[LAU] Affordable well-working USB interface with low latency at 48kHz?

Sam Kuper sampablokuper at posteo.net
Fri Dec 18 15:51:33 CET 2020

On Thu, Dec 17, 2020 at 03:08:54PM +0100, David Kastrup wrote:
> just got an UMC22.  Its codec is a Burr-Brown (TI) PCM2902.  Looking
> up its specs, it's USB1.1 full speed and sports stuff like
> • Stereo ADC
> – Analog Performance at V BUS = 5 V
> – THD+N = 0.01%
> – SNR = 89 dB
> – Dynamic Range = 89 dB
> – Decimation Digital Filter
> – Pass-Band Ripple = ±0.05 dB
> – Stop-Band Attenuation = 65 dB
> – Single-Ended Voltage Input
> – Antialiasing Filter Included
> – Digital LCF Included
> "Not recommended for new designs" (currently the card is being sold
> new everywhere), an USB1.1 (and USB is half-duplex, so this is
> certainly responsible for part of the latency) 48kHz design with a
> 16-bit ADC specified for slightly above 14bit of precision.
> And that's the naked codec, without being impacted by any circuitry
> around it.
> It's more compact for sure than my current solution at one ensemble
> member (mic input into a Mackie Onyx 400F with dead digital circuitry,
> out via the plugin jack into the mic input of a laptop).
> For -p64 (without --sync) I get
>    464.320 frames      9.673 ms total roundtrip latency
>         extra loopback latency: 272 frames
>         use 136 for the backend arguments -I and -O
> (the -O and -I values are independent of -pxx I think).
> For comparison: with my Alesis iO|14 (Firewire, a lot more inputs and
> outputs) I get 81 for the backend arguments regarding additional
> loopback latency.  With a Hammerfall DSP (PCMCIA card via expresscard
> adapter, so routed through a PCI to PCIx converter) it's 31 if I
> remember correctly.

Yes, this is a bit disappointing from the UMC22.

Thank you for taking the time to post the specs & test results, though!

>> I need to ask the exact model of Behringer that my one orchestra
>> colleague got.  That one's performance (regarding latency/dropouts)
>> did not really appear to improve upon my stone-age Tascam US-122L
> I think it might be that model but I haven't asked back yet.

OK, will be interesting to know.

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