Formant synth

Verheyden Tom h5020503 at
Thu Jan 23 15:20:25 CET 1997

>X-Sender: h5020503 at
>Date: Wed, 22 Jan 1997 18:51:03 +0100
>To: synth-diy at
>From: Verheyden Tom <h5020503 at>
>Subject: Formant synth
>Sender: owner-synth-diy at
>Hi there,
>If you want to replace the µA726 in the FORMANT VCO-circuit, just take a
>dual-transistor with almost the same specifications (this is important for
>the 1volt/oct conversion). Make sure that the dual-transistor has an iron
>Place around the transistor a cooling plate (this can be in a star-form,
>wich fits perfectly around the transistor.)
>I use this system for about two years and i've never realy had any problems .
>It even works for more than one VCO (in this case three).
>I rather prefer to keep heat-sources (Like POWER SUPPLIES) out, the formant
>has the best results with an external power supply and a metal (HF-proof)
>I 'll look after the replacing transistor (that I've used) for the µA726 and
>send the number to the mailing list.
>For the BC107C and BC109C can be replaced by BC107B and BC109C, the
>difference is that the C-types have a higher HFE-level. In the FORMANT-case
>is this not really a problem. 
>The BF245 still excists !!!!!!! Otherwise try a B-type (I think I've used them)
>Any other questions about the formant synth are always wellcome
I have looked after the correct value for the replacement transistor for a
µA726. I have used the 2N2916. I don't know of they still excists, but I
think so. 
The problem is that this component doesn't have the same pin-configuration.
You 'll have to bend the pins to the right places on the circuit board. This
can result in some real strange constructions, just make sure that you don't
make any short-circuits. 


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