Anyone run into this with SDA SRS Speakers
Answers
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Wnite, I had a brain **** when I stated your amp was common ground. A common ground amp will measure close to 0 usually 0.5 or so, definitely under 1 ohm. For example, your test measurement of the Marantz confirms it is common ground.Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Interesting how the different RCA cables resolved the issue. I hope it is resolved and not just masked.
I agree with F1Nut, common ground usually is less than 0.5 ohm. All mine are less than 0.1, and often 0.
I am not an electronics wizard by any means, but I vaguely recall some multi channel amps with dual transformers splitting the amplification across the transformers which can increase the ground resistance between channels. Some also state they have large size transformer but with independent windings for each channel or independent secondary windings. I am not sure exactly what either means or how that affects common ground. Given that there are 7 channels and two transformers, I am not sure how the even/odd match up. If there were an even number of channels I could see an even split for the transformers and a greater chance for some channels not to be common ground. I would check if any channels can be combined. If they can, then those two channels should work properly as common ground. -
When I originally took my ohmmeter readings, I was getting about 1.6 ohms. I was sticking the probe into the banana jack which may or may not get the best contact. So, this afternoon I took some banana plugs I hadn't used yet (i.e., no speaker wire attached) and I took out some speaker wires from the Monolith amp and put my empty banana plugs on a couple of the negative speaker jacks (to get better contact). That gave me .1 or .2 ohms. I thought that's where I would end up. But, after the mention about different RCA jacks might be masking the problem, I felt like I better double check. So now I can sleep a little better at night. Thanks so much for all of the help. Hopefully this helps someone else down the line.
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Interesting how the different RCA cables resolved the issue.
I missed this. WTF!?!Political Correctness'.........defined
"A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."
President of Club Polk -
Could it be that some of the amp channels share a common ground and some don't? I'd check all of them out individually again to make certain before closing the book on the mystery.
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So the SRS work with your amp?
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Could it be that some of the amp channels share a common ground and some don't? I'd check all of them out individually again to make certain before closing the book on the mystery.
That's why asked about odds and evens... 1-3-5-7.......2-4-62-channel: Modwright KWI-200 Integrated, Dynaudio C1-II Signatures
Desktop rig: LSi7, Polk 110sub, Dayens Ampino amp, W4S DAC/pre, Sonos, JRiver
Gear on standby: Melody 101 tube pre, Unison Research Simply Italy Integrated
Gone to new homes: (Matt Polk's)Threshold Stasis SA12e monoblocks, Pass XA30.5 amp, Usher MD2 speakers, Dynaudio C4 platinum speakers, Modwright LS100 (voltz), Simaudio 780D DAC
erat interfectorem cesar et **** dictatorem dicere a -
Soooo thinking out loud here, could one use those that share a common ground, would that allow use on those channels?
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I had a similar problem with my system. Massive hum. Hum went away depending on what RCA interconnect cables I used between Pre-Processor and power amp.Their first ask was to replace the RCA cables going from the Marantz Pre Out to the Monolith amp. I replaced the 2 pre out RCA cables that supply the signal to the Monolith channels that the SDAs are on with an old pair of Monster Cables and that fixed the problem (maybe more shielding?).
SOME interconnect cables are grounded at both ends. That is, the shield braid is connected to the jacks at each end, so that the outer contacts of the two RCA connectors have continuity. Some are only grounded at one end, and the cable jacket will have a directional arrow printed on it.. The difference in the cables solved--or created--a ground-loop problem resulting in ear-splitting hum. This was twenty years ago, I don't remember which cables eliminated the noise and which created the noise.
At any rate, the ultimate, root cause was that the RCA output jacks for the main channels of the Pre/Pro were not grounded properly. Pre/Pro went back for warranty repair, the RCA jacks got properly grounded, which totally resolved the issue. I didn't have any problem with the surround channels because all of those RCA jacks were grounded right to begin with.
Consider testing resistance between the outer ring of the RCA jacks and chassis ground of your various components.
There are various grounding schemes for the negative speaker terminals. Some are entirely isolated from chassis ground--perhaps the amplifier is bridged so that both the red and the black terminals are "live". Some are directly connected to chassis ground, and some are connected to chassis ground via a resistor. From one negative terminal, through the resistor, to chassis ground, through the other resistor, and back to the other channel's negative terminal involves both resistors. My big-boy amps use a 10-ohm resistor on each channel's negative terminals, therefore ~20 ohms through the two resistors. Made my 1Bs unlistenable. An eight-inch jumper wire connecting the negative terminals instantly fixed that problem. Other amplifiers may use 100 ohm resistors, or any other value. The total resistance will be double the individual resistors. So it's not as simple as "under one ohm" versus "infinity".Regarding the Common Ground question. My understanding is that a Non Common Ground amp will give you an 'Infinitiy' or 'Open' circuit reading on an Ohm Meter (0.L etc) when checking black-to-black speaker outputs on the back of the amp. Getting a very low resistance reading would indicate contact (not an open circuit). I checked some black-to-black speaker terminals on my Marantz AVR and got anywhere from .4 to .8 Ohms (not zero). I took a reading on a black to red speaker terminal and got an open circuit reading (0.L). I believe that would indicate that the Monolith is in fact a Common Ground amp.
Also: Don't forget to take the resistance of your test-leads into account. My Fluke multimeter needs a 0.2 ohm correction for the resistance of the two test leads. Entirely unimportant for most resistance measurements, but critical when what you're trying to measure could be a fraction of an ohm.
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Thanks Shurkey. Interesting about having resistors on the ground terminals. Also, the old Monster RCA cables I used do have the directional arrow. So presumably they are only grounded on one end. Sounds like I just got lucky that they were handy and that's what I used to replace my RCA cables with. If I had replaced them with regular RCA cables that were grounded at both ends, maybe I would have never solved the issue (I haven't tried replacing the Monster cables with anything else). Regarding the Monolith being common ground; it looks like all of the black speaker terminals are grounded together. I put the ohm meter on the first of the 7 speaker channels on the amp and went across all of the black speaker jacks. I got .2 or .3 ohms on all of them. I did some other random point to point connections and got the same thing. I think it's safe to say that it's a common ground amp and the original issue was from the RCA cables used from the pre outs on the AVR to the external amp.
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Glad to hear the problem is resolved and it wasn't the amp! Great looking system.
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So where is the faulty ground at the RCA jacks? On your preamp? Or at the power amp? I wouldn't count on the interconnect cables to "fix" this, I'd be looking for the root cause.
