K4040 distortion

finally ended to asemble this kit. Voltage is ok in indicated places, bias tuned as in manual written (green led in all tubes). But… I hear in the sound little distortion, like signal is overdrived. Preamlifier is K8020 but it works pretty well with my old Yamaha amplfr. When I conect it to K4040, it is enough to turn 5% of power and I hear a music loud enough. I temporally use JBL Balboa 30 speakers who are far away from good and powerfull speakers range, but… It is looks like overdrive… Maybe K4040 gains to much power… I am not much familiar with tubes, so no ideas, how to reduce gain - tune bias to less, change R65/R68 or other options?

Thanks for answer in advance

P.S. I have checked: speakers conection, preamlf. connection, tried to turn transformers…

Either there are some resistors mixed up in the first stage, or the feedback loop is interrupted, which results in a too high gain.
Check your assembly.


Thanks for reply. Resistors and assembly is seems to be ok. I have changed first tube in the driver and now it works fine.

At approximate measure of amplitude-frequency characters I see more gain on starting 5KHz to 10 KHz and fall down on frequences 50 - 800 Hz. Is any chance to make it more linear ? (I can’t say exact db as I need to go to friend to measure it with professional equipent, but amplifier heavy enought to bring it to 5 store building without elevator just for fun lol.)
I am not talking about equalizer, just is any chances to tune it within current circuit in K4040?