OneRoomStudios

Interwinding Screens vs Can/Flux Shield
« on: January 26, 2020, 07:49:58 PM »
I'm working on a project using an OEP A187A10C (https://docs.rs-online.com/8313/0900766b815288d8.pdf), which has interwinding screens on both the primary and secondaries, as well as the usual can/flux shield. I'm wondering what the best way to go about using/not using these is. Should I connect them all to ground? Connect them to the negative side of each winding? Ground the can and let the interwinding screens fly? Any tips? Thanks!
« Last Edit: January 27, 2020, 12:27:08 PM by OneRoomStudios »


CJ

Re: Interwinding Screens vs Can/Flux Shield
« Reply #1 on: January 27, 2020, 03:39:02 AM »
 ground the can wire to the chassis,

screens usually get tied to signal ground,  which might be the secondary wire that goes to ground if that side of the circuit is single ended,

but experimentation worth a thousand theories, so try screens grounded and un-grounded and see what happens,
If I can't fix it, I can fix it so nobody else can!
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abbey road d enfer

Re: Interwinding Screens vs Can/Flux Shield
« Reply #2 on: January 27, 2020, 03:46:32 AM »
I'm working on a project using an OEP A187A10C (https://docs.rs-online.com/8313/0900766b815288d8.pdf), which has interwinding screens on both the primary and secondaries, as well as the usual can/flux shield. I'm wondering what the best way to go about using/not using these is. Should I connect them al to ground? Connect them to the negative side of each winding? Ground the can and let the interwinding screens fly? Any tips? Thanks!
You can't let them floating. They have to be grounded. The question is where.
Electrostatic shields (that's what these screens are) are a tad controversial. In particular if there's only one...
For mic preamps, Bill Whitlock advocates connecting the E-shield to the reference ground of the mic preamp, since it minimizes the amount of residual RFI hitting the preamp.
OTOH it means that RFI is not killed right at the signal ingress, so it's allowed to penetrate the system.
For line inputs, a different approach is conceivable. Connecting the shield to the earth/chassis takes care of dumping RFI to ground. Whatever residual should not affect a decently designed line receiver.
Indeed, the best solution is using dual shields; the primary shield is connected to the earth/chassis and the secondary shield goes to the audio reference. The drawback is that the coupling between pri and sec is affected in a negative way, resulting in deteriorated HF response.

EDIT: I see that this OEP xfmr has dual shields, so A2 goes to earth/chassis, A3 goes to the preamp's audio ground and the can can go where it's convenient, doesn't matter.

EDIT 2: This is assuming you use it as a mic preamp input. But using it for DI, the answer would be somewhat different.
A2 should go to the instrument ground, A3 to Pin 1 of the XLR, as well as the can.
« Last Edit: January 27, 2020, 03:56:03 AM by abbey road d enfer »
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

OneRoomStudios

Re: Interwinding Screens vs Can/Flux Shield
« Reply #3 on: January 27, 2020, 11:11:59 AM »
Thank you both. That confirms my suspicion. This will be for an instrument preamp, unbalanced Hi-Z in. So this is what I'm thinking.


abbey road d enfer

Re: Interwinding Screens vs Can/Flux Shield
« Reply #4 on: January 27, 2020, 05:13:05 PM »
Thank you both. That confirms my suspicion. This will be for an instrument preamp, unbalanced Hi-Z in. So this is what I'm thinking.
Looks good to me.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.


 

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