daveyf,
You are correct my Signal cable has the red and yellow cables together and each cable has a Speakon end at the sub and a red/yellow connector and a black connector ( at the amp end).
OK, thanks to you both for pointing that out. I see no problem as far as that goes, then, given that each cable is just connecting a single sub to a single amp channel. Al,
I’m assuming if the Signal Cable is picking up EMI from something nearby to cause the hum, adding an external ground screw on my amplifier won’t eliminate the hum?
I suspect that chances are it will eliminate the hum, although I can’t be totally certain about that. But I suspect that even if something nearby is inducing hum in the Signal Cables, providing a better ground path between the subs and the amp (i.e., one that does not involve the AC safety ground wiring) would eliminate susceptibility to that hum. And the fact that connecting the LFE cable does eliminate hum when the Signal Cable Speakon is used would seem to provide confidence in that expectation. Best regards, -- Al |
Al do you have any idea as to why my balanced JR model 8T has no issues when connected in the manner that i suggested? ( which also was the way that REL had suggested to me to do the hook up when I first acquired my sub).
First, it's noteworthy that while in the case of stereo amps having outputs that are not differential (i.e., that are not balanced or bridged) the many REL manuals I've had occasion to look at over the years recommend connections exactly as you have described (red to right positive, yellow to left positive, and the black to either negative connector), but not a single one of those manuals makes that recommendation in the case of amps having differential (balanced or bridged) outputs. Second, while as I had mentioned that approach **might** work with amps having balanced or bridged outputs, depending on the internal grounding configurations of the sub and the amp, and in fact over the years I've seen a number of members here report doing exactly that with no apparent issues, at best connecting a full-amplitude amplifier output to the circuit ground of a sub is poor practice from a design standpoint, and at worst it could have the various adverse effects I described earlier. Just to cite one potential example: I know that many Audio Research balanced amps connect circuit ground to chassis ground/AC safety ground with a 10 ohm resistor. **If** the sub does likewise it would mean that a full amplitude output of the amp would be applied across a total of 20 ohms. And if the two 10 ohm resistors have not been chosen to have particularly high power handling capability one or both of them could burn out, eventually if not sooner. Resulting in hum and/or degraded sonics.
Is there a logical reason why when both subs are connected through the high-level input with the REL supplied speakon cable no hum is audible, but when I use the Signal speakon cables the hum is clearly audible? This is with no RCA cable connected to the RELs LFE inputs and into my preamps outputs.
I don't know. But if you have a multimeter it might be worthwhile to verify that both cables are wired identically, and that no shorts exist between the yellow, red, and black wires of the Signal Cables. Also, I see that the Signal Cable is described as being unshielded. I don't know if the stock REL cables are shielded or not, but if they are perhaps the Signal Cable is picking up EMI from something nearby while the REL cable is not. Best regards, -- Al |
IOW, you have perhaps ONLY listened to the low level connection for all this time! Note the reference to "volume all the way down" in Richard’s statement that ... I had a RCA cable going from both RELs LFE (volume turned all the way down) to the preamp out, while connecting the subs to the amplifier... Also, regarding ... Here’s a suggestion.. hook up just one sub as I do with my Rowland. The red to right positive, the yellow to left positive and the black to either negative connector. While this **might** work, depending on the internal grounding configurations of the sub and the amp, given that the amp has balanced outputs I would strongly recommend against connecting the black wire as you have suggested. The black wire is most likely connected within the sub to the sub’s circuit ground, which in turn is probably connected through a resistor having a relatively low value (i.e., a small number of ohms) to the sub’s AC safety ground. Which in turn is connected to the amp’s AC safety ground via the AC wiring, and the amp’s AC safety ground is in turn connected to the amp’s circuit ground through some unknown but probably low impedance within the amp. Since the amp’s outputs are balanced, a full amplitude signal would be applied to the black wire. Depending on the resistor value and other variables involving the internal grounding configurations of the amp and the sub any number of bad things could happen, including hum, the resistor being burned out, the amp going into protective shutdown mode, or the amp even being damaged. As I said, it **might** work, but IMO it’s not a good approach even if it does. Regards, -- Al |
... surely the more accurate the amp is, the more accurately it will pass on the signal...therefore what REL is basically stating is correct. Hi Davey, My point in that regard was that the more accurate the amp is the more similar the sonics of its outputs will be to the sonics of the outputs of the preamp. Which seems to me to mean, everything else being equal, that there will tend to be less difference between speaker-level vs. line-level connections than there would be if the amp is less accurate, and therefore alters the signals to a greater extent. Best regards, -- Al |
Regarding line-level vs. speaker-level, in the specific case of speaker-level connections to Richard’s amp it seems to me to be possible that the less than ideal nature of the ground path/signal return path between the subs and the amp (with the AC safety ground wiring being part of that path, as I had explained earlier) might be a factor contributing to his findings.
Generally speaking I would not expect comparisons of line-level vs. speaker-level involving amps whose outputs are not balanced or bridged to necessarily have much correlation with comparisons involving amps whose outputs are balanced or bridged.
Also, as I had mentioned earlier in the thread it would seem logical that the more transparent and accurate the sonics of the amplifier are, the less likely REL’s rationale for speaker-level connection is to be applicable.
Best regards,
-- Al
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Signal make some excellent cables at very fair prices, imo.
+1. I've used a couple of their Digital Reference power cords with fine results. And Frank, the proprietor, is a class act. Best regards, -- Al |
Hi Richard,
What I was saying at the end of my previous post is that most likely there is no issue with leaving the black wire (and eventually wires plural) unconnected, at least in your situation.
And even if there is an issue (which I suspect there isn't, given that there is no hum), at most the consequence would be some very minor (and unpredictable) sonic effect.
Best regards,
-- Al
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Quick question for Al, if I were to hook up my two (2) subs to my Rowland stereo amp, would I actually utilize the summed red and yellow cables for each left and right connector and the black cable ( now two) for the ground connector ( that Jeff installed)....or leave those disconnected entirely? ( like what ricred 1 is doing).
@daveyf Connecting the black wire of both subs to the ground connector on the amp seems to me to be an ideal approach. While two ground paths/signal return paths will then exist between each of your subs and the amp (one via connection of the black wire to the ground connector, and one via the convoluted path I described earlier involving the AC safety grounds), the presumably much lower impedance of the direct path to the ground connector will result in nearly all of the signal return currents utilizing that path. That said, regarding Richard’s situation, when he receives the second sub he has ordered, and he has the red and yellow wires from one sub connected to the + output of one channel of his amp, and he has the red and yellow wires from the other sub connected to the + output of the other channel of his amp, with the black wires of both subs unconnected, based on his latest findings with one sub it appears likely that he will have fine results. So while having a ground terminal installed on his amp is theoretically preferable, if he were to do that my guess (and it’s just a guess) is that the resulting sonic benefit would fall somewhere between minimal and none. Best regards, -- Al |
Hi Lalit,
Given that the amps you referred to are SETs they do not have balanced or bridged outputs, so connecting your subs as you have described is perfectly fine.
My statement about counting their blessings referred to what I had said just before that, meaning that those who have connected the black wire to the negative output terminal of a fully balanced (or bridged) amp should feel lucky that (a) it worked ok, and (b) damage didn’t result. As I said, which of those eventualities occurs, in the case of an amp having balanced or bridged outputs, will depend on the internal grounding configurations of the particular sub and amp.
Best regards,
-- Al
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Daveyf 9-22-2019
I connect my subs with the red and yellow summed to the red output per amp and the black to the black output per amp. This is with dual subs and mono blocks.
In the case of an amp having balanced outputs, such as Ricred’s, the black wire from the sub should absolutely not be connected to a negative output terminal of the amp. Doing so would cause the full amplitude signal that is present on that output terminal of the amp to be connected to the sub’s ground. Depending on the internal grounding configurations of the amp and the sub (and more specifically on the impedance through which their circuit grounds are internally connected to their chassis/AC safety grounds) doing so might work, but is very poor practice at best and could very conceivably cause damage at worst. If the outputs of your 8T are balanced (or bridged) that would presumably be the reason Mr. Rowland recommended installing a ground terminal on it. Over the years I’ve seen a number of members here mention that they connect the black wire of a REL sub to the negative output terminal of a fully balanced amp, and the results seem good. To that I say they should count their blessings :-) Best regards, -- Al |
Ricred 9-22-2019
Al,
"So are you saying, then, that the only difference between what worked and what previously didn’t work was twisting the red and yellow wires together, while having exactly the same connections in both cases?" YES I believe the answer to this question is actually "No," since when you initially reported the problem you were connecting the two wires to different channels, while in the case of the good results you have just obtained both wires are connected to the same channel. So the connections were different when you had the problem vs. when you did not have the problem. From your OP: Ricred 9-17-2019
I connected my sub according to REL’s instructions...yellow lead to positive on one channel, red lead to positive on the other channel, and floating the black wire(ground). I get minimum output when connected according to the instructions. Regarding grounding, the ground path/signal return path between the sub and the amp that presently exists, which is providing the good results you have obtained, is as follows: From the circuit ground within the sub via some unknown but presumably low impedance within the sub that connects its circuit ground to its AC safety ground, then via the safety ground wire in the sub’s power cord to the AC outlet, then from the AC outlet via the safety ground wire in the amp’s power cord to the amp’s chassis, then via some unknown but presumably low impedance with the amp that connects the amp’s chassis to its circuit ground. As I alluded to earlier, that path may serve as an adequate ground/signal return path with some and perhaps most designs, depending on the internal grounding configurations of the particular amp and sub. And given that REL recommended doing that, and that the results are good, I would leave well enough alone. Just don’t ever put a cheater plug on the power cord of either the sub or the amp, which would interrupt that path!! So as things stand now I believe the mystery that remains is why with that same ground path you had the problem in the first place, when connecting the red and yellow wires to different channels. The only explanations I can think of, both of which appear to be very unlikely, are: (a)You inadvertently connected one of the two wires to a negative output terminal of one channel of the amp, while connecting the other wire to the positive output terminal of the other channel. That would cause the signals from the two channels to be subtracted from each other, rather than added. (b)Something is wrong with a component or cable. As I say, both explanations seem very unlikely, so I’m at a loss to explain why you had the problem in the first place. Best regards, -- Al |
Wow! Congratulations.
So are you saying, then, that the only difference between what worked and what previously didn’t work was twisting the red and yellow wires together, while having exactly the same connections in both cases? If so, I have no idea how to account for that.
Or are you saying that the red and yellow wires are now connected to the same positive output terminal of the amp, while you wait for the second sub to arrive which will be connected to the positive output terminal of the other channel? If so, it would still be hard to explain why you were previously not getting proper results, with the red and yellow wires having been connected to the positive output terminals of different channels. But it would suggest that previously the outputs of the two channels were somehow being subtracted from each other rather than summed. In other words, a polarity inversion was somehow being introduced on one channel, either in the sub or the amp or in one of the connections between the two. Or perhaps as a result of a miswire in one of the XLR cables upstream of the amp, such that pins 2 and 3 are interchanged at one end of one cable. Although most of those possibilities (aside from an issue within the sub or in its connections to the amp) would have had dramatic negative effects on what you were hearing from the main speakers.
So I’m completely puzzled at this point.
Best regards,
-- Al
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I just received a call from REL. They said I could ground the sub/amp by going from the REL’s LFE to my Rowland Corus preamp while leaving the black lead floating. Not sure that the REL person is realizing that the inputs of your amp are transformer coupled, and the amp’s descriptions at the JRDG website and in the manual state that "transformer coupled input circuitry provides universal component compatibility and virtually eliminates ground loop noise..." So it seems to me that due to the isolation the input transformers presumably provide it is likely that connecting the sub’s ground to the preamp’s ground, via the LFE or whatever, will not result in an effective connection between the sub’s ground and the amp’s ground, which is what matters. On the other hand, though, I suppose it is possible that an adequate ground path between the sub and the amp could be formed via that connection in conjunction with the AC safety ground wires in the power cords of the preamp and the amp, which ultimately connect the chassis of the preamp and the amp together. In any event, given that none of us have much familiarity with how grounds are handled internally in these designs it’s worth a try. And I don’t think it could do any harm to give it a try; just be alert to the possibility of a loud hum. IOW keep the sub’s level control at a low setting when you begin the experiment. Best regards, -- Al |
Yes, I would think that to be highly likely. Given what Jeff has told you, given that REL's recommendation has up until recently been to do that, and given my technical understanding of the situation.
Best regards,
-- Al
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As a point of information, for a great many years prior to the introduction of many of their current models, REL manuals recommended that when connecting to amplifiers whose outputs are balanced or bridged that the black wire be connected to a chassis screw.
That should have and apparently did work well in most cases, although not quite all. An exception being a few amplifier designs in which chassis and circuit ground are completely isolated, in which case the result of doing that would probably be a large hum. Another special case involved some long obsolete early class D designs which had very high DC voltages (something like 24 VDC if I recall correctly) on both their plus and minus output terminals, relative to ground, and therefore required blocking capacitors between the amp outputs and the sub.
I don’t know what the reason may have been for REL to abandon that long-standing recommendation of using a chassis screw when connecting to balanced or bridged amplifier outputs, and now recommending that the black wire be floated.
Best regards,
-- Al
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PM answered.
Best regards,
-- Al
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For sake of comparison, if the high-level connection is a 100 for sound, what is the low-level connection, 80, 90, 95? Your guess is as good as mine on that question, Richard. As I’m sure you’ve seen, REL recommends using speaker-level connections where possible, their rationale being that the signals received by the sub and the main speakers will then both reflect the sonics of the power amp. Although over the years I’ve seen at least one or two members here having extensive experience with subs express disagreement with that philosophy. Personally I don’t use a sub, and I have no particular opinion concerning that rationale. And in any event I would expect the degree of difference that would occur between the two connection approaches to be significantly system dependent. The more accurate/neutral the amplifier’s sonics are, the less difference there would presumably be between the two approaches. Assuming, that is, that the preamp is capable of driving the relatively low input impedance that most subs have at line-level without issue, while simultaneously driving the power amp. Best regards, -- Al |
Hi Richard,
I suspect the reason floating the ground wire doesn’t work in this case is that the inputs of your amp are transformer coupled, so a ground path is not established between the sub and the amp via the preamp, since the preamp’s ground is isolated from the amp’s ground via those transformers. If the grounds of the amp and preamp were not isolated, as is usually the case with most other designs, a ground path having reasonably low impedance would be established between the sub and the amp via the preamp-to-amp interconnections in combination with the AC safety ground wiring of the preamp and the sub.
For the same reason connecting the black wire to a ground point on the preamp would presumably not work either.
While Lalit has very graciously offered to let you try the speaker-to-line level converters he will be receiving, I don’t think it would be safe to use them with your particular amp. I would envision that most such converters would attenuate the level that is provided to their signal input, but would route the ground that is provided to their input directly to their output. Since your balanced amp has full-amplitude signals on both its + and - output terminals (rather than the amp’s - output terminals being connected to its circuit ground), the result of routing both output channels of your amp through such converters to the left and right channel RCA input connectors of a single sub would almost certainly be that the full amplitude signals on the negative output terminals of the two channels are shorted together by the sub’s internal ground. Definitely a no no.
Given that the amp does not provide RCA input connectors, or any other circuit ground connector, the one **possible** alternative I can envision to attaching the sub’s black wire to a chassis screw, as Jeff suggested, would be to solder the black wire to the ground shell of a 1/8 inch mini-plug, while leaving the signal pin(s) of that plug unconnected, and inserting that plug into the amp’s remote on/off jack.
This assumes three things, though:
1) It assumes that the ground shell of the remote on/off jack is internally connected to the amp’s circuit ground. You would need to confirm that with Jeff.
2) I suspect that it wouldn’t matter whether the mini-plug is a stereo type or a mono type. Again, though, that should be confirmed with Jeff.
3) It assumes that you presently have nothing connected to the remote on/off jack. Although if you are presently using it you could probably solder the sub’s black wire to the ground shell of the plug that is being used, if assumption (1) is confirmed by Jeff.
Good luck. Best regards,
-- Al
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