[Patrick Turner]

On Feb 1, 4:04*pm, "Phil Allison" wrote:


The AC30 is neither really "Class A" nor really 30 watts

** False on both counts.

In actual use driving the installed speakers, it is class A all the way.

Most examples will also easily deliver 30 watts rms into a resistive load at
10% THD.

The fools who say otherwise are pedantic jerks.

... *Phil

Depends on exactly what speakers are used with Vox 30 type amps.

Pentode class A efficiency is about 40%, so that if you get 30Watts of
class A PO, then there must be 75Watts of input power, and this
remains constant between idle and clipping, so that each of 4 tubes
tube must have 18.75 Watts of anode Pda even at idle. Clearly this is
not the case with Vox AC30, and last time I fixed on I recall each
tube laboured hard at 15W Pda when the EL84 specs recommend 12Watts,
and sensible hi-fi makers used Pda = 10W per EL84. 30W of pure class A
was not to be had from a quad. Baird hi-fi amps managed 60W class AB1
from a six pack though.

So Vox AC30 give 20W maybe, with a bitta class AB shoved on top, fine,
near enough, and who gives a **** when they are pushed into class C
when over driven on each loud note and chord?.

Usually, 10 watts of pure class A was regarded as max from a pair of
EL84, so 20 Watts class A from a quad.

Whenever some idiot talks about muso amps and class A PO, usually most
of what they say about anything is uneducated crap. Duzzen Madder, its
muso spiel, be happy, don't worry, just smile and don't bother
disagreeing.

Patrick Turner.