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Ground Loop, Ground lift question 
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Joined: Wed Dec 07, 2016 11:28 am
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Location: Pantera, TX.
Given this circuit for my load box/line out, where would you place a ground lift to eliminate 60-cycle hum from a ground loop?

Thanks !

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sound clip: http://www.tonefinder.com/files/841504978622-wiygn2.mp3

"Mike, go find that SM-57... It's prolly lodged up Fretless' poop-chute.

Pop it outta there, place it in front of a cab, and press record, FGT!"


Fri Dec 23, 2016 5:01 am
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Joined: Wed Dec 07, 2016 11:28 am
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Location: Pantera, TX.
edit: Sorted this out. Removed chassis ground (B in above schematic).

This isolates the secondary side of the audio transformer from the chassis ground on the primary side. Thereby isolating it from the 100W tube amp's ground potential - thereby eliminating the 60-cycle hum.

Able to run the amp on 8 for twenty minutes with heat sink and power resistors merely getting warm to the touch, not hot.

Very transparent! Quite amazing, really. It basically sounds like the amp would if I were standing outside my house and running the amp on master vol 8 - only at bedroom levels.

Tone is there. Saturated, warm, crunchy sustain, organic feedback at low volume. :beavis:

Image

_________________
sound clip: http://www.tonefinder.com/files/841504978622-wiygn2.mp3

"Mike, go find that SM-57... It's prolly lodged up Fretless' poop-chute.

Pop it outta there, place it in front of a cab, and press record, FGT!"


Sat Dec 24, 2016 8:51 am
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Joined: Wed Dec 07, 2016 11:28 am
Posts: 1014
Location: Pantera, TX.
Made one final change to the circuit. Changed the wire from the volume pot to the line out jack to a shielded cable. Connected shield to audio ground. Even less prone to noise even at high (amp) volumes.

Image


Sound Clip:
http://www.tonefinder.com/?section=id&value=16763

_________________
sound clip: http://www.tonefinder.com/files/841504978622-wiygn2.mp3

"Mike, go find that SM-57... It's prolly lodged up Fretless' poop-chute.

Pop it outta there, place it in front of a cab, and press record, FGT!"


Sun Dec 25, 2016 4:12 pm
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