[sdiy] Re: Prophet 08 (was Roland DCOs)

[harrybissell at wowway.com]

I found that good, tightly matched capacitors make the
response of a (ladder) filter more sharp (better resonance).

There is less modulation of capacitance with applied voltage
for a film (vs a ceramic)... however at the normal filter
signal levels that could be moot point.

A polystyrene cap is probably not even going to survive wave
solder (85C max). so there are your hand-adds.  If you are doing
high-volume production... it would cripple you.

Look at the Prophet V (3.2) that used the stupid MM5837 noise chip
so they don't have to test and select transistors. When I tried to make
a retrofit for it using analog technology, I did not get a good result
(because they use it for a mod source as well) and ended up with a digital
solution. This is for a $3500 (new) instrument.  Even at that price,
manufacturing is KING !!!

H^) harry


On Thu, 28 Feb 2008 10:32:08 -0800, Dave Manley wrote
> Better? In what ways?  That's a serious question.
> 
> Re process temps:  Even on high volume boards that are SMT, the 
> option exists for low temp (thru hole) parts.  Reflow the top 
> without the thru holes, add the thru holes and then wave solder, or 
> do 'hand adds'.  Both are obviously more expensive, but it is 
> commonly done.  You could then get your 'audiophile' grade 
> capacitors on your VCF.
> 
> Would it sound any better?  Somebody want to do surgery on the P-08 
> or Evolver?
> 
> -Dave
> 
> harrybissell at wowway.com wrote:
> > SMT capacitors have to endure high process temperatures...
> > Only certain dielectrics are suitable ~and~ they will be
> > much larger physically.
> > 
> > oh.... and better too :^)
> > 
> > H^) harry
> > 
> > 
> > 
> > On Wed, 27 Feb 2008 20:44:41 -0500, Bruce Duncan wrote
> >>>>> I was also
> >>>>> surprised by the ceramic chip caps used in the filter, after hearing
> >>>>> discussion about the suitability of different cap materials for audio
> >>>>> use (makes me wonder if the Moog LP uses chip caps in their filter).
> >>>> Its peculiar indeed, i have studied the Andromeda and it seams to
> >>>> use ceramic caps as well.
> >>> Although it might not be a great idea, commercial synths often seem
> >>> to use it as a way to keep costs down. I can't think of any other
> >>> reason why you'd want to put ceramics in there.
> >> SMT film capacitors are large in size, expensive and hard to find in 
> >> a wide range of values in anything other than garden variety polyester.
> >> This is probably the reason ceramics end up on SMT boards in 
> >> commercial synths.
> >>
> >> Bruce
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> > 
> > Harry Bissell & Nora Abdullah 4eva
> > 
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> >
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Harry Bissell & Nora Abdullah 4eva