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TOPIC: Re: MiniDSP sound quality test

MiniDSP sound quality test 9 years 1 week ago #1173

  • paulspencer
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At a recent audio event I heard a MiniDSP system. We decided to do a quick test of sound quality to see what it was doing. So we set it up in a simple passive system, with some Proac clones and some nice valve amps. A simple flick of the switch put it in or out of the signal chain, and this was done while music was playing to make any change obvious. Obviously all xo and PEQ settings were off. There was a very slight gain difference, but even with that we could not hear any difference. All four of us there were unanimous. It did nothing wrong.

We used a good recording and all the parts of the system were transparent enough to allow a fair comparison. That pretty much settled the matter for me. People find it hard to believe that something this cheap could make no difference ie do no harm.

Some seem to prefer to listen for hours to one thing and form an opinion. That way you can believe whatever you want! A test like this really brings out the truth.
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Re: MiniDSP sound quality test 9 years 1 week ago #1175

  • devteam
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Thanks for sharing your experience Paul.. :-)

We're always happy to hear about implementation of miniDSP kits into projects... An A&B switch is indeed one of the best way to perform comparisons about products. In the end, audio is still a subjective feeling and maybe not everybody will agree, but what matters to us is that we're able to get DSP technology out there to fit the needs of speaker builders.

Have fun,
MiniDSP, building a DIY DSP community one board at a time.
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Re:MiniDSP sound quality test 8 years 11 months ago #1272

  • Proger
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Hello,

I made a test with right mark audio :



The left is without minidsp, the right is with minidsp

Like you can see : minidsp has really good quality, but bad dynamic and noise level.
When I plug it, there's a little loose of SPL. But it's so good for its price :D

Sincerely,
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Re:MiniDSP sound quality test 8 years 11 months ago #1277

  • devteam
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Mmmh, these measurements don't line up with what we're seeing on the Audio Precision nor Right Mark Audio Analyzer with an on board sound card, or actually what others are able to see..

Could you please clarify the test conditions?

Thanks for sharing these tests, but I'm afraid that we're not working in the same conditions as we are here.. A 99dB and up is more like what we're working with.

The connectivity and how these tests were performed will tell us on on how you reached these measurements.

Thanks.
MiniDSP, building a DIY DSP community one board at a time.
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Re:MiniDSP sound quality test 8 years 11 months ago #1278

  • john.reekie
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Could be an issue with the power supply, I've noticed that when powered with USB from my laptop some noise is noticeable (by ear, no test equipment needed), it goes away when reverting to good DC supply. Sorry, no measurements to support this, just a conjecture on what may be the issue.

At the event that Paul discusses (I was there, it was my miniDSP), the DC supply was used.
I am not miniDSP support.

"You must ask the right questions." - Dr. Alfred Lanning's hologram.
-> Have you read the User Manual??
-> Have you drawn and posted a diagram?
-> Have you posted a screenshot?
-> Have you posted your config file?
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Re:MiniDSP sound quality test 8 years 11 months ago #1279

  • Proger
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The sound card is a E-mu tracker with analog output,
in the first try, I made a loop with :
jack -- rca-- rca -- xlr (so unbalanced)
in the second :
jack -- rca -- minidsp -- rca -- xlr

(I tried to low the volume, but same noise and dynamic)

The minidsp was powered by usb.

The 80Db of noise level is a fact, I always had a little pink noise when I plug the minidsp (and 96sensitivity LS, the 90Db has no noise)
Now I'm using a 5v transformer, and the problem is always here.

Maybe there is no noise with minidigi, but with analog input, I had it.

Thanks,
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Re:MiniDSP sound quality test 8 years 11 months ago #1282

  • devteam
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Alright, my last post because sometimes, trying to argue and explaining basics of measurements is not the best use of our time. :-) The only reason why I'm insisting is because you are providing false information that requires to be corrected by our engineering team.

1) I see that your sound card measures 96dB on a loop back. How did you ever expect to measure over this noise floor (e.g. a device with 100dB SNR) if your limitation is already on the sound card?
We use for some simple quick measurement a EMU1212 which does 120dB in loop back. That's what I call a reference.. :-) Hope you will understand what I just said here is a simpler version: "it is not possible to measure higher specs than your sound card limitation. That's your bottle neck here."

2) Not sure if you had a look at the measurements we pointed you toward, showing some similar specs to what we're advertising, but in case you didn't here are a couple of quick screenshots I did with Right Mark Audio analyzer software. I'm using a PC measurement software to make sure I'm within similar conditions as you are. Board is powered from a USB port, not a DC supply.

See that in an analog loop back (analog in to analog out) through the miniDSP, we are indeed reaching 99dB DR.





Now typical specs in audio (something maybe you're not aware) typically talk of ADC specs, DAC specs. These are NOT done with an analog loopback. They are done with ADC - > I2S (for the ADC specs) and I2S - > DAC for the digital part. Using both ADC and DAC, you would always get lower specs than what the manufacture are rating because noise floor of both conversions + buffer are combined. The truth is with miniDSP, if you were looking at the ADC only or DAC only (with measurement I just talked about), we can rate each of them with a better spec and that's why we're saying > 98dB on the specs. Because we're doing something called "derating" of the specs. A typical practice in audio engineering.

3) Last but not least: We sent our board to the Audio Precision (world leading measurement company) office for 3rd party approval, we got the same specs. We sent our board to Elektor Magazine (one of the most reputable electronic magazine out there), we got the same specs. Finally, others DIYers are also finding the same specs as us (see DIYAUDIO post)

If you get these specs, it's either your measurements (you will NEVER be able to see a measurement over 96dB because your noise floor is already 96db) or maybe your measurement setup. Gain structure matters, ground loops can throw off measurements, sound card specs matters...

Hope this info helps,
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Last Edit: 8 years 11 months ago by devteam.
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Re:MiniDSP sound quality test 8 years 11 months ago #1284

  • dreite
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Proger wrote:
The sound card is a E-mu tracker with analog output,
in the first try, I made a loop with :
jack -- rca-- rca -- xlr (so unbalanced)
in the second :
jack -- rca -- minidsp -- rca -- xlr

(I tried to low the volume, but same noise and dynamic)

The minidsp was powered by usb.

The 80Db of noise level is a fact, I always had a little pink noise when I plug the minidsp (and 96sensitivity LS, the 90Db has no noise)
Now I'm using a 5v transformer, and the problem is always here.

Maybe there is no noise with minidigi, but with analog input, I had it.

Thanks,


Proger,

You have a problem with your test setup. The EMU Tracker (I have one also) has very low noise on the inputs, but the line/headphone outputs are quite noisy. So, when configured for loopback or two-channel (differential) measurements it can work well, but (depending upon how you configure it for testing) you can run into pitfalls.

If you have access to a low distortion sine-wave generator use that for your signal source and set up the Tracker preamp for monitoring duty only and set both input knobs all the way counter-clockwise. You'll have to use a different program than Rightmark. Try ARTA instead.

Perform a measurement with nothing connected to your Tracker (so you can see the residual noise,) another with the MiniDSP connected but with no input signal, and another with the MiniDSP input signal at 900mV.

I'm measuring dynamic range numbers even better than quoted by devteam.

Hope that helps.

Cheers,

Dave.
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Re:MiniDSP sound quality test 8 years 11 months ago #1285

  • devteam
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Thanks for your very valuable insight Dave on how to configure Arta for a measurement. Looking at the specs of an EMU Tracker, it indeed appears that it should be doing much better than what is quoted here.

DevTeam
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Re:MiniDSP sound quality test 8 years 11 months ago #1287

  • Proger
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The Emu tracker does better in 96KHz and 192KHz, here I set 48KHz, like the minidsp.

If i understand, the minidsp add 15-20Db to noise level ? And can do 100Db noise level and dynamic only with 120Db source or more ???

Maybe my test isn't the best, but when I plug the minidsp, I have a pink noise that I haven't without it.
When I set input of minidsp to -10Db, I have less pink noise.
Now that I put the minidsp in my amp, I can't relly test it anymore. I love them :laugh: but the pink noise is a little problem :(

Do you think a power of 12v can change something ?

Devteam -> have you tested the minidsp in a box ? or balanced revA ? an other ?

I am happy to see the "minidsp team" so active :P

Thank,
Sincerely,
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Re:MiniDSP sound quality test 8 years 11 months ago #1289

  • dreite
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Did you look at the plot I posted on DIYaudio?

www.diyaudio.com/forums/minidsp/175810-a...dsp.html#post2340627

You'll notice those measurements were at 16bit/48khz. (MiniDSP modules powered via USB to the measuring computer.)

Yes, there is a bit of noise on the outputs of the MiniDSP that (probably) wouldn't exist on an analog unit, but it's pretty low. Certainly lower than the measured outputs of my Tracker-Pre and DCX2496. Unless you're listening to Klipschorns using an amplifier with high voltage gain I can't see this being an obtrusive problem.

Cheers,

Dave.
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Re:MiniDSP sound quality test 8 years 11 months ago #1291

  • Proger
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What do you call "low" ?

The DCX has a bad analog input, and there is tweaks for it, (like just remove the input condenser) but it sounds good with digital input.

I have 96Db sensitivity loudspeaker, and I ordered a 107Db sensitivity tweeter.
I am afraid that the little noise I have with my LS will be horrible with it.

My amps are UCD180 and TA2022. The TA2022 make more noise due to better sensitivity. (the ucd looks to work with 2v and unbalanced input)
And the little pink noise is present when I unplug my sound card, but not when I unplug minidsp :S
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Re:MiniDSP sound quality test 8 years 11 months ago #1293

  • dreite
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Well, you're the decision-maker on whether the MiniDSP is too noisy for your application. Apparently it is.

I think "devteam's" only contention was that you were posting inaccurate measurement numbers. I guess you're not convinced otherwise. :)

Oh well.

Cheers,

Dave.
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Re:MiniDSP sound quality test 8 years 11 months ago #1294

  • Proger
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Hum... I am really happy of my minidsp :D And I don't want to change (except if there is a 3way minidsp :lol: )

I just don't understand why I have to set a -10Db at input for removing pink noise, and anyone else.

Maybe, with -10Db the minidsp will have better result on my test, but I can't do it anymore like they are deep in my amp :laugh:

Nobody use 100Db sensitivity LS with minidsp ? :huh:

Sincerely,
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Re:MiniDSP sound quality test 8 years 11 months ago #1298

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OK, I promise this is our last comment as even Dave is giving up on trying to explain basics of measurements... ;-)

1) Measurements: You seem to get confused quite a lot in your statements (e.g. thinking a miniDSP can only perform with a 120dB DR source... That's completely unrelated to the measurements..) So I think that unfortunately, we've reached the point where whatever we try to explain about your incorrect test setup, it won't go through. At this point of time, if you believe that an EMU tracker has a 96dB DR (compared to the 115dB advertised on EMU website), might be best for you to go argue with EMU then... They may have more time/energy than us.. :-)

2) With regards to the "pink noise" you're hearing.. A gain structure issue most likely... The fact that you have to decrease the level of the miniDSP tell me that you're working close to noise floor on one of the device of your audio chain. It could be the miniDSP, it could be the amp (e.g. amp requiring more than 2V for max output), it could be the type of PSU you're providing to the miniDSP (Did you read my first comment about miniDSP PSU could have an issue sharing PSU with class D amp without any filtering?).... Anyway, you may need more investigation than just a plug & play for a miniDSP that is buried in the middle of 6 x Amp modules and a lot of radiation from your transformers.

Finally, miniDSP 2 x 4 is the exact same board as miniDSP kit, so exact same measurements.
At this point of time, not sure if sharing measurements/more information will help you... You may need to read/do a bit more homework on your side about basics of gain structure, basics of measurement setup. It will be more valuable than showing you a graph that you will either not be able to reproduce (incorrect measurement setup) or just won't understand what it means....

Have fun,
MiniDSP, building a DIY DSP community one board at a time.
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