Re: Bug? Clicks while recording audio (In) from MIDI (out)
Re: Bug? Clicks while recording audio (In) from MIDI (out)
- Subject: Re: Bug? Clicks while recording audio (In) from MIDI (out)
- From: Herbie Robinson <email@hidden>
- Date: Sat, 22 Feb 2003 16:04:37 -0500
on 2/22/03 2:05 AM, Herbie Robinson <email@hidden> wrote:
It sure *sounds* a lot like what I hear when I connect a MIDI Out to
an Audio In ... +5V at 31250 bps.
It's very hard to imagine how MIDI bits could find their way into a
digital audio stream. I assume you're recording with built-in audio?
It's not hard to imagine there being an electrical issue (grounding?
I dunno, I do software) ...
I believe there was a recent batch of G4 motherboards with a serious
grounding problem...
How recent?
I think it was the first spin of blowhole models where the
motherboards have 3 IDE connectors, but I'm not sure. The machine I
bought around then was one generation earlier.
I've been having problems on my quicksilver purchased on 4/23/02 with
compu-diginoise appearing in outputs of audio devices attached via USB and
Firewire.
First this was only with the EMI 2|6, which was known to have that problem
on "some machines" - and in fact the problem did not occur with my
powerbook, and in fact gettng the EMagic power supply known to help with
this problem did reduce it, but not eliminate it. But 2 days ago I was
having problems with outputs from my MIO 2882 and the problem went away the
next day without anything having been changed - this was a "motorboating"
sound which seemed to depend on CPU activity.
Are the gounding problems you heard about intermittent in nature?
I think they were related to fans somehow; so, they could be. Many
grounding problems show up intermittently because they depend on
specific cable routings and/or external signals (like cell phones) to
beat with signals in the equipment.
Your second problem could be related to low line voltage (and a
marginally designed power supply) or a power supply that is near
failure.
Depending on how they are implemented, USB and Firewire devices that
are powered off the wire could be susceptible to all kinds of
grounding problems. It would be possible to implement them with
switching voltage converters that isolate the grounds, but I suspect
that at least some designers wouldn't do that, because it costs more.
As these kinds of things are starting to get used for serious audio
work, there is definitely a niche market out there for power hubs
that provide ground isolation. The grounds on a randomly selected
computer are just plain too noisy for serious audio work (at least
with single ended analog I/O).
Of course, the other thing you can do is buy SPDIF or AES/EBU
interfaces and use external converters.
--
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