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Audio measurement gear

amirm

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Is the Averlab comparable to AP? I believe this is Jonathan Novick’s new product. $3,000 seems like a reasonable price for high performance test gear.
https://www.avermetrics.com/products/averlab/
If it were similar to AP, it would be priced 10X higher :). So no, it is not as highly spec'ed. Input voltage range for example is pretty limited so you can't measure power amplifiers with it but for DAC and such, may be fine. Bandwidth is also limited (mine goes to 130 Khz, this one stops at 96 Khz).

The Prism Sound dSound III would be a better comparison to do it.

If you just want to play with something, the Quantum one above seems like a much better bet.
 

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amirm

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Had not seen that one before. Nice to see very high voltage input capability. But does it not have autoscaling? I see those presets in front and worry that you are one wrong click away from damaging in the inputs.

And yes, I can do a loopback on AP.

That graph is the output from Room EQ Wizard it seems. Is that they software they use or did they just use this as a soundcard?
 

BE718

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Had not seen that one before. Nice to see very high voltage input capability. But does it not have autoscaling? I see those presets in front and worry that you are one wrong click away from damaging in the inputs.

And yes, I can do a loopback on AP.

That graph is the output from Room EQ Wizard it seems. Is that they software they use or did they just use this as a soundcard?
My understanding is that is behaves like a soundcard so can be used with various software:

Available PC analyzer software include HpW Works, MATAA, AudioTester, SpectraPlus, VisualAnalyzer, REW, Arta, Steps, and RightMark.

Just for comparison mt Motu 8a loop back. Obviously this doesnt tell us if the DAC or ADC is the limiting factor.

motu loopback.png
 
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amirm

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Ah, lack of custom app from them explains why it has mechanical gain switches on the device itself. As much as it is nice to have choice of other apps, I like to see a dedicated measurement suite of their own.
 

BE718

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Looks like DIY had a group buy where cost was $1199 for 10 of them or $999 for 50. Also some people later in that long thread received them and posted some test results with them.

http://www.diyaudio.com/forums/group-buys/306322-gb-rtx6001-audio-analyzer-ak5394a-ak4490.html
Thanks for that info, at that price I would probably look at another motu - it would have much better re-sale value. I will have to check out the max input voltage on the motu, but whatever way the Quantasylum looks very good for the price. Plus it looks like they are going to release ASIO drivers to allow use with other applications.

QA.PNG


Motu is still better by about 10-12dB

motu v AS.png


EDIT - spot the deliberate mistake (dBFS v dBV) :) I will recalc that later :)
 
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BE718

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The Motu can take up to 34.7 V pk-pk (12.2 V RMS), QA is 56 V pk-pk (20V rms)
 

Blumlein 88

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Been meaning to for some time, but haven't done so. Why not just build a resistor box to attenuate the input of high voltage sources like from amps? That seems all you are missing with regularly available ADCs.
 

amirm

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Been meaning to for some time, but haven't done so. Why not just build a resistor box to attenuate the input of high voltage sources like from amps? That seems all you are missing with regularly available ADCs.
You can do that but one wrong signal or turn of the volume control will blow up the input of the sound card. It is just too high of a risk for a good sound card. In the extreme case, it could even travel upstream to the system driving it and damage that!

BTW, that is all that the one we are talking about has right now. The Quantum Asylum though like my AP has both protection and auto-switching. You need both as the latter takes time to switch.
 

amirm

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BTW, there is a lot of value in standardizing on a known unit beside my AP for these measurements instead of each one of you getting a different unit. :) So if Quantum Asylum is it, that would be good and maybe a group buy can be made. I can also lean on them for marketing value they may get on our forum.
 

Blumlein 88

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You can do that but one wrong signal or turn of the volume control will blow up the input of the sound card. It is just too high of a risk for a good sound card. In the extreme case, it could even travel upstream to the system driving it and damage that!

BTW, that is all that the one we are talking about has right now. The Quantum Asylum though like my AP has both protection and auto-switching. You need both as the latter takes time to switch.
Well what I had in mind was a separate box used only when testing amps, and with no way to turn off the attenuation. So I don't think it all that dangerous done that way. I see the benefit of uniformity in measuring however.
 

Blumlein 88

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How would you do distortion vs power test?
As far as I can tell the Quant Asylum has 100 kohm inputs, and doesn't load the amp even though it takes high voltage.

So you would need to use a test load or an actual speaker (doing both would be a good idea in my opinion). Tap across the load/speaker leads and feed voltage via an attenuator to the ADC. Arrange ADC gain so near max power or slightly over is max voltage. Such measures are usually at 1 khz. You can construct a constant frequency chirp in Audacity that goes from nothing to max. Feed it to the amp and record the result. Small amount of calculation to check voltage vs dbFS levels and you have it then. Good idea in my opinion to repeat the test at 3 or 4 frequencies. A bit of bother, and not completely automatic, but not too terrible.
 

BE718

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Just going back to my cock-up with dBFS v dBV above :). The QA FS input is 6 dBV = 5.6 VPP = 2 VRMS. The Motu has a lot higher FS (with input preamps set at 0dB) of 20 dBV = 28.2VPP = 10 Vrms. So clearly we are not comparing apples with apples.

I calibrated the input of the Motu in ARTA and the results are as follows for an input of -12 dBV:

QA -12dBV (-18 dBFS)


Motu -12dBV (-32 dBFS)
upload_2018-1-14_13-27-16.png


upload_2018-1-14_13-28-16.png



So the Motu is 32 dB away from its FS input, the QA is 18 db away. When the motu is calibrated to dBV you see the noise floor rises as we are adding about 20dB on.

I then set the mot0 to -18dB FS. In all of these tests the motu shows no harmonic distortion visible above the noise floor.

Motu -18 dBFS
upload_2018-1-14_16-12-29.png


All this shows how we do need to cross check our measurements with a known transfer standard. The distortion shown on the QA, is it the ADC or is it the DAC signal generator?

I will hook my meridian explorer up and see how that fairs - we could use that as the DUT to compare our systems, I have no problem sending it to you guys.
 

Blumlein 88

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Just going back to my cock-up with dBFS v dBV above :). The QA FS input is 6 dBV = 5.6 VPP = 2 VRMS. The Motu has a lot higher FS (with input preamps set at 0dB) of 20 dBV = 28.2VPP = 10 Vrms. So clearly we are not comparing apples with apples.

I calibrated the input of the Motu in ARTA and the results are as follows for an input of -12 dBV:

QA -12dBV (-18 dBFS)


Motu -12dBV (-32 dBFS)
View attachment 10056

View attachment 10057


So the Motu is 32 dB away from its FS input, the QA is 18 db away. When the motu is calibrated to dBV you see the noise floor rises as we are adding about 20dB on.

I then set the mot0 to -18dB FS. In all of these tests the motu shows no harmonic distortion visible above the noise floor.

Motu -18 dBFS
View attachment 10058

All this shows how we do need to cross check our measurements with a known transfer standard. The distortion shown on the QA, is it the ADC or is it the DAC signal generator?

I will hook my meridian explorer up and see how that fairs - we could use that as the DUT to compare our systems, I have no problem sending it to you guys.
Very nice post. Thanks.

I almost put up a post three weeks ago about using 3 ADC/DAC devices to cross check and determine what artifacts were coming from which devices. In the end I assumed most would not read thru it all. To my dismay my best cleanest DAC was in a different box from my best cleanest ADC. I suppose if we ship a DAC around we are in a sense about to do this on a group basis. So some discussion of that might be fruitful.
 

BE718

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BTW, there is a lot of value in standardizing on a known unit beside my AP for these measurements instead of each one of you getting a different unit. :) So if Quantum Asylum is it, that would be good and maybe a group buy can be made. I can also lean on them for marketing value they may get on our forum.
I do agree with this, minimising variables is important. I am very tempted to get an AQ just for kicks whatever, but if you could persuade them of the marketing value of its use on the forum then perhaps we could get a better deal :)

I think my only concern is its input FS voltage. Many DACS, although notionally output 2 V RMS FS, they will often be a bit above this which means having to switch in the 20dB attenuator on the QA. This could leave us maybe 15 -to 18 dB below the ADC FS. This is both good and bad. Whilst we wont make the most of the dynamic range and spuria might disappear into the noise floor, we also will reduce the harmonic distortion of the ADC as it approaches 0 dB FS. This could also lead to discrepancies in comparing one DAC to another. Oh dilemmas ! :)

Amir, how does the AP cope with this. I gather its auto scaling input amps, and I assume that is in discrete steps. How large are they? Small enough to keep very close to the ADC FS? I have found on my Motu if I start using the input amps to scale say a 2 v rms input close to FS that noise and distortion also rises.

Alan
 
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Blumlein 88

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I do agree with this, minimising variables is important. I am very tempted to get an AQ just for kicks whatever, but if you could persuade them of the marketing value of its use on the forum then perhaps we could get a better deal :)

I think my only concern is its input FS voltage. Many DACS, although notionally output 2 V RMS FS, they will often be a bit above this which means having to switch in the 20dB attenuator on the QA. This could leave us maybe 15 -to 18 dB below the ADC FS. This is both good and bad. Whilst we wont make the most of the dynamic range and spuria might disappear into the noise floor, we also will reduce the harmonic distortion of the ADC as it approaches 0 dB FS. This could also lead to discrepancies in comparing one DAC to another. Oh dilemmas ! :)

Amir, how does the AP cope with this. I gather its auto scaling input amps, and I assume that is in discrete steps. How large are they? Small enough to keep very close to the ADC FS? I have found on my Motu if I start using the input amps to scale say a 2 v rms input close to FS that noise and distortion also rises.

Alan
This sort of thing is what will need to be worked out some. As an example my Antelope Audio Zen Tour is tricky. One set of line level inputs has variable gain from -6db to +20 db. If you stay at or below +12 db the noise floor moves with gain and the dynamic range of the device is unchanged. If you go above that, then the noise floor begins a rise (though not one to one) and distortion while still very low also starts to go up. So it takes a bit of investigation to make best use of it even though it is pretty good at its worst.
 

BE718

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Notch filter will remove the problem of ADC input distortion close to FS.
 
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