+1 Jim (Jea48). Although it may seem improbable, I would not by any means rule out the possibility that BOTH amps have succumbed to the very high capacitance of the speaker cables. Also, I would add the following to the quotes you provided, this one coming from a respected designer of highly regarded audio electronics and speakers: Pbnaudio 12-1-2017
My gut reaction to this is the very long, highly capacitive speaker wires are at least contributing to this. As someone stated above - try lamp cord. Best regards, -- Al |
I too think it must be the amp but this test will tell for sure. Hopefully Kosst will take my response to this in the constructive spirit in which it is offered: If the problem goes away when the amp is changed, while it would substantially increase the likelihood that the Pass amp is the culprit, it would not by any means be a conclusive indication. It could simply be that the other amp is less sensitive to the effects of a speaker cable having very high capacitance. Also, can you answer a couple of questions I had raised earlier: 1)What is the full model name of the Ortofon Black cartridge? 2)Do the OCOS cables have a "red" termination network, a "black" termination network, or neither. Good luck. Regards, -- Al |
Regarding the exchange Jim (Jea48) and I had a few posts back about the "Ortofon Black" cartridge listed in the OP, and the possibility of trying the phono stage connected directly to the power amp:
In addition to the high output 2M Black moving magnet cartridge, which as I indicated would be unsuitable for use with the non-adjustable loading of the Linto phono stage, Ortofon has two low output moving coil models having the word "Black" in their name. Those are the Cadenza Black and the Quintet Black (or Quintet Black S). Both have rated outputs under the standard test conditions of about 0.3 mv.
I assume the OP’s cartridge is one of those two models, and if so I assume he is using the high gain (64 db) setting of the phono stage. 64 db would boost 0.3 mv to about 0.48 volts, which is about 2/3 of the voltage that would drive the amp to full power. So while performing an experiment with the preamp removed from the signal path is probably within reason, especially if a recording known to have low volume is used, and if care is taken to avoid a large transient when the stylus makes contact with the record, personally I would still feel somewhat uncomfortable about doing that.
Reducing the gain of this phono stage to its low gain (54 db) setting, btw, apparently involves cutting a wire internally, so that wouldn’t seem to be a good way of performing the experiment.
Regards,
-- Al
|
Your welcome, Jim. Looking further at the Linto specs, though, based on the specified input loading of "150 Ohms in parallel with 4.7nF " (i.e., 4700 pf) it would seem clear that the 2M Black (which is a moving magnet design) is not the cartridge that is being used, and presumably what is being used is an LOMC. So let’s wait for further word from the OP on that.
Best regards,
-- Al
|
Jea48 12-2-2017
What are the chances the OP could connect the
Linn Linto Phono Preamp
directly to the inputs of the Pass amp without it playing too loud for a test. That would take the
Pass XP 20
out of the equation.
Hi Jim, In this case that's probably not a good idea, assuming that the "Ortofon Black" cartridge referred to in the OP is the 2M Black. That cartridge has a rated output under the standard test conditions of 5 mv. The low gain (54 db) setting of the phono stage would boost 5 mv to 2.5 volts, which is more than three times greater than the input voltage that would drive the XA30.8 to full power. Also, I see that the remote control provided with his Esoteric K01X SACD player provides volume control buttons, but although I could be wrong I suspect it is provided for purposes of adjusting the volume on their integrated amplifiers or other components, not on this player. Best regards, -- Al |
Kosst, my hypothesis is not predicated on the cables having changed in any way whatsoever. If it wasn’t clear, when I referred to the condition being "sufficiently marginal that minor aging effects or perhaps even a change in AC line voltage have put it over the edge," resulting in ringing or oscillation, I was referring to minor aging effects in the amplifier. Which in turn might have made the amplifier more prone to ringing or oscillation as a result of the heavy capacitive load.
Admittedly, though, the fact that both channels are exhibiting the problem does **somewhat** lessen the likelihood of my hypothesis accounting for the problem.
Also, Peter (Pbnaudio), thanks for your comment. As many here are aware, Peter is a highly experienced designer of well regarded audio electronics and speakers.
Regards,
-- Al
|
Kosst, thanks for the clarification about the multimeter measurements.
I also want to thank Jwpstayman for his very informative post about the OCOS cables. For one thing, it further reinforces suspicion that they have ultra-high capacitance. (I believe that when he referred to a "nobel network" he probably meant to say "Zobel network," which is something that is commonly used with ultra-high capacitance cables such as Goertz to minimize the capacitive nature of the cables as seen by the amp, that might otherwise cause ringing, oscillations, or even damage).
So based on his post a question for the OP would be if his OCOS cables have a "red" termination network, a "black" termination network, or neither.
Regards,
-- Al
|
Kosst_Amojan 11-30-2017
It’s free and harmless to connect a DMM to the amp outputs and determine if the bias is off.
Uberwaltz 11-30-2017
If Kosst reference to DMM means digital multi meter it is possible the op does not have a halfway decent one or even know exactly what he should be testing/looking for. I could use some clarification on that myself, Uberwaltz. I’m not sure how a multimeter measurement at the output terminals of an amp can determine if the bias is too low (or too high), the main possibility Kosst had cited being low bias. DC offset can be checked for in that manner, of course, but perhaps Kosst can clarify how such a measurement can determine if bias is too low. Best regards, -- Al |
I also agree, Todd, that the cables are not a particularly likely culprit. However, as Uberwaltz said just above, and as I said earlier, it is easy enough to perform a test that would rule the possibility in or out. And as I also said earlier there are very strong reasons to suspect that the OCOS cables have very high capacitance, and ... Almarg 11-27-2017
...a possibility [note that I said "possibility," not "probability"] that occurs to me is that its [the cable’s] capacitance might be causing an ultrasonic oscillation in your [the OP’s] amplifier. And perhaps the condition is sufficiently marginal that minor aging effects or perhaps even a change in AC line voltage have put it over the edge.
If so, the volume dependency you [the OP] mentioned might result from the speakers being stressed to a greater degree when an oscillation and a high volume audio signal are both present. So to be sure it’s clear, the **possibility** I suggested was not that the cables might be the culprit in themselves, but rather that the effects of their presumably very high capacitance on the amplifier **might** be. And, once again, it’s a possibility that is very easy to check. Also, a reason that this possibility has been given what Kosst characterizes as "first attention" is that we certainly want to be sure that it has been conclusively ruled out before other findings may lead the OP to incur the trouble, expense, and risk of sending his amp out for a repair that may prove to be unnecessary. So while Kosst finds himself "befuddled by the persistent recommendations that the least likely culprit, the speaker cables, be given first attention," I find myself befuddled by the objections that have been raised against that attention. Regards, -- Al |
Jim (Jea48), in my case there's no particular reason I haven't mentioned the preamp. It's certainly one of many possibilities that can't be ruled out at this point.
Also, +1 to all of the comments by Uberwaltz.
Best regards,
-- Al
|
Jea48 11-28-2017
Al,
Is it possible the P5 is the problem? ... When the OP is using the P5 for the front equipment could the P5, because of some internal problem, be causing the sound problem? I would think it’s unlikely, Jim, but I suppose it’s a possibility. For example, perhaps the MultiWave circuitry is misbehaving and doing funny things with the AC waveform, even when it is supposedly not being used. In any event it’s easy enough to find out, as you suggested. Also, another thing I would suggest that the OP do, if he already hasn’t, is to use the P5’s oscilloscope function to look at its incoming and outgoing AC waveforms. And see if either looks dramatically different than a sine wave. Best regards, -- Al |
Kosst, I assume that I was not included among those to whom your last comment was addressed, even though it mentioned cables. But to further clarify my comment about the OCOS cable (and Peter, thanks for the second): As you may be aware there are a few speaker cables which have ultra-high capacitance, such as Goertz and the old Polk Cobra cables. When used without a Zobel network, and especially when used with solid state amplifiers, those have been known to cause ringing and/or oscillations, and in some cases oscillations which have even resulted in severe damage to the amplifier. After doing some research I have not been able to find an indication of the capacitance per unit length of OCOS, but it is an unconventional coaxial design having an extremely low "characteristic impedance" of about 8 ohms. That suggests a strong possibility that its capacitance is very high. On the other hand, I would expect that the not especially extended 100 kHz bandwidth of the amp, and the relatively modest amount of feedback I believe it uses, lessen its susceptibility to that kind of effect. But it should be easy enough to rule this possibility in or out, perhaps even by using Home Depot or Radio Shack wire for purposes of the experiment, if the OP doesn’t have any other cables of suitable length on hand. Your suggestions about the amp are of course also good ones, IMO. Regards, -- Al |
Is the P5 set to output a pure sine wave, or is it set to one of the MultiWave choices? If the latter, which as I understand it flatten the peaks of the P5’s output waveform (in other words, the MultiWave modes intentionally distort the AC in certain ways), I would suggest that you see what happens with the pure sine wave mode.
Also, it would be interesting to know what the P5’s status screen shows for input and output voltages, and input and output distortion.
Good luck. Regards,
-- Al
|
I don’t know what the capacitance per unit length of OCOS speaker cable is, but given that your cable is fairly long and given also that OCOS is a somewhat unconventional design a possibility that occurs to me is that its capacitance might be causing an ultrasonic oscillation in your amplifier. And perhaps the condition is sufficiently marginal that minor aging effects or perhaps even a change in AC line voltage have put it over the edge.
If so, the volume dependency you mentioned might result from the speakers being stressed to a greater degree when an oscillation and a high volume audio signal are both present.
So I would suggest trying different speaker cables, whenever that may become practicable.
Good luck. Regards,
-- Al
|
