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|10th February 2005, 10:05 PM||#1|
Join Date: Sep 2003
Location: Sammamish, WA
Some questions regarding this audio schematic
I'm attempting to build a USB audio recording interface based on the cirrus logic CS5361 A/D chip. Cirrus Logic suggests the schematic attached to this post for the analog input buffer.
I have a few questions regarding it however.
Will it be suitable for interfacing a balanced dynamic microphone? (Or condensor if I added phantom power) or is this only going to work with line-level signals...
What if I wanted to interface a line-level single-ended (unbalanced) source with it.. Is there a way to do it with minimal circuitry? (Maybe just a transformer to match impedances or what not...)
If I wanted to add a variable resistor for signal attenuation, where would be the best place to put it and what value would you suggest?
I'm not quite sure what I'm doing as far as the analog signal processing goes, however I do have the digital interface worked out (microcontroller code for USB control, etc..)
Thanks for the help!
|28th February 2005, 08:28 PM||#2|
A GUESS, since there are no replies yet...
Looks like you might need a step-up xformer if you are going to use a low impedance mic. What kind of opamps are they?
I will GUESS that since the 20k and 100k are in parallel on the input to the opamp, you could step up your mic 1:6 and sound OK with the existing load setup... (200R to 7.2kR)
If you had a center tap on the secondary I'll GUESS that you could run that to the ground bus and use the two balanced legs of the opamp for your input...
Maybe get one of those switching bypass 1/4 jacks and use the two balanced legs of the opamp input for your line input. (one hot, one ground) Or, get a 600R or even a slight stepup xformer with a center tap and wire it the same way with center tap to ground/balanced. Probably more expensive to use a line input xformer...
I don't have a heck of a lot of real world experience one circuits like this, but that is where I would start to investigate. Try stuff. Doesn't look that expensive to build and experiment with...
--> Jim <--
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