Rhodes Chroma Polaris

> From: rob_ocelot
> 
> 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)

TL048 must be a mistake. I expect they mean TL084, which is a quad FET-input
op-amp that's still widely available, including from DigiKey. It would be a
good choice, as would the TL074, its low-noise version (or selection). These
have a higher slew rate than the LM348, which could reduce distortion a
little at high volumes. But the Polaris still has tons of distortion and
noise from other sources, so don't expect a night-and-day difference.

That said, a friend of mine is working on a replacement for the output board
that gets rid of most of the nasty distortion and digital noise that plagues
the Polaris. I'll keep the list posted.

-- 

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...