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Minidsp Flex Review (Audio DSP)

Rate this product:

  • 1. Poor (headless panther)

    Votes: 4 0.7%
  • 2. Not terrible (postman panther)

    Votes: 16 2.8%
  • 3. Fine (happy panther)

    Votes: 117 20.6%
  • 4. Great (golfing panther)

    Votes: 431 75.9%

  • Total voters
    568

Sokel

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Just so I understand what you were seeing with the Flex, are you saying that if you reduce the Flex volume such that you are no longer clipping you still saw degradation in noise and or distortion?

Michael
Yes,and severe one,specially noise.Multitones was also not good,at all.
All of that in the low's section,high's got a hit too but not as much.
The most odd one was TDH+N (SINAD) vs level.It was all over the place.
 

Sokel

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I'm confused too, the advice always seems to be if you apply a negative total gain of the amount of the total headroom used that stops the clipping? I allow boosts, but i'm still at -30 for most of my listening. Is it clipping?
Clipping,intersample overloads,etc is matters that we don't pay as much attention as we should.
That's why is good to measure things as is,after all the settings and in their working conditions.
 

mdsimon2

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Yes,and severe one,specially noise.Multitones was also not good,at all.
All of that in the low's section,high's got a hit too but not as much.
The most odd one was TDH+N (SINAD) vs level.It was all over the place.

Fascinating, thanks for sharing.

I posted some digital measurements of a 2X4HD earlier in this thread -> https://www.audiosciencereview.com/...idsp-flex-review-audio-dsp.30804/post-1088121 and saw slight degradation in noise with a 80 Hz LR4 HPF but it wasn't that bad. Probably more interesting to try more complicated processing though.

When I get back to my audio stuff later this month I'll measure while applying the LXmini EQ and see what it looks like across a few different DSP platforms. It would be nice if we had some standard EQ profiles that we could apply as a consistent test across DSP platforms to compare degradation.

Michael
 

enricoclaudio

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I can repeat some measurements tomorrow if you guys want me to do so. Today I have another things to do but tomorrow while working out, I can run a new set of measurements.
 

Sokel

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It would be nice if we had some standard EQ profiles that we could apply as a consistent test across DSP platforms to compare degradation.

Michael
I'm all for it!
Specially in Mutitone analyzer I would be happy to make some ready configurations and share with everyone wants to try.
 

enricoclaudio

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Fascinating, thanks for sharing.

I posted some digital measurements of a 2X4HD earlier in this thread -> https://www.audiosciencereview.com/...idsp-flex-review-audio-dsp.30804/post-1088121 and saw slight degradation in noise with a 80 Hz LR4 HPF but it wasn't that bad. Probably more interesting to try more complicated processing though.

When I get back to my audio stuff later this month I'll measure while applying the LXmini EQ and see what it looks like across a few different DSP platforms. It would be nice if we had some standard EQ profiles that we could apply as a consistent test across DSP platforms to compare degradation.

Michael

Michael,

Could you please share the protocol to follow with REW? I do prefer to use REW as I don't need to unplug anything and also can use my Mac Studio. I have both, the RME UCX II and FLEX connected to my Mac Studio via USB already. I can use OUTPUT 4 from the FLEX which is not in use to send signal to the UCX II INPUT 5 on the back, then mute all the other outputs on the FLEX and turn OFF my KH150s :)
 

enricoclaudio

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OK I think I figured it out with REW:

NO PEQ:

NO PEQ.png


10dB GAIN, Low Shelf PEQ @ 20KHz:

10dB PEQ.png
 

enricoclaudio

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Which one?

%:

NO PEQ %.jpg


dB:

NO PEQ.jpg
 

TheBatsEar

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TheBatsEar

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I can repeat some measurements tomorrow if you guys want me to do so. Today I have another things to do but tomorrow while working out, I can run a new set of measurements.
Could you please look into the difference when you feed the device 16/24 bit and 44.1/48/96kHz sampling while at it? I have a suspicion that at least some are super clean (24/48 and maybe 24/96).
 

mdsimon2

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Michael,

Could you please share the protocol to follow with REW? I do prefer to use REW as I don't need to unplug anything and also can use my Mac Studio. I have both, the RME UCX II and FLEX connected to my Mac Studio via USB already. I can use OUTPUT 4 from the FLEX which is not in use to send signal to the UCX II INPUT 5 on the back, then mute all the other outputs on the FLEX and turn OFF my KH150s :)

Here are my settings, there isn't really a "right" answer but is important to be consistent if you want to compare one measurement to another.

First looking at Preferences you want to make sure the sample rate matches the rate you are using in Audio MIDI settings for your output and input devices. If a device has a different sample rate in Audio MIDI settings this will result in Core Audio resampling. If you want to use different sample rates for outputs and inputs (say you want to run the ADC at a higher sample rate) you can do this but you need to run two instances of REW, one running Generator and one running RTA.

Here are my Generator settings. I use no dither and select Lock Frequency to RTA FFT.

1675374106039.png


Here are my RTA settings.

1675374186502.png


I turn Peak off in Trace options.

1675374253370.png


In Appearance I select 64 bit FFT, the other settings don't really matter for this sort of testing.

1675374302180.png


In distortion settings I typically use a 20 Hz to 22000 Hz bandwidth but sometimes will use higher bandwidth depending on the test. I like to use dB over % as it is easier to tell differences.

1675374375336.png


Selecting dBc in the upper right will set the main tone peak at 0 dB and give noise in dB relative to the main tone, not relative to 0 dBFS on the ADC.

1675374455928.png


When setting scales on the RTA I usually like 0 dBc as the max and -160 dBc as min, these should cover you pretty much all DACs other than ones that are really low noise.

End result should look something like this.

okto_4vout_3.5vadc_splitter.png


If you are testing DSP stuff you will need to attenuate the output either in REW or with the DSP volume control such that you are not clipping the output. It is also helpful to run a frequency response sweep so that you can make sure the response looks like what you expect.

Michael
 
Last edited:

enricoclaudio

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Here are my settings, there isn't really a "right" answer but is important to be consistent if you want to compare one measurement to another.

First looking at Preferences you want to make sure the sample rate matches the rate you are using in Audio MIDI settings for your output and input devices. If a device has a different sample rate in Audio MIDI settings this will result in Core Audio resampling. If you want to use different sample rates for outputs and inputs (say you want to run the ADC at a higher sample rate) you can do this but you need to run two instances of REW, one running Generator and one running RTA.

Here are my Generator settings. I use no dither and select Lock Frequency to RTA FFT.

View attachment 261832

Here are my RTA settings.

View attachment 261833

I turn Peak off in Trace options.

View attachment 261834

In Appearance I select 64 bit FFT, the other settings don't really matter for this sort of testing.

View attachment 261835

In distortion settings I typically use a 20 Hz to 22000 Hz bandwidth but sometimes will use higher bandwidth depending on the test. I like to use dB over % as it is easier to tell differences.

View attachment 261836

Selecting dBc in the upper right will set the main tone peak at 0 dB and give noise in dB relative to the main tone, not relative to 0 dBFS on the ADC.

View attachment 261838

When setting scales on the RTA I usually like 0 dBc as the max and -160 dBc as min, these should cover you pretty much all DACs other than ones that are really low noise.

End result should look something like this.

View attachment 261841

If you are testing DSP stuff you will need to attenuate the output either in REW or with the DSP volume control such that you are not clipping the output. It is also helpful to run a frequency response sweep so that you can make sure the response looks like what you expect.

Michael
Great, thanks for sharing. Going to keep these settings are the Standard for testing SINAD with REW.
 

enricoclaudio

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Does it matters setting the FS Sine Vrms at 2.1V vs 4V?
 

enricoclaudio

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That only matters if you want to set the output voltage in volts rather than dBFS. If you want to set the output voltage in volts you should set to the max output voltage of your DAC.

Michael

Here is one with your settings.

FLEX with NO PEQ and NO DIRAC:

FLEX 1KHz.jpg
 

enricoclaudio

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Seems that some kind of device interferes with your gear.
Led lights?A/C?Some kind of motor?Mains noise?PC noise?
All the distortion that appears to start before 1Khz is normally alien to Flex.
Man you are good . I left mains (KH150s) and subwoofer plugged in and ON during this particular measurement. I just muted their outputs in the FLEX. I was too lazy to shut them OFF. Also, my desk LED lights were ON :)
 

enricoclaudio

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Seems that some kind of device interferes with your gear.
Led lights?A/C?Some kind of motor?Mains noise?PC noise?
All the distortion that appears to start before 1Khz is normally alien to Flex.

Man, I got addicted to measuring to the point that I just placed an order over HiFiGo for a E1DA Cosmos ADC + E1DA Cosmos APU :D
 
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