[sdiy] coupler module

[Czech Martin]

The mute can perhaps be done with a simple bipolar 
transistor after a resistor.
If the base current is off, I do not expect
too much distortion. If the base current is on (large!)
the transistor will operate forward (high beta)
and backward (low beta, but still good enough).

So you get much lower amplitude, somehow distorted.
At this low level this won't hurt.
Of course the attenuation will not be infinite,
but -40dB is enough for speaker protection,
or telephone call.

m.c.


> -----Original Message-----
> From: Fdi [mailto:fdi at ran.es]
> Sent: Dienstag, 26. August 2003 18:18
> To: synth-diy at dropmix.xs4all.nl
> Cc: Czech Martin
> Subject: [sdiy] coupler module
> 
> 
> Hi,
> 
> My ideal "interface module" looks like this:
> 
> - 4 output TO "outside world" (balanced +4dB line AND 
> unbalanced -10dB line)
> Overload LED for each input to this section. May be a input 
> level pot for
> each one, otherwise set final level at last module (I preffer this)
> - 2 input channels to the synth, so FROM "outside world" 
> (also in both +4
> bal and -10 unbal)
> - 2 headphone jacks with vol control (L or R switch 
> selectable for each of
> the 4 outgoing channels)
> - and very important: a "mute all" control, sort of a panic 
> button. May be
> relays or something more elegant that cuts the signal 
> inmediately when you
> push it, to protect your ears and your speakers. I think this is VERY
> important.
> 
> I would build this for a medium size modular. But for a 
> larger system I
> preffer to have two or more of this modules each with 2 out, 2 in, 1
> headphones, 1 panic.
> 
> You may even forget about the 2 inputs section, since you 
> normally have one
> or more preamps on your modular, usually associated to the envelope
> follower, that can be used for anything.
> 
> A LED indicating amplitude at the end of the output sections 
> would be useful
> too (so, overload just when entering the interface and 
> amplitude just before
> leaving the interface)
> The two inputs should have overload LEDs too.
> 
> No EQ at all and using best possible op-amps and components, 
> so the transfer
> to and from the outside world is as transparent as possible. 
> I even preffer
> not to have control of amplitude at this module, just good 
> attenuators to
> "pro" and "consumer" line levels.
> 
> I would keep the 2 input channels line level. If I  use a 
> good microphone
> that needs phantom power I use a little good mic pre to 
> condition the signal
> and power the mic.
> --
> 
> 
> 
> f
> *
> 
> 
> 
> 
> > De: "Czech Martin" <Martin.Czech at micronas.com>
> > Fecha: Tue, 26 Aug 2003 10:34:02 +0200
> > Para: "Sdiy (E-mail)" <synth-diy at dropmix.xs4all.nl>
> > Asunto: [sdiy] coupler module
> >
> > Every synth needs a coupling module to the tape machine or 
> mixing desk.
> >
> > I plan to build some soon, containing:
> >
> > -4 balanced inputs, 2 balanced outputs (trafo or electronic)
> > -2 or 4 (several) unbalanced inputs (for other synths)
> > -input or output scaling circuits (the analog synth can 
> have +-13V or
> +-100mV
> > as extremes), the usual levels are -10dBu = 0.245 V RMS ~ 0.35V peak
> > or   6dBu = 1.55  V RMS ~ 2.2 V peak
> >
> > assuming that 0 dBu = 0.775V RMS and sine wave form.
> > So gains of 37,    0.29,  5.9 , 0.045
> > or 0.027, 3.4,   0.17, 22    (reciprocal)
> > can be needed, so a range of 37 to 0.027 seems to appear.
> > This is no problem since resistor networks can be changed
> > if necessary. Plug in connections of resistors on the PCB
> > seems to be a good idea.
> >
> > -A good question is if any EQ is needed. Shelving bass and treble
> > and perhaps some mid bell shaped EQ.
> >
> > I'm not sure if this needed. It could save a mixing desk.
> >
> > -Another question is if any external effects send/return is needed
> > -Certainly a level meter plus overload indicator with hold/reset
> > is needed for the line out.
> >
> > If all features are build, I end up with a little mixing desk.
> > That is certainly too much.
> >
> > So what is your practical experience?
> > What is needed?
> >
> > Martin Czech
> >
> >
> >
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