[HBR] HBR-11/2000. Comments?

[Tuchueh7 at cs.com]

Thanks for the insights, Jim. I especially like the idea of doing the power 
supply and audio amp on a separate chassis. This sounds like a good place to 
start.
1) Speaking of the amp, I am thinking of LC audio bandpass filters at the 
input, outside of the feedback loop. I like to think of the effect of negative 
feedback as not really widening bandwidth but rather equalizing gain at all 
frequencies. Plus you can use the feedback to shape response if you pay careful 
attention to phase margin.
2) Devil 6EH7. I notice that W6TC used the 6BJ6 in his IF. Tube manual shows 
this
bottle has low Gm than 6BA6. Do you suppose he chose this on the basis of 
stability
and ease of application? His design distributes gain more evenly amongst all 
stages than my proposed line-up. I am still playing around with the little 
6EH7 breadboard
(included a picture of same). Right now I am going to try the following to 
tame it
a. Resistive loading of input IF tran. and output IF tran. If no result then 
add:
b. Grid damper resistor. If no result then add: If no result then add:
c. Reduce gain with increased negative bias: If no result then add:
c. Screen damper (resistor or choke) If no result then add:
d. Plate to bottom of input IF tran. capacitive neutralization:
3) See attached pictures of tuning caps:
#1. This is an interesting piece with the stator split (cant see from 
picture)
It also has some curious piston trimmers across the stator. Finally, each
rotor section is insulated and and has no electrical connection.
#2. This piece is fairly straightforward 12-108 mmf nice silver plate. Can be 

padded down to correct value and has advantage of being able to pad out a 
lot of stray capacitance.
#3. Not pictured. I have three pieces of GenRad 10-130 mmf. These will 
require 
some metal work to gang. they are very nice parts.

Mucho gracias, amigo.... I really appreciate your consultation!!!! Barney 

PS The attached pictures were rejected by QTH.com so email me direct if you 
want
to see 'em.

PPS Today I fooled around with the test chassis and found that I could tame 
the 6EH7 somewhat by loading the IF transformers with resistance (390K on the 
input and 68k on the plate side. Also reduced the cathode bypass from .1mf to 
.001mf.
Now I can peak the IFs without oscillation. There is still some regeneration 
I think;
nose selectivity is about 750 cycles and voltage gain for the 6AR8  and 6EH7 
is about
60 dB.