Doepfer

> the doepfer a118 random voltage doesn't sound the same as the
> elektor formant random
> voltage.
> i tested 2 different formants, so i don't think it's in the
> building process.
> i'm not saying one is better than the other, doepfer's more
> stepped formant's more
> smooth/gliding/bubbling. (fast ramps vs soft ramps?)
> is there anything i can adjust to make the a118 sound (more) like
> the formant?

There is no adjustment in the A-118. I took a look at the noise circuit of
the Formant. The circuits are nearly identically. The only difference is
that for the A-118 the emitter of the noise transistor is connected to +12V
via 100k whereas it is connected via 100k+47k (serial) to +15V in the
Formant. The connection between the 100k and 47 k is connected to GND via
22u electrolytic capacitor. You may replace R1 of the A-118 by this combo.
R1 is the 100k resistor next to C1 (2.2u).

But I suppose that the difference in sound results from the noise
transistors but not from this circuit modification: a so-called "TUN" =
transistor universal NPN in the Formant and a BC457/BC549 in the A-118. The
term "TUN" was introduced by the Elektor magazine and a "TUN" could be
chosen from a wide range different NPN transistor types (BC547 and BC549
included). It depends upon the transistor actually used in your Formant
noise module how it sounds. Even the A-118 do not all sound the same as each
transistor generates a bit a different noise spectrum. After all the A-188
(or the Formant noise module) only amplifies the noise generated by the
emitter-base diode in reverse direction (i.e. cathode connected to positive
and anode connected to negative voltage). I suppose that if you exchange the
noise transistors of the Formant and the A-118 the sound will be exchanged
too.

Best wishes
Dieter Doepfer