Problem with levels (impedance mismatch?)

  • Thread starter Thread starter rlorentz
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rlorentz

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Hey, sorry if this doesn't quite fit the topic here but this was the closest I could find :)


For my studio I use a lot of unorthodox gear and patch it in to my mixing console (mackie 1604). Frequently I have problems with gear that only has a "headphone" out.. sound comes through, but it's so so quiet.. even with full volume, full gain, full EQ, it still is extremely quiet.

I'm thinking it's an impedance mismatch, if I understand correctly this gear is expecting a high impedance on the other end (headphones) and gets a very low impedance (mackie in's). So, trying to drive the low impedance takes more current than the output of the gear can give, so the voltage drops, and the sound gets more quiet. Am I on the right track?

If so, is the solution to use an amplifier or an op-amp like a buffer between the gear and mixer? Anyone have any thoughts on schematics for a good general purpose amplifier for this purpose?


Thanks,

Robert
 
Headphones outs can usually provide more gain then a line level input can handle. It's common to only need the output gain at about half way or so. Are you sure there isn't some other issue going on? You should be splitting the signal and sending it to two mono inputs using a TRS to dual TS cable. Otherwise known as an insert cable.
 
thats wierd to read, I just was comparing some speakers and used the headphone out for a pair and it was right at half way to where it matched the standard wiring... so my hr test agrees with that comment...1/2 is about right. Must be some design concept, industry design standard?
 
Yeah, I think it's a cable issue. A headphone amp can drive a line input just fine, BUT if you plug it straight in with a TRS cable, you will be sending a stereo unbalanced signal to a mono balanced input. The result of that is that the right channel will be reverse polarity and summed with the left channel. That will cancel all the center information, which is usually most of the signal. So pay attention to Tex's cable recommendation.
 
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