New Builder with ground question

[Richs1979]

First, hello and Happy New Years.
As a first time builder I'm hoping I can get a little bit of help with my project. After well over a half a century of playing guitar and using some great amplifiers, I finally gave in to my itch to want to build one myself. For years I watched 2 guys do endless magic with these amps. My late brother built and modded some of the best sounding amplifiers I ever played. My kate friend Ed was another whizz. I watched and learned to the point where I was doing my own minor repairs like changing filter caps, pots, and 3 prong conversions. Anyway, I purchased the Hoffman 1 channel AB763 kit. So far I acquired a blank aluminum chassis measuring 20.250 x 8 x 2 inches. After copying pretty much Fender's spacing specs, I have everything fitted and am ready to wire. While I am following Mr. Hoffman's plan to the tee, I'm unsure about the bus ground for the pots. I made just a slight change to the pot layout by switching the bass pot to treble and vice versa. And I installed a future dual gang 250k pot for Master. So it's Volume, Bass, Middle, Treble, Reverb, Speed, Intensity, and Master(future). My question right now is the bus wire for the pots. In reading dozens of posts in the last week, some say not to solder the bus wire to the back of the pots. While others say just cut a piece of wire and do it. I have a terminal to the right of the input jacks which I dedicated for the preamp ground. Any help would be appreciated. Thanks

[shooter]

I use a "on-board buss", Sluckey, probably the best builder here uses and "Off pots buss"


here's a couple pics

[acheld]

The problem with soldering the bus wire to the pots is:  it is a major undertaking to remove even one pot from the chassis once they are wired in.   You can do this, there's nothing real complicated about the procedure -- it just takes time.  Unless, of course, you're ok with just cutting the offending wires (which I am).

Take a look at Steve Luckey's (sluckey) work:  https://www.sluckeyamps.com/phoenix/phoenix.htm and check out how he does this.

No need for very thick wire as you will see on YouTube sometimes.  18-20AWG is fine.

[Richs1979]

I don't mind cutting if that's all it takes. Appreciate all your help.

[Willabe]

I would not solder a ground buss to the back of the pots, no way.

It's a pain to solder to the pot backs. It also forms a ground loop, a small/short ground loop, but a loop never the less.

Do like the guys are telling you, do the ground buss like Sluckey does.

[Richs1979]

The ground loop issue is what I was concerned with. While some pots are semi-floating others are not. I am working with thick aluminum. I couldn't use any star washers to dig in with those pots. So my concern is loss of chassis ground to those pots in the future. And then there's the placement of the filter caps, which I'd like to run alongside the pots using the thin buss wire for their grounds.

[Willabe]

You should read this on grounding if you haven't yet, look at the multiple star grounding, drawings 15:9, 15:10, 15:12, 15:13, 15:14;


https://www.valvewizard.co.uk/Grounding.html

[Richs1979]

So followed everyone's advice and used a suspended bus wire. It's that 2nd to last Hoffman pic that looks like all the pots were soldered to the bus wire. I also like how he lived up those filter caps. I will do the same once I get to that point. This is not easy the first time around. Thanks again.

[Richs1979]

This is what I've done so far. I'll wire the heaters tomorrow. I have read and viewed those docs and I am trying to follow those as best I can. Thanks again for your help.

[Richs1979]

After sleeping on the subject, I pulled that copper wire and followed Mr. Hoffman's bus wire scheme. I'll be wiring the heaters next. Thanks again.

[Willabe]

... used a suspended bus wire. It's that 2nd to last Hoffman pic that looks like all the pots were soldered to the bus wire.

They are.

Doug solders his buss ground wire to the pots.

[pdf64]

I suggest to use thinner, preferably stranded, wire to the pot lugs. Heavy gauge wire like that might put strain on the lugs. Their physical attachment to the wafer, and electrical connection to the track, isn't designed to be load bearing.
The point being that you might end up with dodgy pots.

[mresistor]

Here is a thread from Mike P2P amps of one of his builds.  It shows how to connect the ground buss wire to the pots without soldering to the pots.  I suggest using  some 18-20 guage buss wire. You can get that buss wire at numerous stores like Antique Electronic Supply. The 14 guage copper wire does offer some rigidity to help it stay put though. I haven't read or heard any long term reports of the wire adding stress to the pots that cause problems.

https://el34world.com/Forum/index.php?action=profile;area=showposts;u=5097


buss wire https://www.tubesandmore.com/products/wire-bus-100-foot-spool-tinned-copper

[mresistor]

I forgot to mention   when I use the buss wire to suspend the ground buss along behind the backs of the pots I use an insulated standoff on the power supply end to support the buss wire so as not to put a physical load on the pot terminals. 


Example -   https://www.ebay.com/itm/145854453345

[pdf64]

... I haven't read or heard any long term reports of the wire adding stress to the pots that cause problems. ...

I hereby report that :)

[Willabe]

... I haven't read or heard any long term reports of the wire adding stress to the pots that cause problems. ...

I hereby report that :)