TOPIC:

Hi,

Does anyone know how input sample rate conversion is implemented in the DDRC-22D? In another thread I read it uses "Asynchronous Sample Rate Conversion" (ASRC), but no more information. Is it implemented by the SHARC DSP or by an external chip? If so which chip is in use?
I'm wondering if I could get better Dirac Live performance using other components...

Dml020472

Seems I have to write a reply to myself.
Maybe it can be off interest. My understanding is that the room-correction is done at 96KHz sample-frequency. The incoming signal is upsampled/downsampled to this frequency. My impression is that the minidsp upsampling is not the best. Earlier I used:
(1) Bluesound Node N130 -> minidsp DDRC-22D
Now I use:
(2) Primare NP5 Prisma MK2 -> minidsp DDRC-22D
The Primare NP5 Prisma MK2 is configured to use a fixed output sample rate = 96KHz.
This means the NP5 is doing the upsampling, and my impression is that it sounds better.
Example: the other day I listened to Depeche Mode album Black Celebration on Tidal using (1). I didn't smile.
Yesterday I listened to the same record using (2). Then I smiled.
 

I'm not sure smiling is necessarily the intention with that Depeche Mode album...

I thought that even if the input signal was at 96 kHz it still got resampled by miniDSPs anyway from what I've seen posted here. What matters is if you prefer the sound you have now or not but the difference you're hearing may not be down to the sample rate change.

"I'm not sure smiling is necessarily the intention with that Depeche Mode album..."
I agree on that!

In general I'm interested in why different solutions/technology sound different...

Dml020472 wrote:

In general I'm interested in why different solutions/technology sound different...

That's a very broad question, to which the only answer that doesn't involve near infinite time is "because of reasons".

User "March Audio" has put some effort into this and posted on audiosciencereview:
"I think the lesson here is perform the SRC to 96kHz first to avoid the miniDSPs somewhat sub optimal conversion!"

Measurements of MiniDSP 2x4HD | Page 2 | Audio Science Review (ASR) Forum

The DDRC-22D is basically a miniSHARC + DIGI-FP + VOL-FP with firmware to run Dirac. The ASRC is handled by the DIGI-FP which uses a TI SRC4382.

www.minidsp.com/products/minidspkits/digi-fp
www.ti.com/product/SRC4382

As with all miniDSP products the ASRC is always in operation, even if you are going from 96 kHz to 96 kHz, so I don't buy the comment that converting to 96 kHz before the miniDSP does something beneficial. I should also note that the 2x4HD does not have an external ASRC chip and uses the ASRC built in to the SHARC.

If you read the miniSHARC manual you will see that it is possible to put the miniSHARC in to output slave mode, I don't think this will work with the DDRC-22D but maybe? In this mode you lose the ability to use the DIGI-FP and would need to provide I2S data / clocks to the miniSHARC. I haven't used this mode but I believe in this operation the only output from the miniSHARC is I2S data so you would also need to provide BLCK and LRCLK (and maybe MCLK) from your source to your DAC. IMO a lot of effort for no benefit.

Michael

Thanks for the information.
Resampling 44.1KHz input to 96KHz output vs 96KHz input to 96KHz output is not exactly the same, but I'm not going into a debate about that...

Dml020472 wrote:

User "March Audio" has put some effort into this and posted on audiosciencereview:
"I think the lesson here is perform the SRC to 96kHz first to avoid the miniDSPs somewhat sub optimal conversion!"

Measurements of MiniDSP 2x4HD | Page 2 | Audio Science Review (ASR) Forum

As noted by Michael, this is a basic misunderstanding of how the SRC works in the 2x4HD.
It's a good thing you're not going to engage in debate. 

Dave.

Thanks again to mdsimon2 for an intelligent, informative and friendly answer.
It helped sort out a misunderstanding I had. Misunderstandings are not always welcome, I just have to live with that.
I'm not going into a debate about resampling because it's a big topic, and I have already got answer I was looking for from mdsimon2.
If anyone is interested here is a link to an interesting interview with Rob Watts, the man behind Chord M-Scaler:

Chord M-Scaler - My response to the ASR measurements - YouTube