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Old 20th April 2013, 09:31 PM   #1
rock12 is offline rock12  United States
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Default grounding RCA inputs

This is my preliminary setup a little tuning for tight fits and I can start hardwiring. My? is on the RCA inputs(right side) do I shield these coming thru the alum. top and ground just the one lug. The switches I believe are shielded from the top and ground thru the circuit. This is a tubelab SSE
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Old 20th April 2013, 09:39 PM   #2
DF96 is offline DF96  England
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Generally the screen (outer) of RCA should be isolated from the chassis/case for audio, ad find their ground at the appropriate place in the input circuit.

On the other hand, to reduce RF getting in the outer can be connected to the chassis by a small value capacitor - but few bother to do this.
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Old 20th April 2013, 09:41 PM   #3
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Hi!

You should mount the RCA inputs such that their grounds are isolated from the chassis. On the photo it looks like they are not.

Make a connection from the ground lugs of the RCA to the signal ground inside the chassis.

Best regards

Thomas
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Old 20th April 2013, 09:47 PM   #4
rock12 is offline rock12  United States
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thanks for the input I will hunt down some shoulder washers to isolate my RCA's
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Old 21st April 2013, 02:08 AM   #5
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The infamous "pin 1 problem" also applies to unbalanced interconnects!
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Old 21st April 2013, 04:08 AM   #6
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Quote:
Originally Posted by rock12 View Post
This is my preliminary setup a little tuning for tight fits and I can start hardwiring. My? is on the RCA inputs(right side) do I shield these coming thru the alum. top and ground just the one lug. The switches I believe are shielded from the top and ground thru the circuit. This is a tubelab SSE
Hi.
Im looking for the transformers as you've used for this amp. Could you show me where to buy them?
Thanks much
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Old 21st April 2013, 01:13 PM   #7
rock12 is offline rock12  United States
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I bought the transformers from edcor(just web search for it) the PT is XPWR035 and Output CXSE25-8-5k. There is a 6 week build time from edcor
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Old 21st April 2013, 01:31 PM   #8
forr is offline forr  France
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Quote:
Originally Posted by Speedskater View Post
The infamous "pin 1 problem" also applies to unbalanced interconnects!
If you mean that the RCA body should be connected directly to ground, I am all in favour to experimenting it first. Washers can be retrofitted laterd if really needed.
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Old 22nd April 2013, 06:15 PM   #9
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If you mean that the RCA body should be connected directly to ground, I am all in favour to experimenting it first. Washers can be retrofitted laterd if really needed.

RCA body should be ISOLATED from ground/chassis with a plastic washer both sides of chassis hole and run a wire from the RCA body (usually there's a tab where the threads are on the back of the jack) you run a wire from the ground tab over to your ground buss or star ground point which is your signal ground. No hum this way... I like to attach the signal ground on my ground buss right close to where my cathode resistor ties to ground. That's how I do it.. there are many ways, with your setup you're setting yourself up for a ground loop hum, there are many sources for the hum, which is why you want to take steps to avoid it.

RCA with washers look like this:
Chassis Mount RCA Jack Pair 091-1120

Cheers,
Bob
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Old 22nd April 2013, 07:07 PM   #10
forr is offline forr  France
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Bob,
Avoiding hum generally resorts to a star ground and avoiding ground loops albeit this is only a receipe, not a real philosophy, and may not the best solution in all cases.
Why not set the star ground at the RCA socket ground connected to the chassis ?
Do not forget that, if the input is stereo (twin RCA), the sockets must be close.
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