Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: StevenPituch on February 16, 2020, 03:51:59 pm
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Hi All,
I am about to wire up the speaker jacks on my Hoffman AB 763-2 (Deluxe Reverb). I know the pots and the board use a star ground. I am wondering how to ground the two speaker jacks. It seems the four RCA jacks for the tremolo and reverb are self grounding. So I am assuming the RCA jacks and the speaker jacks grounds do not go back to the single star ground. Can I just connect the speaker ground to the ground tab on the Vibrato Pedal jack? Afraid of ground loops.
Steve
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The speaker side of the output transformer is un-grounded. You can ground it any place you like.
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Ah so no ground loop. I understand. I am learning something new every time I look at this thing.
Thanks, PRR, for the clarification. I enjoy building much more when I understand why I am doing something.
Regards,
Steve
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Since this amp has a NFB loop from the OT secondary, it's important to provide a good ground to the speaker jacks. If you are using switchcraft jacks they will automatically be grounded to the chassis. I don't like to rely on the phone jacks to provide a ground. I've seen too many loose jacks. I prefer to also run a dedicated ground wire back to the power ground lug.
Here's a great grounding scheme for that amp. I use this scheme with these exceptions...
1. I provide a dedicated ground lug for the power cord ground wire.
2. I provide a dedicated ground lug near the input jacks for all preamp grounds, including the input jacks.
3. I don't solder the pot buss to the back of the pots.
https://el34world.com/charts/grounds.htm