OK, some background on what I'm trying to do and the results with the
Mutec MC4.
The objective for all of this was to be able to do a hybrid digital dry/analog wet re-amp with my audio interface being the center of everything. Basically take the analog outputs and go into the audio interface (in this case a MOTU 828MKIII Hybrid) and take the input of the AxeFXII routed through the dry and send that into the MOTU via digital so that it would be pristine. This isn't that far from using USB on the AxeFXII for re-amping, but where it is different is that I can use my default audio interface with a ton of other inputs and monitoring options and not have to change a lot of settings in my DAW or even worse rewire crap in some cases.
The specific problems that crop up have to deal with sample rates (being locked to 48kHz because of the AxeFXII) and the master/slave configuration when going from first take to re-amp take. In a nutshell the source has to be the master clock source so when recording the first take the AxeFXII would be the master device. When re-amping the AxeFXII is no longer the source and is a slave device; you have to change the audio interface to master at this point which is a PITA. Most times it requires restarting your DAW. If you don't have the master/slave configuration right you get jitter, pops or dropout.
The MC4 is a multifunction device that is designed to work with two asynchronous devices and keep them sync'd up. It does sample rate conversions as well, but what I was really excited about was something called X-SRC which is to take two different devices with two different sample rates and clock sources and send the signal to and from each other while converting the sample rate to what was needed for the source. Basically I could keep the AxeFXII at 48kHz (because I have no choice), set the MOTU to 96kHz and send any signal back and forth to each other, in sync at any time.
This is a picture of what I horribly described above:
This didn't work.
Apparently once the AxeFXII is set to receive a digital signal there is no clock output coming out of the AES port and the MC4 needs a reference to lock it's PLL circuit to.
But the MC4 has about a bazillion other options and configurations. One that does appear to do what I was wanting, absolutely flawlessly is BI-DIR/SRC using the MOTU's word clock as the master clock source. I can record a wet and dry track at 96kHz from the AxeFXII and then just change the audio source to AES digital on the AxeFXII and re-amp. One menu change and I'm done. 96kHz is not a problem at all.
The only issue I have found is that there is a bit of latency between the original take and the re-amp'd one which is to be expected. I'm working out a track delay for the dry track (actually applying a negative delay) to compensate. I haven't gotten that far yet and not sure if the precision of that setting will let me get it because it is extremely low (I'm guessing less than 5ms) and to be honest it's just easier to zoom in on the tracks and align them manually by nudging it.
I've been screwing with this issue since the Ultra. This is the first time that I have gotten absolutely noiseless, hum free, non-jittery re-amping WITHOUT using the AxeFXII's own USB audio interface.
One side note here. I wanted to buy the MC6 because it is made for AES which the AxeFXII has, but the MOTU is SPDIF. The MC4 has extremely limited SPDIF functions where the MC6 appears to do more with it. However the MC4 has ADAT/Toslink which the MOTU has as well. I've never messed with ADAT before, but I can tell you right now that I am more than impressed with it. One other note here; the MC4 has a 25DB connector with two AES inputs on it. I went ahead and changed the second input from female to male XLR and rewired the connector to the right pins for AES out. I could have bought or made a new cable from scratch, but this has everything I needed and it was faster for me.
