Stout TMB - When to Use Shieded Cable

[Cornbinder]

Hello:

I am currently in the process of building a Hoffman TMB Stout and have a couple of questions
I am hoping someone can answer. I see in the photos of the prototype it looks like shielded
cable is being used between pin 7 on V1 and the center of the volume pot. And it also looks
like there is a shielded cable between the 500p cap and one side of the treble pot. I realize
this would be to reduce noise interference. However shielded cable is not included in the parts
list. Will shielded cable in these locations make a significant difference or will the cotton
or pvc wire work just fine.

Thanks!

[sluckey]

Personal opinion... I would use shielded cable for the longer wire from treble pot but I would not use shielded cable for that two inch run from the volume pot to tube socket.

The amp will work without any shielded wire. Very easy to put shielded wire in both of those places later on if you feel you need it.

[kagliostro]

My friend say it is good practice to don't use shielded cables becaus they acts as capacitors and alter the signal


he reserves the use of the shielded cable only when it is strictly necessary to avoid noise captation and usually do that  on the parts of the signal path where is indispensable, usually where a small signal is passing, from input jack to V1 grid as an example (remember to connect the input resistor of the circuit on the grid pin of the input tube not to the jack pin)


Franco

[jim]

Its true that shielded cable is a often a remedial mod for parasitic oscillation, hiss, gain noise etc (shield ground to one side only).  It is often needed in high gain amps and amps in small boxes.  It is often prudent to shield the run from input to V1 anyway as this is very small signal and prone to "crosstalk" from larger signals nearby.  Layout and lead dress first.  Leo never used coax in the early amps.  You can add shielded runs later if needed.  Jim