FX Loop massive level drop and sound degradation

When I use FX Loop on Quad Cortex, I get a massive 18dB drop in volume at the Return jack. When I boost the volume at Return jack to match the level on the Send jack, there is obvious sound degradation compared to a sound without FX loop.

I tested the sound degradation with recording a riff with the same preset twice, but on the second time there was FX loop active at the end of the chain and level matched with the 18dB boost. I simply ran a short mono patch cable from Send 1 to Return 1.

Here is the clip:

Does anyone else experience a massive level drop at FX loop? I thought it is supposed to be unity gain when no levels are touched.

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This is not my experience at all - have you tried more than one patch cable? Can you post your preset? I use it all the time and have never had this problem

Maybe also try the same experiment, you did, but with send 2 and return 2 and compare.
And check your levels in the I/O pane as well as in the S/R block.

I thought I’d read somewhere that the return needs a boost to get to unity gain. I vaguely recall someone suggesting +6dB. Anyone else find this to be the case?

Sorry that I can’t help here, but just chiming in with my experience that with everything at 0db on the I/O screen and the FX loop blocks themselves, I get a noticeable INCREASE in volume when enabled unless I manually reduce the send levels by ear.

It would be nice if the manual went over this stuff so we could know what behaviour is intended.

It‘s mentioned here:

If none of these suggestions help, please contact support@neuraldsp.com to troubleshoot.

Guys I realized (mostly) what was wrong. In my preset I didn’t use FX Loop block but used an output block of a row to go to Send 1 and then another row to receive signal from Return 1, and a patch cable to connect the send and return (routing in QC is still very limited, hope they upgrade this stuff). This is when I get the behaviour I described in my original post. However, when I use FX Loop blocks in the preset, there is no volume drop nor sound degradation.

This still leaves a question why this behaviour happened, and the sound degradation also. I will experiment more when I come home from gigs next week, will update then. I now have questions whether return jacks have some pad on them when using them without FX loop blocks. Then what will happen if I plug a guitar straight into return 1 or 2 etc? Anyway, I will test this and update.

was the big volume wheel all the way up? sending it out the row might be affected by overall level

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I think that is it! The volume wheel was nowhere near all the way up. And I now checked that the volume wheel doesn’t affect the reading on the output meters either, which is why the return 1 showed way less signal than send 1 when they should be equal. I think this mystery is solved now.

And maybe the audio degrading that I heard was simply because 18db attenuating and boosting back up, and in between the attenuated signal was being converted to analog and back to digital due to the physical fx loop. I will still test this routing later with volume wheel way up and see if it then sounds normal to me.

I normally run digital effects in the loops in stereo and it works fine … mostly struggling to contain the volume at return
However this weekend tried to run my new fuzz pedal in a mono loop
Gave up in the end … signal degradation was noticeable sound quality reduction was noticeable … ended up putting it back in the front … I think the quad takes gain pedals in the front inputs really well
The effects loop however has been a juggling act since day one !
I think it is another area that neural really need to look at … in my opinion it is a fair way from optimal at the moment … when I compare it to the effects loop on the hx stomp which just seems to work within the realms of its own audio quality without fault .
… I was wondering if more input level options on the loops might be a solution .
Line and instrument level control .
Reading the comments on this feed it is such a mixed bag of results .

Not disputing that there may be improvements/enhancements to be made for the effects loop but wanted to point out that fuzz pedals in particular are notorious for having lower input impedances than many other pedals. The typical 1M ohm setting is often not optimal for them. You will frequently see it recommended that fuzz pedals will sound best as the first pedal in your signal chain (as you observed). You might also try changing the QC’s impedance setting.

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