Soldering the shielded cable onto the pots?

[Structo]

To those that solder the shield to the pots, do you think that improves the grounding any or makes the amp quieter and by that, improves tone?

[NickC]

Lately I've been using isolation washers on the pots, and not soldering a buss bar (or anything else) to the back of pots. Good or bad?

[martin manning]

Lately I've been using isolation washers on the pots, and not soldering a buss bar (or anything else) to the back of pots. Good or bad?

Grounding the pot's case provides some shielding for the element, one end of which might be 1M above ground. This can be a source of hum from stray 60Hz EMF so it's a good idea to ground it either at the bushing or by connecting it to the ground buss.

[NickC]

Lately I've been using isolation washers on the pots, and not soldering a buss bar (or anything else) to the back of pots. Good or bad?

Grounding the pot's case provides some shielding for the element, one end of which might be 1M above ground. This can be a source of hum from stray 60Hz EMF so it's a good idea to ground it either at the bushing or by connecting it to the ground buss.

Thank you Martin. That is good to know. I'm going to make sure to ground the pot cases from now on, even if I don't use them in conjunction with a buss bar.

[glasman]

My method is pretty simple.

1. Using a dremel tool with grinder attachment I mark the back of the pot about 1/8" wide and the length of the pot for each cable.
2. Tin the exposed metal with solder
3. Tin the cable shield
4. Lay the tinned cable shield on the tinned area of the pot.
5. Reflow the solder between the cable and the pot.

Takes only a few seconds. I use a Weller bench iron with 800 degree tip.

FWIW I use a small vise to holder the pot shaft.

Gary

[ayan]

Hey Gary,

I suspect you do this as a harness outside of the amp, then?

G.

FWIW I use a small vise to holder the pot shaft.

Gary

[Structo]

Yeah, that makes sense and would be easier to hold it still.

[glasman]

Hey Gary,

I suspect you do this as a harness outside of the amp, then?

G.

FWIW I use a small vise to holder the pot shaft.

Gary

Yes, I do them outside of the amp.

I always pre-assemble all pots (usually 15 to 30 sets at a time) and bag em for later use. In the SOD II there are 5 pots that get prebuilt. A lot of soldering...

[glasman]

Yeah, that makes sense and would be easier to hold it still.

Just don't touch the housing . I cant tell you how many times I have burnt my fingertips.

[Mark]

Thanks for all the replies and photos, that was very helpful.

A vice is definitely a good idea, if you could genetically engineer an electronics tech, he would have a third arm.

I think the important thing to remember about grounding the shielded cable to the back of the pots is this; the shields cannot be attached to the earth bus bar as this will put the noise you're wishing to eliminate onto the earth of the circuits you're wishing to protect.

I remember seeing a build where a guy put the 240vac cable very close to the earth wire, when he turned the amp up the hum was very loud.

Of course I'm stating the obvious for the sake of new builders, HAD soldered the shields on the back of the pots as it provides stability for the core wire against movement and dry joints, the shield is earthed at a point on the chassis that isn't critical thus ensuring low noise operation. This doesn't mean there aren't other options of course.

[ayan]

Well, Dumble did things differently sometimes.

Gil

Thanks for all the replies and photos, that was very helpful.

A vice is definitely a good idea, if you could genetically engineer an electronics tech, he would have a third arm.

I think the important thing to remember about grounding the shielded cable to the back of the pots is this; the shields cannot be attached to the earth bus bar as this will put the noise you're wishing to eliminate onto the earth of the circuits you're wishing to protect.

I remember seeing a build where a guy put the 240vac cable very close to the earth wire, when he turned the amp up the hum was very loud.

Of course I'm stating the obvious for the sake of new builders, HAD soldered the shields on the back of the pots as it provides stability for the core wire against movement and dry joints, the shield is earthed at a point on the chassis that isn't critical thus ensuring low noise operation. This doesn't mean there aren't other options of course.

[Mark]

Thanks Gil this is the last time I stick up for that bonehead HAD!

[Mark]

I had a crack at soldering to the pot yesterday. I didn't have an issue with the other solder joint melting, though I did find out that you can't solder the braid to the back of the pot when it is attached to the chassis. Any bend in the wire will be an issue.

The braid takes on a life of it's own and moved in an unpredictable manner. I did get the braid on the back of the pot, but it isn't as pretty as the first joint, I was a little concerned about the state of the teflon insulation but it measured fine with a multimeter and I wasn't prepared to megger it (not that I have one.)

(Does anyone do insulation testing on their amps?
Though I don't think this should be necessary unless you have to comply with a standard such as ISO etc.)

Rule 1, solder braids to the back of the pot before you mount it and terminate the other end.