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

David Kastrup dak at gnu.org
Tue Dec 1 16:37:40 CET 2020

David Kastrup <dak-mXXj517/zsQ at public.gmane.org> writes:

> Hi,
> 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).

A note after the fact: the one Mac Mini in question has Thunderbolt
(version 1 or 2) for which there is a Firewire 800 adapter with a
current preowned price tag of about €15 plus portage.  You still need to
go down from FW800 to FW400 (what basically all soundcards have).

However, this particular Mac Mini is connected to a large screen from
Apple using some proprietary interface, and that screen acts sort of
like a monster hub with USB, Thunderbolt, and even an FW800 connector.

So when checking the connectivity of some Mac, it may be worth checking
the screen as well.

With regard to interfaces, I am likely going for Line-in connectors when
available.  Soundcards with insert connectors (I even have a Mackie Onyx
400F with dead logic that can be taken out, leaving only 4 good analog
preamps with unbalanced outputs via the insert connectors) make for
sensible preamps.  I also have some half-broken mixer (one strip dead,
noisy headphone out) that will deliver preamps, and when feeding those
into Line-in or even mic-in of lousy soundcards, the gain is such that
you get good SNR.

There are soundcards in "standalone" mode that will route their inputs
to line out (also handheld recorders) but those tend to do the "routing"
digitally, meaning that you get at least something like 8ms of
additional delay.

So I do get to pass around a number of shoestring and gum solutions that
may or may not prompt some people to get something better.

And it was sobering to figure out that driver support under Linux
appears to die faster than under Windows (MacOSX the jury is still out

Tascam US-122L works well with 64bit Windows drivers, has stopped
working with Linux (and it only ever worked using some undocumented
secret sauce protocol you needed to declare to ALSA).

Mackie Onyx Satellite has stopped working with snd_dice.  I'll see
whether it works with a Mac (though it has really lousy phantom power,
sth like 36V or so which cannot be used in tandem with a hi-impedance
input because of converter whine).

Dug out an old iSight Firewire webcam.  That one works with Linux audio
but requires a buffer size of at least something like 485 samples,
resulting in too much latency for orchestra practice.  That appears like
a design constraint of its Firewire packaging, so it likely will not go
away when connecting to an actual Mac.  It might work for video
conferencing, though it's constrained to VGA size.

For one-mic-per-client setups, something like Focusrite Scarlett Solo
looks like a good idea, but I have not gathered actual experience with
it.  Still, if someone asks for advice, that's likely what I'd point to
when the cost is deemed acceptable.

We'll see...

David Kastrup

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