Some building questions

[Ric Miller]

Hey kids.  "Yes" is the answer to the question, as to whether I'm back to work
or not.  All the 'poop' isn't over yet, but at least I can build again, thank
god.  :)

I'm almost finished building a single panel order for a customer here in the
city (that I started yesterday).  This unit is V4.00 of the 'Deathlehem
Machine'.  :)  (I've built 3 of them before this one.  A very very few of you,
may have heard some of the 'tunes' done on one of the devices.)

In the previous units, I had always built their 'Oscillators' and 'Modulators'
with the dual Nand Gate clocks from the CD4011 quad Nand Gate CMOS chip.
An Oscillator would be setup with a Pitch Control, as well as a switch that
allows that Oscillator to oscillate by itself, or only when their is a
Modulating Oscillator switched into the Input #1 of the first Nand Gate in it. 
(With the Modulator/Oscillator hookup (chosen by a toggle switch), this would
produce a Pulse Width Manual Modulation type of sound when adjusting the Pitch
of the Modulation Oscillator.  (The pitch of the Oscillator controlled by it's
own Pitch control.)

I had various problems on the first 3 units of this machine, though they still
would make some absolutely killer noises.  Even deadlier noises with the
machine plugged into FX units.

My customer Dan had brought his Deathlehem Machine V3.00 back here on Thursday
night (4 Modulators / 4 Oscillators).  It has some more funny problems.

In playing with the unit, I decided to scrap it, and build a different type of
unit for him.
The DM V4.00 unit, has been built, based around 4 Hutchins/Klein/Miller LFOs,
that were published in Barry Klein's book, and had variable waveshape.
(The schematic for the this LFO is up on my webpage as LFO V1.44.)
I've removed the variable waveshape section of this LFO, and changed the Speed
pot from the 100K pot listed in Barry's schematic, to a 2.5 meg pot, for a
greater amount of Pitch variation.  (I KNOW that a 1 meg pot gives a far
greater range of pitch control.  The 2.5 meg pot is to see if it's that much
greater a range.)  I'm sticking with a 0.1uF cap in the Integrator, as I'm most
interested in audio frequencies coming out of this thing.

What I have added as an option for the DM V4.00 machine, is External Frequency
Modulation.  Looking at the schematic, the Schmidt Trigger (in the
Schmidt/Integrator type of LFO) has a 27K feedback resistor.  The Integrator
Output is feeding this Schmidt through a 10K resistor, to the Positive input of
the Schmidt opamp.  I've reasoned, that adding another 10K resistor to this
Positive input, that would allow you to send either the Triangle or Squarewave
output, from ANOTHER LFO input, would allow the Frequency control to happen, in
the first LFO.

I've done this, on all 4 of the LFOs.  Each of these LFOs has switches to send
their output waveform (switchable between Triangle or Square) to either the
output mix opamp, or into another of the LFOs.  (I'm setting this customer's
machine up for cross modulation between each of 2 pairs of LFOs, to see what
happens.)

My big question about this:  After I had layed out the PC board for the
customer's DM V4.00, I came up with the idea of leaving the variable waveform
control in each of the LFOs, and setting up the waveform output to come into a
rotary switch, that would allow that waveform to modulate either of the other 3
LFOs.
Each of the 4 LFOs would also be frequency modulatable by up to all 3 of the
other LFOs.  And all 4 of the LFOs would have jacks on the front panel to allow
frequency modulation to each of them, from the outside world.
Each of these 4 LFOs waveform outputs would be out of separate jacks, as well
as mixed together in a single multiple output.
Each of the 4 LFOs Triangle/Saw and Pulse waveform outputs would be switchable
as the waveform used for frequency modulation.

This would then be a new module from A.R.F. called the 'Voltage Controlled LFO
>From Hell V1.00'.  It would also be entirely capable of functioning as it's own
'noise generator' for those that wish to produce nice evil sounds.  :)
This module would cost about $140 U.S.  (If I've estimated everything
pricewise, correctly, in it.)

While writing all of this, I also thought of using 2 pairs of the 3080 TOA
(chip) as a 'virtual resistor' for Voltage Control over the waveshape of the
unit.  Thoughts, anyone?

Do any of you fine chaps out there that have more electronics knowledge than I,
know of any problems in either of these units that I'm building/thought of? 
I'll be finished the DM V4.00 unit in about another 1 1/2 hours of work, and
will have some answers there myself.  I don't have nearly enough electronics
theory knowledge yet, and am always trying to learn more.  :)

Thanks for any help, and please to pardon this long huge babble.  :)
Take care all,
Ric

Aural Research Facilities - Samples of some modules are now available at:
http://www.pangea.ca/rmiller or http://www.pangea.ca/~rmiller
"I stayed up all night playing poker with tarot cards.
I got a full house and four people died." - Stephen Wright