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March Audio

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OK, I'm convinced :) . After a few senior moments with trying to compare the Motu to the QA I have concluded the QA is actually doing very well!

Below is the motu noise floor with the input amp gain set to 0dB and then +14dB to create a FS of 2V rms. This puts the noise floor above the QA.

motu 0db +14 dB gain.PNG


Now with a -12dBV input signal (250 mV rms) for direct comparison to the QA. I cant explain the curve in the noise floor, but either way the QA is doing better.

motu -12 dBV input FS set to 2V.PNG



So I'm going to push the button and get one.

Amir, as mentioned, do you think it is worth seeing if any other members are interested and contacting QA to see if we can get any accommodation on the pricing?
 
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March Audio

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I received a reply about the pricing of the rtx6001 and some plots of performance.

The price for the RTX6001 is USD 2.495,00 / piece. The freight with DHL to Perth is USD 140
.

The performance was good but not really better than the QA. Ill post the plots later

Ouch! That made the QA look very attractive, so I just went ahead and placed an order. Should be here by next week.
 

Blumlein 88

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I received a reply about the pricing of the rtx6001 and some plots of performance.

The price for the RTX6001 is USD 2.495,00 / piece. The freight with DHL to Perth is USD 140
.

The performance was good but not really better than the QA. Ill post the plots later

Ouch! That made the QA look very attractive, so I just went ahead and placed an order. Should be here by next week.

Let us know how that QA works out. I hadn't noticed, but Demian Martin designed this or had some hand in it.
 

amirm

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Ouch! That made the QA look very attractive, so I just went ahead and placed an order. Should be here by next week.
Ah, most excellent. Remind me to create the thread for source test files so that we can do some apples to apples comparisons and get calibrated. I may also get one for amplifier testing because my Audio Precision input stage doesn't like the high frequencies from them and requires an expensive ultrasonic filter that costs more than Quantum unit as a whole! And then it modifies the output of the amp with that filter which I don't like to see.
 

amirm

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That's pretty comprehensive. I will have to check my Audio Precision analyzer against that and see where it falls. Right now the generator in Prism Sound seems good bit cleaner than on Q401. I actually plan on testing the Exasound E32 DAC as my output and see if it does better than the in-built generator in AP.
 

March Audio

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The QuantAsylum QA401 Audio Analyser has arrived. Whats the first thing I do? Take the lid off of course :) Some Electro porn for you.

IMG_20180123_113216.jpg
IMG_20180123_113245.jpg


IMG_20180123_112748.jpg



With terminated inputs I measured the noise floor (32k FFT Hann)

dBFS with 20dB input attenuator active (dBFsS is nominally 2 volts RMS and 20 volts rms with attenuator active)

upload_2018-1-23_11-51-39.png


Attenuator off

upload_2018-1-23_11-54-19.png


dBV Atten on

upload_2018-1-23_11-59-9.png


Atten Off
upload_2018-1-23_12-0-8.png





More later :)
 
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March Audio

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OK, first set of measurements with the QA. Testing my Meridian Explorer 2. I have decided to take the measurements dBr so its relative to the DACS FS output. This seems to me the most sensible way to compare DAC to DAC results. I will send this DAC to Amir so we can compare to his AP analyser to validate the QAs results. Measurement parameters are shown in the plots, top left. Unless otherwise stated sample rate is 48kHz. Tested using the Meridians Line output. Source is Roon playing test tracks prepared in Adobe Audition.

Both the QA and DUT are connected to the same USB3 Hub (smps powered). This could cause problems, however the QA is isolated so we'll see how we go.

IMG_20180126_122253.jpg




0dB at 1kHz - As you can see this just starts to clip the input of the QA ADC which is nominal 2Vrms. Wide skirt is partly due to the Hanning window and limiting the FFT to 32k. Unfortunately the QA software doesnt offer options such as kaiser.

BTW for those less familiar with the FFT windowinf functions have a looke here:
http://zone.ni.com/reference/en-XX/help/371361H-01/lvanlsconcepts/char_smoothing_windows/


upload_2018-1-26_12-10-52.png


So I applied the QA 20dB input attenuator and re calibrated the dBr full scale. As you can see there was a corresponding drop in harmonic distortion which makes sense.

upload_2018-1-26_12-14-8.png



-1dB at 1kHz

upload_2018-1-26_12-20-27.png



-6dB at 1kHz - N
oted a drop in the noise floor. Not sure if this is the Meridian or the QA.

upload_2018-1-26_12-28-28.png



-60dB at 1kHz - Further drop in noise floor

upload_2018-1-26_12-30-2.png



-138dB at 1kHz -
If I have that right thats the LSB :) Is marker M1 USB packet noise? Noise floor continues to drop.

upload_2018-1-26_12-36-25.png



-96.31dB at 1kHz 16bit waveform -
pretty noisy but not unexpected for 16bit

upload_2018-1-26_12-39-32.png



-96.31dB at 1kHz 24bit waveform -
much cleaner

upload_2018-1-26_12-41-14.png



-6dB at 12kHz -
Some interesting spuria at 500Hz, 23500Hz and sidebands at +- 775Hz.

upload_2018-1-26_12-49-4.png



IMD SMPTE (I think :) ) 60Hz + 7kHz 4:1 - 60Hz + harmonic sidebands on the 7kHz tone.

upload_2018-1-26_12-54-5.png


Zoomed

upload_2018-1-26_12-56-7.png


White Noise + 19.1kHz FR and Imaging


upload_2018-1-26_14-7-52.png



Amir, what other tests would you like?

I will also test my Chord Motu later for comparison.
 
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March Audio

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Chord Mojo. Headphone output volume set to 2v rms at 0dBFS.

0db. Just starts to clip the QA

upload_2018-1-26_16-8-7.png



with 20dB attenuator - this seems to the QA ADC is responsible for some of the harmonic distortion.

upload_2018-1-26_16-9-2.png



-6dB

upload_2018-1-26_16-12-15.png



-60dB - Again we see a large drop in the noise floor. This concerns me as it implies the QAs noise floor is significantly varying with signal level. Need Amir to confirm what he sees on his AP analyser.

upload_2018-1-26_16-13-21.png



-138dB

upload_2018-1-26_16-13-57.png



-96.31dB 16bit waveform

upload_2018-1-26_16-15-20.png



-96.31dB 24bit waveform - some dc/low frequency wandering was noted

upload_2018-1-26_16-15-37.png



12kHz -6dB - mmmmm....same 500 and 23500Hz spuria. So thats certainly the QA then....

upload_2018-1-26_16-17-8.png




IMD SMPTE

upload_2018-1-26_16-18-29.png



Zoomed

upload_2018-1-26_16-18-55.png



White Noise + 19 kHz

upload_2018-1-26_16-20-28.png
 

Wayne

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Yes, I am happy to reach out if we can get more interest. I don't think they have a lot of margins but maybe we can a few cents :).

Just maybe interested...... if you guys will assist me in learning how to make the proper tests.
 

Blumlein 88

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Just maybe interested...... if you guys will assist me in learning how to make the proper tests.

Do you have an ADC? That would be the first step. You may have said you did and I didn't remember.
 
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Wayne

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Do you have an ADC? That would be the first step. You may said you did and I didn't remember.

Thank you for your response.

Nope, just a simple 2.1 system. I have a science background, built a couple of audio amplifiers and power supplies (linear - no SMPS back then) in the late '60's (nothing since). I am not an EE, just got re-interested in HIFI after retiring.
 

March Audio

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Thank you for your response.

Nope, just a simple 2.1 system. I have a science background, built a couple of audio amplifiers and power supplies (linear - no SMPS back then) in the late '60's (nothing since). I am not an EE, just got re-interested in HIFI after retiring.

You can use any cheap usb soundcard if you want to have a play and learn about the measurements and techniques, not that there is that much too it :). You will find plenty of people here willing to assist. However making really meaningful acurate measurements is another thing altogether. The major purpose of the above measurements is so that we can compare to Amirs Audio Precision analyser to confirm the QA analyser is really good enough for the job.
 
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