[sdiy] AC coupling caps on MS20 clone

[Oscar Salas]

Mattias! I really like follow your
posts here like in EM, but IMHO it is not needed bring the
things always to an extreme. 
 
Audio modules with not mixer input are NOT a *not* good
design if you, for example,  are not planning *always*
work with mixed signals. It remembers me the worry
subtraction patch again, sorry but it is more interesting
generate complex waveforms by frequency modulating them than
just mixing them. IMHO.

About "overcomplicatifyizing followed by reduction" most of
times you could arrive to where you came from. So it is a
good exercising for learn and discover and innovate but not
always needed, sometimes common sense is enough.

But thanks your overcomplicatifyizing and my limited
English I misunderstood one of your past mails and imagined
a, maybe, good idea: Patch cables with a blocking capacitor
assambled in the jack male for audio use. Just you need
little capacitor and code the patch cable with some color.

 
Oscar.  

--- On Sat, 8/7/10, Mattias Rickardsson <mr at analogue.org> wrote:

> From: Mattias Rickardsson <mr at analogue.org>
> Subject: Re: [sdiy] AC coupling caps on MS20 clone
> To: "megaohm" <megaohm1 at gmail.com>
> Cc: "Synth DIY" <synth-diy at dropmix.xs4all.nl>
> Date: Saturday, August 7, 2010, 2:34 PM
> On 7 August 2010 07:57, David G.
> Dixon <dixon at interchange.ubc.ca>
> wrote:
> 
> "Yes, but what if the filter has a three-input mixer? 
> (You see,
> that's my dilemma...)"
> 
> Good! Single-input audio modules - requiring standalone
> mixer modules
> which means both extra hardware, scattered controls, and
> reduced
> ergonomics - is also *not* good design imho. :-)
> 
>  "Oh gawd!  Just use the switch, Mattias!"
> 
> :-D
> Sometimes the best solutions come out of
> overcomplicatifyizing
> followed by reduction. ;-)
> 
> On 7 August 2010 12:02, megaohm <megaohm1 at gmail.com>
> wrote:
> >>
> >>>  3) level pot with pull-switch, to select AC
> or DC coupling.
> >>
> >> Too complicated/expensive for my tastes (which are
> simple and cheap).
> >
> > It's no more complicated than a pot and a toggle
> switch. If you use
> > quality toggles (NKK for example) then a P/P pot is
> less expensive
> > than a pot and toggle.
> 
> True, however the pot switch will probably be of lower
> quality.
> 
> >>> The pull-switch solution is my personal
> favourite, but it might
> >>> interfere a bit with another clever thing
> discussed here some weeks
> >>> ago when it came to "bipolar" level pots...
> where the true null point
> >>> can be hard to find, and a pull-switch could
> come in handy when the
> >>> signal is supposed to be totally off.
> >
> > Another benefit is you get the full rotation of the
> pot for level
> > control instead of just half the travel.
> 
> True, a longer travel is better almost all the time.
> 
> The resistor-shunted "bipolar fake log" pot has advantages
> over the
> resistor-shunted "fake log" pot however: it has a flatter
> curve around
> the center null point, whereas the non-bipolar is steeper
> at its end
> null point and then flattens to a log-like behaviour.
> Easier to set at
> low levels. I'd prefer "bipolar fake log" any day,
> regardless of its
> shorter travel - but it needs an extra buffer amp.
> 
> http://www.elby-designs.com/documents/tailoringpotentionometers.pdf
> 
> >>> - With mono plug half-in, BOTH jack tip and
> jack ring goes to plug tip.
> >
> > The reason I don't like this idea/solution is because
> all patchcord
> > plugs are different. When half inserting into a stereo
> jack the tip...
> 
> Great, you just helped me to avoid those deceptive design
> thoughts and
> focus on something better and more reliable. :-)
> 
> > Have you thought of this solution:
> > Use just one cap and one toggle switch.
> > Connect all inputs (after the level pots) to one side
> of a cap. Other
> > side of cap connects to summing point of op amp. Use
> the toggle switch
> > to short the cap when you don't want AC coupling. This
> solution saves
> > you two toggles and two caps.
> 
> It doesn't get much simpler that this, and it's hard to
> justify the
> more advanced ways of doing it. :-)
> 
> /mr
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>