[Patrick Turner]

West wrote:

"Patrick Turner" wrote in message
...
The 845 amps I have been strugling to find time to build
are approaching a stage where I must decide
on the actual working points that would be most suitable for
both 211 and 845 including class A2 operation,
by means of cathode follower buffer choke loaded to the
fixed bias supply.

So far having Ea at 1,000V and Ea at 80mA with RL = 12.5k
could seem OK but it means Pda = 80 watts,
and only KR845 or KR211 look able to take this idling condition,
one reason being that the KR heaters are 10V at 1A instead
of the RCA GE use of 10V at 3.3A.

RCA data gives Pda = 67 watts, and if Pd-filament = 33 watts,
the total tube Pd = 100 watts

Anyone here with actual experience of using either tube
in an SE amp???

ALSO, anyone here have longterm experience of use of Shuguang
845?

Patrick Turner.

I remember reading, not long, ago that the Boss (AJ) found 2 sweet spots
with his 845's, 970v & 1046v. The voltages are rough approximates that are
the best my memory can do at the moment. Good luck and keep us posted on
this venture and why not ping him?

Well yes, between 970V and 1,050V seems about right...

211 has Ra = about 3.3k and 845 has Ra about 1.9k.
So the damping factor of the 211 is poorer and NFB would seem to me
to be almost unavoidable.

The A2 operation means THD tends to rise when grid current happens...
A SRPP with a pair of EL84 in triode looks promising to make the needed
150Vrms drive at low impedance for the 845, and with a choke to bias the
845 grids so the
bias can't change easily when in A2.

AJ may not be reading the group at the moment.

Patrick Turner.



west