Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Planobilly on December 11, 2016, 03:48:20 pm
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On the Hoffman AB763 2 Channel layout the channel one inputs are going to ground through the chassis. The buss is split at the second channel. I assume I am reading the diagram correctly. It is also the ground for the cathodes for the first four tubes.
What is the reasoning that it is it grounded like that?
Thanks,
Billy
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You needn't be too literal when looking at that aspect of the layouts (http://el34world.com/Hoffman/files/Hoffman_AB763_2.pdf).
In most builds, the Vibrato Channel jacks will prevent the buss wire from continuing in a straight line across all the pots. Doesn't really matter, as most pots will cause that buss wire to have continuity to the chassis regardless.
The first layout in the linked pdf looks like the buss wire "breaks" just for drawing convenience, so you don't think the 68kΩ resistors should be soldered to the buss wire.
You'll have to eyeball your build to decide the best way to connect everything.
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This is a nice read on grounding from Merlins web site, if you haven't read it yet. Similar to Doug's thinking.
Just more involved, has isolated/insulated input/speaker (reverb/trem/FX loop) jacks and ground stars but their not always necessary.
http://www.valvewizard.co.uk/Grounding.html (http://www.valvewizard.co.uk/Grounding.html)
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Thanks Guys,
I saw the two 68K resistors and wondered if the buss was broken there just for clarity.
I will go read the valve wizard link.
As I am starting to build and experiment with higher wattage amps, grounding, lead dress and component placement, are becoming a more critical issue. I just am finishing up with a 100 watt high gain build that has given me a serious amount of grief to finally get everything under control.
I am working on a general grounding plan which I will post for feedback in a few days.....still drawing it up.
Thanks for all the help,
Billy