[sdiy] Decent 192kHz USB audio-interface

Andrew Simper andy at cytomic.com
Fri Apr 30 04:43:25 CEST 2021


I just stuck a 100hz sawtooth from my Matriarch (ok so not a signal
generator) into my RME Fireface UCX and it's pretty flat right up to 80khz
when running in 192khz mode:

https://cytomic.com/files/forums/matriarch-saw-direct-out-192khz-rme-fireface-ucx.png

Where is this 40khz bandwidth limit you're talking about for AKM chips? The
Fireface UCX is using this AKM ADC (as quoted from RME tech support):

"Sharp Roll Off Short Delay Filter is in use here.

http://www.asahi-kasei.co.jp/akm/en/product/ak4621/ak4621.html"

Cheers,

Andy

On Fri, 30 Apr 2021 at 08:15, Mike Bryant <mbryant at futurehorizons.com>
wrote:

> Every mic preamp ADC I know of, including several I've designed myself
> which I won't plug here, primarily rely on the ADC itself to set the
> frequency response.  The AFE usually has a 3dB point of around 80kHz or
> higher so as not to affect the overall phase response, then drops like a
> stone to avoid any RF getting to the ADC.
>
> Also AKM and Cirrus ADCs seem to stick to a 40kHz bandwidth at 192kHz
> sampling so it may only be ESS or custom equipped units that can do 80kHz.
>
> -----Original Message-----
> From: cheater cheater [mailto:cheater00social at gmail.com]
> Sent: 30 April 2021 00:49
> To: Mike Bryant
> Cc: Richie Burnett; synth-diy mailing list
> Subject: Re: [sdiy] Decent 192kHz USB audio-interface
>
> You might have a hard time going from chip model to ADC unit. Looking at
> units, looking at the teardowns, might be one way to find out the chip,
> then look it up. However, that still doesn't say anything about the analog
> front-end, which could well mess with frequencies above 22k.
>
> On Thu, Apr 29, 2021 at 6:19 PM Mike Bryant <mbryant at futurehorizons.com>
> wrote:
> >
> > Most high frequency sampling ADCs aren't good to 80kHz.  They have a
> much more relaxed roll-off to about 40kHz to avoid phase effects on the
> audio, then dive.  Probably best to look at the ADCs datasheets from AKM,
> Cirrus and Analog Devices and find an ADC that does what you want, then
> look for units that use that device.
> >
> > -----Original Message-----
> > From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of
> > Richie Burnett
> > Sent: 29 April 2021 11:44
> > To: synth-diy mailing list
> > Subject: [sdiy] Decent 192kHz USB audio-interface
> >
> > Can anyone recommend a decent external USB audio interface that's
> capable of sampling at 192kHz in record and playback?
> >
> > This is a bit off topic, but it's still audio related! ;-)  Some of my
> colleagues do underwater acoustic communications work and have been using a
> "Creative Labs Sound Blaster X-Fi HD 24-bit 96KHz USB Audio Interface" with
> great success to record and playback ultrasonic signals up to 44kHz.  Now
> they are wanting to do similar up to around 80kHz so I'm looking for an
> external audio interface capable of sampling at 192kHz with an analogue
> bandwidth out to around 80kHz.
> >
> > The only application I'm aware of that requires this sort of analogue
> bandwidth is the delivery of composite FM stereo multiplex from studio to
> transmitter site over IP.  So, I know it is possible, but wanted to avoid
> buying lots of audio interfaces and testing them to see which are good to
> 80kHz!
> >
> > Any tips/pointers/experience good or bad would be much appreciated.
> > Off-list is fine if high-bandwidth audio is not considered to be of
> interest to others.
> >
> > Many thanks in advance,
> >
> > -Richie,
> >
> >
> >
> > --
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