Rel Hum issue with PS Audio Stack

Audio Components Amplifiers
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OP were you ever able to resolve? What was the solution?

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If you are using Rels you need two things.

  1. PS Audio Ground Screw (PS Audio will send you one for free). Not sure the exact name for this but if you call them they’ll know what you’re talking about.

  2. Rel/PS Audio Network Cables. Basically it’s a custom cable made by Real with a resistor in each one. This is NOT free and is required to eliminate hum when the power amp is off and the subs are still on. Cost was around $100.

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Thanks and last question: this special cable you mention - is it simply for grounding or is it the actual signal carrying cable replacing what comes with the sub?

I ask because I already have an expensive aftermarket REL high level signal cable with neutrik connector. Am I still using that with BhK or does this $100 cable replace?

I did look for answer in few threads but most say this discussed before with link to empty thread(s) so I wasn’t really able to find answer to that specific question

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Yes. There are two resistors that ground the positive and negative output terminals for each channel to chassis ground–four resistors in all. You can build one yourself for $25 if you’re handy. Give REL a call for the specs.

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I have the BHK 250/BHK pre and two REL SHO/3 subs. The addition of the ground screw kit from PS Audio was all I needed to solve the hum problem, didn’t need the network cables in my system.

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Before you started adding parts from PSA or REL if you have a ground screw on any other device try that first. Connect a single wire to the two Black REL wires and then to a ground point.

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Thanks to all for recent responses. BHK 250 and BHK pre are under consideration as down-the-road purchases for me to pair with Spendor speakers and Rel S5/SHO (already have those) in my main system.

Other leading contender is Luxman class A integrated L-590AXii. Just trying to understand what additional steps might be necessary with BHK, as I’ve never had any hum issues interfacing REL subs (I have 3 different ones across 3 systems) with amps from Audio Research, Cambridge Audio Edge, Marantz, etc.

I saw lots of references to previous discussions but it seems most of those discussions have been deleted or moved to “Do not post” or for whatever the link that someone attempted to leave to those discussions go nowhere. So my ignorance is not from lack of trying to figure it out without further asking about a subject that is apparently well known to the long-timers. I’m new here

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You only need the network cables if you keep your subs on 24/7 and turn off your amp when not in use. That’s when the hum occurs. If you cut off your subs when you cut off your amp they aren’t needed.

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As we know, the subs can turn themselves off after 15-20 minutes with no signal. After installing the ground screws I had no further issue with hum during that idle time although I did before installing the ground screws.

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Hi, @kzk

No discussions have been deleted or moved. What you find in the old in the now Do Not Post category is all there ever was.

If you have additional questions or something you want to discuss, please feel free to post it here if it relates to this thread, or start a new thread on your own. If I can otherwise help, just let me know.

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Got it. Apologies for my misunderstanding

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Not at all! It is confusing.

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Not exactly. The Rel “T” series subs do not auto power off.

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One more question. In order to avoid hum REL/PS Audio suggest plugging an RCA cable from Sub (LFE port and turn off its volume knob) into an unused input port of BHK Preamp (red one right input RCA for example). When there is 1 sub.

Why not an unused RCA port of the AMPLIFIER ITSELF?

A shorter RCA cable, in my system, would simplify this “hum solving” connection between 2 REL T7/i subs (dual stereo) and 2 M1200s monoblocks unused RCA input (the XLR input is the input I use from BHK Preamp to each M1200s).

If 2 Subs must to be connected to my BHK Preamp unused RCA inputs (same right and left unused RCA input I suppose) then a longer RCA cable would be needed. I’d have to purchase it actually.

Subs/M1200 amps distance is short - 2 mt (less cables traffic and confusion behind gear and cost - same route of SpeakON existing cables)
Subs/BHK Preamp distance is long - 6 mt (long cables and cost added)

Thank you guys and @jamesh for your help.

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You can absolutely use the amp’s unused RCA input. Similarly to connecting it to the preamp, this successfully engages the ground connection that you need to get rid of the hum.

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Thank you. Great!