wadiman Posted July 21, 2013 Posted July 21, 2013 Hi guys - Have just got myself an apogee duet which i'll be using as a high quality A/D converter to rip vinyl. I'll be connecting the output from my phono preamp (rca) to the Apogee's input. The Apogee accepts either XLR inputs but no rca. What cable arrangement would you use for this application: Male RCA to Male RCA (good quality) with an RCA to XLR adaptor (like this http://www.ebay.com.au/itm/BESPECO-Adapter-connector-from-XLR-male-plug-to-RCA-female-socket-SLAD315-/380678681693?pt=US_Cables_Snakes_Interconnects&hash=item58a237b45d&_uhb=1) Or RCA to XLR cable (get it made up with Mogami 2549 or something similar - eg http://www.proaudiola.com/product-p/1-m2964-rca-ts-1.htm) Opinions appreciated!
coppinger Posted July 21, 2013 Posted July 21, 2013 I have xlr/rca connections on a DCX2496 crossover,and I must say that I prefer the cable option. The adapter you link to looks of good quality, but they "bulk out" the connection somewhat.
Krispy Audio Posted July 21, 2013 Posted July 21, 2013 Yeah definitely a single cable, you should avoid adapters at all cost. They're great to test things but otherwise the less connections the better.
georgehifi Posted July 21, 2013 Posted July 21, 2013 (edited) Go to Jaycar and get either of these. There is no advantage in running XLR (balanced) unless to run over 10mt of interconects, to reduce increasing noise level. Also some source's outputs just add another opamp into the signal path to reconstruct an xlr (balanced) output from single ended dac chip output. Also I was shocked when i did a repair on a Classe poweramp that it's balanced (xlr) inputs were just an opamp in front of the single ended rca input. http://www.jaycar.com.au/productView.asp?ID=PA3800 http://www.jaycar.com.au/productView.asp?ID=PA3802 Cheers George Edited July 21, 2013 by georgehifi 1
Krispy Audio Posted July 21, 2013 Posted July 21, 2013 Careful though with adaptors. Check your gear first. Most adaptors bridge two pins together, as do most adaptor cables. But there are some components that don't play nicely when this is done. There are also two different configurations of connecting the XLR pins. The most common occurs probably (?) on 99.9% of components, but you may have that 0.1%er. 1
alistairm Posted July 21, 2013 Posted July 21, 2013 Definitely the cable. Doesn't matter how good the adapters are (have tried a few), you're better off with a cable.
betty boop Posted July 21, 2013 Posted July 21, 2013 exactly ! this is an issue for adapters and also for cables that go from rca to xlr. you really dont know how they are actually configured. depending on which is hot pin 2 or 3 and whats left floating. both adapters and these cables are more trouble than anything in my opinion ! worth a read http://www.benchmarkmedia.com/discuss/feedback/newsletter/2008/05/2/helpful-how-tos-how-properly-connect-balanced-outputs-unbalanced-input
fetischizm Posted July 22, 2013 Posted July 22, 2013 I wouldnt even try it without finding out how the shield and ground are treated in both components. many amps wont like the inverting output being shorted to ground at all and the pin 1 may or may not be able to be used as signal ground. if you have to connect RCA to the XLR input, I would consider something like a reasonable line transformer on the RCA, or if you dont mind opamps, a simple circuit with something like an opa1632, or one of the THAT chips. if you are willing to do that let me know, I can arrange a schematic.
fetischizm Posted July 22, 2013 Posted July 22, 2013 (edited) Go to Jaycar and get either of these. There is no advantage in running XLR (balanced) unless to run over 10mt of interconects, to reduce increasing noise level. Also some source's outputs just add another opamp into the signal path to reconstruct an xlr (balanced) output from single ended dac chip output. Also I was shocked when i did a repair on a Classe poweramp that it's balanced (xlr) inputs were just an opamp in front of the single ended rca input. http://www.jaycar.com.au/productView.asp?ID=PA3800 http://www.jaycar.com.au/productView.asp?ID=PA3802 Cheers George many DACs also use additional opamps to convert their natively balanced output to single ended in an instrumentation amp style circuit. in fact most application notes call for such. the majority of current production hifi DAC chips are balanced output as standard and they dont just do it to allow driving long cables. without summing the output, you circumvent many measures they will have taken to improve performance with a symmetrical design, PSRR becomes worse, THD usually somewhat higher etc etc. so generally you will need more series components to get the summed SE output than balanced and if you have a balanced ADC (most of which are again balanced now and for some time) then it doesnt make a great deal of sense to me to go out of your way to avoid using a balanced signal path IMO. Edited July 22, 2013 by fetischizm
georgehifi Posted July 22, 2013 Posted July 22, 2013 (edited) Yes the newer balanced dac chips do, but the great multibit r2r dac chips are nearly all single ended, this is where they slot in another opamp to get xlr outputs. And you didn't mention the pseudo balanced inputs that a lot of power amps have, which are also just another opamp again in front of the discrete bi-polar or fet single ended inputs. Cheers George Edited July 22, 2013 by georgehifi
fetischizm Posted July 22, 2013 Posted July 22, 2013 (edited) presumably someone has to go a bit out of their way to buy a SE DAC these days, they will have had to be after it really, or at least know what they are getting into. no I didnt mention it, because A. it isnt in my experience, I dont care what crap commercial concerns spit out; it doesnt have any effect on me B. its not something that would enter into my reasoning, if you are stuck with such an amp and are modifying, or DIYing the output of your balanced DAC, it wouldnt make any sense to add a summing stage before the output, it costs you less to leave it balanced and the summing stage is happening as late as possible, so even if it were the case, its still the better option. I dont buy and modify equipment, I build how I want it. I mentioned it simply because every now and then I see the flawed reasoning that its adding more circuitry using balanced, when if you have a balanced dac and most modern dacs will at least have that option, then its adding more circuitry to go SE, not the other way around. Edited July 22, 2013 by fetischizm
wadiman Posted July 22, 2013 Author Posted July 22, 2013 Guys - Many thanks for all the opinions! I'll get myself a set of the cables and check with them re the correct wiring. Looking forward to some high quality vinyl rips - hopefully a lot better than my initial attempts with my low-tech Griffin iMic!
georgepapa Posted July 22, 2013 Posted July 22, 2013 (edited) Maybe this might help with the input levels at least. Try -10 or +4dbu line level. The default is mic level at around +14dbu. Preamps can easily overloaded with domestic audio sources. http://www.apogeedigital.com/knowledgebase/duet-2-usb/how-to-connect-external-mic-preamps-to-duet/ Edited July 22, 2013 by georgepapa
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