TC 8Watter No.2

TomCat

With my first tube amp virtually completed, I've had some very positive feedback from a few people who have tried out the amp.

I'm now going to start another one, but with a few differences:
1. Simpler without the tone stack bypass and distortion channel....almost champ like in simplicity. Will keep the Princeton tone stack as it works really well.
2. SS Rectifier instead of the EZ-81 tube rectifier. Not really looking for too much sag as the amp will be for clean tones only.
3. Build it into a combo instead if a mini stack for portability
4. OP tube: - 6550 for more clean headroom as the 6550 has less compression and breakup than an EL34 or 6CA7
5. Loudspeaker: - 10" Celestion Greenback

I'm basically building this one for Mariann. She does not need the distortion channel as she already has two OD pedals on her pedal-board.

MikeM

Sounds fun.. Just curious now, if it's mainly for clean tones why don't you implement a 2 control tone stack? Little more instertion loss but 12ax7s have more than enough gain..

Just curious ?

matta

TomCat wrote 2. SS Rectifier instead of the EZ-81 tube rectifier. Not really looking for too much sag as the amp will be for clean tones only.

Actually single ended amps have little to NO sag... because they are always on and drawing current, there is no time for the sag to occur, quite different in a push-pull amp, but many can't hear any audible difference RE sag, added compression etc in a single ended amp... it would be interesting to hear if you can feel/hear the difference yourself when you compare TC#1 to TC#2.

Cheers

Matt

TomCat

@ Matta....Yes...it will be interesting to see/hear the difference. I also believe the different (6550) O/P tube will also add a character of it's own.

@ Mike.....The tone stack I use is already the two control one i.e. Bass and Treble

MikeM

Ah yes I forget that you used the slightly newer princeton tonestack ?

Tamago

Well done Tom

When my amp is complete, I will avail myself to building more, or doing customs for anyone who needs an amp.

Gearhead

If you're looking for simplicity, why not go for the Big Muff tonestack? One button! Also, what about the EF86 instead of the 12AX7?

I agree with Matta on the sag in class A, therefore my top tip of the day: have a look at the ECL82, two valves make a 14W push-pull! Use a one-triode phase splitter and you can get a tone stack in there as well. Talk about something different...

Karel-Mars

TomCat wrote 2. SS Rectifier instead of the EZ-81 tube rectifier. Not really looking for too much sag as the amp will be for clean tones only.

I usually consider the ss vs. tube recto for tonal reasons. The tube recto gives a smoother tone typically than solid state. You can fix the ss tone with a choke though.

If you want sag, you look at the regulation of the screen grid. There can be as much as a 10mA difference between 0 signal and max signal current consumption

See the data http://tdsl.duncanamps.com/show.php?des=EL34WXT

Class Va Vg2 Vg1 Ia Ig2 Ra S Rk Zout Pout THD Notes
A S/E 250 265 -14.5 70 - 73 10 -15 18,000 9 3,000 8 10 With Rg2 = 2000 ohms
A S/E 250 265 -13.5 100 - 105 14.9 - 29.0 15,000 11 2,000 11 10

Through a 10K resistor that would amount to 100V drop in G2 voltage - some serious sag would occur.