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Old 31st December 2010, 04:19 PM   #1
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Default What do you think about this amp?

Hi guys! I'm curious what would you say about this amp design (attached schematic), what would you do to improve it, what would you change etc,? It's the schematic of an old SS guitar amp that I have. I actually like it's sound on the clean settings. It comes with a 15" speaker, and provides a nice mellow sounds. On the dirty settings it sounds interesting, it has a kinda fuzzy sound, but a little bit on the harsh side, and with some annoying intermodulation distortion. When I use some pedal, its ok, but when once gigged without one, it was a true SS amp, that is, a Gestapo amp

Now, I'll tell you some ideas that I have about it:

-I intend to insert some clippers in it, probably mosfets, although I'm not sure where, I guess after C7, but I'm not quite sure.
- Replace at least all the caps, though I'm considering to change all the resistors to metal film too.
-At one point, I thought maybe I could change the whole first stage with some fet circuit, but I'm having second thoughts about it.

What's your opinion?

Marry Christmas and Happy New Year!
Attached Images
File Type: jpg GA 102_Page_1.jpg (62.6 KB, 170 views)
File Type: jpg GA 102_Page_2.jpg (144.2 KB, 168 views)
File Type: jpg GA 102_Page_3.jpg (48.7 KB, 160 views)
File Type: jpg GA 102_Page_4.jpg (133.3 KB, 153 views)
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Old 31st December 2010, 05:49 PM   #2
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Kumi
The sideways pictures are making it difficult to understand the circuts. I think you will get more responses if you can rotate them for us. Happy Holidays to you.
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Old 31st December 2010, 06:21 PM   #3
wahab is offline wahab  Algeria
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This amp is basically well designed overall..
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Old 31st December 2010, 06:53 PM   #4
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Quote:
Originally Posted by Kumi View Post
I actually like it's sound on the clean settings. It comes with a 15" speaker, and provides a nice mellow sounds. On the dirty settings it sounds interesting, it has a kinda fuzzy sound, but a little bit on the harsh side, and with some annoying intermodulation distortion.
I know it's a cliché to say this, but if it ain't broke, don't fix it.

This is said for a reason.

Many pieces of electronic equipment are destroyed by well-meaning but totally unnecessary 'work'.

If it ain't broke, don't fix it. Find another project.

w
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Old 31st December 2010, 06:55 PM   #5
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Thank you for your answers.

Quote:
Originally Posted by firechief View Post
Kumi
The sideways pictures are making it difficult to understand the circuts. I think you will get more responses if you can rotate them for us. Happy Holidays to you.
Yeah, you're right. I was in a bit of a hurry , so I didn't realize they were uploaded like that. Here they are as they should be.

The point of putting some clippers in there would be to get rid of that intermodulation distortion somewhat, and to mellow it on the dirty settings. I know it can be done, since I already did it with an another SS amp, but that was with opamps in it, and I just replaced the two stock Si diodes with three Ge ones, paralleled with a cap, and it did improve the sound. The thing is that, with amplifiers with opamps I can manage somehow, but this amp is with discrete design, so I'm not quite sure where those clippers should be installed.
Attached Images
File Type: jpg GA 102_Page_1.jpg (69.0 KB, 120 views)
File Type: jpg GA 102_Page_2.jpg (144.2 KB, 49 views)
File Type: jpg GA 102_Page_3.jpg (53.7 KB, 35 views)
File Type: jpg GA 102_Page_4.jpg (133.1 KB, 35 views)
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Old 1st January 2011, 12:13 AM   #6
CBS240 is offline CBS240  United States
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To many caps in the signal path. IMHO, if you design the output stage to be direct coupled so should all the other stages be. If your signal source is unknown then you should have an input cap, but that is the only cap that should be in the signal path for a SS amp. I realize some folks don't mind it because it creates 'gain cells' that act as seperate amplifier stages but this concept can be done direct coupled as well. Also the power supply is a bit weak in terms of filtering. It is best to go with a CRC-C-C PS filter to better seperate the power transformer currents from the audio signal currents.

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Last edited by CBS240; 1st January 2011 at 12:33 AM.
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Old 1st January 2011, 03:30 PM   #7
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If you don't like the dirty sound, run it clean. Build a germanium fuzz (Fuzz Central -- Arbiter Fuzz Face) and run that through the clean setting. Build it with a footswitch bypass and you have the option of either sound at the click of a switch.

Fuzzface:-

fuzzface.jpg


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