[sdiy] The simplest synth ever (was: Russian parts and...)

[Jaroslaw Ziembicki]

----- Original Message -----
From: "mikas" <mikas at turbodsl.lt>
To: "Jaroslaw Ziembicki" <aon.912230836 at aon.at>
Sent: Tuesday, September 14, 2004 5:14 PM
Subject: Re: [sdiy] The simplest synth ever (was: Russian parts
andsynthschematics...)


> > (a) If you don't build the keyboard part, then:
> > - remove VT1...VT7, R1...R14, C1...C6, VD1, VD2, L1,
> > S1.1...S1.N+1 (TL271 doesn't need to be used);

> should i connect pin marked as "1" to +8? to feed R22, R18 and R19...

This I have forgotten: you need a 6.8 volt reference voltage there.
Use a 6.8V Zener diode with a 220 to 270 ohm series resistor.



> > - connect DD1.1 pins 1,2 to ground or to +8V;

> what is the diference?

None. DD1.1 and DD1.2 are unused. CMOS gate inputs just
shouldn't be left floating.



> > - pins 8,9 of DD1.3 = gate input (negative logics: +8V = no gate,
> > 0V = gate; you have to add a 100k "pull-up" resistor between these
> > pins and +8V, and a 1k...4.7k  "protection" resistor from these pins
> > to the gate input jack.

> you mean it like this?
>
>
>                            +----> +8V
>                            |
>                           +-+
>                           | | 100k
>                           | |           DD1.3
>                           +-+  +------+
>                            |  8| &    |
>                            +---+      |
>                            |   |      |
>                 |-----+    |   |      |
>              +-----+  |    |  9|      |10
> gate in   o--| 4,7k|-------+---+      o----
>              +-----+           |      |
>                                +------+
>

I had problems to read this... But I think it's correct.



> >If you need a positive logics, you can use the
> > free DD1.2 gate as an inverter.

> jus in case, can juo drawe it pleas..

No, I won't draw it, I don't like those "text schematics"...
Just do as follows:
- disconnect DD1.3 pin 10 from R15/VD3;
- disconnect DD1.2 pins 5,6 from DD1.1 pin 3;
- connect DD1.2 pins 5,6 to DD1.3 pin 10;
- connect DD1.2 pin 4 to R15/VD3;
- connect the 100k resistor on the DD1.3 input to ground
  instead of +8V (it becomes "pull-down").
Now: 0V = no gate, +8V = gate.


> > (b) You can replace VT9 and VT12 by a CA3046 as follows:
> > - VT9: emitter = pin 3, base = pin 2, collector = pin 1;
> > - VT12: emitter = pin 13, base = pin 12, collector = pin 14.
> > The remaining pins of CA3046 should be left unconnected.
> > CA3086 can also be used (same pinning).
> > An additional circuit for temperature stabilizing can be built later.

> Thank you very much for help.. unfortunatly, i have no time to start
> building it and do not have all chips collected yet, i'm part of
organizers
> team for multimedia festival and so many things to do.. i'll play live
there
> too..
> http://www.smic.lt/centras4/
>
> by for now :)

OK, have a fun!
Jarek