Phasing problem - advice sought

May 6, 2010 12:10 PM

Need a steer from the more technically adept amongst the crew. If I use peripherals with my machine (Yamaha AW2400) I often get a horrible tinny sound - difficult to describe in words, but I think it's some kind of phasing problem. The signal route is: a feed out of the DAW, into the box (Lexicon reverb unit, for instance), then back into the input channels of the DAW, control via "Aux" faders. So....the "treated" signal is being mixed back in with the original, and I think this is where the problem lies. I can't lose the original signal without also losing the "treated" one. The DAW has a phase reverse facility that I've used, but I still get at least a touch of that horrible metallic thinned-out sound. What the fuck is going on? And any ideas about a cure?
posted by MajorDundee (7 comments total)

I'd need to here an example or get more info to be sure. I could be way off.

Am I correct in reading that you are monitoring the effect on the same faders as the previously recorded tracks? If no you can skip the rest of this. If yes you might be creating a feedback loop. That can sound like a flanger without modulation in certain situations. I would describe that as a pretty horrible mettalic sound.

In this case all you need to do is route the outputs to unused tracks. If you don't have free tracks you may need to do some bouncing down to free some up.
posted by dagosto at 1:50 PM on May 6, 2010


When you go in and/or out of a digital recorder (computer or standalone), you get a slight delay from the converters. If you then mix this with the original sound, you will get the nasty sound you describe.

Make sure the reverb unit is set to 100% wet. The reverb itself is decorrelated, hence no problem; it's the copy of the dry signal that's the issue.

If the effect is something that's correlated (say, distortion), but you want a mix of unprocessed and processed signals, you need to do the mix in the unit, and not monitor the original in your DAW. Or you can record the processed signal and skootch it back to line up with the original.
posted by doubtfulpalace at 2:00 PM on May 6, 2010


This may be an impedance problem. Is the output level at +4? That is what it should be. Is the output of the effects unit also +4? It may be -10 and the input of the yamaha is set to +4 or vise-versa. Ideally they should both be +4, but if the reverb is set to input +4 and output -10, it should work as well, as long as the yamaha knows what level signal to expect. This is the only thing I can think of without hearing a sample.

Also you can test the latency and phase of your external audio chain by sending signal out and hooking it directly to another input and recording it to a new track. If you can look at the original and recorded waveforms (a click or synth tom works best for this) and compare them, you can determine how much latency you have and if the return signal is in phase.
posted by chillmost at 2:10 PM on May 6, 2010


Actually, dagosto's idea might be the likely culprit now that I think about it.


Is the signal traveling digitally? If so, make sure the sampling rate and bit rate match.
posted by chillmost at 2:12 PM on May 6, 2010


It sounds like the Outboard gear is not being Delay Compensated correctly adn there is a lag which is causeing Phasing issues. you need to delay compensate the internal track.
posted by mary8nne at 4:50 AM on May 7, 2010


I think doubtfulpalace has got it: lag combined with some dry signal coming back with the reverb. Set it to 100% wet and it should go away.
posted by uncleozzy at 5:43 AM on May 7, 2010


Thanks very much for the advice guys - I'll try all the suggestions and see what happens.
posted by MajorDundee at 11:30 AM on May 7, 2010


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