Why are P/P poweramps louder than SE poweramps?

[dynaleadamps]

I realize there are a TON of factors involved, but for the sake of comparison lets assume the amps are running on the same PSU:

2xEL34 P/P fixed bias "typical" 50 watt amp versus a similar parallel 2xEL34 SE fixed bias version.

I have built a 2xEL34 SE amp and it *seems* to have much less clean headroom (volume) than a 50w P/P.

I think I understand why the P/P is louder, but I may be an idiot.

[Wilder Amplification]

Because on the same power supply you get more "swing" on a push-pull which means more power.

[MWJB]

SE only allows each tube to produce half its possible output (clean W RMS), or more commonly, somewhat less than this. So best scenario for 2xEL34 parallel SE is 20W-ish (likely less).

The push pull allows the other tube to "take over" when the first tube is struggling to cover both halves (positive & negative) of the sine wave, so 2x EL34 in fixed bias PP will allow both tubes to be utilised to full capacity...if the B+ is adequate, if the transformers are adequate, etc. The PP amp will actally make somewhat more than the RMS rating outside of its clean range.

This is the principal factor...others, such as method of bias, plate voltage are more relevant to the amp in question, rather than your basic question. SE amps are sometimes designed to fully adhere to Class A principles, this usually means lower plate voltage and higher plate currents than is typicall found in fixed bias PP & power tube plate voltage has a direct relationship to power output, the more you have of one, the more you get of the other.

[Steve Conner]

Exactly. If you make two amps with the same two power tubes, but one is PP and the other is parallel SE, the PP one will make about 3 times the power.

It sounds like it has more headroom because... it has more headroom.

[Wilder Amplification]

NO SH*T!?