cheapish high performance USB ADC for distortion measurements

[sigmatechnica]

Im looking for a good ADC to make measurements on my other diy audio gear. I'm planning to add some attenuators and buffers to the frontend and make it into a 'proper' measurement instrument Some requirements:

* USB (i suppose spdif could be made to work, i'd have to worry about getting it into the pc though, usb seems easier)
* I don't need load of channels, 2 would be fine. 1 would be fine but they don't tend to come in 1's!
* If it comes with an ok dac in it, great. if not i can use some other signal source for testing. Good dacs seem easier to find and better documented than good ADCs
* linux drivers available. Various ancient m-audio fireware and usb interfaces i have had previously have been problematic in this respect.

I was considering one of the pro audio interfaces from Focusrite, Behringer etc, not sure if they are the best though, after much research on the UMC202HD i discovered the adc in it is not that good. most of the measurements people have done tend to focus on the dac side.

Does anyone have any suggestions of something that might be suitable here?
Thanks!

 

[pozz]

https://www.audiosciencereview.com/forum/index.php?pages/Audio_Equipment_Reviews/

Go to Rankings. Select ADC under Measured System. You will see all the devices* with an ADC measured so far by Amir, and can sort by price, etc.

*Still catching up on adding entries of the last two months.

 

[sigmatechnica]

https://www.audiosciencereview.com/forum/index.php?pages/Audio_Equipment_Reviews/

Go to Rankings. Select ADC under Measured System. You will see all the devices* with an ADC measured so far by Amir, and can sort by price, etc.

*Still catching up on adding entries of the last two months.

Oooh! i didn't know this existed! Had been searching for specific threads on the subject.

Dismayed to discover though that the performance i was hoping for doesn't align very will with my idea of 'cheapish' you get what you pay for i suppose The Focusrite Scarlett 2i2 looks about the best value

 

[Twelvetone]

MOTU (Mark of the Unicorn) M2. Equals/outperforms Sc 2i2 in most/all important ways. Widely available at ~$180. I scored one (used) on eBay for $100 and find it superb.

 

[3125b]

You could have a look at Julian Krauses Youtube channel, he measures USB interfaces: https://www.youtube.com/channel/UC0HrD4cTsQpAZ8KK9jPzzGg
The mic inputs of most of the interfaces tend to roll off in the lows, but depending on your expectations that might be fine.
You have to be realistic about your expectations, you're just not gonna get anything really good for 50$.
So what is your idea of "cheapish"?

I personally would say that it needs to clear the 96dB SINAD (16bit) hurdle by a fair margine to be able to test for transparency of the other device, otherweise what's the point of even measuring?
The Motu M4 would be a decent choice, but it's 250$ new, maybe get a used one.

 

[audio2design]

Total brain fart but there is a low cost AP competitor about $500. Used to have a few.

 

[sigmatechnica]

So what is your idea of "cheapish"?

I personally would say that it needs to clear the 96dB SINAD (16bit) hurdle by a fair margine to be able to test for transparency of the other device, otherweise what's the point of even measuring?
The Motu M4 would be a decent choice, but it's 250$ new, maybe get a used one.

cheapness is hopefully under £100 and I agree, i was hoping for about 100db SINAD. For the record i'm wanting to measure power amplifiers and various analog filters mostly, not other DACs (which wouldn't really be meaningful without spending serious money here)

One can resort to tricks, put a notch filter in front of the ADC to filter the fundamental tone and just examine the residual, presumably to make actual quantitative measurements there though i'd need to calibrate that filter, and the tuneing would drift a bit with temperature etc that would throw such measurements off. I figure it's probably best to start with the best ADC i can get and go from there.

MOTU gear doesn't seem to show up much on UK ebay

 

[Blumlein 88]

Total brain fart but there is a low cost AP competitor about $500. Used to have a few.

Maybe thinking of the Quant Asylum? It isn't currently available as it used an AKM ADC and the fire at their factory still has those in short supply. It also had a problem with noise floor modulation.

 

[Blumlein 88]

https://www.ti.com/tool/PCM4222EVM#... convenient,of the PCM4222 integrated circuit

This is an ADC evaluation board for $149. Doesn't cost much to get it working. A few people have them here on ASR. You aren't going to get better for that kind of money.

 

[Blumlein 88]

Ready made for your budget a Focusrite or similar is about as good as you'll get. For a little more a Motu M2 is the one to get. You can likely get 100 db sinad with them one way or the other. At that budget you'll be constrained getting much better however.

A second hand Focusrite Forte might worth looking for. I had one (sold it to member here). Those are probably going to cost you about $150 2nd hand. They have the same chips and performance as the Focusrite Clarett line.

 

[sigmatechnica]

https://www.ti.com/tool/PCM4222EVM#:~:text=The PCM4222EVM provides a convenient,of the PCM4222 integrated circuit

This is an ADC evaluation board for $149. Doesn't cost much to get it working. A few people have them here on ASR. You aren't going to get better for that kind of money.

That's an interesting option. i'd need some way to get the spdif/aes into the PC though and it would probably be the best part of £200 after tax+postage. Impressive performance of the chip though! that would probably the the ultimate way to go.

I'll probably try to just get a cheap second hand Focusrite. It will probably hold it's value reasonably well if i want to sell it on and upgrade in the future too.

 

[sigmatechnica]

I just won a broken Focusrite Forte for £23 on ebay. seller had stuck 12v up the 5v input. Hopefully it's just the surface mount fuses or at worst the power MUX chip that's dead. Worst that happens i loose £23 and gain a couple of fun evenings trying to fix it!

I'll post some updates on this project if it turns out to be successful. it will be something like what this guy did http://www.pmillett.com/ATEST.htm but with some changes and maybe some additional notch filters

 

[audio2design]

Maybe thinking of the Quant Asylum? It isn't currently available as it used an AKM ADC and the fire at their factory still has those in short supply. It also had a problem with noise floor modulation.

Yup that was it. They have released the 402 now that replaces the 401 due to the AKM fire.

 

[audio2design]

https://www.ti.com/tool/PCM4222EVM#:~:text=The PCM4222EVM provides a convenient,of the PCM4222 integrated circuit

This is an ADC evaluation board for $149. Doesn't cost much to get it working. A few people have them here on ASR. You aren't going to get better for that kind of money.

Add some low capacitance protection circuitry on the front end and it is a pretty nice little package.

 

[staticV3]

You may be interested in the upcoming E1DA Cosmos ADC.
$120 (t.b.d.), 1.8-30Vrms input sensitivity, THD+N is -118 in stereo mode, -121 in mono mode, -126 with the Cosmos APU notch filter sold separately. For reference, the APx555 maxes out at -124dB THD+N.

Spoiler: Photos

 

[sigmatechnica]

You may be interested in the upcoming E1DA Cosmos ADC.
$120 (t.b.d.), 1.8-30Vrms input sensitivity, THD+N is -118 in stereo mode, -121 in mono mode, -126 with the Cosmos APU notch filter sold separately. For reference, the APx555 maxes out at -124dB THD+N.

Ooh that's an interesting product. I'm half way through building my own, It will be interesting to see what performance i get once my own buffers/attenuator/notch filter are added. It's been cheap enough so far upgrading the adc in it later might be an option

 

[Noisea]

Total brain fart but there is a low cost AP competitor about $500. Used to have a few.

Mind telling us manufacturer and product name, please?