50w vs 100w distortion

[dazzlindino]

does a 100w amp distort more than a 50w amp, when both are maxed out on 10 and using a variac to bring down voltage to 90?
and what would the plate voltage be between 120 vs 90 volts?
Thanks

[Enzo]

If the mains is 25% lower, then your high voltage supply will be 25% lower.

[dazzlindino]

does this mean that when you lower the voltage you are also changing the bias?
And does a 100w distort more because of having 2 more output tubes?

[black_labb]

does this mean that when you lower the voltage you are also changing the bias?
And does a 100w distort more because of having 2 more output tubes?

removing other variables such as the different transformers and such and assuming the voltages and such are all the same, then they should both have the same % of distortion.

[dazzlindino]

what part would biasing play as in dropping the voltage, everyone seems to say that amps come biased a little cold,and dont sound "good" but then turn right around run a variac at 90v to make it distort more.

[tbryanh]

what part would biasing play as in dropping the voltage, everyone seems to say that amps come biased a little cold,and dont sound "good" but then turn right around run a variac at 90v to make it distort more.

The bias point stays the same. The bias voltage reduces by the same percent as the plate voltage, so the bias point stays the same.

The reason you can't drop below 90v is because the heater voltages are dropping too. You don't want the heater voltages to drop too much, or the tube won't work.

If you want to drop the B+ voltages more, you can install a seperate heater transformer that is not connected to the variac.

Preamp tubes loose the high end response with B+ voltages, but power amp tubes do not.

Typically you only want to reduce the B+ voltage to the power amp tubes. Then you won't get that brown-out loss of highs in the preamp and driver stages.

PowerScaling.com is where I learned all this.

A variac is a good start, but a Power Scaling board blows the variac away.