Bias too low 5e5a?

[pdf64]

...I bias with a 100-150mV sine wave and increase the output volume until I see the peaks limiting. I then reduce the bias voltage until I can just see cross-over notching and then increase the bias to about midway. I then check the cathode current (I allow about 5mA for screen) and plate voltage to make sure I am inside my happy place (50-65%). I generally like the sound of this setting, but give myself the liberty of tweaking by ear.

I don't think it's a good idea to set bias by monitoring the full or high power output wave.
Because at high signal levels, there will be an inevitable kink in the wave at the point where 'the other' tube cuts off and there's a big change in the operating conditions from class 'A' to B. The big issue being that kink can be 'biased out' by adjusting the bias close to class A
And close to max power there's the issue of slight overdrive causing a bit of bias shift and the bias then being set too hot to compensate for that.
Of course by also checking the idle plate current you are mitigating for both of those, but it's surely better to keep the output signal down to a medium level whilst 'biasing by crossover notch elimination', within the safe intended class A area of operation.

[christarak]

Thanks for that pdf64. I will try biasing the notch out at . I'm wondering if I may end up with too cold a setting if that's my only reference point (the cooler point). I then find my "hot point" where I just see the tops of the sine wave rounding off. I then find the point where my sine wave is clear and there's no notch. There's only one way to find out :-). I'll try the "notch elimination at a medium volume level" method and see where that is on the idle power dissipation & Cathode current range. Thanks for the excellent tips, pdf64, as always.

[Enzo]

Never lose sight of the fact that these are just guitar amps, and not hifi amps.

[etneccas]

Help!!

And don't confuse low volume and low power. It takes the entire amp circuit to make sound come out the speaker, so it isn't always just the last part - the power amp - that is at issue.

Your amp could be oscillating at RF. It will still pass signal that way, but the sound tends to sound "washed out" and weak.

I agree with nickb, I doubt the bias is your problem.

I need to get this amp back to the tone beast it was...…..
What should I check next?
Ever since I put the 200ma choke in This amp has sounded sterile at best lacking punch and chime
How do I know if it is oscillating at RF?