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ADC/DAC knowledgeable bods required ;)

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ADC/DAC knowledgeable bods required ;)

Postby russianpolecat » Sun Feb 15, 2015 3:29 pm

Hello. So, I purchased a new ADC (PCM4222) and a new DAC (PCM1794) last yr from Ross Martin Audio in the states -

http://rossmartinaudio.com/

I haven't got them yet, there is often quite a waiting time because they are a tiny operation (which I'm fine with, I understood that before I ordered them). I ordered them as an affordable upgrade on my RME Babyface. My question is this really, how would I go about connecting these up? It sounds like an obvious question, but I'm not that technically minded in these areas, and if you look on the website there is infos about clocks/filters and stuff -

"PCM4222 ADC Analog To Digital Converter. 32, 44.1,48, 88.2, 96, and 192 Sample Rates Bit Depth 24,20,18,16 Word Clock Out Master Clock Out/In Selectable Filter Response Led VU Meters With Overflow Indicators. LME49724 op amps AES, SPDIF COAX and Optical Outs. +4Db +-18Dbfs Balanced XLR and 1/4” TRS Inputs".

I've started to read up on things, and it would seem best to set the ADC as the master clock and then connect via SPDIF to my Babyface, and then back out via SPDIF to the DAC. Would that be correct? If so, I'm thinking the Babyface becomes redundant and I could replace it with something much cheaper no?

Thanks in advance,

Chris
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Re: ADC/DAC knowledgeable bods required ;)

Postby mathias » Sun Feb 15, 2015 7:05 pm

some thoughts to your question from my side:

it is always best nowadays to use the internal clock of an ADC/DAC (speaking of quality build products).in the past there have been bad clocks that would have benefitted from an external, more accurate clock. but that's mostly irrelevant now.
set the babyface to sync via spdif, if that's your prefered connection. i would use optical, but coax is also perfectly working.
even when the clocksignal is a little weak (which could happen with very long coax-cables or bad/dirty optical connection-points) the rme interface is able to extract a clean clock in most situations and sync perfectly.
once the signal is converted to digital, there are no more worries about jitter. you only may loose sync between the devices and that is pretty obvious to hear normally. i wouldn't sell the babyface for something cheaper. rme has very good drivers, you've got digicheck, totalmix and a very stable syncing behaviour. i doubt you will get something of similar quality/features for less money.

from your description i read, that you have seperate devices for adc and dac. so they have both their own internal clock.
to get the most out of this configuration, it would be best to let every unit use its own clock for conversion. that would mean to use two different independent digital interfaces to the computer.
on their website i see that they offer the DAC with integrated usb connection for a very low price (like 50 $ or so). maybe you can still change to that option.

this way every converter could run on its own clock. additionally you could play out a 24 bit 96khz playback and record back via 24bit 44,1khz.
this a common technique to avoid internal src, which is regarded to give high quality results.

if you don't go that route, i would sync the DAC directly to the ADC via wordclock, short cable.
system 1: windows 8 32 bit - samplitude prox, tracktion6, reaper
system 2: mac osx yosemite - reaper(32+64bit), tracktion6(32+64bit)

both systems on: macbook pro (late 2009), core 2 duo 3,06 ghz, 4 gb ram, graphic: nvidia geforce 9600M GT 512 MB
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Re: ADC/DAC knowledgeable bods required ;)

Postby mathias » Sun Feb 15, 2015 7:23 pm

before i forget:
check the available drivers for the usb option. for rerecording with a different samplerate a recording program different from the one playing back would be necessary.
system 1: windows 8 32 bit - samplitude prox, tracktion6, reaper
system 2: mac osx yosemite - reaper(32+64bit), tracktion6(32+64bit)

both systems on: macbook pro (late 2009), core 2 duo 3,06 ghz, 4 gb ram, graphic: nvidia geforce 9600M GT 512 MB
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Re: ADC/DAC knowledgeable bods required ;)

Postby russianpolecat » Sun Feb 15, 2015 8:28 pm

Hi Mathias, much thanks for your advice. You seem to be suggesting that the ADC - Babyface element is quite straightforward (as in if this was the extent of my setup it would work fine), and that potentially issues are most likely to be with Babyface/DAC because of the added piece of gear? As in preamp/ADC/Babyface/DAC/speakers in the round with clock issues for the DAC in this setup? Did I read that right? I'm not sure about the option for the DAC to have a USB, I hadn't looked into that. If there are potential issues perhaps one option would be to use the Babyface for monitoring while recording, and then add sync up the DAC to the Babyface later on for mixing (I only record a max of two trks at a time - vocals/acoustic or electric guitar etc. so wouldn't be too much of a hassle if quality is overall improved). The only thing there though is I wouldn't be able to do the analogue summing thing which I did think might be a good idea.
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Re: ADC/DAC knowledgeable bods required ;)

Postby mathias » Sun Feb 15, 2015 9:21 pm

no i didn't mean, that there will be issues, when using both at the same time while the adc is the clockmaster. it will work correctly in that setup.

you would have to test for yourself if it makes a difference soundwise, when the DAC is clocked from the ADC or uses its internal clock. it probably won't make a big difference, but check yourself (blindtest!).
for mixing, when you don't need the inputs anymore, i would definitely change to the DACs internal clock.
and sure, you can also use the babyface for monitoring. it has very good converters also.

additionally i was proposing, that with those two devices and two independent digital inputs to the computer, you have the option to avoid src inside the computer and do the downsampling via roundtrip, which is a highquality option with good converters.

how would you play out channels for analog summing? do you have another multichannel-converter?
system 1: windows 8 32 bit - samplitude prox, tracktion6, reaper
system 2: mac osx yosemite - reaper(32+64bit), tracktion6(32+64bit)

both systems on: macbook pro (late 2009), core 2 duo 3,06 ghz, 4 gb ram, graphic: nvidia geforce 9600M GT 512 MB
mathias
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Re: ADC/DAC knowledgeable bods required ;)

Postby russianpolecat » Mon Feb 16, 2015 11:35 am

Hi Mathias, I wasn't thinking of a multi buss setup in relation to analogue summing, it was just an idea for the master fader through a preamp or something like that. I haven't looked into in depth. Can I ask about the filters - these seem to be related to aliasing? Should they always be on?

Chris
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Re: ADC/DAC knowledgeable bods required ;)

Postby mathias » Mon Feb 16, 2015 9:01 pm

what i understand about the filterswitch on these units is, that it changes the type of the decimationfilter used in the conversion.
one seems optimised for linear phase, the other for less groupdelay.
a good converter has always (or should at least) a decimationfilter with low aliasing, so this is just an option that suits different tastes. in which circumstances one or the other may be preferable is probably a matter of hearing tests, or you rely on the expertise of others.
you may ask the company directly, for info on that. they have built it that way and will sure give you some guidance how to use it.
system 1: windows 8 32 bit - samplitude prox, tracktion6, reaper
system 2: mac osx yosemite - reaper(32+64bit), tracktion6(32+64bit)

both systems on: macbook pro (late 2009), core 2 duo 3,06 ghz, 4 gb ram, graphic: nvidia geforce 9600M GT 512 MB
mathias
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Re: ADC/DAC knowledgeable bods required ;)

Postby russianpolecat » Tue Feb 17, 2015 12:03 pm

Thanks Mathias.
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