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DIY tube amp w/ overdrive feedback
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notbob
May 20, 2012, 7:27:48 PM5/20/12
to
As a retired geezer, I'm getting into hobby electronics. I've been a
mechanical person most of my life, including soldering and wiring, so
building my own amp is no biggy. I've had tube amps, so know what that
self sustaining feedback is, though I may not know the proper term.
Anyway, my question to the group is, is there a minimum power (watts)
I need to build to to get that sustaining feedback, or will even small
5-10W tube amps do it? I jes want a lil' practice amp that will feed
back like my old MB Mk II. I'm studying tubes, now. I figure a
simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
project. TIA
nb
--
vi --the heart of evil!
Support labeling GMOs
<http://www.labelgmos.org/>
mechanical person most of my life, including soldering and wiring, so
building my own amp is no biggy. I've had tube amps, so know what that
self sustaining feedback is, though I may not know the proper term.
Anyway, my question to the group is, is there a minimum power (watts)
I need to build to to get that sustaining feedback, or will even small
5-10W tube amps do it? I jes want a lil' practice amp that will feed
back like my old MB Mk II. I'm studying tubes, now. I figure a
simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
project. TIA
nb
--
vi --the heart of evil!
Support labeling GMOs
<http://www.labelgmos.org/>
The_Chris
May 20, 2012, 7:57:50 PM5/20/12
to
On Sun, 20 May 2012 23:27:48 +0000, notbob wrote:
>
> Anyway, my question to the group is, is there a minimum power (watts) I
> need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a simple
> 12ax7 w/ a couple pwr tubes will be enough, like that AX84 project. TIA
>
> nb
I know nothing about amp circuits, but even my 'amp u plug and play'
>
> Anyway, my question to the group is, is there a minimum power (watts) I
> need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a simple
> 12ax7 w/ a couple pwr tubes will be enough, like that AX84 project. TIA
>
> nb
which is a SS thing that plugs into my guitar gives good feedback with
good (Duncan Distortion) pickups... I'm sure there are many parts of the
puzzle... distance from the amp is a factor too... I'm sure you can do it
with a 5 watt amp.
Lost in The Wasteland
May 20, 2012, 8:19:01 PM5/20/12
to
On Sunday, May 20, 2012 6:27:48 PM UTC-5, notbob wrote:
> As a retired geezer,
congraads
> is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project.
This is an example of a 5w SE (single ended amp) using a 12ax7 and a 6v6:
http://www.flickr.com/photos/78972607@N00/6784533951/in/photostream/
I resurrected from an old garage .
Which sounds incredibly great for home recording .. the Kalamazoo Model
uses a 5w SE el84 which sounds a bit more British - which I no longer have.
Either of these amps will go into natural feedback when cranked all the up
.. If your the goal is being able to co-exist with another person in the house it may even be too much for that. Certainly adding clean boost gadget between the guitar and amp may get your desired levels.
For feedback to occur - one tends to need enough air pressure from the speakers and sound waves in the room too to start oscillating so a somewhat moderate volume is needed, thus I personally wouldn't go smaller than 5w .
Being retired you certainly have the chance to
build more than one too! The AX84 has many canned
kits to choose from. I personally wouldn't go
smaller than 5w .
I've actually scored old PA amps from ebay to, gutted, then
made my own. It is a cheap way to score the iron.
If you haven't discovered tedweber.com .. check out his kits too.
> As a retired geezer,
congraads
> is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project.
http://www.flickr.com/photos/78972607@N00/6784533951/in/photostream/
I resurrected from an old garage .
Which sounds incredibly great for home recording .. the Kalamazoo Model
uses a 5w SE el84 which sounds a bit more British - which I no longer have.
Either of these amps will go into natural feedback when cranked all the up
.. If your the goal is being able to co-exist with another person in the house it may even be too much for that. Certainly adding clean boost gadget between the guitar and amp may get your desired levels.
For feedback to occur - one tends to need enough air pressure from the speakers and sound waves in the room too to start oscillating so a somewhat moderate volume is needed, thus I personally wouldn't go smaller than 5w .
Being retired you certainly have the chance to
build more than one too! The AX84 has many canned
kits to choose from. I personally wouldn't go
smaller than 5w .
I've actually scored old PA amps from ebay to, gutted, then
made my own. It is a cheap way to score the iron.
If you haven't discovered tedweber.com .. check out his kits too.
notbob
May 20, 2012, 8:40:47 PM5/20/12
to
On 2012-05-21, Lost in The Wasteland <smapper...@yahoo.com> wrote:
> I've actually scored old PA amps from ebay to, gutted, then
> made my own. It is a cheap way to score the iron.
>
> If you haven't discovered tedweber.com .. check out his kits too.
Thnx. I've got the time to perp the crime, so am tearing apart
> I've actually scored old PA amps from ebay to, gutted, then
> made my own. It is a cheap way to score the iron.
>
> If you haven't discovered tedweber.com .. check out his kits too.
everything I have lying around. Coupla 'puter monitors, a dead
microwave, etc. I'm not gonna buy a kit. Jes hack something together
as I learn. First, gotta get a good safety setup. And a couple math
refresher books. It's a fun way to pass the time. ;)
Lost in The Wasteland
May 20, 2012, 9:28:49 PM5/20/12
to
On Sunday, May 20, 2012 7:40:47 PM UTC-5, notbob wrote:
> On 2012-05-21, Lost in The Wasteland
>
> On 2012-05-21, Lost in The Wasteland
>
> > I've actually scored old PA amps from ebay to, gutted, then
> > made my own. It is a cheap way to score the iron.
> >
> > If you haven't discovered tedweber.com .. check out his kits too.
>
> Thnx. I've got the time to perp the crime, so am tearing apart
> everything I have lying around. Coupla 'puter monitors, a dead
> microwave, etc. I'm not gonna buy a kit. Jes hack something together
> as I learn. First, gotta get a good safety setup. And a couple math
> refresher books. It's a fun way to pass the time. ;)
>
>
I don't know how much of monitor one can
> > made my own. It is a cheap way to score the iron.
> >
> > If you haven't discovered tedweber.com .. check out his kits too.
>
> Thnx. I've got the time to perp the crime, so am tearing apart
> everything I have lying around. Coupla 'puter monitors, a dead
> microwave, etc. I'm not gonna buy a kit. Jes hack something together
> as I learn. First, gotta get a good safety setup. And a couple math
> refresher books. It's a fun way to pass the time. ;)
>
>
use for a amp .. other than the detachable
power cord !
Americans tend to live in a largely disposable materialist world where
many would rather replace than repair.
notbob
May 20, 2012, 10:17:55 PM5/20/12
to
On 2012-05-21, Lost in The Wasteland <smapper...@yahoo.com> wrote:
> Americans tend to live in a largely disposable materialist world where
> many would rather replace than repair.
I found a great video tutorial on how to rewire the microwave's
> Americans tend to live in a largely disposable materialist world where
> many would rather replace than repair.
transformer. Who needs TV!? ;)
boardjunkie1
May 20, 2012, 10:38:02 PM5/20/12
to
On May 20, 10:17 pm, notbob <not...@nothome.com> wrote:
Jeez.....
> On 2012-05-21, Lost in The Wasteland <smappersmap...@yahoo.com> wrote:
>
> > Americans tend to live in a largely disposable materialist world where
> > many would rather replace than repair.
>
> I found a great video tutorial on how to rewire the microwave's
> transformer. Who needs TV!? ;)
>
> nb
>
> --
> vi --the heart of evil!
> Support labeling GMOs
> <http://www.labelgmos.org/>
Wanna build an amp? Buy the right parts....or just buy an amp.
>
> > Americans tend to live in a largely disposable materialist world where
> > many would rather replace than repair.
>
> I found a great video tutorial on how to rewire the microwave's
> transformer. Who needs TV!? ;)
>
> nb
>
> --
> vi --the heart of evil!
> Support labeling GMOs
> <http://www.labelgmos.org/>
Jeez.....
Flasherly
May 21, 2012, 12:48:00 AM5/21/12
to
On May 20, 7:27 pm, notbob <not...@nothome.com> wrote:
> As a retired geezer, I'm getting into hobby electronics. I've been a
> mechanical person most of my life, including soldering and wiring, so
> building my own amp is no biggy. I've had tube amps, so know what that
> self sustaining feedback is, though I may not know the proper term.
>
> Anyway, my question to the group is, is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project. TIA
In the strict sense it's overcoming the threshold of receptivity, all
> As a retired geezer, I'm getting into hobby electronics. I've been a
> mechanical person most of my life, including soldering and wiring, so
> building my own amp is no biggy. I've had tube amps, so know what that
> self sustaining feedback is, though I may not know the proper term.
>
> Anyway, my question to the group is, is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project. TIA
a PU is capable of receiving, with just enough of the proper frequency
to overload what the amp thinks its hearing from the PU, which I at
least know isn't, because at that point the amp's talking back to
itself, having a jolly one-way conversation, forgetting the PU
entirely, and drifting along like jelly rolling all over on a roll.
Since when that happens and the ol' tubes get wet, red hot, and
creamy, things can actually can pass for being totally sensuous,
unless of course one happened to be playing to closetful of cloggers
or iron maidens of Irish toe-tapping persuasion in the next room or
door. The one place where it never happens, or it is not supposed to,
is classical guitar;- but, now, everybody knows nobody really plays
one like Santana, not even the supposed classicist of rock'n'rule,
Lindsey Buckingham. I don't get it near as much, or it just seems not
to, if I don't go around much past half volume with two EL84s through
YellowJack 6L6s converters off a basic Bassman geared PCB. How low I
can go is where I want to set two sets of 12ax7s: 1) namely the amp's
gain, 2) fed by a BlackFinger Electro Harmonix's two 12ax7s cranked at
the first stage, similarly with nothing much on the second compression
stage. Everything is on the Milky EQ Highway at that point. It's for
reading PDF sheet music from a 42" monitor, that is, with my back to
everything I can crank off the amp's power stage, probably 20-watts
potential while cradling the guitar. So I guess I'm at least twice
over your projected 5watts, maybe up to 15watts before the screaming
starts. I've also got a LED wattage meter I can hook between the 4
12" speakers and amp to get real-time feedback. I use it on some 250-
watt speakers, though it's rated just 100watts. Hey - build me a 400-
watt amp, too, if you got the spare time.
jim
May 21, 2012, 1:24:39 PM5/21/12
to
On 5/20/2012 5:40 PM, notbob wrote:
> On 2012-05-21, Lost in The Wasteland<smapper...@yahoo.com> wrote:
>
>> I've actually scored old PA amps from ebay to, gutted, then
>> made my own. It is a cheap way to score the iron.
>>
>> If you haven't discovered tedweber.com .. check out his kits too.
>
> Thnx. I've got the time to perp the crime, so am tearing apart
> everything I have lying around. Coupla 'puter monitors, a dead
> microwave, etc. I'm not gonna buy a kit. Jes hack something together
> as I learn. First, gotta get a good safety setup. And a couple math
> refresher books. It's a fun way to pass the time. ;)
>
> nb
>
What you mention above is not worth salvaging when building amps.
> On 2012-05-21, Lost in The Wasteland<smapper...@yahoo.com> wrote:
>
>> I've actually scored old PA amps from ebay to, gutted, then
>> made my own. It is a cheap way to score the iron.
>>
>> If you haven't discovered tedweber.com .. check out his kits too.
>
> Thnx. I've got the time to perp the crime, so am tearing apart
> everything I have lying around. Coupla 'puter monitors, a dead
> microwave, etc. I'm not gonna buy a kit. Jes hack something together
> as I learn. First, gotta get a good safety setup. And a couple math
> refresher books. It's a fun way to pass the time. ;)
>
> nb
>
Start with a broken guitar amp, or a used or broken old tube hifi or PA
amp. Check ebay and CraigsList. Run a CL ad in Musical Instruments for
neglected/broken tube amps wanted.
You need iron (high voltage power transformers with filament windings,
and output transformers -- specialty parts NOT in monitors or
microwaves), tube sockets and a chassis. DO NOT use the microwave tube,
unless you want that amp to REALLY cook ;^)
I get 90+% of my parts through tubesandmore.com and partsexpress.com
If I need tubes, tubedepot.com
jim
May 21, 2012, 1:28:10 PM5/21/12
to
On 5/20/2012 4:27 PM, notbob wrote:
> As a retired geezer, I'm getting into hobby electronics. I've been a
> mechanical person most of my life, including soldering and wiring, so
> building my own amp is no biggy. I've had tube amps, so know what that
> self sustaining feedback is, though I may not know the proper term.
>
> Anyway, my question to the group is, is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project. TIA
>
> nb
>
That sort of feedback doesn't take brute power, if you have enough gain
> As a retired geezer, I'm getting into hobby electronics. I've been a
> mechanical person most of my life, including soldering and wiring, so
> building my own amp is no biggy. I've had tube amps, so know what that
> self sustaining feedback is, though I may not know the proper term.
>
> Anyway, my question to the group is, is there a minimum power (watts)
> I need to build to to get that sustaining feedback, or will even small
> 5-10W tube amps do it? I jes want a lil' practice amp that will feed
> back like my old MB Mk II. I'm studying tubes, now. I figure a
> simple 12ax7 w/ a couple pwr tubes will be enough, like that AX84
> project. TIA
>
> nb
>
and you're close enough to amp/speaker. You'd be surprised at how
little volume you really need, if you have enough gain. Need some help
with low gain? Touch the headstock to the cab for a second.
notbob
May 21, 2012, 2:01:30 PM5/21/12
to
On 2012-05-21, jim <inse@ttle> wrote:
> That sort of feedback doesn't take brute power, if you have enough gain
> and you're close enough to amp/speaker. You'd be surprised at how
> little volume you really need, if you have enough gain.
Yep. Both my JMF T60 and 100W MBmkII could do it at fairly low volume
> That sort of feedback doesn't take brute power, if you have enough gain
> and you're close enough to amp/speaker. You'd be surprised at how
> little volume you really need, if you have enough gain.
when I used the master circuit.
Rufus
May 21, 2012, 2:54:36 PM5/21/12
to
--
- Rufus
Lost in The Wasteland
May 21, 2012, 7:27:20 PM5/21/12
to
On Monday, May 21, 2012 12:24:39 PM UTC-5, jim wrote:
>
> Start with a broken guitar amp, or a used or broken old tube hifi or PA
> amp. Check ebay and CraigsList. Run a CL ad in Musical Instruments for
> neglected/broken tube amps wanted.
Does that work ? never thought of that.
>
> Start with a broken guitar amp, or a used or broken old tube hifi or PA
> amp. Check ebay and CraigsList. Run a CL ad in Musical Instruments for
> neglected/broken tube amps wanted.
>
> You need iron (high voltage power transformers with filament windings,
> and output transformers --
heavy duty and generally over engineered.
>
> partsexpress.com
PE is great .. I like their individual component selections ( caps, resistors) -
I usually order extra of popular values for backup on almost any order to replenish what I use - keep them in a parts bin. You can see some of that in the Gibson video.
Jim
May 21, 2012, 7:50:07 PM5/21/12
to
On 5/21/2012 4:27 PM, Lost in The Wasteland wrote:
> On Monday, May 21, 2012 12:24:39 PM UTC-5, jim wrote:
>
>>
>> Start with a broken guitar amp, or a used or broken old tube hifi or PA
>> amp. Check ebay and CraigsList. Run a CL ad in Musical Instruments for
>> neglected/broken tube amps wanted.
>
> Does that work ? never thought of that.
I've had mixed results. I get plenty of unrealistic replies from guys
> On Monday, May 21, 2012 12:24:39 PM UTC-5, jim wrote:
>
>>
>> Start with a broken guitar amp, or a used or broken old tube hifi or PA
>> amp. Check ebay and CraigsList. Run a CL ad in Musical Instruments for
>> neglected/broken tube amps wanted.
>
> Does that work ? never thought of that.
with Crates, Behringer and the like who expect to get a few dollars less
than what the junk would be worth if it was running. But I've picked up
a few amps for a fair price. Not ripping them off, and allowing me to
fix the amp with less out of pocket than what it's worth when it's done.
I haven't ran in ad in a long time, because I have a backlog of projects.
I've also purchased from "as is" for sale ads on CL.
>
>>
>> You need iron (high voltage power transformers with filament windings,
>> and output transformers --
>
> That is where the old PA come in handy - those things from the 50/60 were
> heavy duty and generally over engineered.
that I bought off of ebay. It's now a Matchless Lighting circuit.
>
>>
>> partsexpress.com
>
> PE is great .. I like their individual component selections ( caps, resistors) -
> I usually order extra of popular values for backup on almost any order to replenish what I use - keep them in a parts bin. You can see some of that in the Gibson video.
>
trays are getting low. I always buy at least 10 of the same value, but
it seems like I need to up that in certain values!
west
May 21, 2012, 11:21:45 PM5/21/12
to
RichL
May 21, 2012, 11:39:57 PM5/21/12
to
"west" <west...@att.net> wrote in message
news:jpf0o8$qdh$1...@dont-email.me...
Easy with a 5-W Valve Jr., especially with a semi-hollow-body guitar.
news:jpf0o8$qdh$1...@dont-email.me...
notbob
May 22, 2012, 12:46:38 AM5/22/12
to
On 2012-05-21, notbob <not...@nothome.com> wrote:
> Yep. Both my JMF T60 and 100W MBmkII could do it at fairly low volume
> when I used the master circuit.
Wow! I finally got this same overdrive feedback from my Fender Bandit I SS amp. I
> Yep. Both my JMF T60 and 100W MBmkII could do it at fairly low volume
> when I used the master circuit.
was beginning to think it couldn't be done with an all SS amp, but I was
wrong. Not exactly Hendrix crazy runaway feedback, but satisfactory.
OTOH, haven't plugged in my orig tube screamer, yet.
nb
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