TOPIC:

Thank you. The story is not exactly simple, is it?

I am keen to try something along these lines, but on the other hand I am starting to wonder just how much it matters if I take the analog outputs and run them straight into AJ A4 and then off to digital processing.

You could go HDMI into an HDMI to SDI converter ($75 for a bidirectional Black magic converter) and then to 4 x 2ch AES3 SDI audio deembedder IF you are not dealing with HDCP.

I found the AVR Key will NOT strip HDCP. on the audio port without special firmware from HD Fury. I am trying to get this to deal with the HDCP that the nanoAVR adds to even unencrypted input run through it.

The AVR Key does not help. This project is dead in the water unless (a) minidsp stops encrypting unencrypted HDMI going through nanoAVRs or I can strip HDCP. Instead I will have to go nanoAVR to HDMI to 7.1 analog converter (and those generally suck, quality wise).

HDFury is sending me custom firmware for the AVR Key to try. There is no reason for the "audio" HDMI port to have HDCP on it: even with HDCP only video is encrypted, audio is sent in the clear in the horizontal blanking interval in "data islands", and the audio port has black video. Now, some sources might chose to not send audio if they can't negotiate HDCP but that is a different issue: if they can negotiate HDCP for video, then the audio is as plain as day (well, relatively speaking).

I still think miniDSP should not apply HDCP on output in the nanoAVR if it did not negotiate it on input.

Now, in your case, if you just want A to D or D to A converters for the DDRC-88D none of this HDCP crap applies and the AJA ADA-4 would work fine for 4 analog channels at a time,

Well, the custom firmware for the AVRKey did not pan out. I ended up getting an HDMI to SDI converter from hdtvsupply that would sink HDCP on the HDMI side. As for the AJA ADA4s, they work, though the noise floor seems a bit high to me.

I am yet to test the ADA4's that I bought second hand, due to lack of a HDMI converter. But if the noise floor is a bit high, that won't sit well with my horns, and I will have to find a low-noise replacement.

Which won't be easy, based on the difficulty so far in finding something at a sensible price.

Well, I have to verify WHERE the hiss is coming from. Signal chain is nanoAVR HDMI to SDI to AES3 to AJA ADA4 DACs. So, I would presume it;s the DACs, but, of course, the nanoAVRs could be introducing it digitally, or the SDI to AES3 deembedder could (though, bits is bits, right?).

Now, I have not heard too many other complaints about the nanoAVRs being noisy so I am tempted to blame the ADA4 DACs and I can't really see the deembedder introducing the noise. However, the deembedder is ALSO a 4ch DAC so I can try that (and get another one to daisy chain for the other four channels if it pans out and abandon the ADA4s).

To their credit AJA was quick to give me noise and THD specs for their ADA4. Around 94 dB S/N and 85 dB THD. Adequate for "broadcast quality", but a bit lacking for my use. To be fair, these are little boxes with wall wart power supplies so they are doing the best they can, and might, indeed be adequate for "broadcast quality". At $390 list or around $200 on sale for 4 channels of D/A, one gets what one pays for. These aren't bad, but they aren't great: fiddling with the level budget between DAC and amp can mask most of that noise: the room isn't exactly the quietest: it's under the kitchen and water pipe and dishwasher noise is not unusual. Still...

Now, I also asked Blackmagic for their DAC specs, (their SDI to audio converter provides 4x2ch AES digital audio or 4x1ch balanced analog audio) and they refused to provide them.

For now, I will likely fiddle with the level budget between DAC and amps, but will look for something better.

And, that's just the point of this exercise: I can spec out DACs and amps on a per channel (or at least per channel pair) basis. I am not tied to the bundle inside a monster does it all pre-amp.

Right now, the room is split, with amps in the front for mains and center (subs are powered), and amps in the back for surround, and I've been putting a 4ch DAC at each end. I am eyeing a used Lucid ADA 8824 (24 bit 48 kHz, 8ch A/D and D/A) unit for around $400. These are normally used in recording studios so the specs are a bit better than "broadcast quality": about 103 dB THD+N on the D/A side. But, then I'll have to run FOUR XLR cables to the back instead of two: not sure if I can get an XLR snake thin enough to fit in my floor cable protector. Maybe I'll just keep all the equipment in one place and run speaker level signals to the back. Not sure yet (I have this "thing" about keeping amps close to speakers).

I am starting to wonder whether the DDRC-88A has adequate A/D and D/A after all. 94 dB SNR (also 103 dB) should not be that hard for the DDRC-88A to achieve, being a modern device. 24-bit DACs are routinely in the 115+ dB area for SNR. Even $80 in-line USB DACs are measuring at 110 dB, these days.

A pity we have not heard from miniDSP themselves in this thread, yet. Would love to know the measured SNR they are getting from the DDRC-88A. Imagine if it was, like, 110 dB? We could pack up this thread and get on with it.

Would also love to know if miniDSP themselves have any recommendations for A/D and D/A units to use with a DDRC-88D.

I started this thread because my 2011 miniDSP 2x8 kit board definitely has too much noise for my high-sensitivity horn speakers. Proven by listening. So I thought, "let's avoid the A/D inputs and D/A outputs that miniDSP built into the DDRC-88A, by buying the DDRC-88D and source my own AD and DA." I never suspected that affordable AD and DA converter units with high SNR would prove a major search.

Still, the search is needed if one is using digital crossovers on active main speakers, like my horns. We really don't want a *second* D=>A=>D conversion in the signal path.

Well, the Behringer SRC2496 2ch DAC is supposed to be good, and available for $199, Behringer general quality notwithstandinng. But, to say the damn thing is industrial is an understatement. Then there is the Lucid 8824 and 88192, the former around $400 on ebay for 8ch D/A and A/D with decent specs (AES or ADAT to/from balanced analog).

I ended up going with a Lucid ADA 8824 8 channel DAC. It does D/A and A/D. 105 db SNR. About US$400 on ebay.

One warning: you will need a PC with a USB to Midi interface (around US$40) to set the levels. Dunno about Windows but Linux with a Midi works out of the box.

Yamaha has 8 ch DACs with fixed output levels (-10 dBV or +4 dBu, switched).

Thanks for letting us know. Would be interesting to know if you can confirm a better noise floor than the ADA4, or any other advantage too.

From email with AJA SNR and THD D/A on the ADA-4 are 94 and -85 dB, respectively. From the Lucid ADA 8824 manual SNR and THD are 105 and -86 dB respectively. -85 db THD is 0.005%.

A to D figures are similar (better SNR on the Lucid ADA 8824, actually).

Two things:

1. THD is at full scale output.

2. Older Lucid ADA 8824 power transformers tend to hum a little. A piece of cardboard between transformer and chassis helps a lot to take care of this. I can still hear it in mine if I put my ear to it or listen in a VERY quiet room. I do not find it a problem. It is normally 10 feet or so away when I watch movies.

You might want to also look at Yamaha 8 channel DACs, though they have fixed level outputs of -10dBV or +4dBu so volume control will have to be done elsewhere. Also it is strictly D to A. I think they have an A to D equivalent.