Hello,
I've got the same problem on UFX Mic input 10 (Mic inputs 8, 11 and 12 behave normally).
Loud hiss and crackling when input is open, no level change when switching to "Instrument".
Noise gets lower when dynamic mic (XLR) is plugged in (but still too much hiss to be usable).
Noise gets even lower when a condenser mic is plugged in (but stil very present).
No reduction of noise level when switching to "Instrument" and connecting an instrument with a TRS jack.
I had this problem episodically before, on and off, but at such low levels that I could easily get rid of it with the expander and forgot about it. The problem got suddenly so much worse that using the expander is not anymore a solution.
As noise level follows the level set in the channel settings in Total Mix, it seems the PGA2500 is performing like it should and it seems to point to a problem in the previous stage, specially as it depends on the connected mic.
I suspect a defect TL072, a bad solder or a bad capacitors in the input stage.
Am I correct, or could the PGA2500 still be the cause of this abnormal hiss/crackling?
Unit bought almost 6 years ago, no warranty anymore.
I have a concert next week, need these mic/instruments inputs and don't have time to return it.
I ordered both TL072 and PGA2500 provisionally at FARNELL yesterday, received them today and could replace them this weekend.
Could you please tell me, based on your experience with a problem that seems to be relatively common on those units, if a bad PGA2500 could be responsible or if the cause has to be entirely in the previous stage around the TL072?
This would help me tremendously.
Best regards,
Todor
