Distortion on line inputs

[dfahrner]

I'd like to use the MZX "Line In" jacks to eliminate a mixer, connecting another keyboard's line outputs so that the second board is routed through the MZX master effects and volume control.  But I get a lot of distortion if I try to raise the external keyboard's output level to match the MZX internal voice levels, either with the external keyboard's volume control or with the MZX External In volume (which adjusts the level, but the distortion is still there).  Distortion is the about same with several different external keyboards, including Korg Krome and Kronos, and a Casio PX-5S.

 

There's no distortion when connecting those same line outputs to the MZX "Audio In" jack, even when the external keyboard's output level is raised so its volume is significantly higher than the MZX internal voices.  Specs for the Line In and Audio In jacks are the same: 9.0K ohm input impedance, 200 mV input voltage.  It's like the distortion is coming from the "External Part" circuitry, where the Line In signals are mixed with the Mic In, routed to DSPs,  system and master effects, etc.  Has anyone else seen this problem?  Or is it a problem with my MZX? 
 

df

[Brad Saucier]

You should be able to dial in a level that does not distort.  If distorts too easily you may have a malfunction.  As far as getting the sound levels to match, I would turn down the internal sounds rather than try to turn up the external.  Let us know how it goes. 

[dfahrner]

OK, I have things set now so that the line inputs aren't distorting, but I'm not sure exactly which level adjustment solved the problem...there are so many places to set levels: on the external device, on the MZX balance screen, mixer screen, effects screen, etc., etc...at some point I'll have to go through and try to figure out where the distortion was coming from, but everything seems to be working now...

df