Cgs synth

Hooray!

This was a definite case of RTFQ...Read The F***ing Question.
I had put in 2 x 2N3906 transistors, rather than a 2N3904. I've
replaced one with an alternative (BC547) and things are much
better. The signal still tails out as I turn the pot down, but
checking the outputs from the Analogue Systems VCO, they are
borderline to run the module anyway...(PLS - ±5V, SAW +8/-2V).
Nevermind, I just bought a Doepfer Pre-amp module off of eBay
so I'll check it out with that when it arrives.

Many thanks, and I can get on with builbing the VCO.

Stuadh

--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> Hmmm...
>
> There are likely to be two problem areas-
> 1) construction
> 2) interface.
>
> 1) you seem think you have this sorted. In fact, it is very unlikely
that
> any components were damaged at any stage, short of doing
something
> catastrophic like reversing the power supply. There may
however still be
> construction errors. For example, if an alternate type of
transistor was
> used, the collector and emitter connections may be the other
way around to
> what is shown on the PCB.
>
> 2) The SAW output is the main output. If it is excessively quite,
either
> there is either
> 2a) a construction problem (see reversed transistors) or
> 2b) an inadequate signal being fed into the device. This wants
a sawtooth
> wave that is in the area of 5 to 10 volts in hight, before
attenuation (via
> the pot). It seems to me that you may be feeding it a signal that
is simply
> too weak. In that case, see the gain stage of the stomp-box
adapter to boost
> your signal level. (or another suitable pre-amp)
>
> Ken
>
>
>
> >
> >No discernible change.
> >
> >(Very prompt again, thanks)
> >
> >Stuadh
> >
> >--- In cgs_synth@yahoogroups.com, sasami@h... wrote:
> >> Something is amiss. First, try putting a 100n capacitor in
> >series with the
> >> input. This will get rid of any DC offset that may be upsetting
it.
> >>
> >> If that fails, report back :)
> >>
> >> Ken
> >>
> >>
> >> >
> >> >
> >> >I've just completed my first GCS module, hurray. I'm not
sure
> >if it
> >> >works, though. It is the simple wavefolder. Thing is,
should
> >> >there be large parts of the range that are silent. When you
> >turn
> >> >the Pot to give the lowest resistance to the incoming
signal,
> >> >there is some output, but for most of the travel, there is
> >nothing.
> >> >The SAW out is also particularly quiet. Is this normal? I've
> >> >replaced the TL072, both transistors, the pot and I've
checked
> >all
> >> >the resistors are correct. Any ideas
> >> >
> >> >Yours Aye
> >> >
> >> >Stuadh
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >See the following URLS for the CGS Modular Synth home
> >page:
> >> >Main: http://www.cgs.synth.net/
> >> >Secondary: http://otherunicorn.0catch.com/synth/
> >> >Yahoo! Groups Links
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >>
>
>_________________________________________________
_
> >_____________________
> >> Ken Stone sasami@h... or sasami@c...
> >> Modular Synth PCBs for sale
> ><http://www.blaze.net.au/~sasami/synth/>
> >> Australian Miniature Horses & Ponies
> ><http://www.blaze.net.au/~sasami/>
> >
> >
> >
> >
> >
> >
> >See the following URLS for the CGS Modular Synth home
page:
> >Main: http://www.cgs.synth.net/
> >Secondary: http://otherunicorn.0catch.com/synth/
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
>
__________________________________________________
_____________________
> Ken Stone sasami@h... or sasami@c...
> Modular Synth PCBs for sale
<http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies
<http://www.blaze.net.au/~sasami/>