XLR Question

You won't see this one every day....

I've recently converted a listening room to dual use - listening and recording.  I'm trying to use the 2 channel system as a monitor for the recording studio.

The 2 channel pre-amp is an Onkyo 5508 pre-pro (stereo mode) which has a set of stereo xlr balanced inputs available.  So, I want to take the output of my PC audio interface (Pre Sonus  Audiobox) into the Onkyo.

The Audiobox allows the PC recording system to connect to a monitor via balanced 1/4 inch trs out (phone plug). I got a trs to xlr cable and it works perfectly into a pair of active m-audio studio monitors.  However, no signal is evident when I connect the same trs-xlr cable into the Onkyo

Other than a faulty input on the Onkyo, any idea what might cause the monitors to work but not the pre-pro?

thanks in advance
According to the manual:

Connecting a Balanced Audio Source

You can connect a balanced audio source to the AV controller’s BALANCE L/R INPUT jacks by using two XLR audio cables. To use the balanced input, you must assign it to an input selector (➔ 47). If you connect a mono source, use the BALANCE L INPUT jack and set the “Input Channel” setting to “Mono(L)” (➔ 47). The AV controller’s balanced INPUT jacks are wired as shown.

Pay attention to:   To use the balanced input, you must assign it to an input selector (➔ 47).

Looks like you need to assign that input?

Stupid question, but are you sure that assigned the XLR input to the source you are selecting?  Some of those fancy AVPs allow you to assign any physical input to a source.

I definitely assigned the balanced audio to the games input and selected games as my source for playback.  I probably should have noted that in my op
Just from a black box point of view it sounds like the Onkyo might not be working. Have you tried any other sources with it?
Hi Marty,

Just a guess, but perhaps the XLR inputs of the Onkyo are actually unbalanced, with XLR pin 3 (that would usually carry the inverted signal in a balanced signal pair) being grounded (i.e., connected to XLR pin 1 in the Onkyo). And perhaps the AudioBox device generates the non-inverted signal that ends up being provided via your adapter cable to XLR pin 2 of the Onkyo by putting its inverted output signal (that ends up being applied to XLR pin 3 on the Onkyo) through an inverter stage (such as an op amp configured as an inverter).

In that scenario the result would be exactly what you’ve found.

Also, if my speculation is correct, and given also the low 51 ohm output impedance of some or all of the AudioBox models, shorting the signal it provides on XLR pin 3 to ground might not be healthy for it if done on a prolonged basis.

Best regards,
-- Al

Also, Marty, an inexpensive potential solution you may want to consider would be an ART DTI Transformer/Isolator ($60 plus appropriate cabling). Manufacturer’s description here.

I’ve used one for non-critical voice recording applications, and for those purposes, at least, it seems to work well.

Best regards,
-- Al

Many thanks to all


good diagnostic idea.  I'll have to dig up a balanced source and some xlr to xlr cables, but I'll try that first


if that fails, I'll try the transformer
Page 17 has the pin outs of the Onkyo XLR input:


Thanks, Mofi.  I had looked at that before posting, though, and it doesn't make clear how the input circuit treats what it describes as the "cold" input on XLR pin 3.

Best regards,
-- Al

I have one further question re: the Art DTI.  Have you used "one in/two out".  In my case, that would be balanced via trs out from the Audiobox into the DTI and unbalanced via RCA to the Onkyo simultaneously with balanced via either trs or XLR (they accept both connections) to the M-Audio active monitors.

There's enough utility in that arrangement (if it works) to justify the purchase under any circumstance.

Thanks again
the Onkyo 5508 you must go into the menu and turn them on or select them. Its in the sub menu. then they work fine. I own the 5508 scroll to the XLR selection elect then scroll left or right and select on
68 Pete

Thanks, but - as noted in my 2nd post - I've already done that. Still no luck.  But thanks for the input, I appreciate it.
Hi Marty,

No, I’ve never tried a one in/two out application of the DTI. My application just involved converting two channels of balanced line-level audio to unbalanced, in a relatively non-critical application as I said.

I would expect that what you are proposing would function, but I’m not sure how well. For one thing you would in effect be converting the balanced inputs of the active monitors to unbalanced, since one end of the secondary winding of the DTI’s transformer for each channel would be grounded by the unbalanced input of the Onkyo. And I suppose hum issues might be another possible consequence. But if good results from that arrangement would be helpful, as you said, it may be worth gambling $60 to find out :-)

Best regards,
-- Al

Thanks so much Al.  Worst case, I'll just run the trs cable into the desktop monitors.  I can always just unplug them and replug them in the DTI and then on into the Onkyo as/when needed.
martykl            I  would try it again, I had the same problem when hooking up Oppo player to my 5508. I do not use the unit any more since i dismantled my home theater. But i remember after selecting XLR you must scroll to the right or left of it (not up down) and select i think it was balance. Good luck Pete
Do you have a PlayStation/Xbox or Game console optical out still connected to the OPT1 or to an HDMI input jack? What I am driving at is if the Digital Input selector for GAME on the pre is set to something that has an active digital connection?

I ask because the default for Onkyo is to give priority to a digital signal and ignore the analog input if a digital input is detected....

The only other input into the Onkyo is a Rhea phono amp into the rca input labeled "Aux".   This is strictly a two input system - you can listen to either my extensive collection of LPs or PC recordings of me warbling away on drums, bass, acoustic and electric guitar, keys and vox.  

You could describe me as sort of like Prince, except with little to no natural talent.