• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Negative Feedback Ground

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi all.

I'm building a mullard 5-20, first time tube power amp project for me.

Can anyone advise me how the ground side of the negative feedback loop should be connected? I had assumed that it would enter the ground plane nearest to the feedback connection, but I'm concerned that this will introduce large currents near the input stage, & cause hum. What if I just connect o/p jack ground to chassis?

Cheers
Eduardo
 
As I recall, the secondary isn't connected to anything inside the circuit but the NFB loop, so it can't cause hum in and of itself.

The number one absolute best way to guarantee minimal ground loop hum is to ground the signal input jack directly to the first stage ground return, or if the jack is chassis mounted, ground the stage to the jack, and only the jack. Then run wire to the OPT secondary for the NFB, or whatever.

Tim
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.