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Printer2 4th September 2018 06:20 PM

Mini-amp for Output Tube Distortion
We have had a few threads where the OP's were interested in output tube distortion, one asked it to go to a pedal. So how about a pair of 6AK6's driven by a 12AX7? Using a 12V laptop supply which supplies the heaters and a step up module for the high voltage. The speaker can just be a resistor and a pot used to send the signal to the next device. Should have no preamp distortion. Or maybe should go Paraphase? Hmmm...

Thomasha 4th September 2018 06:41 PM

Looks good!
And the 6ak6 has the highest output power/ filament current I know!
Only 150mA for 1 W!

This one would probably have almost 2W. Would you mic it or use the signal at the speaker and reduce it to line levels?

Printer2 4th September 2018 06:46 PM

I was thinking of doing the line level, pick a good load value that will give you the distortion characteristic you want.

22uf 4th September 2018 07:06 PM

So the idea here is to have power amp distortion in a pedal? How is this possible with only 12v? Iíve seen 12ax7 pedals but they are at low voltage and donít make use of the tube properly due to the low voltage?

Printer2 4th September 2018 08:21 PM

DC-DC 8~32V To 45~390V High Voltage Boost Converter ZVS Step-up Booster Module 699993580165 | eBay

22uf 4th September 2018 08:37 PM

Ah right of course. Great idea

mozz 4th September 2018 10:27 PM

Is this any different than a Herzog? What about using one of those voice coils dummy loads Weber used to sell?

Printer2 5th September 2018 12:02 AM

A Herzog is a Champ, I suggested an AC-4 but the amp is single ended. This is Class AB push-pull, the only question mark is the output transformer. I have a few suitable ones but they are not readily available. I have some 70V transformers I may try. Will it be enough gain? May need a FET up front to warm up the signal, or another pedal. I just wanted to put together the simplest circuit that may be up to the job. Could go two Self-Split if more gain is needed, I hope not.

mozz 5th September 2018 12:42 AM

You can get a PP 10k transformer for $16 with multiple primary and secondary taps.
Spec sheets are saying 10% distortion in class a SE. I think that might be better. You would have a second triode for gain if needed.

Printer2 5th September 2018 01:13 AM

Not where I live.

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