Hi Zers, Exo, Sebi, Nigel,
Thanks for the support, i always feel a bit 'unsure' when trying
to second guess someone elses design.
It seems that the drawings posted were 'early' ones, later ones
had the capacitors 20 and 22 shown correctly.
Still, i spose it shows we're not asleep ...
As to the anode loads (resistors), yes i thought them a bit low
too, but ive seen lower in places, and didn't clock it.
However i looked up a bit on that valve, its a B7G base with an
anode plate that must be less than a square cm each side, so i
do agree with Nigel on that, those values are suspiciously low,
or maybe they might be intended for supply voltages in the area
of sixty or seventy volts.
I suggest posting the details of that valve for perusal, or the
URL to the details. All i found was a picture of it.
I am guessing that the main purpose of this adaptation is to
drive a valve output section to the speakers.
Extensive tests were done some years ago based on so many people
claiming that valves 'sound' better. For myself, my hearing is
not critical enough to distinguish. After much carrying on and
getting many people involved, the outcome of these tests (from
electronics weekly i think) finally decided that where the signal
transferred from unit-to-unit and especially between sound-to-
signal (mic) and between signal-to-sound (speakers) then the use
of valves made a difference, but they made no indication of what
that difference might be, other than 'noticeable'
They concluded that within a circuit there seemed to be no
difference whether the amplifying is done with transistors or
valves (assuming similar signal to noise ratios)
Based on the above, maybe this is why a CD player is being put
together in this way. For the purpose of driving a valve output
amp.
If thats not the case, then yes - it seems rather pointless.
Regards, John