Well, I'd say that the ratio of my technical to non-technical articles
is about 10:1, while yours is about 1:10, and over the years I'd be
willing to bet that I've posted about 10 times more designs, fully
worked out, with component values included and, lately, simulated,
than you have.
---
>You aren't either. Both of you start to cluck and peck when people do
>design circuits. No surprise.
---
Actually, what you like to call "clucking and pecking" is nothing more
than criticism, but you try to cast it in a light which mitigates its
validity by besmirching the veracity of the criticizer.
---
>>
>>> >Or is that legwork _we're_ supposed to do in order to flesh out your
>>> >divine revelation?
>>>
>>> Chickenleg work!
>>
>>It's half the story - a few component values make it a lot easier to
>>work out what a circuit is doing.
>
>You can't look at a circuit this simple and see what it's doing? OK,
>no surprise.
>
>John
---
If he can't, so what?
Why not make it better by helping him out with a few component values
and a circuit description instead of making it worse by insulting him
for no reason?
---
JF
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Wed, 02 Mar 2011 20:40:27 -0600, John - KD5YI <sop...@invalid.org>
>wrote:
>>Well, I thought designing a circuit included supplying component values.
>>No?
>
>I posted topologies. Values can be scaled to the application, but you
>need a topology first. If I were actually going to build this, for
>money, of course I'd have to define specs and then compute values.
>That's just grunt work.
>
>John
---
Being the grunt work that it is, then, one should be able to take a
schematic devoid of component values and then hand it over to a grunt
with the expectation of getting back a working circuit some time
later?
One thing about topologies which is misleading is that if the
component values aren't defined, the topology might look fine but the
realization of the circuit will be impossible under economic or
technical constraints.
An example which springs to mind is a circuit which was posted some
time back which looked good, but which on closer inspection you said
needed a choke with an inductance of near 1 henry, as I recall, and a
Q of about 200 somewhere in the audio range.
I went looking for one, just for grins, but found only unobtanium so,
unless I missed something, (got a source?) your guess was wrong and
the topology bogus.
---
JF
John Larkin
<jfi...@austininstruments.com> wrote:
>On Wed, 02 Mar 2011 18:52:53 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Wed, 02 Mar 2011 20:40:27 -0600, John - KD5YI <sop...@invalid.org>
>>wrote:
>
>>>Well, I thought designing a circuit included supplying component values.
>>>No?
>>
>>I posted topologies. Values can be scaled to the application, but you
>>need a topology first. If I were actually going to build this, for
>>money, of course I'd have to define specs and then compute values.
>>That's just grunt work.
>>
>>John
>
>---
>Being the grunt work that it is, then, one should be able to take a
>schematic devoid of component values and then hand it over to a grunt
>with the expectation of getting back a working circuit some time
>later?
"One" should? I couldn't say. I usually design all of a circuit
myself, but if we brainstorm/whiteboard circuits, we may include
values, or one of the people might go off and finish it. Could be me,
could be somebody else, whoever is responsible or volunteers. We
usually check one anothers' work before we release a board. We have no
techs, so everybody does grunt work.
But all circuit designs start with ideas and topologies. If someone
has never seen a folded cascode, or an opamp's V+ used as a signal
output, or a bootstrapped photodiode, all I may need to do is present
the concept, and then they can run with it.
The laser controller I'm working on now, all the resistors on one
sheet are 100 ohms and all the caps are 0.33u. That reduces the grunt
work considerably. This scheamtic will run about 25 B-size sheets, and
I'll do maybe 18 or so of them, with other people contributing others,
like the FPGA, the ARM, and the PCIe interface. This is a rush job, 7
weeks from start to 1st article, so several people are tossing in
sheets.
>
>One thing about topologies which is misleading is that if the
>component values aren't defined, the topology might look fine but the
>realization of the circuit will be impossible under economic or
>technical constraints.
>
Sure. A complete electrical/thermal/mechanical design ought to be done
before something goes into production. Lotta grunt work. Newsgroups
are for playing with ideas without consequences.
>An example which springs to mind is a circuit which was posted some
>time back which looked good, but which on closer inspection you said
>needed a choke with an inductance of near 1 henry, as I recall, and a
>Q of about 200 somewhere in the audio range.
>
>I went looking for one, just for grins, but found only unobtanium so,
>unless I missed something, (got a source?) your guess was wrong and
>the topology bogus.
Bogus? Because you can't order some part? Nothing wrong with playing
with a topology if it might work. Whether it's practical or affordable
is part of the downstream analysis. If every idea has to be
immediately and exhaustively analyzed for cost and parts availability
and subtleties, you won't come up with many ideas.
As usual, you're just being bitchy. Why are you so hostile to playing
with ideas? Why do you refuse to do it yourself?
John
John Larkin
Millions of the "GE" circuit have been used for decades. The mosfet
hybrid is a very reasonable headphone amp.
Post a circuit, doofus. You've forgotten how to do anything but whine.
John
John Larkin
All you ever criticize is my personality. You said nothing about this
circuit. On the rare occasion when you do post a circuit, or critize
one, you're usually wrong the first few times.
Old hen.
John
John Larkin
<jfi...@austininstruments.com> wrote:
You're whining about everything but the circuit. Diversionary tactic.
Old hen.
John
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Thu, 03 Mar 2011 07:14:08 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>>An example which springs to mind is a circuit which was posted some
>>time back which looked good, but which on closer inspection you said
>>needed a choke with an inductance of near 1 henry, as I recall, and a
>>Q of about 200 somewhere in the audio range.
>>
>>I went looking for one, just for grins, but found only unobtanium so,
>>unless I missed something, (got a source?) your guess was wrong and
>>the topology bogus.
>
>Bogus? Because you can't order some part?
---
Because it's unorderable, AFAIK.
Find me an inductor with an inductance of 1 henry and a Q of 200 at
1000Hz, OK?
After all, it was _your_ call, not mine.
---
>Nothing wrong with playing
>with a topology if it might work. Whether it's practical or affordable
>is part of the downstream analysis. If every idea has to be
>immediately and exhaustively analyzed for cost and parts availability
>and subtleties, you won't come up with many ideas.
---
The impossibility of an idea not working isn't a barrier to the
initial flash, so why would you say something like that?
---
>As usual, you're just being bitchy.
---
No, as usual, I'm being critical, and you don't like it when the
finger's being pointed at you.
---
Why are you so hostile to playing with ideas? Why do you refuse to do
it yourself?
---
Straw man.
---
>John
---
JF
John Larkin
<jfi...@austininstruments.com> wrote:
Stop whining and clucking about personalities and design some
electronics. That's not a straw man, that's what this ng is about.
Think about what happens to my bizarre headphone amp if the inductor
is replaced with a constant-current source.
John
John Fields
---
Not true.
I usually criticize some aspect of your work which is flawed and then,
when you refuse to acknowledge the flaw, criticize that part of your
personality which is scared to death to admit to error.
Remember the relays with infinite gain, for example?
---
>You said nothing about this circuit.
---
Nor will I, since I don't care anything about it.
---
>On the rare occasion when you do post a circuit, or critize
>one, you're usually wrong the first few times.
---
Even if that were true, which it isn't, at least I admit to error and
fix the problem, whereas you try to fix the blame.
In truth, I post and criticize circuits quite often, and on a rare
occasion I'll be wrong with one or the other or both.
Of course my record pales next to yours since you never make mistakes,
eh?
---
>Old hen.
>
>John
---
Ah, yes, the contribution of the banty rooster is so much greater than
that of the hens since without his crowing the sun couldn't rise.
---
JF
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
---
I see.
Now I'm supposed to be coerced into getting into an argument with you
about your crap circuit?
Better luck next time, dude.
---
JF
Pomegranate Bastard
<DoNotAttemptT...@anytime.org> wrote:
>On Wed, 02 Mar 2011 23:07:38 -0600, John - KD5YI <sop...@invalid.org>
>wrote:
>
>>>
>>> Moer proof of you utter stupidity. I have posted links several times
>>> here to photo sites that have all of my library of photos that I feel
>>> someone could see.
>>
>>Really?
>
> Yes, dumbfuck.
>
>> I could post a photo site
>
> Yes, if your IQ wasn't that of a circus flea.
>
>> of anyone I choose
>
> No, you cannot. You can only post YOUR site. If you post someone
>else's site you are posting THEIR site, you dumb whore for a mother
>bastard.
>
>> and you would not
>>have any idea they were not mine.
>
> Can you really be that stupid? I alter my original assessment. Your
>IQ is only 15.
What is your IQ, Mr Nymbecile?
John Larkin
<jfi...@austininstruments.com> wrote:
>On Thu, 03 Mar 2011 07:16:33 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Thu, 03 Mar 2011 06:12:05 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>>
>>>On Wed, 02 Mar 2011 17:11:41 -0800, John Larkin
>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>>>You're not playing the game. You are sitting in the henhouse, clucking
>>>>about the people who do.
>>>
>>>---
>>>I'm playing, all right, just not the way you find acceptable, which is
>>>to heap adulation on you.
>>
>>You're whining about everything but the circuit. Diversionary tactic.
>>
>>Old hen.
>>
>>John
>
>---
>I see.
Good. I'm glad we finally agree on something.
>
>Now I'm supposed to be coerced into getting into an argument with you
>about your crap circuit?
I suppose it would be cruel to trick you into discussing electronics.
So, keep on cluckin' !!!
John
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Thu, 03 Mar 2011 11:16:36 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Thu, 03 Mar 2011 07:16:33 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Thu, 03 Mar 2011 06:12:05 -0600, John Fields
>>><jfi...@austininstruments.com> wrote:
>>>
>>>>On Wed, 02 Mar 2011 17:11:41 -0800, John Larkin
>>>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>>>You're not playing the game. You are sitting in the henhouse, clucking
>>>>>about the people who do.
>>>>
>>>>---
>>>>I'm playing, all right, just not the way you find acceptable, which is
>>>>to heap adulation on you.
>>>
>>>You're whining about everything but the circuit. Diversionary tactic.
>>>
>>>Old hen.
>>>
>>>John
>>
>>---
>>I see.
>
>Good. I'm glad we finally agree on something.
>
>>
>>Now I'm supposed to be coerced into getting into an argument with you
>>about your crap circuit?
>
>I suppose it would be cruel to trick you into discussing electronics.
>So, keep on cluckin' !!!
---
The truth _is_ you have less of an interest in discussing electronics
in a give-and-take kind of way than you do in exalting yourself, so I
prefer to generally opt out of any threads you infect.
---
JF
John Larkin
<jfi...@austininstruments.com> wrote:
I didn't "infect" this thread, I started it. So why have you posted so
much cluckey blather here?
You refuse to discuss this circuit, then you attack me personally for
not doing give-and-take discussion of this circuit!
John
Phil Hobbs
I bought myself a reel for $600 or so from Newark. Given that JFET
makers have been dropping like flies lately, I'll probably buy a couple
more reels over the next few months. That way I can keep designing them
in even if they go away. (Crossed fingers.)
Cheers
Phil Hobbs
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Thu, 03 Mar 2011 12:07:36 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>>---
>>The truth _is_ you have less of an interest in discussing electronics
>>in a give-and-take kind of way than you do in exalting yourself, so I
>>prefer to generally opt out of any threads you infect.
>>
>>---
>>JF
>
>I didn't "infect" this thread, I started it.
---
Then it was diseased from the beginning.
---
>So why have you posted so much cluckey blather here?
---
You call it "cluckey blather" in an attempt to belittle it, I call it
what it is: criticism.
---
>You refuse to discuss this circuit, then you attack me personally for
>not doing give-and-take discussion of this circuit!
---
It's not an attack, it's an observation, and it's not about this
circuit in particular, it's about your fanatical need to be in
control.
---
JF
lang...@fonz.dk
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> I've always sort of liked the classic "GE" tape head/mic preamp
> circuit:
>
> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
> but it occurred to me that it might also make a nice headphone amp...
>
> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>
> Audio tends to be nonsense, but at least the audio guys have fun
> playing with circuits, whether they make a lot of sense or not.
>
> John
speaking of bizarre : http://tubetime.us/?p=85
I'm sure someone here will love it ;)
-Lasse
Bill Sloman
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 3 Mar 2011 00:10:16 -0800 (PST), Bill Sloman
>
>
>
You are the one who complains all the time. You may have personal
preferences about the nature of the threads that get started here, and
the responses that get posted, but they are only of interest to you.
You are welcome to demonstrate your preferences by choosing to get
involved with particular threads and in your particular reactions to
other responses, but your whining about the nature of those responses
doesn't make the group a more attractive or rewarding environment.
In the meantime, I'll post a circuit when I've got a circuit worth
posting. Posting a example - without comnponent values - of a circuit
that has been used in millions, for decades, doesn't strike me as a
profitable use of bandwidth, but that is a personal preference.
--
Bill Sloman, Nijmegen
ChrisQ
> I'm foggy on how such a cascode reduces noise - improved distortion,
> bandwidth, and PSRR I can understand but how does two transistors end up
> less noisy than one? I know with tubes a cascode was considered a low
> noise alternative since two triodes in cascode would have lower noise
> than a single pentode, with similar gain.
>
It doesn't. For lowest noise figure at the input, you use a single
silicon pnp transistor, which has a lower base resistance than npn. rb
is effectively in series with the source. Follow that with an op amp
typically. You can also parallel input transistors, but the advantage
soon drops off.
I'll see if I can find the circuit for a 12 channel mixer input stage
that I designed around 1974. The noise figure related to a 600 ohm
source was around 3 or 4 dB, from what I remember, with thd < 0.05% .
Noise figure is quite important for pa applications, where you also have
a lot of power gain from input to speakers...
Regards,
Chris
Bill Sloman
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 03 Mar 2011 06:39:42 -0600, John Fields
>
>
>
Waste of time. Unfortunately, it isn't going to change.
I largely confine myself to criticising the alleged facts that you
post from time to time - you are an uncritical consumer of right-wing
propaganda, with a depressing tendency to recycle it here. This isn't
a personality defect - though the fact that you keep on doing it does
reflect an unfortunate strain of insecure vanity - but rather reflects
you failure to learn critical thinking during your tertiary education,
presumably because you confined your attention to subjects that you
understood to be immediately useful.
<snip>
--
Bill Sloman, Nijmegen
John Larkin
What I did was spin a signal-level bipolar circuit into a
bipolar-mosfet power amp of similar topology.
The resulting dynamics is very interesting. Well, not to you.
John
John Larkin
<jfi...@austininstruments.com> wrote:
>On Thu, 03 Mar 2011 10:22:31 -0800, John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>
>>On Thu, 03 Mar 2011 12:07:36 -0600, John Fields
>><jfi...@austininstruments.com> wrote:
>
>>>---
>>>The truth _is_ you have less of an interest in discussing electronics
>>>in a give-and-take kind of way than you do in exalting yourself, so I
>>>prefer to generally opt out of any threads you infect.
>>>
>>>---
>>>JF
>>
>>I didn't "infect" this thread, I started it.
>
>---
>Then it was diseased from the beginning.
>---
>
>>So why have you posted so much cluckey blather here?
>
>---
>You call it "cluckey blather" in an attempt to belittle it, I call it
>what it is: criticism.
Criticism would have some content. You know, something having to do
with the circuit. All you've done is whine.
>---
>
>>You refuse to discuss this circuit, then you attack me personally for
>>not doing give-and-take discussion of this circuit!
>
>---
>It's not an attack, it's an observation, and it's not about this
>circuit in particular, it's about your fanatical need to be in
>control.
Electronic design is all about control. Of signals.
But you probably meant some sort of personal control. How does posting
a circuit, and opening it for discussion, suggest control? I thought
discussing circuits is what s.e.d. is for.
You're just a crabby old git who won't discuss electronics.
John
John Larkin
Wild. Sort of a single-slope ADC and a PWM driver. I wonder what the
sensitivity is like.
I bet you do a similar thing with a single tiny-logic schmitt gate.
Vaguely a superregenerative idea, namely triggering along a slowly
decaying exponential.
John
John Fields
Chieftain of the Carpet Crawlers
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>Stop whining and clucking about personalities
Stop with the retarded colloquialisms (or attempts at them). You
stupid fuck. That is about as plain as it gets.
You show with nearly every post just how little a man you are. If you
even get that qualification.
Your personality is that of a circus flea.
Dance, motherfucker.
My Name Is Tzu How Do You Do
<jfi...@austininstruments.com> wrote:
That's funny.
It brought up a memory of work today, we saw that weird food guy and
some "chef" somewhere was frying up a whole pan full of rooster mop tops
(the little frilly things on their heads).
I can't believe some of the stuff that guy eats.
Bill Sloman
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 3 Mar 2011 15:21:33 -0800 (PST), Bill Sloman
>
>
>
I haven't got a relevant application at the moment, so of course it
isn't interesting to me.
The universe is full of potentially interesting things. Some of them
are also interesting to other people. If you weren't quite so self-
obsessed, you might not expect everybody else to be interested in what
happens to have caught your fancy today.
--
Bill Sloman, Nijmegen
Chieftain of the Carpet Crawlers
Pretty good stuff.
It will go way over Sloman's head.
Bill Sloman
<theslipper...@thebarattheendoftheuniverse.org> wrote:
> On Thu, 3 Mar 2011 14:42:40 -0800 (PST), "langw...@fonz.dk"
Along with the hundred other things a boy can do with a 555.
So someone has used a 555 to make a less than impressive radio-
receiver. Why would anybody be interested, if they hadn't fixated on
the device early in their career and never moved on?
--
Bill Sloman, Nijmegen
George Herold
> Bitrex wrote:
> > I'm foggy on how such a cascode reduces noise - improved distortion,
> > bandwidth, and PSRR I can understand but how does two transistors end up
> > less noisy than one? I know with tubes a cascode was considered a low
> > noise alternative since two triodes in cascode would have lower noise
> > than a single pentode, with similar gain.
>
> It doesn't. For lowest noise figure at the input, you use a single
> silicon pnp transistor, which has a lower base resistance than npn. rb
> is effectively in series with the source. Follow that with an op amp
> typically. You can also parallel input transistors, but the advantage
> soon drops off.
It's the base resistance that's important? Not that I disagree. I've
been testing these 'low noise' power supplies with cap multipliers on
the output and the negative supply with the pnp always seems to have a
bit less noise.
George H.
George Herold
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Thu, 3 Mar 2011 15:21:33 -0800 (PST), Bill Sloman
>
>
>
>
>
>
> - Show quoted text -
Yeah, I didn't get the inductor part. Do I have to spice it? Or does
it have to do with head phone dynamics.
Say, and what about using the postive rail of an opamp as an output?
I never heard of that.
George H.
George Herold
>
> - Show quoted text -
Chieftain of the Carpet Crawlers
Oh, sorry, oh guru.
You are right, that is what 90% of the rest of the world has done. Not
moved on.
Or could it be that it is *you* that has the problem?
You are the one that is not impressive.
Fred Bloggs
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Wed, 2 Mar 2011 14:55:18 -0800 (PST), Fred Bloggs
>
>
>
>
>
> <bloggs.fredbloggs.f...@gmail.com> wrote:
> >On Mar 2, 4:33 pm, John Larkin
> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> On Wed, 2 Mar 2011 12:03:38 -0800 (PST), Fred Bloggs
>
> >> <bloggs.fredbloggs.f...@gmail.com> wrote:
> >> >On Mar 2, 11:40 am, John Larkin
> >> ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> >> >> I've always sort of liked the classic "GE" tape head/mic preamp
> >> >> circuit:
>
> >> >>ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
> >> >> but it occurred to me that it might also make a nice headphone amp...
>
> >> >>ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>
> >> >> Audio tends to be nonsense, but at least the audio guys have fun
> >> >> playing with circuits, whether they make a lot of sense or not.
>
> >> >> John
>
> >> >bias to stabilize the operating point against Vbe and reverse leakage
> >> >collector current change with temperature- a textbook circuit...
>
> >> Which textbook?
>
> >> John- Hide quoted text -
>
> >> - Show quoted text -
>
> >of transistor circuits- you remember the S- functions, mainly ICQ
> >stability. The big three were HFE, VBE, and ICBO. Then the rest of
> >your circuit is just ac-bypass and the shunt-series feedback for
> >signals. I've seen it dozens of times.
>
> I bet you haven't seen the bipolar+mosfet version, with inductive
> pullup, used as a power amp.
>
> John- Hide quoted text -
>
> - Show quoted text -
I don't see the MOSFET being all that much of a change. And as for the
inductor pull-up, this just doesn't make sense for low wattage high
impedance headphone loads. Your inductive reactance needs to be a good
few integer multiples of the load impedance, making these things
prohibitively large if not unobtainable for a headphone app- you would
use far less iron/ ferrite by boost switching your supply to
accommodate the output swing...guess that's why I've never seen the
inductive pullup here.
John - KD5YI
> On Wed, 02 Mar 2011 22:45:48 -0600, John - KD5YI<sop...@invalid.org>
> wrote:
>
>> On 3/2/2011 10:24 PM, John Larkin wrote:
>>> On Wed, 02 Mar 2011 22:06:41 -0600, John - KD5YI<sop...@invalid.org>
>>> wrote:
>>>
>>>> On 3/2/2011 8:52 PM, John Larkin wrote:
>>>>> On Wed, 02 Mar 2011 20:40:27 -0600, John - KD5YI<sop...@invalid.org>
>>>>> wrote:
>>>>>
>>>>>> On 3/2/2011 8:32 PM, John Larkin wrote:
>>>>>>> On Wed, 2 Mar 2011 17:59:58 -0800 (PST), Bill Sloman
>>>>>>> <bill....@ieee.org> wrote:
>>>>>>>
>>>>>>>> On Mar 3, 2:11 am, John Larkin
>>>>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>>>>> On Wed, 02 Mar 2011 18:36:25 -0600, John Fields
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> <jfie...@austininstruments.com> wrote:
>>>>>>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>>>>>
>>>>>>>>>>> I've always sort of liked the classic "GE" tape head/mic preamp
>>>>>>>>>>> circuit:
>>>>>>>>>
>>>>>>>>>>> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>>>>>>>>>
>>>>>>>>>>> but it occurred to me that it might also make a nice headphone amp...
>>>>>>>>>
>>>>>>>>>>> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>>>>>>>>>
>>>>>>>>>>> Audio tends to be nonsense, but at least the audio guys have fun
>>>>>>>>>>> playing with circuits, whether they make a lot of sense or not.
>>>>>>>>>
>>>>>>>>>>> John
>>>>>>>>>
>>>>>>>>>> Even though you scorn and ridicule audio, there's nothing wrong with
>>>>>>>>>> anyone seeking perfection there, just as there's nothing wrong with
>>>>>>>>>> your search for perfection in the genre which pleases _you_ to pursue.
>>>>>>>>>> So, speaking of fun, why don't you do a complete design and assign
>>>>>>>>>> values to the circuit components and identify the semiconductors?
>>>>>>>>>
>>>>>>>>> You're not playing the game. You are sitting in the henhouse, clucking
>>>>>>>>> about the people who do.
>>>>>>>>
>>>>>>>> He's not playing your game, which involves telling John Larkin how
>>>>>>>> cute his circuits are.
>>>>>>>
>>>>>>> He's not designing circuits, which is what this newsgroup is about.
>>>>>>>
>>>>>>> You aren't either. Both of you start to cluck and peck when people do
>>>>>>> design circuits. No surprise.
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>>>> Or is that legwork _we're_ supposed to do in order to flesh out your
>>>>>>>>>> divine revelation?
>>>>>>>>>
>>>>>>>>> Chickenleg work!
>>>>>>>>
>>>>>>>> It's half the story - a few component values make it a lot easier to
>>>>>>>> work out what a circuit is doing.
>>>>>>>
>>>>>>> You can't look at a circuit this simple and see what it's doing? OK,
>>>>>>> no surprise.
>>>>>>>
>>>>>>
>>>>>> Well, I thought designing a circuit included supplying component values.
>>>>>> No?
>>>>>
>>>>> I posted topologies. Values can be scaled to the application, but you
>>>>> need a topology first. If I were actually going to build this, for
>>>>> money, of course I'd have to define specs and then compute values.
>>>>> That's just grunt work.
>>>>>
>>>>> John
>>>>
>>>> Not really. I have a few circuits I could throw out and claim that they
>>>> are topologies and you would not be able to use them without values.
>>>> Granted, mine are more complex than the one being discussed, but I'm
>>>> hoping to make a point.
>>>>
>>>> John (not Larkin)
>>>>
>>>
>>> I think circuit topologies are fun to play with. Lots of textbooks
>>> show, and discuss, circuits without explicit values. Once you have a
>>> topology, then you can proceed to specs and component values.
>>>
>>> If you think all circuits should be posted with values, post some.
>>>
>>> John
>>
>> You are correct, John. Now you have a topology. Please post the
>> component values.
>>
>> Thanks,
>> John
>
> Given i/o specs, the DC analysis is simple. But there are two AC
> aspects that are sort of interesting: the lf response, and loop
> stability. I'm sort of disappointed that nobody has commented on
> either.
>
> As I'm disappointed in how many people want to whine and cluck about
> personalities, and avoid actually discussing electronics.
>
> John
Okay, I put some values to it. It looks like a nice circuit, I admit.
Good gain, low distortion, reasonable input impedance. Mind you, I
didn't try to optimize it. I did notice that the feedback took higher
than expected resistance and I was a bit surprised that the emitter
capacitor of the output stage made the response do a camel hump at the
beginning if too high.
So, critique away. I might learn something.
Version 4
SHEET 1 880 680
WIRE 32 -496 -240 -496
WIRE 352 -496 32 -496
WIRE -240 -400 -240 -496
WIRE 32 -400 32 -496
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SYMBOL npn -32 80 R0
SYMATTR InstName Q1
SYMATTR Value 2N3904
SYMBOL npn 288 -224 R0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL cap -272 144 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
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WINDOW 3 0 56 VBottom 0
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SYMATTR Value 1k
SYMBOL res 336 368 R0
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SYMATTR Value 1.8k
SYMBOL cap 432 384 R0
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John Larkin
The thing you guys have in common is that you suck at electronics, and
you know it. That pretty much explains everything.
John
John Larkin
wrote:
Yeah, C3 gives the overall amp response a low frequency bump, and C1
and C2 each contribute a low frequency rolloff. They all have to be
balanced to make it flat. Probably eliminating C3 is a good idea, if
the DC biasing still works. When I used this as a tape head preamp,
the LF boost was an asset, part of the tape head response
equalization.
R2 could be a lot lower. The open-loop voltage gain of Q1 is just
R5/R2, which is only 5, which is pretty low... even lower when it's
loaded by Q2. Or, another way to look at it, R2 kills the
transconductance of Q1, and adds noise.
If you do my power amp version, with a mosfet for Q2 and an inductor
for R4, there's another LF rolloff and the loop stability situation is
horrifying.
John
John Larkin
Old trick. Here's a bipolar-swing version.
ftp://jjlarkin.lmi.net/Opamp_boost_2.JPG
A similar thing is sometimes done to boost the current of an LM317, by
using its input current to drive the base of a PNP "helper"
transistor.
I use a variant of this circuit as a current splitter in my NMR
gradient amps.
I can't spell, or type, either.
John
John Larkin
Terry Newton
> I've always sort of liked the classic "GE" tape head/mic preamp
> circuit:
>
> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
> but it occurred to me that it might also make a nice headphone amp...
>
> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>
I plugged this into LTspice and with a bit of twiddling appears
to work well, at least under simulation. I used a supply V of 15V,
transistor input resistor (R1) = 100K, input capacitor (C1) = 1uF,
transistor emitter resistor (R2) = 3.3K, feedback resistor (R3) = 22K,
cap in series with feedback resistor (C3) = 10uF,
bypass capacitor (C2) = 2200uF (needs to be big or lose LF gain/damping)
output capacitor (C4) = 470uF (let it charge before connecting)
inductor size of 10 henries (for sim assuming perfect, 0 ohms)
transistor collector resistor (R4) = 3.6K but can vary,
mosfet source resistor (R5, parallel with C2) = 47 but can vary.
Transistor = whatever (2N5550 in sim), mosfet = IRL530.
These values optimize for medium output power (570mW) into 50 ohms
and reasonable power (around 300mW) into 32 ohms and 100 ohms but
with off-center clipping. R4 and R5 can be varied to deliver the
desired power into the desired load... some of the values I tried...
100 ohm load.. R4=22K R5=22 PDQ=1.5W PDR5=0.3W
Pout=730mW into 100, 370mW into 50, 220mW into 32
50 ohm load... R4=9.1K R5=22 PDQ=2.2W PDR5=0.9W
Pout=1000mW into 50, 660mW into 32, 530mW into 100
50 ohm load... R4=5.6K R5=33 PDQ=1.6W PDR5=1.1W
Pout=788mW into 50, 490mW into 32, 400mW into 100
50 ohm load... R4=3.6K R5=47 PDQ=1.2W PDR5=1.1W
Pout=570mW into 50, 330mW into 32, 290mW into 100
32 ohm load... R4=5.1K R5=22 PDQ=2.5W PDR5=1.7W
Pout=1180mW into 32, 760mW into 50, 380mW into 100
32 ohm load... R4=3.3K R5=33 PDQ=1.7W PDR5=1.7W
Pout=790mW into 32, 560mW into 50, 280mW into 100
32 ohm load... R4=2.2K R5=47 PDQ=1.2W PDR5=1.6W
Pout=500mW into 32, 400mW into 50, 200mW into 100
(PDQ is mosfet dissipation, PDR5 is R5 dissipation)
R5 sets the overall power level, then adjust R4 to achieve
balanced clipping.
Output impedance is fairly low, not much variance as load changes.
Gain is approximately R3/R2 plus a bit. Distortion increases as
R4 (and open loop gain) decreases but it appears rather "tuby".
A 10 henry inductor is probably overkill, anything 1H or more will
probably be fine, for a HP amp there's plently of overhead and the
negative feedback will mostly correct for deficiencies, smaller
inductors just have less output at 20hz. Could probably use the
secondary of an output transformer with the primary insulated..
but watch out for core saturation. Should have fairly low resistance,
preferably less than a few ohms (can tweak values to compensate).
Someone in the thread said large inductors are "unobtainium" but
that's BS, transformer windings ARE huge inductors, for this level
of power a winding of a power transformer will probably work.
For class A amps using an inductor or transformer output doubles
efficiency and halves the supply voltage needed for a given output.
It also presents a high impedance at audio frequencies so that only
the load determines the impedance (thus the gain) of the output stage.
It's possible to use a resistor load but won't perform as well.
>
> Audio tends to be nonsense, but at least the audio guys have fun
> playing with circuits, whether they make a lot of sense or not.
>
> John
But this one does make sense. There's a reason this basic circuit
has been around about as long as transistors...
Terry
Bill Sloman
Not really. Most of the people who post here haven't used a 555 for
years. Not because they don't know about it or don't like it but
because the kind of problem that it was designed to solve started
being solved in other wau=ys around 1980.
> You are the one that is not impressive.
I don't impress me. I see no reason why I should impress you.
--
Bill Sloman, Nijmegen
John Devereux
> On Mar 4, 4:43 am, Chieftain of the Carpet Crawlers
> <theslipper...@thebarattheendoftheuniverse.org> wrote:
[...]
>> You are the one that is not impressive.
>
> I don't impress me. I see no reason why I should impress you.
:) Tempting to put that on my sig.
--
John Devereux
asdf
> I've always sort of liked the classic "GE" tape head/mic preamp circuit:
>
> ftp://jjlarkin.lmi.net/GEcircuit.jpg
>
> but it occurred to me that it might also make a nice headphone amp...
>
> ftp://jjlarkin.lmi.net/GE_headphone_amp.JPG
>
>
> Audio tends to be nonsense, but at least the audio guys have fun playing
> with circuits, whether they make a lot of sense or not.
>
> John
Ironically, it looks somewhat similar to the old style fuzz face guitar
effect.
http://geofex.com/Article_Folders/fuzzface/fftech.htm
Chieftain of the Carpet Crawlers
<bill....@ieee.org> wrote:
>
>Not really. Most of the people who post here haven't used a 555 for
>years.
You do not know that, and you saying it does not make it true.
You are an idiot to think so.
Chieftain of the Carpet Crawlers
wrote:
Only if it is a collection of stupid remarks.
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>On Thu, 03 Mar 2011 14:44:58 -0600, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Thu, 03 Mar 2011 10:22:31 -0800, John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>>
>>>On Thu, 03 Mar 2011 12:07:36 -0600, John Fields
>>><jfi...@austininstruments.com> wrote:
>>
>>>>---
>>>>The truth _is_ you have less of an interest in discussing electronics
>>>>in a give-and-take kind of way than you do in exalting yourself, so I
>>>>prefer to generally opt out of any threads you infect.
>>>>
>>>>---
>>>>JF
>>>
>>>I didn't "infect" this thread, I started it.
>>
>>---
>>Then it was diseased from the beginning.
>>---
>>
>>>So why have you posted so much cluckey blather here?
>>
>>---
>>You call it "cluckey blather" in an attempt to belittle it, I call it
>>what it is: criticism.
>
>Criticism would have some content.
---
It does, and the content accurately enumerates your foibles, which is
anathema to you since you've managed to convince yourself and are
trying to convince everyone else that you're perfect in every way.
---
>You know, something having to do with the circuit.
---
There are no rules here, as you've proved by your gross abuse of the
newsgroup with your legion off-topic posts, and if I choose to not
comment on your circuit, that's my right.
---
>All you've done is whine.
---
Not so.
What I've done is simply point out technical errors which you've made,
over the years, and then been forced to respond to the calumny you
invariably invoke in order to try to make your stance seem unsullied.
---
>>>You refuse to discuss this circuit, then you attack me personally for
>>>not doing give-and-take discussion of this circuit!
>>
>>---
>>It's not an attack, it's an observation, and it's not about this
>>circuit in particular, it's about your fanatical need to be in
>>control.
>
>Electronic design is all about control. Of signals.
>
>But you probably meant some sort of personal control. How does posting
>a circuit, and opening it for discussion, suggest control? I thought
>discussing circuits is what s.e.d. is for.
---
Then why do you defy the group's charter by posting off-topic,
irrelevant nonsense?
---
>You're just a crabby old git who won't discuss electronics.
---
With you, since all you're interested in is fostering your agenda, the
inflation of your ego.
However, with others I have little reticence to join in a discussion,
and often do.
For instance, I'll refer you to the
"Driving Triac Directly with 555 Output?", the
"Looking for cheap, simple PIR detector module" and the
"24-bit on tap at Apple?" threads.
---
JF
John Larkin
<jfi...@austininstruments.com> wrote:
My agenda is, and always has been, to design electronics. My ego has
been tuned to further that end. Electronics design requires a
combination of arrogance (to believe you can do things other people
can't) and humility (to avoid the thousands of possible mistakes) and
compulsiveness (to get it all done, all right.) And, more than
anything else, brutal honesty. Not many people an manage all that, and
lots of other people don't like the people who can.
There's not many things more fun than doing this with other people who
know how. Especially since the whiteboard was invented.
John
John Larkin
Except that it makes distortion, and a headphone amp shouldn't!
John
John Fields
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
---
On the above, I'm not at odds with you except for the "brutal honesty"
part which, when you're found to be in error, all of a sudden doesn't
apply to you.
---
JF
George Herold
Intersesting thanks. Is there a reason not to take the feedback from
the output (transistor collectors) rather than the opamp itself?
George H.