Ok, rather than hijack an earlier thread, thought I'd start a new one.  Re: my recently revived polaris, I'd written...

...Anyway, only one question.  When pushing my master volume up past ~ 1/3 full scale, it gets pretty noisy. I gather this is "normal".  Was there ever a fix for this?  Do dedicated analog voltages/ground from the power supply board help?

In a response on the thread, bkuris wrote...



I found that upgrading the opamp on the output board really improved the sound of these units after doing the well documented grounding change (which I can't remember but involved cutting a wire I believe). I can run them at full volume without worrying about hiss, bass sounds clearer and more like you would want from a synth...  I can't remember the exact parts that I ordered but they were in the $3-$15 range, likely something from burr-brown (maybe a newer TI excaliber TL207x) that was well regrading in the DIY audio community.  The change wasn't subtle.  Next time I have a unit open I'll take a closer look.  It isn't a difficult mod -- remove old chip, add socket, add new chip.   I'm sure someone industrious could do a drop-in board instead...

Ok.  I'd put a socket on my output board long ago... Think there's an LF347 op amp in there now... It may indeed have helped the overall sound quality over the LM348 - too long/too many beers ago for me to recall... Anyway - how about this well documented grounding change?  What is it?  The op amp may have improved sound quality, but I still get a lot of noise when the master volume is raised...

Thanks,

Steve