Removing bass procedure - Slucky AB763 (Tonestack vs cathode bypass vs coupling)

[ToneJunkie]

I tried to search but I did not find what I was looking for...


How do you decide where to remove bass in the circuit?  I play the amp below with the bass control at 8 oclock... virtually off.  Where would you start as far as tuning bass in a clean pedal platform amp? 

[ToneJunkie]

This is my amp and what it sounds like...

[sluckey]

I'd replace the bypass caps on the preamp triodes with 5µF caps and replace the .1 coupling caps between the PI plates and 6V6 grids with .047µF or .022µF caps. I probably would not mess with the tone stack, but verify the pots are correct value and taper.

But why? I think the tone in that video is great. And I noticed the 335 is set to the neck pickup. There's a lot more room for treble just by switching to the bridge pickup. Then you could turn the amp's bass up some more.

Nice band and the amp looks great with the bare chassis look. (Is that Hoffman's Stout chassis?) Reminds me of the old Ampeg Portaflex. Is that you on guitar?

[John]

Following Sluckey's suggestions will let you get the pot off 8. For fun, I'd try lowering the bypass caps, but keeping the .1 in there just to see what it sounds like. Easy enough to swap after after giving a listen if still too much bass.


But damn Slim!! that is great music, love it!

[tubenit]

I'd replace the bypass caps on the preamp triodes with 5µF caps and replace the .1 coupling caps between the PI plates and 6V6 grids with .047µF or .022µF caps. I probably would not mess with the tone stack, but verify the pots are correct value and taper.

+1 

Tubenit

[ToneJunkie]

Cool I will incrementally make those changes :-)   Maybe just the bypass caps for this weekend .  I like my sound pretty dark but the bass can be in the way... don't like it boomy.
All you gentlemen helped me with this stout chassis amp several years ago.  Its been my main amp ever since... a lot of gigs and practice time on it!
Yep me playing guitar and thanks for the kind words.  Thanks again! 

[dude]

That was indeed awesome, not so often you hear solid, tight Jazz. Thanks for posting, not too bassy to me.

[jazjamr]

I followed your posts when you were building your amp. I was also building in the Stout chassis. I started with the Hoffman 6v6 Plexi schematic but chose to use the JTM 45 shared cathode on V1.I also used .1uf phase inverter caps. I have always played Strat style guitars and love the tone of a Strat through a JTM45 or 1986 Bass circuit. I lowered the cathode bypass cap from the 25uf on the schematic to 5uf. This helped reduce bass. The 500pf Mix resistor bypass cap gives me plenty of highs. Blending V1A and V1B balances the tone. Even with decreasing the cathode cap value I still keep the bass at about 9:00. I have always played Fender Amps 1967 Showman.1963 Bandmaster but this little head sounds great, is easy to carry and has plenty of volume to keep up with our drummer. Your group sounds wonderful and I love Your Tone.

[ToneJunkie]

Thanks Jazjamr!   Yeah I built a JTM45 too although it is with KT66's.  It's a cool amp that use when I go stereo when I play large stages.  The AB763 and the JTM45 at the same time is pretty stellar.   I was not able to get the 5uf bypass caps in there for this weekends shows so I will be trying it next weekend 



 

[dude]

I agree with jazjamr, I'm a strat player too, love the AB763 but I too changed the preamp cathode caps to 4.7uf, The BF circuits seem to me, to be very bassy. But in the JTM 45, one side .68uf other 220uf or higher works for me, as like jazjamr, I can balance the two volumes and I have the tone stack too. Great amp, the 6V6 Plexi.


You works looks great.