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Discussion Starter · #1 ·
Hi everyone:


Well, I was racking my brain trying to figure out how to get one more audio analog input.


I have an Asus A7N8X deluxe that has two (2) internal audio line level inputs ("CD" and " Aux") and one external audio input ("Line Input"). Without going into the details of the I/O equipment, I was coming up one short on audio inputs.


I plan to purchase Atman's new video capture card which provides for a combination of multiple video inputs and PDI. Great! But no audio inputs or switching.


What to do? I need total of four (4) audio AI's. I began to look at the microphone input. Hmmm. An issue of impedance, voltage reduction and curve. I figured there were plenty of microphone to line level converters, but what about the other way around: line level to microphone?


I found this CONVERTER . No battery required and $35.00. They make a microphone and RIAA phono types. Perfect.


While this work around is not any audiophiles dream, it will be fine for my purposes. I will use this for the VCR audio input which is infrequently used and does not start out that great to begin with.


Any body know of anyone else who makes any of these? Or have another solution for not using the microphone input?


I thought I would post this info for feedback as well as for anyone else scratching their head over trying to get one more input without drastic measures: outside switching or routing to pre-pro for switching.


EDIT: Does microphone have a curve like RIAA phono? I suppose it depends on the mic type but is there a mic curve that is standardly employed in PC mic inputs? If flat, then just an issue of impedance and voltage.


DFA


P.S: Have not tried to purchase one yet so don't know any more than it's (possible) existence. This company is in UK but does not show any place to buy or purchase direct so this is why I am interested if any other sources are known.
 

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Discussion Starter · #2 ·
Bump...


No feedback on this???


DFA
 

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Mic input usually goes through an internal amp or boost, and some mic inputs are mono. Of course, it depends on the sound card itself.


Best to feed a known test tone in and see how it compares to the same fed in via Line.


Of course, the other option may be to get another sound card that has more inputs. The SBLive (at least mine) has CD/Line/Aux/TAD, and with the Digital I/O board has an additional Line2.


If signal level isn't an issue, there are also cables that have more than one MPC2 connector (the one that usually goes to CD-ROM's audio out) that'd let you put two devices on the same line. Drops the level quite a bit though, maybe some diodes or something might help? My electronics knowledge is weak - I'm more of a software guy.


Brandon
 

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Discussion Starter · #4 ·
bhiga:


Thanks for the response.


Not using a sound card. I'm using the built-in sound of Asus A7N8X which is quite good. Everything is encoded to digital and sent out the SPDIF. The SPDIF output from hardware MPEG decoder is passed through on the same single SPDIF output.


To put a line level input into a microphone input, it is necessary to attenuate the signal about 50 dB. If there is no curving of the microphone inputs on PC's than that would be about it. Even if some curving is needed, I can do that with the "Sound Storm" equalizer and recall that setting when the HTPC uses the microphone (Girder configuration)


I'm quite certain the A7N8X microphone input is stereo. Even if not, OK for infrequent VCR use. The alternatives to creating just one more input are not enthralling. I don't want to route to one of the pre-pro inputs (which I don't have yet anyway) because many times the big stuff (audio equipment) will not be fired up and the stereo audio analog outputs are used to go from HTPC direct to the TV for listening with TV speakers.


The problem: what does the circuit need to be like. I think it only a matter of a few (3 to 4) resistors per channel. I could make that and fit it in a Zalman fan speed controller box like a dongle!


EDIT: Just located this page for this CIRCUIT . A simple voltage divider, kind of what I figured. I can handle that but a commercially fabricated dongle thingy would be nice. 40 dB is his attenuation recommendation for consumer audio.


DFA
 
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