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Alternative Sound Cards and Dac combo - RME PCIe + DAC

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For the last ten months or so, experimenting with AES3 from the computer to the DAC has brought results. Average, below average, and wow this is really something. The results will be revealed shortly. I learned quite a bit about pro levels being very different from small stuff in the regualr Hi fi world, still come across some weird numbers, so still grasping.



As a recap, AES3 is the newer nomenclature for AES/EBU (a mouthful that has now seen the light of day)an electrical balanced version of the coax S/PDIF transmission protocol originating in the Pro Audio and DAT recording era and CD a few years earlier. AES3 is limited to 192kHz (DSD64 over DoP) maximum. This is a limitation that I can live with, since HQPlayer can convert DSD to PCM on the fly for casual listening, or DSD_DISCs are burned to DVD which can play in my SACD player, Accuphase DP-720, for that realistic experience that SACD explores and delivers quite well indeed. For higher than DSD64, a higher speed protocol is necessary, for those that want the faster rates, then USB is currently it.



I use AES3 and not the coax model, since the computer is 25m away in another part of the house along with a noisy UPS. Coax S/PDIF maxes out at 10m, AES3 can run to 100m. The choice of cable requires a 110ohm impedance, however a single twisted pair shielded is not that cheap, about USD400 plus the install. An alternative is to use CAT5e cable with suitable connectors. Cat5e has plenty bandwidth for AES3, has plenty of cores to work with, many twisted pairs and it's very inexpensive. S/PDIF is not a routable protocol, so it can't bend around Ethernet switches and routers, so it's point to point only.



Tecnec Cat5 XLRF.jpgCat 5 to XLR Adapter



There is an AES3 unbalanced system which uses 75 Ohm coaxial cable that can run to 1000m, the choice of interfaces becomes an exercise in voltage levels to make sure everything is OK. Most of my gear has the XLR connector, so I'm used to that, plus the Cat5e was already pulled in.



The experiments do away with USB, there's nary an A or B connector in the path. The main reason is sound quality, I found AES3 less fatiguing than USB on the DACs I tried, plus it's always on. If USB is broken, the DAC or computer/player usually need a restart, AES3 just picks up where it left off. A lot is mentioned about buffer filling, and S/PDIF having no clock master to sync pulses and all that. Well time has moved on and techniques have evolved to overcome these issues with clever clock and de-jitter systems. Whether a streamer or computer has an AES3 output, the interfacing to a DAC is often simpler with AES3, thus avoiding incompatibility with USB (driver) issues where the DAC just sits there in silence. This doesn't happen with every DAC, but the possibility cannot be ruled out.



The music server is a HP Z800 workstation complete with four 1TB drives in RAID5, enough horsepower to manage, edit, tag, SRC, burn CD/DVD, and playback audio files. I've tried a Mac Mini previously with Windows and Mac programs to play from the Z800, the SQ didn't change much if at all. Even tried NAA, found the limitation with the hardware in the Mac Mini the main limitation. I can understand the Aurender a purpose built audio server, which has processes cut to a minimum, with the better SQ as a result, however if the PC is your choice, it really doesn't matter what PC hardware you have, the players make the difference to the sound, exclusively. The HP Z800 has a PCIe bus with a few slots spare. Pro audio cards slot right in. I chose the RME HDSPe AIO, since I only need 2ch playback, since previous dealings with consumer type cards like the Creative gear just had too many hiccups with drivers and software. Hardware interfacing is a DB9 connector to a short snake some 200mm long with the XLR output the target to connect to the DAC.


So the chain is HQ Player --> PCIe bus --> RME HDSPe AIO AES 3--> XLRM output --> XLRF to Cat 5e Adapter --> CAT 5e Adapter to XLRM --> DAC


HDSPeAIO.jpgThe breakout cable is a very short length digital cable, I don't think it will cause much noise, cause I don't hear any :)



I have four DACS that accept S/PDIF, three of them accept AES3 + Coax, one only a coaxial RCA input. I choose the hard way and went with the DAC in the DP-720 with RCA coaxial input only. This input is designed for 0.5 to 0.7 Vpp, AES3 outputs a lot higher some 11db higher. The sound is not so great, below average, coarse, raspy and undefined, just unlistenable when over-driven. To interface the XLR signal 2-7 Vpp to a coax 0.5 to 0.7 Vpp requires an adapter, which still can be more than the allowable design limit. RME produce an ADI-2, AES3 balanced/unbalanced AES3 optical to either XLR voltage levels or coax S/PDIF outputs, which is a better option. Physically the ADI-2 is small enough to be fitted to a wall behind the audio rack out of site, as once setup does not require adjustments.





I stuck with the combo a few months of the RME HDSPe AIO and the ADI-2 feeding the Playback Designs MPD-3 or the DP-720 DAC, sometimes the Grace Design M920, it never quite reached the SQ I could hear from the SACD player though. Mainly the image was rather short not tall, focus of individual instruments was fuzzy, and the micro details were missing. For casual listening this wasn't tooo bad, but not for critical/enjoyable listening.



In a moment of clarity and inspiration, why not try the XLRM analog outputs of the DAC in the ADI-2? The ADI-2 has transformers on the inputs for isolation, so why not. For the connections, the CAT 5e Adapter to XLRM needed to be converted to a single RCA connection for the ADI-2. The ADI-2 automatically detects the levels for coax or AES3, so a simple XLRF to RCA adapter was used which used Pin 1 & 3 as the GND, Pin 2 as the hot. For those interested the ADI-2 can accept 192kHz PCM on the optical inputs.



For playback, now this was the wow moment. The height of the image was restored some 1m, the micro details came back and the first time in a long while, I was enjoying digital file playback, and played for many hours well into the night. The sharp focus of individual instruments in space is still with the DP-720 and spinning CD or SACD. Can't quite get there with the ADI-2, but the line has to be drawn somewhere. Could be with the power supply, currently using a 120W computer brick wringed out to 24Vdc. The ADI-2 accepts either AC or DC voltages, so could also use a simple transformer with no SMPS noise :) I wouldn't say the SQ is coloured in anyway, nor warm, fairly neutral, partners well with the rest of the electronics.






RME HDSPe AIO PCIe card & breakout cable EUR550 delivered

RME ADI-2 AD-DA AES3 to Coax converter EUR503 delivered

Cat5e to XLR, XLR to RCA adapters USD60 delivered



Look, the DAC market is really crowded with sub USD1000 DACs, so finding value and performance is often fraught with difficulties as to which to choose. The nearly 10 times the price MPD-3 DAC is now de-commissioned, and I don't miss it after a few weeks of it being absent, guess that says something after listening to that DAC for nearly 3 years now.



Totally recommend the ADI-2 for great bang for buck D to A conversions using the AES3 input, or if you have a USB to S/PDIF converter to hand then try that approach.

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Great post, One and a half.


I've wondered about these sound cards myself. The big question for me is how they compare with the JCAT, SOtM, and Paul Pang USB cards from a sound quality standpoint.



Yes , good question! The jcat sotm cards are principally usb transmission enhancers that are connected to the PCIe bus. No doubt they do make a difference but I have not tried them. Given the popular usb regeneration and jitterbug type of usb treatment the need for usb cards may be relegated to the few desktop style computers. There's no restrictions on using the the USB cards with a regen or jitterbug either, my estimation is the quality of the USB gives the regen less work to do to improve the final delivery to the DAC.


The RME cards are actually complete recording multi channel with either analogue or digital inputs as the source and using the computer as a recorder, typical digital audio workstation. The cards are bundled with a mixer application which took some getting used to.

The AIO has its own DAC, but I didn't test this as you need a different breakout cable and due to distance the DAC needs to be close to the amp.

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