Backwards Capacitors

[bnwitt]

Saw a little video on YouTube regarding identifying the outer foil/shield lead of non polarized capacitors and orienting them to the high impedance or chassis end for lower noise sensitivity in an amplifier.  Anyone doing this?:

https://www.youtube.com/watch?v=BnR_DLd1PDI

Barry

[VMS]

There are few threads on the subject here but thanks for sharing the video.


How do you guys orient the caps on a TMB tone stack? For example on this vibro champ do you flip the .047 cap so that the outer foil side is connected to 15k resistor?


And what about the caps on the tremolo circuit?

[tubenit]

Barry,

Nice to see you posting!  Yes, quite a few of us have been doing this for a number of years.

Look in ARCHIVES:   http://el34world.com/Forum/index.php?topic=11427.0           (50 posts & over 10,000 views)

With respect, Tubenit

[bnwitt]

Tubenit, it's good to be alive and posting  

From what I saw in the video I posted, the orientation is toward chassis ground or the high impedance portion of the circuit.  So the outer foil connects to plate on a coupling cap with the other lead going to grid.  I've never built a Hoffman or Fender layout amp that wasn't dead quiet, so I was surprised by this being even relevant or known.  Of course in a radio receiver I could see it being more of an issue.

I've had my hands in lots of amps though that would hum loudly when I got my finder near or on a capacitor body and now I'm wondering if this may have been part of it.  It would seem that a well laid out amp wouldn't have these issues nor would an amp chassis which is properly shielded but I've had to put aluminum plates under some of the high gain amps I've built (like the Komet) in order to shield it from a 4x12 speaker cabinet's feedback and now I wonder if proper orientation of the caps might have eliminated the need for the plate.

[tubenit]

I have found that changing the caps to proper orientation does make a difference in the noise level in my amps.

with respect, Tubenit

[bnwitt]

Well, I guess I'll be breaking out the Oscope for the caps on this Hoffman AB763 I'm building. Thanks Tubenit and VMS

[Ed_Chambley]

I have found it makes a difference in coupling caps the have the shield towards the plate, not the grid of the next stage.  To tell you the truth, I have only noticed a difference in tight builds.  I get bored sometimes, so I opened up a hardwired amp i got from someone.  If I squeezed the cap while in the circuit and it always makes more noise.


So I turned them all one way and then turned them all the other way.  Did not notice much difference until I squeezed them.  So I just decided not to squeeze my caps while I was playing.    Seemed to work fine.


I do know it is the "proper way" to do it.  Also I found the printing on the cap can be on either side.

[kagliostro]

The line or point printing in the cap (if present) was for that purpose on the old cap

on new cap they didn't follow such a standard

Franco