Hi Laurence,
I had a similar effect once (but with an internal audio device in a
notebook):
The ADC's sampling rate jumped by a few percent in the moment some other
program decided to play some acoustic speaker through the card. My
guess: Windows 'helpfully' jumped in when the other program asked for a
different sampling rate than the first, and activated a resampling
process (most likely implemented in software). In that case, it helped
to use a second ("dummy") audio device as the DEFAULT soundcard (= audio
device number '-1'), use that one for the windoze system sounds etc, and
another (real) audio device for Argo & Co.
On the windows driver development kit, there is a dummy driver called
'MSVAD' (microsoft virtual audio device). It's intended to be used by
software developers, but maybe (I didn't try this) it can be used as a
dummy 'default audio' device. Alternatively, use an unused bluetooth
audio device, or an el-cheapo USB audio device for the same purpose.
Then, there will hopefully only be *one* application using your external
24 bit sound blaster.
Second alternative: If there's an ASIO driver for your 24-bit device,
use it. ASIO only allows exclusive use, which means once it is allocated
by one application, no other application can hijack it. You may even
uninstall the 'standard multimedia' drivers for your card; the ASIO
drivers will keep working. At least they did with a Creative Extigy
which I had been using several years ago.
All the best,
Wolf .
Am 06.12.2011 21:16, schrieb Steve Dove:
Hi Laurence,
Just a stab: it's unlikely an oscillator is coming up on different
frequencies but it may be that in one 'mode' it's using the USB
device's clock and in the other cuddly Widnows is nicely using it's
sample-rate-converter on you. How to make it stop doing that I don't
know - boot order or such?
Cheers,
Steve
On 12/6/2011 7:51 PM, Laurence KL7UK wrote:
Im using an external 24 bit sound blaster (USB) @ 96k on one of the dell
pc's in Alaska and not sure if its the PC or the card but it
occasionally and annoyingly on PC reboot "moves" 20Hz or so (dang it) -
so here I am looking at DCF39 and in fact its off the scale somewhere
for a couple of days - that and Stefan may have been visible but I was
looking/cal'd in the wrong place.
It apparently flips to one rate or another - checking up what it flipped
to last time comes up with the same cal figure using Argo. Highly
annoying but not being able to physically throttle the devices
(electronically or physically!) Im a bit restrained. As an example in
one state using Argo cal of 1000Hz the offset is 1003.2 and
alternatively 1023.7 Hz - Not sure if anyone else has seen a simliar
issue but its annoying - it appears only to "flip" when the PC is
booted. At the moment its on spec and giving a nice daylight view of
DCF39 or the 137.777 window - Ill move it down to 136.172 and HGA22
windows later
Laurence KL7UK Alaska remotely operated from (freezing cold) Oklahoma
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