Budget 192khz A/D

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abbey road d enfer

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ruffrecords said:
What about noise shaping? This is a 32 bit AtoD so presumably at some point this will be dithered down to 24 bits at which point there is the opportunity to include some noise shaping. Usually this is arranged to improve the S/N in the audio band at the expense of higher noise out of band. Fine if you want to make your specs look good but bad news if you are looking to see significantly beyond the audio band.

Cheers

Ian
I believe that is the subject of the quote in the ESS board datasheet.
"The ES9822 PRO has an Ultra-Low Noise Floor Bandwidth of 200kHz"
http://www.esstech.com/files/1816/0767/3501/ES9822PRO_DS_brief_v0.2.6.pdf
I read it as "the noise spectrum is shifted above 200k".
 

Tubetec

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Im in two minds about signing the NonDis agreement with ESS , if I cant refer to any of the data here for the purposes our discussion its all a bit pointless  :(
 

Rocinante

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Another consideration is the BEIS adds. I've been wanting to use his pcb/kits for awhile as the sp ed cs are great. Well worth looking into. At least he isnt a Ross Collins.
 

Tubetec

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I did have a look at the Beis A/D , down sides are for your 150 euro you dont get any USB connectivity or I2s for that matter ,also your limited to 192khz .
For starters I might just get the 39.99 DIYINHK 384khz i/o board ,then get a few of the cheaper A/D i2s boards like the PCM1802/1808(ebay) and WM8782 from Audiophonics.fr . Of course in terms of noise and distortion none of those boards give state of the art performance , but they might have good enough bandwidth upto 80khz or more .
Dedicated audio ADC's often tail off the frequency response well before FS/2 , for the vast majority of music recording purposes thats no problem , but when for instance we want to look at  resonances in small audio transformers response upto or above 100khz is a major plus.
 

abbey road d enfer

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Tubetec said:
when for instance we want to look at  resonances in small audio transformers response upto or above 100khz is a major plus.
OTOH, I've never had any issues with transformers that resonate at more than about 60kHz. I've never seen it consequential to the audio quality or EMI/RFI.
 

Rocinante

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DAC doesn't seem to be a problem IME. The AD on the other hand...
I have optical inputs via a MOTU 2408MK3 which I use solely as a bridge for my ADAT and SMUX converters so the BEIS works for me but with so few reviews I am hesitant. Currently I have a LUCID and RME AD-2 using optical. BEIS seemed convinced that his AD-24 would work with the MOTU.
In my case I need them tied together via clock and adat.
Still i will continue watching this thread with interest.
Do you need more than 192k?
 

Tubetec

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Yeah Dac performance appears to be an order of magnitude better than A/D, although the newest A/D convertor chips narrow the gap considderably . 
Ive recently done some multitrackrecording at 96khz and Im really happy with the results , maybe for simple stereo recording I might be tempted to go higher . The main reason Id like to have the facillity of 384 or 768 khz is for use with REW. Ive done a couple of very simple tube preamps , low impedance(in tube terms) ,low noise, high current ,high bandwidth(around 100khz) , it would be nice to have a measurement system better than this so we can fully evaluate all the harmonics and distortion behaviour . I did post an interview with Rupert Neve lately in Brewery , he's of the opinion usable bandwidth upto around 200khz makes a difference in his designs , I guess it greatly depends on source material too .

My main computer interface is a Tc electronic 24D , co-ax ,optical , adat i/o, 2 mic ins, 2 line ins and four outs , upto 192 khz sampling. 
Thanks once again for the interest Rocinante.
 

hellalive

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Mind that usually mid budget interfaces like the TC you mention may to add distortion at higher sample rates - it will work well at 96kHz, but maybe suffer at higher sample rates. I like to check for audible harmonics generated by intermodulation in these interfaces, both hitting converters from the analog and digital realm, and using my ears (and scopes). I started doing this since I noticed the problem on a (prehistoric) focusrite - recorded drums on an Apogee AD16, played back on a DA16 and all worked great, brought home and it seemed like it had lost all the depth and definition. Got back to the studio with my interface and on the same monitoring system the focusrite was adding a lot of distortion, maybe because of bad implementation of filtering in the conversion stage, or who knows. Experienced this with various other interfaces. Using a sweep at frequencies higher than the audible may reveal the problem - you'll actually hear chirping sounds, but you'll need a good system and the volume cranked. Sweep on the additional octaves, but I wouldn't go over nyquist :)

Hitting analog back with a 96kHz recording is usually more pleasant to me than lower rates, and has more definition on high frequency transients - they seem to be more realistic. Never heard differences with higher sample rates than 96kHz, so i stick to that (also CPU and HDD space issues).

For measurement purposes, if you want to sample 100kHz stuff and see real resonances, go at least 384 imho - but I don't know if you can really have good results with a kit going this high..

Hope this helps
 

trobbins

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I had a look recently for commercial product with sampling > 192ks. The ADI-2 Pro FS droops badly from about 140kHz at 384k/s sampling - perhaps related to the bandwidth of the low-distortion opamps just as much as the digital interface chip.

I have had a need for automated REW style measurements for audio, and 96kHz bandwidth can be limiting as it is not just the first resonance frequency of say output transformers that is important, but rather the measurement of gain and phase margins that can require measurement bandwidth well beyond 96kHz, as the consequences for feedback level and stability revert back in to the audio range below 20kHz. A PicoScope (eg. 2206B) with 3rd party FRA4PicoScope app seems the simplest existing method for >100kHz measurement.
 

abbey road d enfer

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A PicoScope (eg. 2206B) with 3rd party FRA4PicoScope app seems the simplest existing method for >100kHz measurement.
Is it what you use?
I've often looked at Pico products. I have a question I haven't found a solid answer. It seems the filter option works with only specific combinations of hardware. Does it work with the basic 2204? Does it require specific probes?
Sorry for hijacking the thread...
 

trobbins

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No I don't have a Pico - but a NZ friend has, although he hasn't used it for that application - but it got me looking. Pico have a forum, so if the filter info is not obvious (I remember searching through Pico docs for some details - they are a little short on some details) then that would be the place to go - hopefully it is as good as the REW forum.
 

Tubetec

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There is a discontinued model ADC-216 from Pico , it does come up cheap on ebay once in a while , it has 16 bit vertical resolution(none of the 220x series are 16 bit). Quotes a S/N of around 100db and analog bandwidth of 166khz in mono mode . Works with the version 5 of the pico software provding FFT etc


Seems to be a few workarounds for the parallel port issue.
 
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abbey road d enfer

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There is a discontinued model ADC-216 from Pico , it does come up cheap on ebay once in a while , it has 16 bit vertical resolution(none of the 220x series are 16 bit). Quotes a S/N of around 100db and analog bandwidth of 166khz in mono mode . Works with the version 5 of the pico software provding FFT etc
Thanks for the tip. Interesting but the parallel port is a deal breaker.
 

Tubetec

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Seems to be limited to 32 bit os as well , but can be done with viritualisation . Even if the interface proves tricky no reason not to throw an older laptop into service purely to run the software end on its own dedicated system .
The maker created a parralel port to usb adapter but there long since sold out .
 

abbey road d enfer

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The least expensive current offer from Pico compatible with BW and resolution requirements is the 4262 at $1125. I wonder if the Enhanced vertical resolution feature is actually capable of providing noise measurements equivalent to a 24-bit soundcard.

"Pico have a forum"
Yes, I have submitted there, still waiting for approval.
 

Tubetec

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4262 replaced the ADC-216
Theres a laptop express/pcmcia card to parrallel port adapter on ebay for around 15STG that might work with the 216 , for the little money involved its worth the risk , you might end up up with a pretty decent measurement setup good to 160khz and change out of a 50 .

The Quant Asylum QA-401 was mentioned some way back in this conversation by Hanafri but I overlooked the reference until recently ,
due to shortages of the ad/da chips they had to cease production of the old model but they have just release the QA-402 . Along with its companion products it makes a neat job of it all .


Software is still in development .
 

abbey road d enfer

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4262 replaced the ADC-216
Theres a laptop express/pcmcia card to parrallel port adapter on ebay for around 15STG that might work with the 216 , for the little money involved its worth the risk , you might end up up with a pretty decent measurement setup good to 160khz and change out of a 50 .
That would be another ratsnest of boxes and wires, which I want to avoid as much as I can.
The Quant Asylum QA-401 was mentioned some way back in this conversation by Hanafri but I overlooked the reference until recently ,
I have one that is used as an expensive paperweight.
Software is still in development .
Software is always in development at QA, since they seem to rely on users to do it.
Matt is a nice guy, but everytime I had a request, he told me it was easy to do, if I was not able I should ask someone...
 
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