[sdiy] Synthesizers...

[Oren Leavitt]

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. :-)

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

> 
>>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.
The voltage references will be derived off of a 10.000 volt reference IC.


- Oren