Antelope Orion stereo output gain issue

[benqbasic]

Hi All,

I have an Antelope Audio Orion Studio rev 2017 that I've recently taken out of storage. I'm experiencing a gain balance issue with the main stereo output. The right output has 8dB less gain than the left. It doesn't seem to be a software or digital problem since the output discrepancy fluctuates with volume adjustments. As I increase the output, the imbalance grows. I can see the output voltage is lower on the faulty channel.

Unfortunately, this unit is out of warranty, and I'd like to attempt to fix it myself first. Although I'm not very experienced with SMD, I want to pinpoint the issue and only replace the faulty components if possible. The main output utilizes a BB PCM1792. Each channel has two OP1662 opamps. Based on the datasheet, I assume it is just the V/I to filter circuit, this is followed by some transistors (balanced output?) into a relay to select A/B output.



Any assistance would be greatly appreciated. What should I be looking for. Sending the unit back to Antelope would be a costly endeavor as I'm located in New Zealand.

Thanks in advance!

 

[Khron]

Got an oscilloscope? Or would you dare MacGyver a makeshift probe, and poke around on that board, using the unit itself to view / monitor said signals?

If it were my unit, i'd reverse-engineer that entire output stage and see what's what, in order to get an idea what to expect at the various circuit nodes. No idea how feasible something like that might be, in your case, though...

 

[benqbasic]

No scope anymore, but i probably have a probe that could use with an audio interface and a software scope.
There is a secondary board that sits above this and which feed the DAC. I would also need to MacGyver up some jumpers as well or inject a signal post DAC. Tomorrow i will start measuring all the voltages at least.

 

[evil grill]

Aren't those outputs impedance balanced?

 

[Ike Zimbel]

Do you have a means of testing capacitors? I would look at the 47/35 electrolytics first. You might also get an indication of it being a bad cap (or not) by doing a frequency sweep. If it's down at LF but closer to normal at HF, could be a bad cap. And, I do not like the look of the lower solder joint on the cap above the upper 1662 on the right. One more thing, might be a relay failure so check that relay. None of the other parts in the picture (besides e-caps and relays) should be prone to failure from prolonged storage.