What are the AD/DA converters inside Quad Cortex ? why no AES/EBU output?

Hello, asking here since i couldn’t find the info just no where else:

i’ve heard it can do +48v phantom for mics; so you can use it as some sort of pre-amp to record acoustic guitar (and human voice, also why not?)

Then this question comes up to the mind:

What are the AD/DA converters that you guys have put inside the Quad Cortex ?

and are they of the same level or any comparable to the quality of AD/DA converters that are in audio interfaces such as RME, Apogee, PrismAudio, Antelope, Universal Audio Apollo etc ?

and why you couldn’t fit an AES/EBU output?

i’m really curious to hear about this before making the step.

thanks

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Up ! Wondering the same, I have the quad and for me the converters sounds better than my Apollo solo but it would be nice to know wich one are inside.

I’ve always found it strange that there are no details available on this since release. If they’re really good, that would definitely be a great marketing point. Frustrating not to know, that’s a fairly important spec

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HI, not information on the AD/DA but it might give some hints about IO: Quad Cortex Customer Success Story | Analog Devices

Regards,
/Michael

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The SRU seams to have SPDIF, but it is not used for some reason.

I return on this topic because today i have done a try :
Guitar— qc UNLOADED-- Real amp
Guitar—hx effects UNLOADED—Real amp

Hx sounds Better…what a fuck?!

Qc introduces a lower quality sound in real amp.

Also hx is more near in sound to the Guitar directly in the amp.

Then i have used only overdrives (guitar—digital unit with the same od—real amp)…hx really Better.

But IN THE BOX, i prefer QC over HX.

but this try has confused me…ouch!!!

I too have noticed a difference between the sound quality of the analog outputs (all of them) and the USB outputs. The analog outputs sound more dull, lifeless and less sparkly. The usb outputs sound clear and balanced. I used a A/B switch to monitor on the same FRFR. The A channel had the analog output of the QC and the B channel had the analog output of my interface (with the QC being fed into it via USB). The difference is marked. Like the digital to analog converters in the QC are lacking a little bit. I have a friend that has a QC too, I will try to test his to see if I find the same thing with his unit.

How it sounds is a useful guide, but it can be a bit subjective. Are there any other indicators in terms of dB levels or THD+N or anything you can give it a bit more objective? It could just be your particular setup or unit. There’s too little information to generalize from anecdotal information.

@idimata Agreed, not implying that all QCs sound like this. Just relating to what the OG said about him liking the sound in the box better. This is something I had noticed even before doing the A/B test. Today I went further and took some readings using sine sweeps (no blocks on the grid). The analog outputs show a 2-3dB roll off starting at 3K vs a dead straight response from the USB output in the box AND also measured from the analog output of an Apollo Twin X. This would align with the perceived difference in sparkle I mentioned. I will test my friend’s unit to see if it behaves the same but I’m guessing it’s my unit and this could still be within Neural DSPs accepted range. Cheers.

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I̶ ̶h̶a̶d̶ ̶a̶c̶t̶u̶a̶l̶l̶y̶ ̶n̶o̶t̶i̶c̶e̶d̶ ̶t̶h̶i̶s̶,̶ ̶a̶f̶t̶e̶r̶ ̶I̶ ̶t̶e̶m̶p̶o̶r̶a̶r̶i̶l̶y̶ ̶r̶a̶n̶ ̶i̶t̶ ̶i̶n̶t̶o̶ ̶m̶y̶ ̶F̶i̶r̶e̶f̶a̶c̶e̶ ̶b̶e̶c̶a̶u̶s̶e̶ ̶I̶’̶d̶ ̶r̶u̶n̶ ̶o̶u̶t̶ ̶o̶f̶ ̶U̶S̶B̶ ̶p̶o̶r̶t̶s̶.̶

̶I̶ ̶a̶s̶s̶u̶m̶e̶d̶ ̶i̶t̶ ̶w̶a̶s̶ ̶a̶ ̶p̶r̶o̶b̶l̶e̶m̶ ̶w̶i̶t̶h̶ ̶t̶h̶e̶ ̶i̶n̶t̶e̶r̶f̶a̶c̶e̶,̶ ̶b̶u̶t̶ ̶t̶h̶i̶n̶k̶i̶n̶g̶ ̶a̶b̶o̶u̶t̶ ̶i̶t̶,̶ ̶i̶t̶’̶s̶ ̶q̶u̶i̶t̶e̶ ̶u̶n̶l̶i̶k̶e̶l̶y̶ ̶t̶h̶a̶t̶ ̶t̶h̶e̶ ̶i̶n̶p̶u̶t̶s̶ ̶o̶n̶ ̶a̶n̶ ̶R̶M̶E̶ ̶i̶n̶t̶e̶r̶f̶a̶c̶e̶ ̶w̶i̶l̶l̶ ̶b̶e̶ ̶a̶n̶y̶t̶h̶i̶n̶g̶ ̶o̶t̶h̶e̶r̶ ̶t̶h̶a̶n̶ ̶f̶l̶a̶w̶l̶e̶s̶s̶.̶.̶.̶

I’ll try to test it this weekend if I remember.

Edit; See below, sound difference was a Logic issue, not a QC issue.

In my case it was the attenuation of QC passing the line with all blocks off. Restoring the level of signal with gain block…the difference Is similar as other units…line6, Headrush…etc etc.

I think this is true. The outputs and the converters on the QC aren’t as good as using a decent interface has been my experience. I have a monitor controller so I can switch between hearing the DAW outputs as either the QC or my other interface and the interface is definitely brighter (sounds better). I’m also on the fence as to how good the signal is on the way in (recording the signal) vs other interfaces. In my opinion, the QC is first and foremost a modeller and I just doubt it could rival high class interfaces which are built solely for that task and it’s the easiest thing to skimp on. What would be a good test is testing the DI from the QC vs an Apollo and/or other middle of the road interfaces.

OK, so no, the QC is an excellent interface. Something in my big practice logic session is borked, makes tracks set to stereo sound muddy and awful, but set to surround (even though still stereo) sound significantly better.

I’ve just done a round of testing on a new session;

Using QC over USB, recorded a dry track, and a QC USB direct of a preset as a benchmark. Then:

DI from RME out 5 > QC in 1 … (preset) … QC out 3/4 > RME 3/4

DI from RME out 5 > QC in 1 … (preset) … QC out 1/2 > RME 3/4 (using XLR to 1/4" adapters on the QC outs)

All identical to the original direct USB recording.

Then I wanted to test the DI signal, so looped that original dry DI through the RME to re-record, and to the QC to re-record:

RME Out 5 > RME in 3

RME Out 5 > QC in 1 (and recorded dry USB track again)

Again, both of these sound identical. Using option + click solo to quickly flick between samples, I cannot hear a difference between any of the preset recordings, or the 2 DI tracks. Listening using Hifiman Arya’s, all playing out of the RME fireface.

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Are the waveforms visibly identical? Or is there a difference?

Mostly the same, subtle differences between certain setups if you pixel peep at max zoom, but that might be down to me being an idiot.

Note - I did have to add +4dB to the XLR outs. I only did that by ear, might have needed a touch more, not sure if that was to do with my XLR > 1/4" adapters…

Everyone should reach out to Julian Krause and request a QC test. I emailed him ages ago, seeing if he’d mind doing a review of the QC as an interface, but I never heard back, and it hasn’t happened yet. Perhaps if he gets a few more requests from people he’ll consider it.

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Great idea to contact Julian Krause! His channel seems focused on 2-channel audio interfaces, but perhaps he’ll consider it

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I would be very interested in what he says. From what I can gather from my research on DIs and interfaces is that there are two main criteria. 1 is the dynamic range and 2 are the preamps imparting a tone/colour on the sound. Even my Audient interface has different preamps for the High-Z and the Mic inputs so the DIs sound different depending on which you use. Maybe not massively noticeable but if you’re chasing the best you can get and you have the options I’d rather be using the best option. Converters aren’t an issue these days and I think some people get mixed up between converters and preamps. Also it’s great you did your tests but I think something a bit more scientific is definitely warranted considering no one even knows what the QC uses.

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