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Old 24th October 2008, 07:37 PM   #1
Dappel is offline Dappel  United States
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Default My Son of Ampzilla

Yes, I am a newbie here. I am looking for help and I hope I might be able to help others here someday as well.

I bought this amp in 1982, I guess that dates myself doesn't it. Well it has a few minor issues. Where I'd like to begin is to find a decent description of the bias setting procedure. I've read in another post about a 8 pages description that may be out there, but it wasn't posted the best I can tell.

I do have the schematic already, that was pretty easy to find.

Thank you in advance-
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Old 24th October 2008, 08:28 PM   #2
Dappel is offline Dappel  United States
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Default Re: My Son of Ampzilla

Quote:
Originally posted by Dappel
Yes, I am a newbie here. I am looking for help and I hope I might be able to help others here someday as well.

I bought this amp in 1982, I guess that dates myself doesn't it. Well it has a few minor issues. Where I'd like to begin is to find a decent description of the bias setting procedure. I've read in another post about a 8 pages description that may be out there, but it wasn't posted the best I can tell.

I do have the schematic already, that was pretty easy to find.

Thank you in advance-

In fact while I'm at it, there are actually 4 pots per board. One is for the bias, one is for DC offset, but the other 2, I'd certainly like to know where they should be set.
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Old 25th October 2008, 03:32 AM   #3
lineup is offline lineup  Sweden
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Have a look at member ACD from Denmark website.

http://www.audio-circuit.dk/
-> Schematics -> D-G ->
Gas Ampzilla Power Amp (Schematic)
GAS Ampzilla III Power Amp (Schematic)
GAS Ampzilla 2 Power Amp (Schematic)
GAS Ampzilla 2 II Power Amp (Schematic)
GAS Ampzilla 2 III Power Amp (Schematic)
GAS Grandson of Ampzilla Power Amp (Schematic)
GAS Son of Ampzilla Power Amp (Schematic)
GAS Thoebe RIAA (Schematic)

Now, the Son if Ampzilla schematic is not very high quality.
But maybe useful, anyway.

Regards Lineup
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Old 25th October 2008, 03:38 AM   #4
lineup is offline lineup  Sweden
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Sorry,
you have the schematic already
Let's try and find the 8 pages description .. somewhere ...
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Old 25th October 2008, 03:44 AM   #5
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The last two pots are for the current limiting.

Set them to fold back above 250W into 2R.
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Old 25th October 2008, 03:45 AM   #6
lineup is offline lineup  Sweden
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Here is one manual
and stuff about GAS Line
http://www.davidsaudio.com/html/gas_line.html
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Old 25th October 2008, 07:12 AM   #7
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oh my god,, davids audio.. the man must have
100K $$$$ worth of audio gear (every SAE piece there is)
WOW!!!

P.S. nice wife between them pair of 5,000$ infinity speakers , too...
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Old 25th October 2008, 03:22 PM   #8
Dappel is offline Dappel  United States
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Default My Son of Ampzilla

Quote:
Originally posted by djk
The last two pots are for the current limiting.

Set them to fold back above 250W into 2R.

DJK- I know which two you are referring to, but unfortunately I'm not sure how to go about what you suggested. If you would be willing to shed a bit more light on the how to: it would be great.
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Old 25th October 2008, 09:35 PM   #9
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On my own design power amps I set up the bias by applying a 1vac signal to the input then monitor the output on a scope.
I slowly increase the bias voltage until the crossover distortion goes.

I the ntest it again by increasing and decreasing the input signal to ensure there is no crossover distortion.
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Old 14th December 2008, 08:41 PM   #10
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A friend has given me his old Son of Ampzilla, which does appear to have some problems. I've got a decent stable of test equipment, so I'll be taking a crack at the thing in the near future.

Sounded good at first but after a few hours there was audible distortion at very low power, some hum (ground loop?) and the amp simply never warmed up in the slightest. I'm guessing bias problems.

Anyone done any modifications to them? Looks like the famous IC in the bias circuit is really a transistor array--this unit actually has four discrete transistors inserted in the IC socket! I'm guessing they're a matched set.
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