power amp bass response

[JD0x0]

Fender preamps are bassy, so that's no surprise. Cut some bass at coupling and/or cathode bypass caps. I generally find cutting bass earlier in the signal chain sounds better, as the preamp wont have to deal with bass frequencies that ultimately wont be used, if you were to cut bass later in the signal path.

[bepone]

higher inductance output transformer would help but is the most expensive solution

[pdf64]

higher inductance output transformer would help …

I don’t understand why, could you explain?

[roberto]

It is the opposite, indeed.
But a bassy circuit with the OT unable to reproduce it is the worst solution.

[bepone]

actually it is correct, you just need to think more about. more inductance means tight and on ears heard like "less" bass,
less inductance means flubby , soft bass, heard like "more" bass. but here "more" bass means increased distortion and 2H, 3H what produce feeling and hearing of more bass. you have more but bad quality bass. lack of inductance increases lower frequency to upper , and also phase shifts and distortion in that area. you want to keep this phase shifts and distortion as low as possible in usable frequency spectrum, ie. you want more inductance.

i wound several output transformers with different laminations, high and low inductance, with the same bobbin.the same amp. and did test with two. it is not suprising that low end is better with hi quality laminations, high inductance, it is tight and "normal". with other , some regular laminations made for average power transformer you have this unwanted effect of flabby bass.

the same is if you mount this bobbing from EI laminations to C core which can fit this bobbin , also hi inductance type.. C core laminations are usually made with 0.1 laminations or less, inductance is high, losses low on the B-H curve, and bass is again tight.

[pdf64]

Thanks for explaining your thinking.
However, I wonder if it’s relevant to this thread, which is regarding a high power bass amp, which seems likely to have a beefy OT with adequate inductance for that application. And so for guitar use, it will probably have plenty of inductance.
The potential fault with your rationale seems to be that it is predicted on amp in question currently having an OT with very low primary inductance?

[bepone]

lets explore more problem in details. i have 0 experience with Traynor.. so i know nothing about output transformers used there so i can just speculate.
but what i can see from schematic it is using 6KG6a tubes, which are TV output tubes and are LOW IMPEDANCE tubes (high current tubes). output transformer is for sure lower inductance type if compared to 6L6 output models per example. if the OP changed the sockets and fit some other tubes there, you can have not designed output transformer for purpose. again i'm speculating but can be.

[bepone]

Hello, I have a 67 Traynor YBA-3 that I had changed onto a guitar amp buy rebuilding the entire front end. Although I replicated the Fender AB763 ( twinn reverb ) preamp section ( no reverb or tremolo ) I still find the amp extremely bass heavy.

ejla, when you have time, can you share some gut shots so we can inspect what you did and what are the output tubes now?

[thetragichero]

but what i can see from schematic it is using 6KG6a tubes

i'm showing 6ca7/el34 besides the very first ones with 7027: https://www.thetubestore.com/lib/thetub ... ematic.pdf

[hebaton]

hey gys, it'S been a while since I looked up this thread but, THe amp was born with 6CA7s for sure !

[hebaton]

You can try reducing the 0.1u at the PI input and/or the two 0.1u after the PI to 0.047 or 0.022. No danger of anything bad happening.

DId just that, installed .022 WOrks just fine. I'm happy !