On 27 Sep, 03:46, "Phil Allison" wrote:
"Bo-Lennart"



I can see that there is some talk around QUAD II amplifiers from
1960's.
I have 3 of those amplifiers. I have tested them and all works. But I
don't have tubes to all of them. So I have to move around the tubes to
have the amplifiers checked.
Do You think there is some value in these 3 amp's???

** Good examples go for high prices on eBay.

They have been used by the Swedish Television as control-rooms
amplifiers.
There seems to have some modifications at the input. There is a
transformer at the input, so there is a balanced input, instead of the
ordinary unbalanced input.

** Original condition is best for sale value.

About the tubes (it uses KT77 for the output-stage),

** The Quad 2 uses KT66s ( or 6L6GTs ) and these give the best results.

KT77s (or EL34s ) cannot be used unless extensive internal modifications
are in place to compensate for the different bias and gain of that tube.

Seems your Quad 2s are heavily modified.

...... Phil

Thank's Phil for Your reply.
Well, there is labeled on the chassie "KT77". But , as You mentioned,
on all schematics I found on the net, they all show KT66.
I also found that the resitor R12 is at 150 ohm instead of the 180 ohm
that are stated everywhere.
But do You think that could be a modification to get the right bias
for that KT77?

That's the only change that I can see concerning the original
schematics.
Well, about the input modification. (transformer at the input). It
seems that it might have been done at the factory.
Do You think the Swedish Television ordered a custom-tailored
version???

OK.......let see if there is more reply's coming in.

Thank's Phil

Bo-Lennart Karlsson
SWEDEN