cd player - xlr output buzzing

Outstanding! I'll let you know when I can come down for the Sam Adams.

-- Al :)

UPDATE

After all the discussion, had a custom cable made with pin 3 unconnected.

Works like magic.

Thanks for all the help ppls.

Bleoberis and Almarg, I was in fact thinking that the **output** of the CD player is where this pin 3 to pin 1 thing might have to happen. I understand Almarg's concerns but I have yet to see any line level electronics that could be damaged by this (we do this to our stuff all the time).

Something else you might look into is lifting the ground of the CDP's power cord. It might be as simple as a ground loop.

Good suggestion by Dave about the Jensen transformers. A number of Audiogon members have reported using them, with no perceivable sonic side-effects.

There is an excellent paper at Jensen's site about interfacing balanced and unbalanced equipment:

http://www.jensen-transformers.com/an/an003.pdf

Note that among the various approaches it describes, the adapter cable approach is shown for rca to xlr input, but NOT for xlr output to rca input. Although it certainly can be done sometimes, if the output impedance and drive capability of the output circuit permits, or if pin 3 is left open.

Here is a lower priced alternative to the Jensen transformers:

http://www.bhphotovideo.com/c/product/381596-REG/ART_DTI_DTI_Transformer_Isolator.html

http://www.artproaudio.com/downloads/specsheet/dti.pdf

I've used this device in non-critical voice recording applications, and in that application it has seemed perfectly transparent sonically.

I'm inclined to think that the problem is not due to noise floor sensitivity, because it seems to be inversely related to volume control setting, it is intermittent, and it is not present on the rca output (where the output level is only 6db lower than on the xlr output).

Good luck!
-- Al

nifty device!!

hmm good question -- how can one test for noise floor interference?

I wonder if one of these XLR to RCAwould help

You should be able to find less expensive models by other Mfgers if you Google around

I also noticed that your CD player's output voltage on the XLRs is 4 Volts and that your preamps input voltage is only 215 MV ... could it be possible that you are picking up some of the noise floor from the CD player because of it's high output relative to the preamps very low input sensitivity ?????????

Sam Adams it is - the cherry flavoured one. We can get it here in Australia!

Just book your flights and I'll chuck a prawn on the BBQ

I suspect that Atmasphere was thinking xlr input when he wrote his post, rather than xlr output.

Heineken or Samuel Adams would be great as far as I'm concerned :)

-- Al

haha we have come full circle (kind of) in that this is the opposite of what Atmasphere first posted!

The key is then whether pin 3 is left floating or not?

I just picked up some of these;
http://www.amazon.com/Hosa-GXM-133-Female-Male-Adaptor/dp/B000068O4D

I know for certain that these have pin 3 tied to pin 1, thus, if the buzzing continues tonight when I test it, I'll have a cable made leaving pin 3 floating.

If that does not work, then I'll have an XLR->RCA yard sale and you are all invite. Beer is on me.

Yes, splitting the rca is perfectly safe, and the very low output impedance of the cdp will mean that any sonic effects of having two loads and two cables attached to each of the rca outputs should be negligible.

Ground loop issues might still be a possibility, along the lines of what Dave suggested. But if need be those could be addressed with cheater plugs, or connecting to different ac outlets, or isolation transformers or other measures that are commonly used to address ground loop problems.

Re your last question, if my theory is correct, then yes the buzzing would remain if you continued to use the adapter cable. It is conceivable, though, that it might be avoided with a specially constructed cable that left pin 3 unconnected.

Good luck!
-- Al

ahh yes thanks - understand now.

presumably it is safer to simply split the RCA signal?

Even if the manufacturer were to confirm it is okay to ground xlr pin 3, the buzzing would remain nevertheless?

Thanks Al - the difficulty I'm having in finding any consistency to testing the problem is that when it is connected to the preamp, the buzzing is only at low volumes and sometimes even disappears after a minute or two.

When I use the exact same connection/cable to a Vincent KHV-1 headphone amp, there is no buzzing detectable at all. This would indicate that the cable is possibly fine, but there is something the preamp is disagreeing with?

I can't explain that with any kind of certainty, but realize that when the adapter cable is in place you are most likely connecting one of the two outputs of the driver stage in the cdp (the output which drives xlr pin 3) to the chassis of both the cdp and the component to which it is connected (the preamp or headphone amp). That will expose both the signal return current flowing through the cable, and the output driver device, to noise voltages that may exist on or between the two chassis, as a result of leakage paths between ac hot or neutral and the chassis, and/or as a result of the fact that chassis and ac safety ground are common.

Those noise voltages would figure to be different between the headphone amp and the preamp.

And all of this will be happening while the output driver device is most probably being forced to supply more current than it is designed to supply.

In any event, I would not operate the cdp with xlr pin 3 grounded without first receiving assurances from the manufacturer that that will not cause improper operation, and that it will not cause damage or degraded long-term reliability.

Regards,
-- Al

Hi Dave - thanks, too, but tried disconnecting everything except the cd player, preamp and speakers. Used the RCA output from the cd player, no probs. Used the XLR output, same issue. It seems like the preamp can't handly the XLR output of the cdp, whereas my headphone amp can. A pity because the XLR output of the cdp actually sounds better than the rca output....

"there is buzzing and harmonics in the speaker output at low volumes."

"It is okay at higher volumes."

It sounds a little like a ground loop and this may be the smoking gun

"The only reason I don't use the RCA output is that it runs directly to another amp/system and the RCA cable is far longer than the XLR->RCA cable.

If the other >>"amp system"<< is in another room ... it is probably plugged into an outlet that is fed from the opposite side BUS in your main panel box that your main system's outlet is fed from

Main system and preamp plugged into outlet fed from BUS A ... other amp system in the other room plugged into outlet fed from BUS B ...this will create a ground loop

Try disconnecting the RCAs that feed the "other system" in the other room from your preamp and see if the noise goes away

Thanks Al - the difficulty I'm having in finding any consistency to testing the problem is that when it is connected to the preamp, the buzzing is only at low volumes and sometimes even disappears after a minute or two.

When I use the exact same connection/cable to a Vincent KHV-1 headphone amp, there is no buzzing detectable at all. This would indicate that the cable is possibly fine, but there is something the preamp is disagreeing with?

My guess would be that your adapter cable already shorts pin 3 to pin 1 (most xlr-to-rca adapter cables and adapters do that). And I would further guess that the reason for the problem is that the cd player, which has a low 22 ohm output impedance, cannot tolerate having its "cold" output signal (xlr pin 3) shorted to ground, with the only current limiting being provided by that output impedance.

Using an adapter plus an rca-to-rca cable would be no different, electrically.

I would suggest asking the cdp manufacturer if the player can tolerate having xlr pin 3 shorted to ground.

Shorting one side of a balanced input to ground via an adapter would not be a problem, but I would avoid doing so with any output unless the manufacturer confirms that it is ok, and/or the output impedance is known to be considerably higher.

To answer the question in your preceding post, the wiring configuration could be checked with a multimeter or ohmmeter.

Regards,
-- Al

hmm how do i do that? it is an actual 1m long cable, do i need to open it up somehow?

Check and see how the adaptor is wired. Sometimes if pin 3 is left floating, the result is a buzz. So the adaptor should have pin 2 tied to the center pin of the RCA, pin 1 of the XLR tied to the RCA ground, and pin 3 of the XLR tied to pin 1 of the XLR. That should sort it out.