Help with Traynor YBA-1

[toneseeker74]

My late 60's YBA-1 has too much bass that I cannot dial out. This is the 1967 circuit: 6CA7 tubes, no choke. Using 4x12 cab with either G12-65 or Vintage 30 speakers.
I have reduced the cathode bypass caps on the first preamp tube to 10uF. I reduced the bypass caps after the phase inverter from .1uF to .022uF. Neither mod made a noticeable difference.
I changed the slope resistor in the tone stack from 47k to 56k and 33k. Slight difference in the mids, but the bass is still tubby.
Thought?

 

[zzmoore]

Re: Help with Traynor YBA-1

That is kind of surprising...especially the PI (coupling) caps.
I usually prefer getting "rid of" the bass early in the circuit, but there certainly is no right or wrong way.
But back to your by-pass cap at V1.....even if you cut it in half, the 10 mics is probably still by-passing full audio. Do you have a pair of test leads.?
I would go down to at least 4.7 mics.....or even much lower given how you are hearing things at this point.
Is the rest of the amp Kosher, and resistor values measured reasonably close to spec.?
Throw up some pics if you can. Those are Very Nice amps IMO.
good luck