[Trlog] SBDVP finale

[Pete Smith]

Quick correspondence with W9CF (who is in Trieste without a DOS PC 
currently) suggests that the reason SBDVP won't work with the SB16 PCI card 
I was trying to use is that SBDVP uses one DMA for both writing and reading 
sound files, while the SB16 PCI wants to use separate DMAs.  I have a note 
in to Creative to ask them whether there is a way to make the card use a 
single DMA, but no answer yet.  In the meantime, it's working fine with an 
SB16 ISA card.

The real reason for this post is to mention a simple interface design I've 
worked out that lets me run SBDVP (and presumably other sound card 
programs) through the microphone jack on my SO2R box, rather than into an 
audio input in the back of the Mark 5.  The whole purpose was to be able to 
use SBDVP in an SO2R setting, and it seems to work just fine.  PTT and 
audio switching all work as they should, just by running SBDVP with a -p1 
switch.

The circuit uses Radio Shack iso transformers for both the microphone input 
to the sound card, and the line out from it to the switchbox.  Inside the 
interface, besides the iso transformers, is a DPDT toggle switch that I 
have wired either to run the microphone through the sound card (normal for 
contest operation, and permits reprogramming voice messages on the fly) or 
direct to the SO2R box (for operation when the TR computer is off).  A 
fixed 50:1 voltage divider reduces the sound card's "line out" level to one 
more suitable for microphone inputs.  I use the sound card mixer's level 
controls to set all the output levels equal, and leave them alone thereafter.

The circuit is so trivial that I'm sure anyone who cares can figure it out, 
but this is mainly to confirm that it does work, and Rigblaster-style 
complexity isn't needed.  If anyone really, really wants my crummy 
schematic, drop me a note and I'll send you a scan.

73, Pete N4ZR




73, Pete N4ZR
The World HF Contest Station Database was updated 23 Feb 03.
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