[sdiy] HV audio paths & to have or not to have DC bias on long runs? Shielding?

[anthony]

I am still in the middle of finishing up the 6V6GT amp that I began building 
from a neat-looking Wards Airline Bakelite radio.

One advantage that I noticed was that, although the audio power tube and the 
rectifier tubes were octal, almost everything else was 7-pin mini, except 
for 2 9-pin mini sockets at the end farthest from the power transformer. 
"Great place to put the preamp stages!" I said amd I was right for the most 
part. The problem is that the volume and tone controls are on the opposite 
end of the 9-pin mini tube sockets - which was fine when the audio preamp 
tube was the 6AV6 right in the middle of the chassis.

At first I strung up some coaxial cable for audio that I thought looked like 
it would be able to handle the HV, but as it sat there on my bench for days, 
I began to have my doubts. Then I remembered that I have just about all of 
the shielding that I have ever taken off of long multistrand cables (like 
SCSI and twisted-pair printer cables) and I took pains to keep the braids 
intact. Well it's easy to bunch this up over wire with even the thickest 
insulation. I'm just concerned about picking up hum from the wires to the 
heaters and such. I have the grounding set up as a sort of "dual star" 
system which I think will work pretty well.

OK so here's my main question: is it better to let the audio between the 
preamp stages and the volume and tone controls have the DC bias on it or 
not? That is: should I mount the coupling capacitors close to the tubes? Or 
should I put them on the pots for the volume control? The latter is the way 
I have it now - even the cap to the power amp stage is soldered to the 
unused 6AV6 socket right next to the power tube. Should I only bother with 
shielding wires if I get problems from hum? It would be a simply matter to 
just run some braid down one end of a wire and then put some heatshrink 
around that. The whole chassis itself isn't really all that big so we're not 
talking about long distances. Should I mostly just worry about shielding the 
wires from the input jack?


thanx in advance guys,
aa