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Actual Analogue Bandwidth of Interfaces

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Actual Analogue Bandwidth of Interfaces

Postby ruffrecords » Tue Mar 02, 2021 11:33 pm

Everybody uses an interface these days and they are readily available with sample rates up to 196KHz. But is the analogue bandwidth available from the seas wide as the sample rate would lead you to expect? I have been looking for an interface with a large bandwidth for audio equipment testing to replace an ancient Ferrograph test set that goes up to 150KHz. But so far, all the readily available interfaces seem to have a built in filter that drops the response soon after 20KHz not matter what the sample rate. The best I have found so far is the KOMPLETE Audio 2 which is 3dB doing at about 70KHz at its highest sample rate.

One interface that may do better is the PUC2 by Yellowtec. This is a professional grade interface that Hugh Robjohns reviewed a few years back but all he said about bandwidth was "The high‑end roll‑off is determined by the sample rate, of course". Does anyone know if that is the case for the PUC2 or does anyone know of any interface that does achieve an analogue bandwidth commensurate with the sample rate?

Cheers

Ian
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Re: Actual Analogue Bandwidth of Interfaces

Postby James Perrett » Tue Mar 02, 2021 11:52 pm

I haven't noticed that behaviour with the setups that I've used at 96kHz. This includes the Zoom U-44, Focusrite Saffire Pro26io together with a Sonifex RB-ADDA1 and Audient ASP008 feeding various digital inputs. I've not gone any higher than 96kHz sampling though.

If you need the high frequency range for looking at bias circuits I wonder if something like a Pico Scope might be more appropriate?

https://www.picotech.com/oscilloscope/2 ... 0-overview
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Re: Actual Analogue Bandwidth of Interfaces

Postby Hugh Robjohns » Wed Mar 03, 2021 12:00 am

I can't say I've noticed many interfaces that "roll off soon after 20kHz" when operating at double sample rates, but I have found a few that don't retain the theoretical bandwidth when working at quad and higher rates... not that I'd be the slightest bit concerned about that.

I know that some of RME's interfaces are available with full audio bandwidths at elevated sample rates specifically for scientific applications involving ultrasonic measurements, although sometimes you need to flash them with specific firmware to re-configure the anti-alias filtering appropriately. I'd suggest contacting RME directly to check on suitable interfaces.
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Re: Actual Analogue Bandwidth of Interfaces

Postby Folderol » Wed Mar 03, 2021 11:16 am

I know by actual measurements that the KA6 has a flat response to at least 40kHz, when running at 96k (it's highest rate).
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Re: Actual Analogue Bandwidth of Interfaces

Postby Martin Walker » Wed Mar 03, 2021 8:19 pm

When I used to review a lot of audio interfaces for SOS I always checked the actual -3dB points at different sample rates, and while most did provide a bandwidth of approximately half the current sample rate, I did receive some whose maximum bandwidth seemed to be around 40kHz however high the sample rate went, and a few that seemed restricted to 22kHz whatever the sample rate (which would seem to defeat the purpose of higher sample rates apart from having better high-end filtering.

Unless such things are mentioned in reviews, all you can really do (apart from measuring the thing yourself) is to scour the appropriate user manual for the full specifications before making a purchase.


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