On 4/7/06, Dieter <[EMAIL PROTECTED]> wrote:
All of the above. Particularly concert work, but recording can also be latency-sensitive if the performer wants to hear himself post-effects.
Yeah, but no longer ;-) Most of the work I do is in a medium-sized church; for that I'd like AT LEAST 30 inputs + 10 outputs; more is better.
No, but for live (concert etc) work that's not feasible - the signal has to go through the effects loop in realtime.
>> Which applications care about latency?
>
> Live work.
Recording studio?
Concert?
Other?
All of the above. Particularly concert work, but recording can also be latency-sensitive if the performer wants to hear himself post-effects.
> LOTS of inputs / outputs
What is LOTS these days?
Sgt. Pepper was done with a 4 track tape. :-)
Yeah, but no longer ;-) Most of the work I do is in a medium-sized church; for that I'd like AT LEAST 30 inputs + 10 outputs; more is better.
> 2. A semi-pro-level / amateur mastering sound card with external connection
> box. Better than PCI sound cards, but not used for pro gear, and
> particularly not for live work. Balanced inputs still important but not
> essential, 48V not essential. Latency still important, but most amateurs
> will work around it if they have to.
I'm thinking something like 2. a "pro-sumer" level product. (Low end pro,
high end consumer)
I'm thinking a "2" level device might be useful for capturing sounds
in the field (e.g. wildlife). Laptop plus box plus mics.
> For 1, low latency is critical. You want as little delay between the sound
> hitting the mic and it being returned to the speakers as possible.
If we are talking recording studio, mic -> box -> artist's headphones,
do you see the signal going to the CPU and back? I'm thinking
the signal could go straight through the box to the artist's headphones,
and a digital copy goes across Ethernet to the computer to be recorded
on the hard drive. Latency of data going to the hard drive is not critical.
No, but for live (concert etc) work that's not feasible - the signal has to go through the effects loop in realtime.
>> 5.25" < 19" therefore no problem. Even I can fabricate rack ears for
>> a 5.25" box.
>
> True. But you probably can't fit 60 XLR connectors on a 5.25" faceplate
> :-)
How many XLR connectors can you fit on a PCI/PCIe card edge?
I don't have dimensions handy, but I'm thinking you'd need a doublewide
card edge? How many card slots does your computer have?
I'm thinking modular. You have 'x' number of audio channels per box.
If you need more than that, you use more boxes. A full height 19" rack
will hold a LOT of 5.25" boxes. Add some sort of timestamp to keep channels
from different boxes in sync. And/or in sync with video.
The question I see is whether to go with the balanced XLR for the high end,
or unbalanced RCA or 1/4" (or even 1/8"?) phone jacks for the consumer.
I think most instruments (electric guitars, synths, etc.) use unbalanced
1/4" mono phone jacks? Yes, in many cases the artist will want to mic the
speaker, to capture the artistic distortion of their favorite tube amp and
speaker, but in other cases you might want to plug in directly.
Can these be converted with a balun like the $3 RF baluns for converting
between 300 Ohm twinlead and 75 Ohm coax? Or some converter chip, like
the boards for converting single-ended SCSI to differential SCSI? Could
the board be set up to go either way? Have a box for XLR and a box for
1/4" phone. Mix and match the boxes in your 19" rack to fit your needs.
You can construct a pretty simple cable to go from unbalanced phone jack to balanced XLR (so long as you don't turn the phantom on that channel ;-) and with 24 bits of precision you can do the scaling between line level and mic level in software without much penalty. So if you've got balanced XLR then you can rig unbalanced 1/4in into it.
I like the idea of having both XLR boxes and 1/4in boxes that are interchangeable, though.
Another thing to note: timestamps are not good enough for synchronisation, there has to be a system-wide clock. Otherwise the different clocks will drift. JACK, for instance, gets quite upset when one sound source has more samples than another in the same time period; this is why you can't just stack several sound cards into a box and hook them all up with JACK.
Tom
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