[sdiy] Synthesizers...

[Roy J. Tellason]

On Thursday 19 February 2009 12:55:48 am Oren Leavitt wrote:
> Hi Roy and all,
>
> Roy J. Tellason wrote:
> > On Wednesday 18 February 2009 12:05:58 am Oren Leavitt wrote:
> >>Did somebody say "Synthesizers"?!?
> >>
> >>Hi Tom and all,
> >>A busy past few work weeks have kept me busy.
> >>But when I can get some SynthDIY in edgewise...I have been working on
> >>some "odds and ends" type analog modules.
> >>
> >>1) A "0 - 10VDC" volt meter module that uses a nice little 0-10V Simpson
> >>analog meter movement that I happen to have sitting around. A couple of
> >>banana jacks for the +/- inputs and a polarity reverse switch.
> >
> > I have a few odd meters laying around that I've been meaning to do
> > something with.  Got one sitting here already in a nice metal box that's
> > 0-20uA,  too, I snagged it off ebay a while back as an impulse purchase, 
> > fairly cheap.
> >
> >>2) Adapter interface panel with several rows of connected 1/4" phone
> >>jack <-> 1/8" mini phone jack <-> banana/binding posts.
> >
> > I've had idle thoughts for a while now about building something of the
> > sort, more likely a box than a panel,  and with a whole lot more variety
> > of connectors than that.  Add in XLR and RCA for starters.  :-)
>
> I thought about RCAs, but I have tons of those RCA to 1/4" phone plug
> adapters. Any RCA plug near my synth has an adapter on it. :-)

I don't really have any particular desire to use them much,  but they're all 
over all sorts of stuff,  and I have a whole mess of them,  so I might as 
well include them in the mix...

> >>3) Output interface panel with 3 input mixer, bass/mid/treble EQ, master
> >>level control, buffered output that can drive a 600 ohm line, and power
> >>on/off transient supression.
> >
> > Got schematic?  That sounds useful, particularly that last bit about the
> > transient supression.
>
> It is (slowly) in progress.

Ok...

> I have an old schematic of an earlier output interface I did that has a
> 3 input mixer, bass/treble, master level, boosted output buffer, but no
> transient suppression.
> I have to dig it up, scan it and post it.

I'll look forward to it then.  Though the older version might be just fine 
too.

> The transient protection will simply consist of a small relay with one
> second turn on delay at power-up, immediate shut off at power-down.

I have something of the sort in one of my amplifiers,  it'll also disconnect 
the speaker on any dc-on-output fault,  too.  I should probably revisit that 
circuit one of these days.

> Adam Schabtach suggested THAT corp's balanced line driver IC's for
> output - might try them...

I saw that,  and am not clear as to the advantage that you'd get from using 
those,  but then I'm not that famliar with their parts anyhow.

> >>4) A "standards" panel with a precision 1.0000 and 10.000 volt
> >>references, 440Hz and 1000Hz sine wave tone sources.
> >
> > What are you using for those?  I started a 440Hz sinewave oscillator
> > (used a phase-shift circuit and figured I'd trim it if I needed to) but
> > never packaged it up and tested it,  though it's mostly built.
>
> Wein bridge oscs for the tones. I have a 1kHz wien osc that has stayed
> exactly at 1000Hz for years. It's a simple "light bulb" based circuit.

I've seen those,  never felt the need for getting that complicated yet.



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