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

David Kastrup dak at gnu.org
Sun Nov 22 23:30:04 CET 2020


I am currently trying to get the members of my accordion orchestra to
commit to rehearsals using Jamulus.  Under Linux, Jamulus uses jackd to
access sound.  There is a "JamulusOS" bootable image that will use Linux
to access the soundcard.

Now I want to recommend something to band members (and/or get it myself)
when their sound quality and/or latency is not up to par.  My own
collection of sound cards here tends to be Firewire, and supporting that
is not really feasible (the finances would be strained by requiring a
Thunderbolt->Firewire adapter and Thunderbolt is not a given, while
Firewire is not something modern people can think about, and my
Expresscard Firewire adapters still require an actual Expresscard slot).

My own solution right now is an Alesis iO/14 which runs with a roundtrip
latency of about 160 samples at 48kHz.  I've just dug out my
still-not-resold RME HDSP Multiface with a PCMCIA Adapter in an
Expresscard-to-PCMCIA adapter which is sort of a reference interface and
it delivers 62 samples roundtrip delay.  Which is impressive but nobody
has the interfaces for that anymore and it would not be a recommendation
because of its pricing.

I've lent out one Tascam US-122L interface and Tascam has 64bit drivers
for it on its web page that work reasonably well.  Wow.  Under Linux, I
have not been able to get it to work recently and it uses really obscure
and undocumented Alsa modes to get at the data: to provide full-duplex
at higher sample rates (48kHz?  96kHz?  24bit?  Don't remember) via
USB1.1, it has its own protocols that are not class compliant.

So while it miraculously does work with modern Windows, it would not be
a useful option for JamulusOS.  And I am sure I'd get a JamulusOS setup
to run on other people's hardware, and don't have what it takes to make
Windows dropout-free, what with all its secret background processes.  So
that interface is only good for people who feel competent at hardware
jiggling with Windows.

So I am lacking a reasonably solid recommendation of (possibly older but
reasonably quality) hardware with 1 or 2 mic inputs and +48V phantom
power and likely USB2.0 HiSpeed class compliant, possibly 2 headphone
outputs (the lockdown permits two households convening), good
reliability/support under Linux (meaning no obscure software and/or
Windows required for dealing with hardware mixers and mic preamp
boosts), reasonably low roundtrip latency at 48kHz (does not need to be
the insane 5ms from the RME DSP Multiface).

Something that I would not mind taking back.  And which is dirt cheap
these days.

I know, I know, wishful thinking.  But I will not persuade people to buy
old laptops for this feat, and while I might try starting them off their
built-in soundcards/mics to get them warm to the idea, I need a good
path forward.

Thanks for useful suggestions!

David Kastrup

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