The TL074/084 in that position is not a great idea. First, the LM348 is a Bipolar op amp, while the TL074/84 are JFETS. Not necessairly a problem, but in my Polaris the TL chip sounded harsh. It's not a great chip either anyway. I finally put in two OPA2211 on a quad adapter (Brown Dog), which sounds great.
The OPA2134 is a FET chip, too, and while better than the TLs not as good as the more recent chips from TI, AD and National.

Since I had the S/H polyprop cap problem (tuning broken) I decided to do a proper recap while at it, and replaced every electrolytic (with low ESR HQ ones), all the polyprop caps and also most of the polyesters (never heard of those going bad anywhere else, but in the Polaris film caps obviously got bad) - using polyropylene and polystyrene caps. I also replaced the multilayer ceramic at the output with a high quality polyprop film cap.

Well worth it, as after recalibration my Polaris now sounds killer. The re-cap not only resulted in better timing but better sound as well. And it will remain stable and working for a long time, too.

So if you've got a soldering iron and desoldering station, I can highly recommend it. Just be carefull with static electricity and the membrane panel.

--- In chromapolaris@yahoogroups.com, "rob_ocelot" <rob.ocelot@...> wrote:
>
> I was checking out Youtube videos of the Polaris today and I came across this gem:
>
> http://www.youtube.com/watch?v=TlXI0QBOAZw
>
> Text in the video reveals that the owner replaced the last LM348 quad op amp (Z3 on the output board) with a TL048cn. The end result is supposedly a punchier sound and more defined low end. I did some more research and came across someone else saying to use a Burr Brown OPA2604 -- which is a dual op amp.
>
> Anyone here attempted this mod or something like it?
>
> I'm contemplating using the 2604 since the TL048 appears to be obsolete and difficult to find. If I were to use two 2604's then is it possible to tie the 12V supply for each chip together? (effectively making a quad op amp)
>