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Audio measurement gear

SIY

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Or better. I have no problems getting 20 dB below that with signal averaging and characterizing loopback. Pete's interface can get you another 10 dB.
 

Blumlein 88

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Hi - question for ya'll relevant to this thread.

I do a large portion of my listening out of my OTL tube amplifier. I'd love to have an affordable measurement setup such that I can quantify the harmonic distortion profiles of various input/output tubes and see if there is a correlation to my subjective listening preferences.

Would the QuantAsylum QA401 be a good choice for this use case? The price is reasonable and it seems to be getting very positive feedback.

Also, I have never taken audio measurements before, so I will have to do a fair amount of learning. I am not an electrical engineer, although my first degree is in a STEM field (now work in healthcare), I'm confident I can figure it out.

Thanks!
If you are going to be doing speaker/amp level measurements the QA401 is probably a good deal. A soundcard and something else like the Pete Millet interface could work too. The QA401 is set up for your needs, and likely cleaner than what you are measuring. There is a question not resolved in my mind in regards to noise floor modulation, but that isn't going to be a problem for your purposes.
 

Blumlein 88

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Any suggestions for a reasonably priced competent USB-based ADC solution? I've been thinking about getting the RME ADI-2 Pro just because it is such a Swiss army knife, but can't justify paying the price for my modest needs.
Like SIY said, a 2i2 can do a lots. A 2nd hand Forte is a quieter cleaner device. You can get those 2nd hand for $200. But it is a discontinued interface which it is appears they aren't going to support in the future on the software side. The same ASIO drivers as offered initially. They do work fine with Windows 10 and the current Mac OS. Really clean microphone pres on this if you care.

I'd sort of like the RME offering too, but I just don't need it for testing. I'd like the quietest thing going, but don't really need it.
 

gvl

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What does the QA401 have additional to offer over say a Scarlett 2i2 ? Just better integration with the software measurement tools?
 

amirm

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What does the QA401 have additional to offer over say a Scarlett 2i2 ? Just better integration with the software measurement tools?
It has a scalar and software tailored for measurements. These things are very important.
 

Blumlein 88

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What does the QA401 have additional to offer over say a Scarlett 2i2 ? Just better integration with the software measurement tools?
I've not had hands on one. But it offers you the chance to connect speaker level signals without harm. You can do that with a 2i2 without possibly damaging it unless you create or get some sort of box to drop the signal level. It would be much more convenient.
 

L0rdGwyn

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A sound card plus an interface like Pete Millett's will be able to get you capabilities to get those spectra at a very low cost.

If it helps, I wrote a series of articles on this in AudioXpress. Here's part one of the series, with links to the other parts at the end.
Thanks! I'll take a look at your articles and the possibility of using a sound card.

If you are going to be doing speaker/amp level measurements the QA401 is probably a good deal. A soundcard and something else like the Pete Millet interface could work too. The QA401 is set up for your needs, and likely cleaner than what you are measuring. There is a question not resolved in my mind in regards to noise floor modulation, but that isn't going to be a problem for your purposes.
Thanks for the reply. I've reached out to QuantAsylum as well to hear their thoughts on my particular use case. I understand that it is probably overkill, but another appealing aspect of the QA401 is the total package and the included software.
 

gvl

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I'm considering the QA401 too as it is a good package at a reasonable price. The only bummer I don't think it can feed a DAC with a digital stimulus, or can it?
 

SIY

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Use your computer to send the data. The QA401 can then be used to look at the output (I think- I haven't used one yet).

The 2i2 also won't send digital data. The card I used before it, the M-Audio 192, had spdif in and out and very good performance. Too bad it doesn't fit in my current computer...
 

gvl

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Use your computer to send the data. The QA401 can then be used to look at the output (I think- I haven't used one yet).

The 2i2 also won't send digital data. The card I used before it, the M-Audio 192, had spdif in and out and very good performance. Too bad it doesn't fit in my current computer...
It would be nice if it provided an integrated solution that could send out a digital output and take analog DAC measurements with a push of a button. My understanding it can do it for amp testing, but not for DACs. That's what I wanted to say. From memory there is an option to send the test signal to the default Windows audio device, but unclear how well that works if it is not using the WASAPI exclusive mode.
 

SIY

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If you can scare up an older computer with a PCI slot, the M-Audio card I used will do that (assuming you have software like ARTA or Virtins Multi-Instrument). I see them on eBay for $50-75.
 

gvl

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Well, here is a recent DAC evaluation application note for the QA401 using the option I mentioned before. So seems it can do more than I thought by enabling test signal mirroring to the Windows default audio decice:

https://quantasylum.com/blogs/news/rapid-dac-evaluation

They sort of imply they use the audio interface in exclusive mode, but at the same time they say changing the system volume changed the measurement results which is odd as if they were writing to the device directly system mixer should have had no effect. Also suspicious is the statement that you can change the bit depth in the Windows audio device settings which probably indicates the test signal may be subject to resampling by the OS.
 

Blumlein 88

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gvl

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One other reason besides the noise floor that makes me want the ADI-2 Pro is the 768kHz sampling rate.
 
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