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Single ended tube amp Lead Dressing
Single ended tube amp Lead Dressing
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Old 7th June 2012, 03:02 PM   #1
Goldstache is offline Goldstache  United States
diyAudio Member
Join Date: Dec 2011
Default Single ended tube amp Lead Dressing

I finished my AA764 Fender Blackface Vibro Champ Amp and it sounds great! Except........
I am having a ground issue with the guitar on this amp. I know my guitars are grounded as well as they can be, as they don't hum like this through any of my other amps.
I used shielded wire from input jack to V1a. However I didn't terminate or solder the the shielding to ground on both sides of the run. Should I do that? The shielded cable has the hot and shield isolated from eachother of course.
Lead dress looks good in the amp, however it could be that too.
Thought about moving the input jack resistors closer to V1a.
Any pointers where to solve this slight hummmmmmm.????????
It cancels when I touch strings of guitar and input jack of amp.
Do I need to isolate the input and output jacks????
Any thoughts?
Thanks for the help!!!!!!!
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Old 14th June 2012, 03:50 AM   #2
gingertube is offline gingertube  Australia
diyAudio Member
Join Date: Oct 2004
Location: Adelaide South Oz
The input jack should be an insulated type which does not connect the ground side to the chassis.

Then use shieled wire from the jack to the amp input - the shield at the amp circuit end end should connect to the 0V (ground) side of the grid leak resistor.

If the Input Jack is the non-insulated type then you only need to connect the shield at one end and it probably won't matter which end - so long as the circuit uses a 0V connection direct to chassis. If you use a back to back diode or 10 Ohm resistor or any of those other 0v to Chassis schemes then you must use insulated input jack with shiled connected both ends as per the top of this post.
Hope this helps,

Last edited by gingertube; 14th June 2012 at 03:54 AM.
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