Adcom amps
Jamaludin Mohd Yusof
I have an Adcom 2535 that I am using to power my dual center and
surrounds. It sounds reasonably good, but the 'thump' every time I turn it
on or off is very annoying and, i suspect, cant be good for the speakers.
My old NAD 2100 that i use for the front channels has no such problems.
Can anyone recommend any alternatives to the 2535? I have had a reply to
an earlier post saying that the 535 II also produces a thump on power-up.
Is this true for all Adcom amps? This, combined with a noticeabley better
bass response from the NAD, is sorts turning me off to Adcoms...
Comments please.....
Miguel Barrio
In article <51mqo0$t...@nntp.Stanford.EDU>,
Jamaludin Mohd Yusof <jamal@ctr-next9> wrote:
...
>Can anyone recommend any alternatives to the 2535? I have had a reply to
>an earlier post saying that the 535 II also produces a thump on power-up.
Hi,
I have a 535II and it does produce a VERY slight thump on power on. But
it's volume is well below any reasonble listening level. You could get a
digital storage scope to look at that. Well, maybe not. I'll try to do
that with mine and post what I see.
I wouldn't worry about it, though.
Miguel
Pete
jamal@ctr-next9 (Jamaludin Mohd Yusof) wrote:
>I have an Adcom 2535 that I am using to power my dual center and
>surrounds. It sounds reasonably good, but the 'thump' every time I turn it
>on or off is very annoying and, i suspect, cant be good for the speakers.
>My old NAD 2100 that i use for the front channels has no such problems.
>Can anyone recommend any alternatives to the 2535? I have had a reply to
>an earlier post saying that the 535 II also produces a thump on power-up.
>Is this true for all Adcom amps? This, combined with a noticeabley better
>bass response from the NAD, is sorts turning me off to Adcoms...
>Comments please.....
I believe that some companies add components which prevent turn on
"thump". Other companies do not add this, I think the thinking is
that this is just one more device in the music pathway. My Adcom 5400
"thumps" too. Many mid and high end amps have some "thump" while most
mini-systems do not have this. I do not think this will damage your
speakers, but it may piss you off.
--
Pete
Jamaludin Mohd Yusof
In article <51noau$f...@usenet11.interramp.com> p...@interramp.com (Pete)
writes:
> that this is just one more device in the music pathway. My Adcom 5400
> "thumps" too. Many mid and high end amps have some "thump" while most
> mini-systems do not have this. I do not think this will damage your
> speakers, but it may piss you off.
> --
> Pete
>
it would have negligible effect if well designed...
The NAD keeps the speaker protection on until the amp is warmed up and
doesnt degrade the sound while playing... I somehow doubt that
mini-systems have anything like this going on..
The Adcom also thumps and crackles (loud click through the speakers) on
turn OFF which sounds like the power supply discharging or something...
that seems much more likely to be damaging than the soft turn-ON thump...
It does piss me off occasionally....
Jamal
Norm Strong
In a previous article, jamal@ctr-next9 (Jamaludin Mohd Yusof) says:
>I have an Adcom 2535 that I am using to power my dual center and
>surrounds. It sounds reasonably good, but the 'thump' every time I turn it
>on or off is very annoying and, i suspect, cant be good for the speakers.
>
>My old NAD 2100 that i use for the front channels has no such problems.
>Can anyone recommend any alternatives to the 2535? I have had a reply to
>an earlier post saying that the 535 II also produces a thump on power-up.
>Is this true for all Adcom amps? This, combined with a noticeabley better
>bass response from the NAD, is sorts turning me off to Adcoms...
Adcom amps, in general, thump on turnoff. This is due to the fact that
they aren't very well engineered. ( Don't get excited. I didn't say
they didn't sound good, just that they aren't very well engineered.)
--
Norm Strong (bg...@scn.org)
2528 31st S. Seattle WA 98l44
Armand
In article <Dxw90...@midway.uchicago.edu>, mba...@midway.uchicago.edu (Miguel Barrio) says:
>
>In article <51mqo0$t...@nntp.Stanford.EDU>,
>Jamaludin Mohd Yusof <jamal@ctr-next9> wrote:
>...
>>an earlier post saying that the 535 II also produces a thump on power-up.
>
>
>I have a 535II and it does produce a VERY slight thump on power on. But
>it's volume is well below any reasonble listening level. You could get a
>digital storage scope to look at that. Well, maybe not. I'll try to do
>that with mine and post what I see.
>
>I wouldn't worry about it, though.
>
>Miguel
I have a 535II also, and the thump is more musical than the amp is!
Bright, harsh, aggressive, and totally non-musical. That's why it was
banished to video hell. As far as alternatives? Anything else. I'd rather
hear my brother sing. He's tone deaf, but at least he doesn't "thump".
Armand
Jamaludin Mohd Yusof
> Adcom amps, in general, thump on turnoff. This is due to the fact that
> they aren't very well engineered. ( Don't get excited. I didn't say
> they didn't sound good, just that they aren't very well engineered.)
>
> --
> Norm Strong (bg...@scn.org)
> 2528 31st S. Seattle WA 98l44
Dont worry, I have no trouble with the concept.... I think pretty much
the same thing, which is why I am asking for recommendations for
alternatives..... something in a 3 or 4 channel amp to power center and
surrounds (i would like at least 100 for the center....)
Thaks again..
Pete
bg...@scn.org (Norm Strong) wrote:
>Adcom amps, in general, thump on turnoff. This is due to the fact that
>they aren't very well engineered. ( Don't get excited. I didn't say
>they didn't sound good, just that they aren't very well engineered.)
>--
>Norm Strong (bg...@scn.org)
>2528 31st S. Seattle WA 98l44
Hi,
Perhaps you can be more specific. What are the features that you
consider poorly engineered (designed?). I believe that the higher end
5xxx series were designed in part by Nelson Pass. I do not know for
sure of the level of his involvement and whether his expertise was
utilized in the 5400, 5300, and 5200. I think I have seen posts from
him on this newsgroup, perhaps he will see this and let us know. I
think that he is an individual who is familier with good amp design;)
--
Pete
Liming M. Voo
Pete (p...@interramp.com) wrote:
I think Norm meant the engineering of the structural construction. A well
known good audio designer may not be well skilled in mechanical design of
the supporting structures for the audio electronics.
Liming
Craig Siever
How about weak power supplies? There are certain _compromises_
involved between the design phase and production phases in most
_mass produced_ items no matter who designs them. The design may
be good but the implementation may not be. You never get something
for nothing, not in this world.
Craig
Paul Wilcox
Ahh, the ARC Classic 60 that I used to own thumped on turn off also. I guess it was
not well engineered. Maybe this also had something to do with its weak power supply.
Miguel Barrio
For rec.audio.tech readers, this has to do with the 'thump' that many
Adcom amps produce during turn-on and turn-off.
In article <324496...@coastalnet.com>,
Craig Siever <cn4...@coastalnet.com> wrote:
>How about weak power supplies? There are certain _compromises_
>involved between the design phase and production phases in most
>_mass produced_ items no matter who designs them. The design may
>be good but the implementation may not be. You never get something
>for nothing, not in this world.
Hi!,
My Adcom GFA-535II has quite a hefty power supply: it's 60 w/ch but it
still has one full independent supply for each channel and each of these
is quite big. I KNOW this doesn't prove anything, but it does give you
some hints! (the thing weights around 25 lbs. also).
After looking at the driver during turn-on and turn-off (yeap, take the
grille out and just look at the speaker cone!) I presume that the whole
thing is related to some feedback that gets into the 'incorrect' region
(makes the thing oscillate just barely) during this transient.
It might also be related to the DC servo that elliminates CD offsets in
some of Adcom's amps. The GFA-535II differs from the GFA-535 precisely
in this feature, if my memory serves me right.
Frankly, I don't know why these amps have this behavior but I think that
there is nothing to worry about.
BTW, could anyone with a 'good' amp (read Pass Aleph, Krell or something
of the sort here) look at their speaker cones while the amp is being
turned on???. If you do so I'd be glad to see your findings in this
thread.
Thanks a lot!.
Miguel
Dave Smith
Miguel Barrio wrote:
> BTW, could anyone with a 'good' amp (read Pass Aleph, Krell or something
> of the sort here) look at their speaker cones while the amp is being
> turned on???. If you do so I'd be glad to see your findings in this
> thread.
>
> Thanks a lot!.
>
> Miguel
--
My Krell KMA-100's (around 8 years old, so hardly state of the art)
do *nothing* visible (or audible) to the cones when switched on.
They contain at least one relay (you can hear it) which protects
the speakers during switch on. I cant say I have noticed anything
audible at switch off either.
This is a valid comparision to your 25 Kg Adcoms. They contain
1.1 KVA transformers each side (monoblocks) and weigh it at some 38 Kg
if memory serves. Certainly a risk for my poor old bad back.
As was noted many times before. The implementation can always spoil
an otherwise good design.
If you have big power supllies, I would want some protection for
my speakers. I believe there are ways to do this that do not
degrade the audio quality (eg are out of circuit when operating
"normally") certainly the latest krell & mark levinson gear
contains a LOT of "protective" circuitry.
------------------------------------------
Dave Smith. My opinions are only mine.
and I reserve the right to be wrong
work .... dave....@guildford.ericsson.se
home .... da...@aparty.demon.co.uk
Craig Siever
My man Pete asked "What are the features that you consider poorly
engineered (designed?)." To which I answered "How about weak power
supplies?"
Sorry if you confused this as an explaination for the thump. Offhand I
would say that the Adcom referenced here does _not_ have circuitry
to disengage the speaker output during power up. Sounds like your
ARC didn't either.
Craig
Paul Wilcox wrote:
>
> Craig Siever wrote:
> >
> > How about weak power supplies? There are certain _compromises_
> > involved between the design phase and production phases in most
> > _mass produced_ items no matter who designs them. The design may
> > be good but the implementation may not be. You never get something
> > for nothing, not in this world.
> >
Miguel Barrio
Hi!,
I just got a couple of quotes from Adcom's web page. This refer to their
GFA-5500 power amp (200 watts/channel I believe). This document is at:
http://www.soundsite.com/adcom/gfa5500.html
OK, here it goes:
1) This talks about the power supply capabilities:
"High Capacitance Storage
Each channel has nearly 120 Joules of energy storage, adequate for 14
kilowatts of power at 10% ripple. Under normal operation, the power
supply ripple voltage is less than 1%."
"Separate High Voltage Front End Supplies
The front end circuitry of each channel is supplied power by its own
high voltage system - including separate transformer windings, bridge
rectifiers and filter capacitors for each channel."
Clearly, the power supply is no sissy.
2) This talks about the 'turn-on thump':
"In Rush Limiting
The power supplies feature inrush limiting which prevents the high
current surges which would normally accompany the charge cycle of the
transformer and the power supply capacitors on turn-on."
"Doubly Regulated Active Current Sources
The current sources in the GFA-5500 are doubly regulated for absolute
stability. This stability gives the front end circuitry the ability to
ignore supply fluctuations, noise and signals from the other channel
(crosstalk). It also provides operation which does not vary with
temperature or age. The voltage references driving each source are
filtered passively, with different time constants, which allowing for
staggered turn-on of the sources, giving low turn-on thump."
^^^^^^^^^^^^^^^^^^^^^^^^^
So, apparently, they know about the thump and probably made sure it's
nothing to worry about. I do agree, however, that it might have been
'neat' to have a relay that would decouple the speaker terminals from
the circuit during turn-on and turn-off. Someone posted something saying
that Krells do have such a thing, so I guess that it souldn't be a
problem to have such circuitry. Maybe Adcom's designers felt this was
not the path to follow (I wonder if the Pass Aleph has such relay
circuitry).
BTW, I must say that Adcom didn't overlook these aspects: my preamp has
a relay circuit that won't send any signal to the power amp for a couple
of seconds after turn-on. Of course, this works if your power amp is
connected to the switched output of your preamp and turns on when the
preamp does.
Hope this helps!. Enjoy the music!.
Craig Siever
Miguel Barrio wrote:
>
> Hi!,
>
> I just got a couple of quotes from Adcom's web page. This refer to their
> GFA-5500 power amp (200 watts/channel I believe). This document is at:
>
> http://www.soundsite.com/adcom/gfa5500.html
>
> OK, here it goes:
>
> 1) This talks about the power supply capabilities:
>
> "High Capacitance Storage
> Each channel has nearly 120 Joules of energy storage, adequate for 14
> kilowatts of power at 10% ripple. Under normal operation, the power
> supply ripple voltage is less than 1%."
>
> "Separate High Voltage Front End Supplies
> The front end circuitry of each channel is supplied power by its own
> high voltage system - including separate transformer windings, bridge
> rectifiers and filter capacitors for each channel."
>
> Clearly, the power supply is no sissy.
Hey Miguel, is this the same page that says of the 5500:
High Current Output
Each channel uses 10 Power Mosfet output devices. These devices are each rated to
handle 20 amps of output current. This
output capacity is adequate to deliver full power into 2 ohm loads, and the amplifier
is completely stable driving 1 ohm or
less.
20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to me. Guess it
depends on your neighborhood :^)
XOXO
Craig
Miguel Barrio
In article <324718...@coastalnet.com>,
Craig Siever <cn4...@coastalnet.com> wrote:
>Hey Miguel, is this the same page that says of the 5500:
>
>High Current Output
>Each channel uses 10 Power Mosfet output devices. These devices are
>each rated to handle 20 amps of output current. This output capacity
>is adequate to deliver full power into 2 ohm loads, and the amplifier
>is completely stable driving 1 ohm or less.
>
>20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to me.
>Guess it depends on your neighborhood :^)
EACH. Guess reading abilities also depend on the neighborhood |-P
Miguel
Alex Rodriguez
In article <324718...@coastalnet.com>, cn4...@coastalnet.com
says...
>High Current Output
>Each channel uses 10 Power Mosfet output devices. These devices are
each rated to
>handle 20 amps of output current. This
>output capacity is adequate to deliver full power into 2 ohm loads, and
the amplifier
>is completely stable driving 1 ohm or
>less.
>
>20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to
me. Guess it
>depends on your neighborhood :^)
My arithmatic tells me its more than 20 amps.
10 MOSFET devices multiplied by 20 amps each gives me 200amps
capacity. That seems pretty manly to me. Maybe for a welder 200amps is
not manly but for a sterophile, its just fine and dandy.
--
-----------------
Alex '86 Dodge Omni GLH Turbo
ad...@columbia.edu '87 Alfa Romeo Milano Gold
'88 Vitus/Dura-Ace **gotta sell this bike**
__O '91 Specialized Epic CF/Ultegra STI
_-\<,_ '93 Excell Macalu Professional / Deore DX
(_)/ (_) '95 Litespeed Ultimate/Magic/Dura-Ace
Warren Lampitt
Miguel Barrio wrote:
>
> For rec.audio.tech readers, this has to do with the 'thump' that many
> Adcom amps produce during turn-on and turn-off.
If the thump is really is bugging your butt, I have a possible
solution: My system (2 GFA 535's and a GFA 2535) is plugged into the
Adcom ACE-212 line filter and sequence switch. Upon start-up, the
ACE-212 turns on the preamp (GTP-500) and the surround decoder and lets
it warm up for about 15 seconds before providing power to the power
amps. This eliminates the thump. Upon shut down, the order is
reversed. The result is no thump on start up and I have no idea why!
Warren
--
Technical Editor, WebDoctor
Gretmar Communications
http://www.gretmar.com/webdoctor/home.html
Miguel Barrio
In article <32489C...@gretmar.com>,
Warren Lampitt <war...@gretmar.com> wrote:
>Miguel Barrio wrote:
>>
>> For rec.audio.tech readers, this has to do with the 'thump' that many
>> Adcom amps produce during turn-on and turn-off.
>
>If the thump is really is bugging your butt, I have a possible
>solution: My system (2 GFA 535's and a GFA 2535) is plugged into the
>Adcom ACE-212 line filter and sequence switch. Upon start-up, the
>ACE-212 turns on the preamp (GTP-500) and the surround decoder and lets
>it warm up for about 15 seconds before providing power to the power
>amps. This eliminates the thump. Upon shut down, the order is
>reversed. The result is no thump on start up and I have no idea why!
Hi!,
My Adcom preamp does the same: if you connect the power amp to the
switched output and leave the power amp always on, then when you turn
the power of the preamp on both are powered but the preamp will wait a
couple of seconds before sending any signal to the power amp (Oh, yes,
GTP-400 and GFA-535II) to allow for it to stabilize. The thump (though
very slight) is still there. I've tried powering the power amp
independently but there's no difference.
I am not at all concerned about this, though. The thump is very slight
and for what I've read in Adcom's web page, they know about it and it is
supposed to be there. Moreover, they made sure it's not harmful.
Miguel
Craig Siever
So you're avering that the Adcom produces _200_ amps from MOSFET
_output_ stage devices? Hats off to the folks of Adcom for developing
a 10X current amplifier, with MOSFETs no less. And this puppy only
weighs 50 pounds too! You're a product of advertising _hype_ Miguel.
Best you do a little research in Electrical Theory 101 before "buying"
the "Hight Current" claims of Adcom. While 20 Amps peak/channel is enough
to kill you, it's not quite enough to power a "killer" system, particularly
a system that drives low impedance/high reactance speaker loads. The
Adcom just doesn't have enough "grunt" to handle it. Stewart Pinkerton is
right, claims such as these _are_ advertising fluff.
Regards,
Craig
Miguel Barrio wrote:
>
> In article <324718...@coastalnet.com>,
> Craig Siever <cn4...@coastalnet.com> wrote:
> >Hey Miguel, is this the same page that says of the 5500:
> >
> >High Current Output
> >Each channel uses 10 Power Mosfet output devices. These devices are
> >each rated to handle 20 amps of output current. This output capacity
> ^^^^
>
> >is adequate to deliver full power into 2 ohm loads, and the amplifier
> >is completely stable driving 1 ohm or less.
> >
> >20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to me.
> >Guess it depends on your neighborhood :^)
>
Henry Pasternack
Craig Siever (cn4...@coastalnet.com) wrote:
: So you're avering that the Adcom produces _200_ amps from MOSFET
: _output_ stage devices? Hats off to the folks of Adcom for developing
: a 10X current amplifier, with MOSFETs no less. And this puppy only
: weighs 50 pounds too! You're a product of advertising _hype_ Miguel.
: Best you do a little research in Electrical Theory 101 before "buying"
: the "Hight Current" claims of Adcom. While 20 Amps peak/channel is enough
: to kill you, it's not quite enough to power a "killer" system, particularly
: a system that drives low impedance/high reactance speaker loads. The
: Adcom just doesn't have enough "grunt" to handle it. Stewart Pinkerton is
: right, claims such as these _are_ advertising fluff.
There's no technical reason to doubt that an amplifier using 10
large output devices per channel could produce peak currents of one
hundred amps, assuming proper drive circuitry and devices rated at
20A. This is equivalent to a momentary power output of 5kW into
a 1 Ohm load, definitely in the "grunt" category. Even 20A is more
than sufficient.
-Henry
--
ATTENTION! Reply to h...@nortel.ca (hen...@nortel.ca won't work).
ae...@flight.els
>10 MOSFET devices multiplied by 20 amps each gives me 200amps
>capacity. That seems pretty manly to me. Maybe for a welder 200amps is
>not manly but for a sterophile, its just fine and dandy.
There is no way in hell that ANY Adcom amp will produce 200 amps of
current. I'd be very surprised if they could provide even 50 amps of
current. Further, Adcom's drive capabilies are pretty much limited to
4 ohm impedances. Yes, they'll drive a 2 ohm load, but even their
mighty GFA-5800 acts like a 30wpc amp at this resistence, and quickly
runs out of power. And I mean quickly!
I've compared the GFA-5800 (250wpc) with a Krell KSA-150 (150wpc) on a
pair of Thiel CS 5i's, which dip to 2 ohms or less, and the KSA-150
clearly outperformed the GFA-5800.
Adcom has touted "high current" for some time now, and while I'll
admit that they do provide substantial value for the money (in the
proper system), they are NOT high current amplifiers.
Henry Pasternack
ae...@flight.els wrote:
: There is no way in hell that ANY Adcom amp will produce 200 amps of
: current. I'd be very surprised if they could provide even 50 amps of
: current. Further, Adcom's drive capabilies are pretty much limited to
: 4 ohm impedances. Yes, they'll drive a 2 ohm load, but even their
: mighty GFA-5800 acts like a 30wpc amp at this resistence, and quickly
: runs out of power. And I mean quickly!
: Adcom has touted "high current" for some time now, and while I'll
: admit that they do provide substantial value for the money (in the
: proper system), they are NOT high current amplifiers.
How do you know? Have you ever measured the current capability
of an Adcom amplifier? Or do your ears have ammeters in them?
Maybe there is something else entirely going on that explains
your impressions of high current capability.
mcree_randy@tandem.com(Randy McRee)
I'd like to de-lurk for the moment in order to point out a couple of things.
First, the original article stated that there were 10 output devices EACH rated
at 20 amps. But the next poster implied this meant 20amps per *channel*: of course,
this is wrong it should imply (if we are very simplistic) 200 amps per channel.
So 200 amps DOES sound like quite a bit. But the original Adcom article doesn't
actually say that, we inferred it. There's lot of reasons why it might not be so rosy.
But what I would like to point out is that the way a typical output device (i.e. a MOSFET)
is rated is very different from the way in which a power amplifier is rated.
Thus, when stating that an output device is rated at 20 amps I would expect that this
would correlate with the MOSFET manufacturer's spec sheet. This is a very reasonable
rating, but it is instantaneous. Without an (infinite) heat sink the device will thermally
destroy itself. So when using a device like a MOSFET (or transistor) to actually build
an amplifier a 20amp rating will not translate into the ability to sustain this current into a load.
Another problem is that, due to internal impedance in the output devices, the amplifier
may not be able to supply all its current into a small output impedance. However, it
very well might be able to do so into a higher (say 8 ohm) impedance--given the
appropriate input signal.
This seems to have been missed or ignored by "ae...@flight.els", below.
In summary, instantaneous output capability may be very different from the sustained output.
Also, current output into low impedance can be significantly different from higher impedances.
Jeff Chen
Craig Siever wrote:
>
>
> High Current Output
> Each channel uses 10 Power Mosfet output devices. These devices are each rated to
> handle 20 amps of output current. This
> is completely stable driving 1 ohm or
> less.
>
> 20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to me. Guess it
> depends on your neighborhood :^)
>
> Craig
Since each Mosfet Device is rated to give 20 amps and we have 10 of them for
each channel, I think this means that we should have 100 amp per channed (10 devices
are divided into two groups). I hope this is "manly" enough to you.
Jeff
Del Cecchi
200 Amps. It's a power Amp and a welder too. 2 2 2 machines in 1. :-)
Also, 200 amps and a 1 ohm load is 200 volts. pretty high power supply.
200 Amps and 1 ohm load is 40 KW, not 5 KW. Since an outlet is only good for 1
to 1.5 KW, you won't get 200 amps for long before the breaker goes.
Of course, Underwriter's labs would be interested in this because it is
potentially lethal, and a fire hazard.
--
Del Cecchi
cecchi@rchland
Henry Pasternack
Del Cecchi (cec...@signa.rchland.ibm.com) wrote:
: 200 Amps. It's a power Amp and a welder too. 2 2 2 machines in 1. :-)
Assuming ten 20A devices in total, there are five per rail, and the
maximum peak current output is only 100A.
: Also, 200 amps and a 1 ohm load is 200 volts. pretty high power supply.
You can deliver 200A into a reactive load with zero output voltage.
: 200 Amps and 1 ohm load is 40 KW, not 5 KW.
I said 100 Amps (see above). 100A peak sinewave into 1 Ohm resistive
is 5kW.
: Since an outlet is only good for 1 to 1.5 KW, you won't get 200 amps for
: long before the breaker goes.
Peak currents are only delivered in short bursts. The filter caps
provide the power and the average line current is much lower.
: Of course, Underwriter's labs would be interested in this because it is
: potentially lethal, and a fire hazard.
There is no hazard because the power supply primary is fused.
ae...@flight.els
>Another problem is that, due to internal impedance in the output devices, the amplifier
>may not be able to supply all its current into a small output impedance. However, it
>very well might be able to do so into a higher (say 8 ohm) impedance--given the
>appropriate input signal.
>This seems to have been missed or ignored by "ae...@flight.els", below.
Didn't miss it, just wanted to keep it short.
Keith & Kathy Bickford
Pete wrote:
>
> bg...@scn.org (Norm Strong) wrote:
> >Adcom amps, in general, thump on turnoff. This is due to the fact that
> >they aren't very well engineered. ( Don't get excited. I didn't say
> >they didn't sound good, just that they aren't very well engineered.)
>
> >--
> >Norm Strong (bg...@scn.org)
> >2528 31st S. Seattle WA 98l44
>
> Hi,
> Perhaps you can be more specific. What are the features that you
> consider poorly engineered (designed?). I believe that the higher end
> 5xxx series were designed in part by Nelson Pass. I do not know for
> sure of the level of his involvement and whether his expertise was
> utilized in the 5400, 5300, and 5200. I think I have seen posts from
> him on this newsgroup, perhaps he will see this and let us know. I
> think that he is an individual who is familier with good amp design;)
> --
dealer show you inside, you'll agree. Maybe some amps are over
engineered. Keith
Craig Siever
Adcom claims that the 5500 is a "High Current" amplifier and yet does _not_
rate its' (5500) current capability on the Adcom web site previously mentioned.
If the Adcom's power supply _could_ deliver your 100 amp/peak theoretical
rating don't you think they (Adcom) would publish that rating instead of using
the "High Current Capability" pseudoterminology so prevelant in today's advertising
claims? I believe that the current available is determined by the power supply,
not the output devices. The 1 ohm load you speak of does not take into
consideration the reactance of a speaker system such as the Thiels (which is where
this whole thread started) mentioned, a much more demanding load requiring
more than 20 A to be driven at the high volume levels the original post mentioned.
The original question was whether or not 500 wpc were enough to drive the Thiels
to high volume levels because the poster's Adcom could not.
The whole issue here is whether or not the Adcom (and many other claimants) truly
produce the "High Current" they alude to in their advertising claims and if so,
_why_ don't they mention amperage ratings.
Craig
Henry Pasternack wrote:
>
> Craig Siever (cn4...@coastalnet.com) wrote:
> : So you're avering that the Adcom produces _200_ amps from MOSFET
> : _output_ stage devices? Hats off to the folks of Adcom for developing
> : a 10X current amplifier, with MOSFETs no less. And this puppy only
> : weighs 50 pounds too! You're a product of advertising _hype_ Miguel.
> : Best you do a little research in Electrical Theory 101 before "buying"
> : the "Hight Current" claims of Adcom. While 20 Amps peak/channel is enough
> : to kill you, it's not quite enough to power a "killer" system, particularly
> : a system that drives low impedance/high reactance speaker loads. The
> : Adcom just doesn't have enough "grunt" to handle it. Stewart Pinkerton is
> : right, claims such as these _are_ advertising fluff.
>
> There's no technical reason to doubt that an amplifier using 10
> large output devices per channel could produce peak currents of one
> hundred amps, assuming proper drive circuitry and devices rated at
> 20A. This is equivalent to a momentary power output of 5kW into
> a 1 Ohm load, definitely in the "grunt" category. Even 20A is more
> than sufficient.
>
Pete
Craig Siever <cn4...@coastalnet.com> wrote:
>Adcom claims that the 5500 is a "High Current" amplifier and yet does _not_
>rate its' (5500) current capability on the Adcom web site previously mentioned.
Unfortunately, this appears common, show me a web page where an amp
manufacturer includes this info. Even if you can actually find one, I
bet that they are few and far between.
>If the Adcom's power supply _could_ deliver your 100 amp/peak theoretical
>rating don't you think they (Adcom) would publish that rating instead of using
>the "High Current Capability" pseudoterminology so prevelant in today's advertising
>claims? I believe that the current available is determined by the power supply,
>not the output devices.
You seem to be saying that the Adcom could not deliver a 100A/peak
merely since it is not directly addressed on their webpage. Most
webpages (and many owner manuals) only provide a small amount of info,
sad but consistent in the audio industry.
>The 1 ohm load you speak of does not take into
>consideration the reactance of a speaker system such as the Thiels (which is where
>this whole thread started) mentioned, a much more demanding load requiring
>more than 20 A to be driven at the high volume levels the original post mentioned.
>The original question was whether or not 500 wpc were enough to drive the Thiels
>to high volume levels because the poster's Adcom could not.
If I recall correctly, the ariginal amp was a 555 (I or II) which is
an older model and different from the 5500.
>The whole issue here is whether or not the Adcom (and many other claimants) truly
>produce the "High Current" they alude to in their advertising claims and if so,
>_why_ don't they mention amperage ratings.
Perhaps a rep from Adcom will see this and provide an answer, hell if
one of you engineering types has a device which can measure
power supply output without having to get invasive and you live in the
D.C. area you are welcome to try it out on my 5500 ;)
>Craig
--
Pete
A device which is exploding.
> Does this mean it can put out 100 Amps?]]
>
>Perhaps a rep from Adcom will see this and provide an answer, hell if
>one of you engineering types has a device which can measure
>power supply output without having to get invasive and you live in the
>D.C. area you are welcome to try it out on my 5500 ;)
In the case of bipolar transistors, it's fairly well known that
gain drops off seriously well before the rated maximum current,
most often at about 1/3 of max amps for the parts I've seen. Since
MOSFETS are voltage controlled devices, the above is included only
for completeness. Another consideration is Safe Operating Area :
for a given voltage across the device, there will be a maximum
current through it which will not exceed the maximum power dissipation
when multiplied by the voltage. Linear amplifier output stages
(ie Class AB) are dissipation limited rather than current limited
in real world designs. This is exacerbated by the tendency of speaker
loads to present reactive loads to amplifiers, which increases the internal
amplifier dissipation for a given power delivered to the load, sometimes
by a factor of two or three. (A recent Journal of the AES has more details.)
Most amplifiers I've opened up have output stages that, according to
device specs, can deliver at least four times the rated current into
4 ohms, and dissipate at least three times the worst case waste heat
into a resistive load. In my experience, the current rating of the
output devices _never_ determines the power which an amplifier can
deliver to a load, and furthermore anybody who did design an amplifier
in that manner would be catching cones in his teeth after he'd
turned it up a few times.
Francois.
David E. Merchant
ae...@flight.els wrote:
>
> >10 MOSFET devices multiplied by 20 amps each gives me 200amps
> >capacity. That seems pretty manly to me. Maybe for a welder 200amps is
> >not manly but for a sterophile, its just fine and dandy.
>
> current. I'd be very surprised if they could provide even 50 amps of
> current. Further, Adcom's drive capabilies are pretty much limited to
> 4 ohm impedances. Yes, they'll drive a 2 ohm load, but even their
> mighty GFA-5800 acts like a 30wpc amp at this resistence, and quickly
> runs out of power. And I mean quickly!
>
> pair of Thiel CS 5i's, which dip to 2 ohms or less, and the KSA-150
> clearly outperformed the GFA-5800.
>
> admit that they do provide substantial value for the money (in the
> proper system), they are NOT high current amplifiers.
At home, we use an Adcom 5800 to drive some Koss electrostatic speakers.
On the speakers, we have a 3 amp slo blo fuse. One of the fuses has
blown while playing 1818 Overture at max volume when the cannon fired.
The SPL meter, 9 feet away, pegged at over 118 db, yes it did hurt my
ears.
The 5800 can drive these ESL's, which are highly reactive, with droops
down to 2 ohms, with no trouble at all. Bear in mind, it is only hooked
up to a 15 amp circuit, but the caps in it do hold a charge for a
while. If you turn it off with music still driving it, while at high
volume, it still takes about 3-5 seconds to bleed down and stop
playing. Also, I can't give you a max instantaneous amp rating without
installing quick blow fuses in the speakers and I don't want to do that
for fear of damaging the speakers themselves.
Hope this sheds more light.
Don't understand why you say the Adcom can't hold up to the Krell. I
had just the opposite results!
David
nelson pass
Dave Smith wrote:
>
> Miguel Barrio wrote:
>
> > BTW, could anyone with a 'good' amp (read Pass Aleph, Krell or something
> > of the sort here) look at their speaker cones while the amp is being
> > turned on???. If you do so I'd be glad to see your findings in this
> > thread.
Since you ask,
The Adcom amplifiers have about a 1 volt turn on thump, which may
sound loud enough, but will not cause damage of any sort. The Pass
products have a thump of comparable size, as did the Threshold
products before them.
Quite a few other high-end amps have larger thumps, which is
why they employ output relays.
Adcom had the option of installing a relay, however they are on a
tight budget with these products, and the money would have to have
been removed elswhere. Also, in addition to providing a potential
source of degradation in the output connection, output relays are
a substantial portion of warranty repair.
-np
nelson pass
As far as I am aware, the output of the GFA 5500 is current limited
to about 20 amps, regardless of the rating of the output stage.
This translates to about 1 kilowatt peak into 2 ohms.
-np
Ernst C. Land, Jr.
In article <324994...@novell.com>, je...@novell.com says...
>
>Craig Siever wrote:
>>
>>
>> High Current Output
>> Each channel uses 10 Power Mosfet output devices. These devices are
each rated to
>> handle 20 amps of output current. This
>> output capacity is adequate to deliver full power into 2 ohm loads,
and the amplifier
>> is completely stable driving 1 ohm or
>> less.
>>
>> 20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly"
to me. Guess it
>> depends on your neighborhood :^)
>>
>> XOXO
>> Craig
>
> Since each Mosfet Device is rated to give 20 amps and we have 10
of them for
>each channel, I think this means that we should have 100 amp per
channed (10 devices
>are divided into two groups). I hope this is "manly" enough to you.
>
> Jeff
Actually, considering bi-polar power this means 200 amps/side. My
welder is jealous.
R/Ernst
ae...@flight.els
> How do you know? Have you ever measured the current capability
>of an Adcom amplifier? Or do your ears have ammeters in them?
No need to measure them. If they run out of steam into low
impedances, which they do, then their current drive is very limited.
Check out Mr. Nelson Pass' post, as he believes the 5500 is current
limited to 20 amps. While even 20 amps is respectable, the amp will
die into a 2 ohm load.
Jeffery D Coates
Gents,
I think you're confusing a couple of points here...from the Adcom copy,
they employ MOSFETS with a 20A max rating each. All that means is that
they will fail if asked to pass more than 20A in a given circuit...the
200A number being thrown around is from a misled calcualation...Just
because the output deveices COULD handle it (which may or may not be
true) doesn't mean that they are in a circuit designed to make them
...the theorectical capacity of a given output device makes for good
ad copy, but in this instance has nothing to do with the ampifiers'
actual output current.
Jeff
and please folks...at $1000 retail, the Adcom isn't out to get the
Krells and MLs of the world...just to give the rest of us a good sounding
product for short money!
In article
<3248E7...@coastalnet.com>, Craig Siever
wrote: >So you're avering that the Adcom produces _200_ amps from MOSFET
>_output_ stage devices? Hats off to the folks of Adcom for developing
>a 10X current amplifier, with MOSFETs no less. And this puppy only
>weighs 50 pounds too! You're a product of advertising _hype_ Miguel.
>Best you do a little research in Electrical Theory 101 before "buying"
>the "Hight Current" claims of Adcom. While 20 Amps peak/channel is enough
>to kill you, it's not quite enough to power a "killer" system, particularly
>a system that drives low impedance/high reactance speaker loads. The
>Adcom just doesn't have enough "grunt" to handle it. Stewart Pinkerton is
>right, claims such as these _are_ advertising fluff.
>
>Regards,
>Craig
>
>
>Miguel Barrio wrote:
>>
>> In article <324718...@coastalnet.com>,
>> Craig Siever <cn4...@coastalnet.com> wrote:
>> >Hey Miguel, is this the same page that says of the 5500:
>> >
>> >High Current Output
>> >Each channel uses 10 Power Mosfet output devices. These devices are
>> >each rated to handle 20 amps of output current. This output capacity
>> ^^^^
>>
>> >is adequate to deliver full power into 2 ohm loads, and the amplifier
>> >is completely stable driving 1 ohm or less.
>> >
>> >20 Amps of current/ch for a 200 wpc amp doesn't sound very "manly" to me.
>> >Guess it depends on your neighborhood :^)
>>
Scott Guest BNR
"ae...@flight.els", I do not believe the Adcom amp "will die into a
2 ohm load" given that it is current limited at 20 amps. 20 amps
of current through a 2 ohm resistive load is 800 watts! The GFA-5500
may not be able to deliver this on a continuous basis, but should
be able to deliver during short-term peaks.
It seems that the original basis for your opinions that the Adcom
amps "run out of steam" and "will die" into low impedances was
a comparison of the Adcom GFA-5800 with a Krell KSA-140 driving
set of Thiel speakers (if I remember correctly). Now, the Adcom
may not sound as good as the Krell driving the Thiels (that is
a matter of opinion), but 5800 does have the power amd current
capability to drive those speakers without "dying" as you put it.
--
----------------------------------------------------------------
Scott Guest - Sr. MSS Nortel Technology
SPM OC-3 HW Dev.(3H44) 35 Davis Drive
ph (919) 991-2215 Research Triangle Park, NC 27709
ESN 6-294-2215 E-mail: cnc...@nortel.ca
FAX (919) 991-7754
----------------------------------------------------------------
Craig Siever
Exactly, current capacity is the responsibility of the power supply.
So if the Adcom is "high current" then _why_ doesn't Adcom include
amperage ratings for continous and peak environments on their web
site? This is a rhetorical question that doesn't require an answer
from you, unless of course you care to join in :^) We've got the
tail wagging the dog here in this thread. The output stages (of course)
do not determine current capabilities of the amplifier, that's determined
by the power supply. Nowhere on the Adcom web site does it quote the
current capabilities of any of the amplifiers. No where does it define
the "high current" claims in terms of amperers available. They don't even
rate the current _draw_ in wattage, instead they prefer volt/amps. I
believe their (and many other manufacturers) claims ("high current") to be
advertising bunk and until they come out with real world ratings of current
capacities my mind will not be changed. We can talk theoretical capabilities
all day long but unless someone has tested the Adcoms or Adcom avers specs
I won't be convinced of their "high current" claims.
Craig
Francois wrote:
[snip]
> In my experience, the current rating of the
> output devices _never_ determines the power which an amplifier can
> deliver to a load
[snip]
>
> Francois.
Craig Siever
Jeffery D Coates wrote:
>
> Gents,
> I think you're confusing a couple of points here...from the Adcom copy,
> they employ MOSFETS with a 20A max rating each. All that means is that
> they will fail if asked to pass more than 20A in a given circuit...the
> 200A number being thrown around is from a misled calcualation...Just
> because the output deveices COULD handle it (which may or may not be
> true) doesn't mean that they are in a circuit designed to make them
> ...the theorectical capacity of a given output device makes for good
> ad copy, but in this instance has nothing to do with the ampifiers'
> actual output current.
> Jeff
Thank you.
>
> and please folks...at $1000 retail, the Adcom isn't out to get the
> Krells and MLs of the world...just to give the rest of us a good sounding
> product for short money!
>
Agreed. Sonic characteristics of the Adcom were never at question here. Just
the current capabilities. Highly reactive/low impedance loads require ample
current capabilities, something that the Adcom is not at its' best trying
to provide (regardless of wpc ratings). Luckily, only the more esoteric
speaker designs require this type of grunt.
Craig
Randall Bradley
This reminds me of a not so interesting story:
"...usually my vehicle will do 0-60 in 6 seconds, but when I
run it with a trailer somehow it barely moves it, what's wrong
with my vehicle?" Well, the answer is, don't try to use your
MOTORCYCLE to tow a trailer!
Amps and speakers need to be properly applied, just as the silly
story illustrates.
BTW, the 1 usec pulse capability of a MOSFET is a VERY HIGH current!
The caps will dump a very high current, short duration peak (probably)
current, but the iron and the mains will determine the long-term
current capability - thus the difference in weight and power between
adcomm and BEAR Labs, or Krell...
_-_-randy
ra...@rdrc.rpi.edu <--- email here!
"...BEARs are fuzzy on most things..."
Randall Bradley
Glad you asked:
The BEAR Labs Symphony No.1 amplifier (138lbs./180watts) is fully
DC coupled, NO SERVOs, and has a nil turn-on thump, no output
relays of any sort. "it's balanced and blueprinted!"
_-_-randy
ra...@rdrc.rpi.edu <---- email here!
"BEARs frequently go 'whump', but never thump!"
Steve Zipser (Sunshine Stereo Inc.)
And I'll bet it is killer on DARK STAR!!!!!!!
Dancin Bears live forever!
Zip
Yves C Vidal
In article <52m5em$b...@ultra0.rdrc.rpi.edu>, ra...@ultra0.rdrc.rpi.edu (Randall Bradley) writes:
> Glad you asked:
>
> The BEAR Labs Symphony No.1 amplifier (138lbs./180watts) is fully
> DC coupled, NO SERVOs, and has a nil turn-on thump, no output
> relays of any sort. "it's balanced and blueprinted!"
>
> _-_-randy
Is this one single-ended like the first one or fully balanced all the way to
the output connectors ? Please, give us more information. Thanks.
Yves
m. mattson
>: 200 Amps. It's a power Amp and a welder too. 2 2 2 machines in 1. :-)
> Assuming ten 20A devices in total, there are five per rail, and the
>maximum peak current output is only 100A.
> There is no hazard because the power supply primary is fused.
At even 100 amp, you sure wouldn't catch me laying MY hands across the
outputs at full bore!
Mark
The truth as I perceive it to be.
Your perception will be different.
Del Cecchi
In article <52c6lf$e...@bmtlh10.bnr.ca>, hen...@bnr.ca (Henry Pasternack) writes:
|> Del Cecchi (cec...@signa.rchland.ibm.com) wrote:
|>
|> : 200 Amps. It's a power Amp and a welder too. 2 2 2 machines in 1. :-)
|>
|> Assuming ten 20A devices in total, there are five per rail, and the
|> maximum peak current output is only 100A.
Somebody said 200 amps.
|>
|> : Also, 200 amps and a 1 ohm load is 200 volts. pretty high power supply.
|>
|> You can deliver 200A into a reactive load with zero output voltage.
Sorry, only into a short circuit, or at the zero crossing of a capacitor.
|>
|> : 200 Amps and 1 ohm load is 40 KW, not 5 KW.
|>
|> I said 100 Amps (see above). 100A peak sinewave into 1 Ohm resistive
|> is 5kW.
|>
Somebody said 200 amps. Maybe not you.
|> : Since an outlet is only good for 1 to 1.5 KW, you won't get 200 amps for
|> : long before the breaker goes.
|>
|> Peak currents are only delivered in short bursts. The filter caps
|> provide the power and the average line current is much lower.
|>
|> : Of course, Underwriter's labs would be interested in this because it is
|> : potentially lethal, and a fire hazard.
The Adcom GFA 5800 is rated to drive 250 watts at 8 ohms or 400 watts at 4 ohms.
This is the big brother of the 5500 that talks about the 10 20 amp devices. The
RMS voltage at peak power is 45 volts, add in the "dynamic headroom" and you are
in the 60 or so volt range. Personally I consider 50 or 60 volts at 5 to 10 amps
hazardous. Better not run those speaker wires under the rug.
|>
|> There is no hazard because the power supply primary is fused.
The outlets in my house are fused too, and they are both a fire hazard and
potentially lethal. The adcom web page lists the maximum power consumption as
1440 VA so the fuse must be 15 amps or maybe 7.5 amps per side. Still make toast.
Note that is continuous power consumption.
|>
|> -Henry
|>
|> --
|> ATTENTION! Reply to h...@nortel.ca (hen...@nortel.ca won't work).
--
Del Cecchi
cecchi@rchland
Henry Pasternack
Del Cecchi (cec...@signa.rchland.ibm.com) wrote:
: |> Assuming ten 20A devices in total, there are five per rail, and the
: |> maximum peak current output is only 100A.
: Somebody said 200 amps.
So what?
: |> You can deliver 200A into a reactive load with zero output voltage.
: Sorry, only into a short circuit, or at the zero crossing of a capacitor.
A capacitor is a reactive load.
: Somebody said 200 amps. Maybe not you.
So what?
: The outlets in my house are fused too, and they are both a fire hazard and
: potentially lethal. The adcom web page lists the maximum power consumption as
: 1440 VA so the fuse must be 15 amps or maybe 7.5 amps per side. Still make
: toast. Note that is continuous power consumption.
So what? It's legal according to Underwriters Lab.
Sometimes I think the usenet is a very stupid thing.
Stewart Pinkerton
cec...@signa.rchland.ibm.com (Del Cecchi) writes:
>In article <52c6lf$e...@bmtlh10.bnr.ca>, hen...@bnr.ca (Henry Pasternack) writes:
>|> Del Cecchi (cec...@signa.rchland.ibm.com) wrote:
>|>
>|> : 200 Amps. It's a power Amp and a welder too. 2 2 2 machines in 1. :-)
>|>
>|> Assuming ten 20A devices in total, there are five per rail, and the
>|> maximum peak current output is only 100A.
>Somebody said 200 amps.
Somebody was wrong.
>|>
>|> : Also, 200 amps and a 1 ohm load is 200 volts. pretty high power supply.
>|>
>|> You can deliver 200A into a reactive load with zero output voltage.
>Sorry, only into a short circuit, or at the zero crossing of a capacitor.
In case you weren't aware of it, inductors and capacitors (y'know, like
in speaker crossovers) ARE reactive loads. If the phase angle of the
load goes to 90 degrees at a particular frequency, then you dump maximum
current at the zero voltage crossing point.
>|>
>|> : 200 Amps and 1 ohm load is 40 KW, not 5 KW.
>|>
>|> I said 100 Amps (see above). 100A peak sinewave into 1 Ohm resistive
>|> is 5kW.
>|>
>Somebody said 200 amps. Maybe not you.
And 5 is still a long way from 40.
>|> : Since an outlet is only good for 1 to 1.5 KW, you won't get 200 amps for
>|> : long before the breaker goes.
>|>
>|> Peak currents are only delivered in short bursts. The filter caps
>|> provide the power and the average line current is much lower.
>|>
>|> : Of course, Underwriter's labs would be interested in this because it is
>|> : potentially lethal, and a fire hazard.
>The Adcom GFA 5800 is rated to drive 250 watts at 8 ohms or 400 watts at 4 ohms.
>This is the big brother of the 5500 that talks about the 10 20 amp devices. The
>RMS voltage at peak power is 45 volts, add in the "dynamic headroom" and you are
>in the 60 or so volt range. Personally I consider 50 or 60 volts at 5 to 10 amps
>hazardous. Better not run those speaker wires under the rug.
50 volts a.c. is not officially regarded as hazardous and there should
be no question of overheating from speaker wires of adequate gauge (that
would imply you're dropping significant power in the cable).
>|>
>|> There is no hazard because the power supply primary is fused.
>The outlets in my house are fused too, and they are both a fire hazard and
>potentially lethal.
Does your insurer know this? Better get 'em fixed quick if you really
mean this!
>The adcom web page lists the maximum power consumption as
>1440 VA so the fuse must be 15 amps or maybe 7.5 amps per side. Still make toast.
>Note that is continuous power consumption.
It's only continuous consumption if the amp is running at full power
continuously. This does not happen even on thrash metal! Less than a
tenth of this average power would be REALLY LOUD.
--
Stewart Pinkerton | If you can't measure what you're making,
A S P Consulting | how do you know when you've got it made?
(44) 1509 880112 |
"I canna change the laws o' physics" - the other Scotty
David E. Dimond
In article <52bm1u$7...@sjx-ixn6.ix.netcom.com>, ae...@flight.els says...
>
>
>>10 MOSFET devices multiplied by 20 amps each gives me 200amps
>>capacity. That seems pretty manly to me. Maybe for a welder 200amps is
>>not manly but for a sterophile, its just fine and dandy.
>
>There is no way in hell that ANY Adcom amp will produce 200 amps of
>current. I'd be very surprised if they could provide even 50 amps of
>current. Further, Adcom's drive capabilies are pretty much limited to
>4 ohm impedances. Yes, they'll drive a 2 ohm load, but even their
>mighty GFA-5800 acts like a 30wpc amp at this resistence, and quickly
>runs out of power. And I mean quickly!
>
>I've compared the GFA-5800 (250wpc) with a Krell KSA-150 (150wpc) on a
>pair of Thiel CS 5i's, which dip to 2 ohms or less, and the KSA-150
>clearly outperformed the GFA-5800.
>
>Adcom has touted "high current" for some time now, and while I'll
>admit that they do provide substantial value for the money (in the
>proper system), they are NOT high current amplifiers.
>
I am in no way, shape, or form qualified to enter into an Adcom vs. Krell
debate. However, I AM qualified to speak to the ability of an Adcom
GFA5500 to act as an arc-welder. The last time mine blew up, it fried the
voice coil of a JBL D-130 15" so bad that re-coning was impossible. When
I took the driver to our local repair depot, the gentlemen behind the
counter was amazed at the damage and politely inquired 'what the hell did
you plug this into??.' When I responded with 'an Adcom' he just smiled
and said 'ahhhh, that would explain it.' So I guess 'High-Current' can
be a rather subjective thing -- Surely it's not a gas-fired thyratron,
but it provides all the amperes I need.
As an aside, the band I work for as sound engineer recently blew up one
of the Crowns we use for FOH, and I was compelled to substitute the Adcom
for the evening. The band never sounded so good. I was VERY impressed
with the Adcom's ability to perform in the role of professional FOH amp.
Darrin Tebbe
> I am in no way, shape, or form qualified to enter into an Adcom vs. Krell
> debate. However, I AM qualified to speak to the ability of an Adcom
> GFA5500 to act as an arc-welder. The last time mine blew up, it fried the
> voice coil of a JBL D-130 15" so bad that re-coning was impossible.
This is usually caused by the amp passing pure DC to the speaker. It
does not take many amps of DC to fry an AC device.
DT
D E Dimond
In article <32646D...@ix.netcom.com>,
..
>
>> I am in no way, shape, or form qualified to enter into an Adcom vs. Krell
>> debate. However, I AM qualified to speak to the ability of an Adcom
>> GFA5500 to act as an arc-welder. The last time mine blew up, it fried the
>> voice coil of a JBL D-130 15" so bad that re-coning was impossible.
>
>
>This is usually caused by the amp passing pure DC to the speaker. It
>does not take many amps of DC to fry an AC device.
>
>DT
ummm, yes, I realize this. But let me clarify: The current produced
during the catastophic self-destruction of the amp was of sufficient
quantity and duration to not only liquify the edge-wound aluminum voice
coil, it also was enough to arcweld the magnet to the core. The air gap
was essentially gone, and the magnet and core structures were arc-pitted
beyond salvage.
I don't recall offhand the rail voltage but assuming in the vicinity
of +/- 60V, I'd guess-timate the finals are capable of producing about
28 Amps wide open. I have neither the time or inclination to actually
model it and run it through p-spice for 'real' numbers. My only point was
that it is imperative to look beyond the marketing 'spec-manship' when doing
a competitive analysis. I suspect the alleged '200A' figure was an
instantaneous value based on the slew rate of the device and the charge
on the P/S caps; and this number is entirely in line if treated as an
instantaneous and not a continuous value.
(and btw, you should have seen what it did to the capacitors in the
crossover before the finals opened up!)
peace,
d^2
pmoe...@hotmail.com
> Exactly, current capacity is the responsibility of the power supply.
> So if the Adcom is "high current" then _why_ doesn't Adcom include
> amperage ratings for continous and peak environments on their web
> site? This is a rhetorical question that doesn't require an answer
> from you, unless of course you care to join in :^) We've got the
> tail wagging the dog here in this thread. The output stages (of course)
> do not determine current capabilities of the amplifier, that's determined
> by the power supply. Nowhere on the Adcom web site does it quote the
> current capabilities of any of the amplifiers.
>
>
> Francois wrote:
>
> [snip]
>
> > In my experience, the current rating of the
> > output devices _never_ determines the power which an amplifier can
> > deliver to a load
>
> [snip]
>
> >
> > Francois.
I would also like to point out to other commentors above, that having 10 output devices per channel, each rated at 20A max, does NOT allow it to pass 10 * 20A = 200A. There are only 5 devices on each supply polarity, so the device rating would only permit 100A safely (far more than the current limit setting, so of course it's only academic).
hootervil...@yahoo.com
ScottW
> Rip Van Winkle emerges from his 24 year slumber.
Mine is getting a bit glitchy. Wiggle the volume control and the balance shifts.
It's really annoying, I'm constantly listening to see if the image seems centered or do I have to get up and kick the 'ol bird.
Anyway...Adcom offers MC support but gives zero specs on loading. That's just nuts.
I was looking at getting a new OC9 MLII as it's a great match for my tonearm mass and it's a 25 ohm. I made adapters to accommodate my 100 ohm preamp.
But I'd prefer a preamp that supported a range of MC loads. They aren't common.
ScottW
MiNe109
with adjustments if you want a separate unit.
ScottW
I wonder if it will drive my passive attenuator box...
I'm not sure I want to go down this path...if I get this bug going I'll want to get my quad panels replaced....and that's not cheap.
ScottW
MiNe109
> On Wednesday, July 8, 2020 at 5:59:51 AM UTC-7, MINe109 wrote:
>> On 7/7/20 10:47 PM, ScottW wrote:
>>> On Tuesday, July 7, 2020 at 8:29:50 PM UTC-7,
>>> hootervil...@yahoo.com wrote:
>>>> Rip Van Winkle emerges from his 24 year slumber.
>>>
>>> I'm surprised Adcom still in business. So I looked at their
>>> preamp. Mine is getting a bit glitchy. Wiggle the volume control
>>> and the balance shifts. It's really annoying, I'm constantly
>>> listening to see if the image seems centered or do I have to get
>>> up and kick the 'ol bird.
>>>
>>> Anyway...Adcom offers MC support but gives zero specs on
>>> loading. That's just nuts. I was looking at getting a new OC9
>>> MLII as it's a great match for my tonearm mass and it's a 25 ohm.
>>> I made adapters to accommodate my 100 ohm preamp. But I'd prefer
>>> a preamp that supported a range of MC loads. They aren't
>>> common.
>>
>> I think it's Adcom with new owners. I'd look at Pro-ject for
>> something with adjustments if you want a separate unit.
>
> All their phono stages are separate...and it's my line section that's
> flaky...so I'd need two units....but the RS is appealing... I wonder
> if it will drive my passive attenuator box...
better information.
> I'm not sure I want to go down this path...if I get this bug going
> I'll want to get my quad panels replaced....and that's not cheap.
My pair is the survivors of my original and my replacement pairs.
ScottW
I notice that Pro-ject lists a couple local dealers but only one mentions any of their products on web site and they're TTs.
Most of them no longer exist.
One of their dealers turns out to be Best Buy dabbling in high end.
For a time our big box electronics store, Fry's Electronics had a high end home theater room with Martin Logans but I haven't been over there in years.
The business is barely a shadow of what once was.
Can we claim to have lived in the golden era of high-end?
ScottW
MiNe109
end dealers in big cities still exist and there are custom installers
doing good business but it's mail order for anything you can't get at
Best Buy.
On the positive side, digital can be transparent for next to nothing.
New speakers designs such as waveguides also bring good performance at a
cheaper level but availability is at the mercy of parent companies. Home
theater has a quality bottleneck due to OEM parts all AVR makers use.
The market is changing, of course. Streaming music, lifestyle music
players and soundbars rule. Headphone stuff is good and fun, though.