Shoulder washer for 12a

[angelodp]

Looking for a source and correct part # for an isolation shoulder washer that will work on a 12A switchcraft jack.

[Bruciep07]

Hoffman sells the correct fiber shoulder washers. I think the correct keystone part numbers are...
534-3069 shoulder washer
534-3222 flat washer
Look em' up, pretty sure those are the correct ones. I got the measurements from the keystone PDF and just ordered the same size ones from mcmaster Carr cause they're just around the corner from me...

[David Root]

If that's the same one as the Switchcraft 11 uses, that is Mouser 502-S-1029

[angelodp]

Thanks guys, appreciated.

If we are trying to keep ground loops to a minimum then why aren't all input and output jacks isolated on most amps.

Ange

[M Fowler]

I've had more trouble with noise and ground loops using the Cliff jacks then I ever had with Switchcraft, so I am sticking to Switchcraft.

Of course it must be just me not fully understanding grounding to have had such problems

Mark

[David Root]

In a thick aluminum chassis I use two shoulder washers, one on each side of the hole. This absolutely ensures no chassis contact in my experience. However it can leave you a bit short on threading for the nut and washer, if so use the long jack.

In a steel chassis you can use only one washer, but I have found that it is easy to pinch the washer a little if it's slightly off center and this can allow chassis contact sometimes, sometimes not, but instead I sand down each shoulder a bit on both washers so they will fit inside without touching each other to the point where you cannot get the jack tight in the hole.

[Structo]

Well they make a flat fiber washer as well.

I use a shoulder washer on one side and the flat washer on the other.

You do have to drill the hole a little bigger for the shoulder washer to fit.

[angelodp]

Mark, with switchcraft the sleeve is grounded to the chassis, so how do you avoid loops. Are you using the chassis as a ground plane. I know that my Dlite has distributed ground points that use the chassis as a ground plane and it works fine. The input of the Dlite uses switchcraft and has a ground wire that goes to a ground node ( screwed to the chassis ) that has all the pots, pre-amp board, relays and panel switches on it. But the input jack is also grounded via contact to the chassis. I assume that would be a small loop there? I take it that some are isolating that jack. Did HAD on the input jack.

ange

[David Root]

Tom that's right the chassis hole needs to be 7/16. I have the flat washers too but they don't give me the same confidence as the shoulder washers.

HAD grounded the guitar input jacks directly to the chassis as far as I can see looking at pix.

The only place I have found jacks have to be isolated is if you have an internal buffered loop, I guess because when in use you have a plug in each jack, send and return.

[M Fowler]

Ange,

Yes the switchcraft jack does reference to ground at that point so I don't run the buss bar to the input jack like you see in some amps.

Run the buss bar between the pots and tone board allowing me to tie all the grounds of the pots and board to the buss bar. Then either terminate near the input jack or in some amps daisy chain back to star ground.

In some amps I run individual wires back to the star point. Others will have mini star points and then back to star.

But it only gets attached to the chassis at one point.

Each type of amp has it's own design.

Really frustrating was on one build which I have built this same circuit many times caused me so much trouble I didn't know what the hell was going on with that amp. Humm, buzz and frustration. Even switched to all cliff jacks, elevated filaments, rewiring and all.

Mark

[Bruciep07]

Just to add to my earlier post, mcmaster carr PN 93920A170... 50 of them for $7.50... same size as the switchcraft S1029 but 1/3 the price...