Shielded wire on pots?

Started by sopapo, January 10, 2023, 09:50:52 AM

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sopapo

Rob, im not sure if i am understood well, the thing that  at the other end doesnt need a ground can be ex. the the input wire from Jack to switch?
Antonis, your concern its about the legs of the bjts not fitting enough tight isn't?? Or that the bjts pick some kind of noise..

antonis

Quote from: sopapo on January 12, 2023, 02:08:48 AM
Antonis, your concern its about the legs of the bjts not fitting enough tight isn't?? Or that the bjts pick some kind of noise..

Both.. :icon_wink:
(a loose Base contact might appear as a high value resistance intermnittently "added" on Base spreading resistance with all nasty consequences..)
"I'm getting older while being taught all the time" Solon the Athenian..
"I don't mind  being taught all the time but I do mind a lot getting old" Antonis the Thessalonian..

GibsonGM

Quote from: sopapo on January 12, 2023, 02:08:48 AM
Rob, im not sure if i am understood well, the thing that  at the other end doesnt need a ground can be ex. the the input wire from Jack to switch?

To be simple about it, the 'rule' is that you only ground a shield at one end.  This makes the shield act like it is part of the enclosure, a metal tube around the conductor(s) that is an extension of the enclosure!  What end is grounded is usually a matter of what is more convenient, tho Rob does point out that this can change capacitances in some places that may matter, such as in an opamp FB loop.   Generally shields will be used on input wiring, or long runs taking off to pots and so on.  But again, it will only help with crosstalk, and likely won't do a lot on a well-designed high-gain build   :)     

I always shield input wires in amps, and most dirt pedals, since these are easy to do upon building, harder to retrofit... and rarely have gone beyond this level of concern (with no horror stories to-date).   
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sopapo

#23
Thanks GibsonGM, so i was already doing It well, conecting the shields to the jacks on the switch I/O wires...
Another question, if I change the bc549c transistors that I have to bc549b (with less hfe gain) It would have less noise or its the opposite?? Or the same noise...
It depend of the stage?? On the first stage that has no clipping its better high or low hfe? And in the last stage that has no loop??
Thanks for all

bartimaeus

Quote from: sopapo on January 14, 2023, 02:23:32 AM
Thanks GibsonGM, so i was already doing It well, conecting the shields to the jacks on the switch I/O wires...
Another question, if I change the bc549c transistors that I have to bc549b (with less hfe gain) It would have less noise or its the opposite?? Or the same noise...
It depend of the stage?? On the first stage that has no clipping its better high or low hfe? And in the last stage that has no loop??
Thanks for all

https://www.diystompboxes.com/smfforum/index.php?topic=93779.0

sopapo

Thanks Bartimaeus, its a great thread, I didn't see It in my searches. Ok, so I am gonna try this too.