# miniDSP DDRC-22D power supply and noise



## mrderrick (Sep 5, 2010)

Does anyone who uses one of the DDRC-22 series have any experience trying an upgraded power supply?
I am specifically interested in any comments regarding the 22D.
I am considering inserting a 22D between my BDP-1 and DirectStream Dac.
The Dac drives Atma Sphere M60s with Avantgarde Duo Omega horns that are extremely sensitive.
I have gone to great lengths to keep system noise to an inaudible level.
Will the 22D introduce any noise and would an after market beefed up linear power supply make any difference?
Or is it already dead silent?

Currently I use a Rives Parc between the Dac and M60s with no noise introduced into the system.
But my listening space is an asymmetrical nightmare and the Parc, which does an excellent job, can only correct my bass response.

Any thoughts?

MrDerrick


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## Lumen (May 17, 2014)

No replies from a 22D owner yet, so thought I'd add a 2¢ commentary:

I, too, was apprehensive about inserting yet another component in the signal chain of my lovingly-voiced, high-end 2ch system. Of particular concern was the additional AD-DA conversion stage necessitated by the miniDSP, especially for (GASP!) playing vinyl. But the needs of the many (good sound in a wide sweet-spot) outweigh the needs of the few (an uncorrected room). I haven't taken the plunge for my 2ch system, but the home theater uses Dirac Live to excellent effect. As Wayne states in Post #20 of this thread, the stock miniDSP 22D is close enough to a cable as to cause listeners to never look back.

If it's any consolation, you can read a review of the 22D here.


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## mrderrick (Sep 5, 2010)

Thanks for the input!
I have read everything posted that I could find.

I am trying to avoid a past experience with a highly regarded correction device, the DSPeaker Anti Mode Dual Core 2.0.
While a highly regarded solution for bass correction, I could not integrate it into my system successfully.
I have no doubt that it worked extremely well for many others.
It struck me as a unit that you could build a system around, but might not integrate well into an existing system.

If I read correctly, returns are not an option with the purchase, I could be mistaken though.
Downloading the 14 day trial software is not an option for me as I do not play back via a PC.

I do have a turntable build on indefinite hold, when it materializes, I will use a PS Audio NPC to convert to a digital signal to feed to a spare input on the DDRC-22D.


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## phosphorein (Apr 5, 2012)

I use the DDRC-22D as the input to a Benchmark DAC/amp system. No extraneous noise is generated by the DSP box using the standard power supply. This device is highly recommended.


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## AudiocRaver (Jun 6, 2012)

mrderrick said:


> Does anyone who uses one of the DDRC-22 series have any experience trying an upgraded power supply?
> I am specifically interested in any comments regarding the 22D.
> I am considering inserting a 22D between my BDP-1 and DirectStream Dac.
> The Dac drives Atma Sphere M60s with Avantgarde Duo Omega horns that are extremely sensitive.
> ...


MrDerrick:

I saw your post last night and was hoping to fire up the 22D to verify before I answered. It is not in my current configuration, which is in constant flux.

From memory, I will say that the 22D came across as a complete noise-free unit in my use. Being digital all the way through, the 32-bit internal processing, with 24-bit in and out, is as pristine as one could hope it to be. I realize that noise in a digital unit can turn into jitter which causes sidebands similar to IM distortion, but my experience with the 22D left me thoroughly impressed with its sound quality.

That said, I hope to pull it out for a quick couple of measurements in the next day or two so you will have a more in-depth answer. If I get to it, I will post the result in this thread. No guarantees, though.


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## mrderrick (Sep 5, 2010)

Thank you Wayne for offering to take a closer look.
I made an inquiry in the miniDSP forum regarding after market power supplies and noise.
Apparently the poster I was corresponding with indicated that the 22D is the quietest and when he tried a better power supply it did not make a difference.
He has tried all three DDRC units, the analog to analog, digital to analog and the digital to digital.
Laying out almost a grand with a no return policy is now my biggest hurdle!


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## AudiocRaver (Jun 6, 2012)

I see your decision, and although I have only the DDRC22D to measure, *complements of our generous sponsor miniDSP,* I can tell you that it measures mighty quiet. I did a few tests and here is what I found:

Remember first that since the DDRC-22D is digital in and out, you cannot actually measure an analog noise level directly. What I did was (1) run a SPDIF coax directly from one computer to another, where I could record then analyze several test signals. Then I (2) replaced the SPDIF coax cable with coax, then DDRC-22D, then coax into the next computer, and re-ran the test signals. Sample rate differences had to be dealt with, too, which is always fun.


(1) was 48 kHz sample rate all the way through the recording and analysis.
(2) was 48 kHz into the DDRC-22D and 96 kHz out of it, so the recording and analysis were at 96 kHz.
The noise analysis actually is more like an IM distortion measurement. Noise in the DDRC-22D would not change the digital processing in a way that contributed to analog noise levels after DtoA conversion, which would happen in a succeeding DAC or AVR. It could theoretically cause timing jitter, which could affect the DtoA process in a way that contributes to sideband noise, much like an IM distortion measurement.

Even if there was something there that one wanted to correct (and there was NOT) it would be difficult to tell where that jitter was coming from. Changing the power supply might make no difference at all.

I ran three measurements:

500 Hz
250 Hz + 8 kHz, 4:1 (DIN)
19 kHz + 20 kHz, 1:1
What I saw was a dramatic _decrease_ in sideband noise going from (1) to (2).

For all three signals types:
(1)The measured sideband noise components consisted of a dozen or so frequencies above 1.5 kHz, totaling to roughly -90 dB, or about 70 dB below the -20 dB signal level.
(2)The measured sideband noise components only existed at 3 or 4 frequencies above 8 kHz, and totaled to about -100 dB, or about 80 dB below the -20 dB signal level.

In conclusion, the sideband noise from the DDRC-22D is extremely low, and there is no way to predict if a better power supply would help or not, except by buying a few and testing sidband noise levels with each of them. As low as the measurements are, though, I would spend my time and money elsewhere.


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## mrderrick (Sep 5, 2010)

Thank you for taking the time to take additional measurements.
My previous experience with the DSPeaker AntiMode Dual Core showed that a better PS increased the SSI, but did not help with self noise.
The 22-D appears to be extremely quiet own its own and does not need the aid of a beefier PS.

I have been in communication with miniDSP and they are receptive to my concerns and I believe will work with me regarding my remaining worries.

I appreciate all of the input and efforts put forth by the community here!


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