Expo convertors with tubes ?

[Debby and Gene Stopp]

>IMHO:  For the life of me, I don't get the purist thing at all.
>A circuit that makes a beautiful sound is a good circuit.

Yes, my sentiments exactly. In fact, Eric Barbour's Phattytron looks like a
fine example of this concept. If there were two VCO's in parallel, then all
of my wishes as expressed in my previous email would be realized. Now the
gears are turning.... I have the impression that two VCO's in parallel would
not be easily set to arbitrary intervals with a single tuning knob (due to
the ladder-set CV), like with traditional exponential VCO's.

Can they be set to the SAME frequency, and then track in unison? Then,
tube-to-tube variations would allow slight differences in the frequencies,
for a richer sound. Dividers could be used for sub-octaves (tube dividers
were common in old organs). Of course this line of thought would be easily
shot down if the required tube matching were not feasable, if there were
just too much variation.... in any case, the divider concept is still valid
for that multi-oscillator sound, right?

OK now I'm getting some serious cravings for a new project.... I've put
myself through a crash-course in tube electronics recently in order to fix
all my old amplifiers (which are all working fine now, I might add), with
lots of very helpful advice from Eric. I think that I'll cruise the surplus
houses in the next few weeks, looking for transmformers and sockets..... one
place I know of has used tubes ("pulls", they call them) for $5 each, and a
tube test before you pay! Must check their selection next time.

- Gene

-----Original Message-----
From: Scott Gravenhorst <chordman at flash.net>
To: synth-diy at mailhost.bpa.nl <synth-diy at mailhost.bpa.nl>
Date: Saturday, December 11, 1999 8:28 AM
Subject: Re: Expo convertors with tubes ?


>"Debby and Gene Stopp" <squarewave at jps.net> wrote:
>
>>May it be justifiable to "pollute" the pure-tube concept just
>>a bit in order to gain the synthesis advantages of wide-range tracking
>>oscillators?
>
>IMHO:  For the life of me, I don't get the purist thing at all.
>A circuit that makes a beautiful sound is a good circuit.  I
>don't understand why it would make a difference *what* you make
>it with.  A curious challenge, perhaps and that has it's merits,
>but why not use the entire pallete of parts to which we have access?
>The expo converter is a great example of something that a transistor
>does by it's very nature and does it well.  There is nothing wrong
>with that or with mixing vacuum tube technology with that of solid
>state.  I think that it makes sense to use whatever components best
>fit the function.  And after all, semiconductors (most) and tubes
>share a common element: silicon!
>
>-- Scott Gravenhorst                 | Linux Rex, Linux Vobiscum
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>
>
>