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miniDSP OpenDRC Conversions?

watchnerd

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I currently have an miniDSP OpenDRC-DI. It has digital inputs and outputs and looks like this:

_mg_0852.jpg

For system architecture reasons, I want to convert it to this:

_mg_0845.jpg

Using one of these:

_mg_0620.jpg


_mg_0628.jpg


Cost is cheap, $80 for the parts.

Questions:

1. Has anyone done such an installation? Seems simple, perhaps even solderless, but wondering if there are any gotchas.

2. Is the analog output good, decent, or crap?
 
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watchnerd

watchnerd

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Lots of surface mount parts to solder. Are you up for that part?

I'm not sure I'm following. The board comes fully assembled.

From what I can tell, it connects to the SHARC board inside the miniDSP via the headers.
 

RayDunzl

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RayDunzl

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RayDunzl

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RayDunzl

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watchnerd

watchnerd

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I'd never head Zappa's version before, thanks.

------

Back to the analog section of the OpenDRC-DA:

Looking inside the box, I don't see any beefy power supplies (picture from the 8 channel version).

1113322w.jpg



(Aside: Hmmm, lots of space, I wonder if I could fit my RaspberryPi + HiFiBerry Digi+ Pro inside there, but I'd have to drill some holes...)


On the other hand, I'd be connecting to an analog pre-amp with the option of using an active gain stage, so hopefully long XLR runs shouldn't be a problem even if the analog output of the OpenDRC-DA is a bit on the wussy side.

I hope.

This leaves the usual suspects of internal noise and distortion as the big potential concerns.
 

RayDunzl

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Looks like the DAC board is the same one used in the $799 Dirac Live version, FWIW.

I enquired about the Dirac version.

Same hardware, different has-to-be-loaded-at-the-factory "firmware" - that renders it incapable of using other thrid-party filter generators like rePhase or AcourateDRC or whatever..

So, I passed on Dirac for functionality issues, so I wouldn't just be called "cheap".

For whatever reason, after running the Dirac demo, I wasn't impressed by the before/after nor by the multi-point measurements required.
 
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watchnerd

watchnerd

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There are some interesting comments about embedded DAC quality from this review of the miniDSP 4 x 10 (different DAC chip), which I found to be great at putting things in perspective:

[paste]
Do I think the DAC quality is important? Absolutely, but here's the thing. I used to be fiercely focused on the DAC. I've owned professional DAC's such as the Mytek DIGITAL 192 STEREO DSD DAC, Lavry DA11 and Grace Design m903, high end Hi-Fi DAC's such as Auralic MX+ and DAC's such as the cheap, but well renowned Objective2 DAC and many, many others.

Before I ventured into active loudspeaker systems and using DSP to optimize the sound quality of my system, the DAC was one of the main variables I could tinker with and rolling DAC's and opamps were a big part of the «audiophile» hobby. If the highs were a bit harsh I'd read tons of reviews trying to find a warmer DAC, found one and purchased it and but found that the warmer DAC had too little details, so I went out and looked for another one with more warmth and details, but got one with less bass impact and ... Well, you get the idea.

The point of telling you this is that you may be in that situation today. You may be concerned about the 4x10 HD's DAC quality, because that's what you normally consider an important contributor the overall sound quality of your audio system, and yes, you are right. A good DAC is important, but being able to do bass management to get rid of huge peaks in your frequency response, being able to time align speakers or even individual drivers and maybe even take it a step further and run them actively is so much more important.

We often hear that a system is no stronger than its weakest link; this is true, and this is why we must make sure our weakest link is optimized, and our weakest link often the loudspeaker, and the interaction between the room, the loudspeakers and subwoofers.

With DSP in your system you will be able to remove those pesky bass peaks, get even levels across all frequencies, adjust the tonal balance to suit your subjective preferences and time align the speakers to create better holographic imaging and a wider soundstage with better pin pointing. These are the things we should focus on, and when we have these things right, we can start focusing on the DAC to squeeze the last ounces of performance out of our music.

[/end paste]
 

RayDunzl

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After you build it, post some of those fancy -160dB measurements we all crave.
 
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watchnerd

watchnerd

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After you build it, post some of those fancy -160dB measurements we all crave.

Here are some simple summary measurements of the DAC posted by a guy on the miniDSP forum:

[paste]
digital I/O noise floor........................... –126.07dBFS due to asynchronous S.R.C. dither noise.
analogue XLR noise floor.................. –96.23dBFS average RMS below fullscale*
*as recorded through Apogee A/D converter!!!
Subtracting Apogee’s noise floor of –116dBFS would leave a calculated –97.17dBFS residual noise floor due to the OpenDRC alone.

[end paste]

Without a graph, I can't fully interpret. But while seemingly not stellar or over-engineered, it seems to be in the "good enough" and "not very likely to be audible" range.



 
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watchnerd

watchnerd

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Here are some measurement graphs for the internal ESS DAC, posted by the miniDSP engineering team:

DR.JPG


noise_floor.JPG

I wouldn't call them stellar, by any means, but I don't see anything to worry about, either.
 
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