MOTM

Just for possible interest, I've been expanding on a past idea/post from way
back where I described how to emulate several Doepfer modules on the MOTM
that MOTM doesn't have. I've continued that and managed to emulate a bunch
more that MOTM doesn't offer but may not be obvious that they can be
emulated. Here's a list:

1) Quadrature LFO like Polyfusion had, that outputs 4 sinewaves (or can be
any waveforms on the MOTM) each 90 degrees out of phase with each other. Or
a tri-LFO that outputs 3 waveforms 120 degrees out of phase, or any other
combo you'd want.

2) Half and full wave rectifiers like the Dotcom modular has.

3) Envelope follower. Works great, and makes a good poor man's breath
controller if used with a mic.

4) Clipper, for clipping off the top and bottoms of waveforms, plus more.

5) AND and OR boolean logic.

6) Pseudo-VC ADSR.

7) Sequential Switch like Doepfer has but only two positions, not four.
This was one I decribed way back when.

8) Trigger and/or Gate Delay. I had previously mentioned two different ways
to do it, one using a 700, and one using the 850. Came up with a third way
that uses a Mixer and another EG. Also came up with a forth way that uses
an external digital delay plus an amplifier (Art Tube MP). Who says you
can't use digital delays for non-audio?


I can't remember if the MOTM-700 has been discontinued. But if people wanted
to know what that little used module is good at, numbers 2,3,4,5, and one of
8, all use the MOTM-700 in some way. Goes to show you that if a module
becomes discontinued, you might possibly lose out on a bunch of other
funtions too.

-Elhardt
(The Book of the Secrets of Synthesis)

ac writes:

>>3,4 & 6 Oakley, 7 STG<<

Seems that ac probably meant this go to the list. Yes, there are other
companies that put out modules that do all those functions. The point here
was to show that buying addition specific modules for most of those
functions isn't necessary.

To add to the list:

2b) A rectifier can also be created using the older Ring Mod on the 110 VCA
to add a second way to do it. The new RM on the 190 shifts all over the
place and isn't reliable though. A rectifier is needed as one of the parts
for an envelope follower.

5b) Figured out how to do an XOR logic function too, using the Ring Mod on
the old 110 VCA as the main component.

9) Semi-Phase Shifter.

10) Creating a HP filter from a LP, LP from HP, Band Reject from Band Pass
and vice versa. Should anybody want a 24dB/oct Hi-pass filter for example,
just use a 24dB Low-pass, invert the signal going into it, and mix that with
an equal level of straight signal and you'll end up with a 24dB hi-pass
filter. This had been talked about ages ago. I didn't pay much attention
because I had no need for such a thing. But I accidently patched it up when
trying to do something else and it works really well.

-Elhardt

On 4/23/08, Kenneth Elhardt put forth:

>
>"2b) A rectifier can also be created using the older Ring Mod on the 110 VCA
>to add a second way to do it. The new RM on the 190 shifts all over the
>place and isn't reliable though. A rectifier is needed as one of the parts
>for an envelope follower.

How do you do that?? Although adding a rectifier switch to the 820
would have been a good idea.

I'm glad I didn't sell my 110. Imho, it's a better ring mod than the
190. I often use it for velocity. I'll use the velocity output of
my Pro 4 as one input and the output of an 800 as the other input,
and use the resulting output to control a VCA. Having separate knobs
for each input is very handy.

Mark writes:

>>How do you do that?? Although adding a rectifier switch to the 820 would

have been a good idea.<<

I'm not sure if you're asking about the rectifier or the envelope follower,
so I'll just answer both. Just feed the same signal into both the X and Y
inputs on the ring mod and you'll get a rectified signal out since when the
signal is positive, the two positives multiply to give you a positive out,
and when the signal goes negative, the two negatives multiply and also give
you a positive output. Then for an envelope follower you just feed that
ring mod output into the 820, set the LIN/LOG knob to 10, and set the
Up/Down knob to between about 4 to 5 depending on how fast you want the
envelope to respond.

On 4/29/08, Kenneth Elhardt put forth:

>Mark writes:
>>>How do you do that?? Although adding a rectifier switch to the 820 would
>have been a good idea.<<
>
>I'm not sure if you're asking about the rectifier or the envelope follower,
>so I'll just answer both. Just feed the same signal into both the X and Y
>inputs on the ring mod and you'll get a rectified signal out since when the
>signal is positive, the two positives multiply to give you a positive out,
>and when the signal goes negative, the two negatives multiply and also give
>you a positive output.

Thanks :)

>>I'm not sure if you're asking about the rectifier or the envelope

follower,
so I'll just answer both. Just feed the same signal into both the X and Y
inputs on the ring mod and you'll get a rectified signal out since when the
signal is positive, the two positives multiply to give you a positive out,
and when the signal goes negative, the two negatives multiply and also give
you a positive output.<<

That doesn't sound right. Squaring a signal (i.e. multiplying it by itself)
doesn't rectify it, in the general case. Consider a sine wave as an input
signal. There is a trigonometric identity as follows:

sin^2(x) = 1/2 (1 - cos(2x))

for all values of x [where "^2" represents raising to the second power in
ASCII]. A cosine wave is merely a sine wave shifted ninety degrees, so your
output is a sine wave of twice the frequency (because of the 2 in front of
the x)and half the amplitude (because of the 1/2 at the beginning) of the
input, with positive-only DC bias (because of the subtraction from 1).
That's not a rectified sine wave.

--Adam

Adam Schabtach writes:

>>That doesn't sound right. Squaring a signal (i.e. multiplying it by

itself) doesn't rectify it, in the general case. Consider a sine wave as an
input signal...<<

Yes, you're right. When a waveform is multiplied by itself it distorts its
shape into something else, as you pointed out, it's squared. What I should
have said is that it acts kind of like a rectifier for the purposes of an
envelope follower, since it takes the negative portion of the waveform and
moves it up into the positive side, even though its shape is modified too.
But that shouldn't matter much for the purposes of an envelope follower.
For a true rectified wave, the MOTM-700 can be used along with the MOTM
mixer for inverting one of the signals and for matching the levels of the
inverted and non-inverted portions.

-Elhardt