AW: [sdiy] Newbie & Zener D equivalents

[Nils Pipenbrinck]

Hi All,

> I'm a newbie and I'm trying to build a Noise Generator from an old
Practical Electronic Sound
> Synthsizer modul http://omega.tellus.vallentuna.se/anders/pdf/pess5.pdf

Hi Sandro, welcome to the list.


> The schematic needs a zener diode marketed in 1973 (!) by Semitron Ltd as
Z1J.
> Which equivalent Z diode can I use in place of that ? ( possibly available
in Italy).

Well, you will most likely not find a direct replacement for that diode.
It's a zener specially made to make noise. Those are rare these days. (btw,
I would be happy to hear that I'm wrong on this point. I've been looking for
noise-diodes for a couple of month, but never found them).

I'm not such an expert, but I think you should just buy some zeners and try
them. I would start with a 5.1 or 5.6V diode (e.g. try and error method).

Also you can use a normal transistor and use the basis-emitter diode. The
base-emitter diode of the 2N3904 NPN tranny for example behaves a little bit
like a 6V zener. It's however very weak, and not designed to pass high
currents. For your schemantic it's save to put it in, the 100K resistor will
limit the current.

Anyways, it's not a direct replacement for the Z1J, Whatever diode you put
in there where the breakdown point is reached it will make noise, but it
will never be the Z1J-noise.

> 2nd Q - circuit needs also 2 caps about 0.01 uF - may I use polyester type
or better ceramic disks?

Don't use the ceramic disks. Film caps are a lot better.


Besides - It might not be such a good idea to build the circuit at all.
Unless this circuit is part of a retro machine, and you're looking for
_exactly_ this sound you might better stick with something more modern.

The circuit from René Schmitz page is pretty equal in function and needs
just a few easy to get parts (http://www.uni-bonn.de/~uzs159/ then click on
"noise"). For the unnamed opamps TL072 is the part you want.


Regards,

	Nils Pipenbrinck
	(who btw has solved his power-supply issue by replacing a 7915)