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Old 16th June 2009, 02:43 PM   #1
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Default pre amp for gain clone as guitar amp

seems gainclone is favorite as guitar amp
what is the best pre amp for gainclone
intended to use as guitar amp
if possible with pcb design
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Old 16th June 2009, 06:11 PM   #2
kscharf is offline kscharf  United States
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Default Re: pre amp for gain clone as guitar amp

Quote:
Originally posted by engel dela pena
seems gainclone is favorite as guitar amp
what is the best pre amp for gainclone
intended to use as guitar amp
if possible with pcb design
Look at the preamp portion of this project, pcb is available.
http://sound.westhost.com/project27.htm
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Old 16th June 2009, 06:33 PM   #3
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While Rod Elliott's is certainly a good design, I would say that anyone requesting the "best" look for something more involved like a Roland JC/Peavey Rage style front end.
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Old 17th June 2009, 03:04 AM   #4
ChrisA is offline ChrisA  United States
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Default Re: Re: pre amp for gain clone as guitar amp

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Originally posted by kscharf


Look at the preamp portion of this project, pcb is available.
http://sound.westhost.com/project27.htm

The above looks exactly like one channel of a Fender Bassman 5f6a but built with op amps rather then 12AX7 tubes. Basically it is just two gain stages with a tone stack between. You might conceder actually using real tubes. They clip naturally without need of that diode network. The above circuit uses a dual p amp and the "AX" tube has two triodes in one package, R and C values in the tone stack are close, bright switch works the same way.... Funny how little has changed in 50 years. (I think the 5f6a is about 50 years old.)

My son is high school age and does not remember the tube era. I took him to the music store just the other day we demoed a small Fender tube amp, the "Champ" with a Strat. After only two or three chords he heard the difference. The tone is much different.

Tube PRE-amps un-like power amps are easy to build because there is no expensive output transformers and the HT power supply can be vary small. 100 mA is very large for a preamp PS.
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Old 17th June 2009, 09:37 AM   #5
Ted205 is offline Ted205  United Kingdom
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you could try the marshall lead 12 layout - http://www.drtube.com/schematics/marshall/3005.gif

no clipping diodes in the preamp
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Old 17th June 2009, 08:30 PM   #6
kscharf is offline kscharf  United States
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Default Re: Re: Re: pre amp for gain clone as guitar amp

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Originally posted by ChrisA



The above looks exactly like one channel of a Fender Bassman 5f6a but built with op amps rather then 12AX7 tubes. Basically it is just two gain stages with a tone stack between. You might conceder actually using real tubes. They clip naturally without need of that diode network. The above circuit uses a dual p amp and the "AX" tube has two triodes in one package, R and C values in the tone stack are close, bright switch works the same way.... Funny how little has changed in 50 years. (I think the 5f6a is about 50 years old.)

My son is high school age and does not remember the tube era. I took him to the music store just the other day we demoed a small Fender tube amp, the "Champ" with a Strat. After only two or three chords he heard the difference. The tone is much different.

Tube PRE-amps un-like power amps are easy to build because there is no expensive output transformers and the HT power supply can be vary small. 100 mA is very large for a preamp PS.
I guess using tubes in the low level stages is one way to get the "tube sound" cheaply, though I would think that it was the power stages clipping that actually generated the "crunch" that make tube amps what they are.
A pair of 6L6's (or maybe a quad of them in PP-P) would be about equal in power to a single LM3886 output stage. The cost (tubes, output and power tranny's) will be several orders of magnitude greater though. OTOH, two or three 12AX7's in the preamp would only cost two or three times the price of the op-amp version. (Less if you don't pay for audiophool priced tubes).
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Old 17th June 2009, 10:41 PM   #7
ChrisA is offline ChrisA  United States
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Default Re: Re: Re: Re: pre amp for gain clone as guitar amp

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Originally posted by kscharf


I guess using tubes in the low level stages is one way to get the "tube sound" cheaply, though I would think that it was the power stages clipping that actually generated the "crunch" that make tube amps what they are.
A pair of 6L6's (or maybe a quad of them in PP-P) would be about equal in power to a single LM3886 output stage. The cost (tubes, output and power tranny's) will be several orders of magnitude greater though. OTOH, two or three 12AX7's in the preamp would only cost two or three times the price of the op-amp version. (Less if you don't pay for audiophool priced tubes).
It depends on what part of "the sound". Tube amps even when run clean, sound like tubes. If you were a jazz guitarist playing a electro-acustic you'd still be wanting a tube amp, one with a really clean and bright sound.

I think most of that sound is in the preamp. And the rest is in the speaker. Ecept for the case of way-loud bands who over drive their power amps

When overdriven the over drive can happen in the power or the preamp stage. I'd prefer a system that over drives in the pre stage just so that you can run it at lower volume. Many of the old amps would only over drive if you turned the volume up to 8 to 9. But that is not so good for practicing at home late at night.

Many classic recording where made in the studio using a 5 to 18W tube amp with a mic on the speaker cab. Or some times even inside the cab.

You can't compare "power" between tubes and SS by using watts. A 60W tube amp driving a 4x12 cab is concert level loud where as a 60W SS amp is a little weak. The reason is that you simply can't run SS amps to 120%. Because clipping a SS power amp will blow a speaker.

You are correct about cost. Tube power amps are very expensive but tube preamp is not.

Back on-topic: You asked what was "best". Not cheapest or easiest to build so I thought "a Fender Bassman-style front end done with tubes" But op amps save you money and bulk.
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Old 17th June 2009, 11:31 PM   #8
Minion is offline Minion  Canada
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I am just finnishing building a guitar amp useing a different Power amp IC ( A Bridged 140W TDA7293) ....

This is the Preamp Design I am useing , I just cobbled it together from other curcuits but is simular to a design I have used before ...

Click the image to open in full size.

It has a Very heavy nice squealy metal tone with the Gain Cranked and does a nice cleaner bluesy tone with the Gain lower and the Tone controll has a lot of Control and versitility.....

For a Power supply I use a 12v ac Transformer for the Heaters and run a Voltage doubler to get +/-15v for the Opamps and power the Plate off of the Positive Rail of the Chipamp PSU ......


Cheers

Sorry the Schematic is pretty crappy quality , I had to resize it to post it ....
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Old 18th June 2009, 11:49 AM   #9
kscharf is offline kscharf  United States
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Default Re: Re: Re: Re: Re: pre amp for gain clone as guitar amp

Quote:
Originally posted by ChrisA



When overdriven the over drive can happen in the power or the preamp stage. I'd prefer a system that over drives in the pre stage just so that you can run it at lower volume. Many of the old amps would only over drive if you turned the volume up to 8 to 9. But that is not so good for practicing at home late at night.

That's probably why the amps have two or three gain controls. The final gain control is just before the power amp and sets the actual volume. The first gain control if cranked up all the way will drive the final stage of the preamp into clipping, yet you can turn down the gain to the power amp to limit the volume.
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Old 22nd July 2009, 09:00 AM   #10
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minio ,
how is your project?
pls email me
engel9mcnaly@yahoo.com
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