<html>
Hey,<br>
<br>
<blockquote type=cite cite> I would like to send out a challenge
<br>
to the tube gurus out there who are "carrying the torch".
</blockquote><br>
(Bill looks up..)<br>
<br>
<blockquote type=cite cite>Here is my challenge; I would like to see
somebody come up <br>
with some synth DIY tube projects on a website designed for <br>
the tube novice. For starters, how about a VCO built <br>
entirely from a few common tubes (12AX7 etc.), that <br>
produces various waveforms, with V/Oct scaling and FM <br>
input</blockquote><br>
This would be far in advance of current technology. The current vacuum
tube VCO are sawtooth relaxation-oscillators, not capable of Sines or
Triangles. If you can only have one waveform, sawtooth is probably the
one to have. To do a sine oscillator, several approaches could be taken -
voltage variable capacitances, variable inductors etc..<br>
<br>
<blockquote type=cite cite> I think that this could be an incredibly
<br>
PHAT sounding oscillator. </blockquote><br>
I guess I should make a recording of my tube VCO with a couple of (SS)
filters applied.. The files I heard on Eric's site do not do the machine
justice..<br>
<br>
<blockquote type=cite cite>So, any brave souls up to the challenge?
</blockquote><br>
My time (and space) are super-limited right now, but this would be a good
I/O project for an old computer.. See, we need a special controller for
the Sawtooth VCO because it has a non-linear voltage response curve. We
must build a 2-3 octave resistive step ladder and control each note with
a gate (and step) of it's own.. This could be a simple key-contact
device, or one under MIDI/computer control.<br>
<br>
There was such a device for the commodore 64, that provided something
like (256?) open-collector outputs for controlling home stuff.<br>
<br>
PS In exchange for a beer, I'd be happy to send a 2D21 Thyratron to
anyone building the VCO. This is the only strange tube in the
circuit.<br>
<br>
<br>
<br>
<br>
<div>+----------------------------------------------------------+</div>
<div>| "The" Bill Layer -
Frogtown, Minnesota. U.S.A. |</div>
<div>| Vacuum tubes, Analog, Motorcycles and Other Alternatives |</div>
<div>+----------------------------------------------------------+<x-tab> </x-tab></div>
<div>+---------------------+
+---------------------------------+</div>
<div>| <blayer@uswest.net> | |
<b.layer@vikingelectronics.com> |</div>
<div>+---------------------+
+---------------------------------+</div>
</html>