MOTM

>Now that I have VCOs (beautiful! amazing!) I have started patching all
>kinds of neat stuff, and have noticed a few things about my older modules.
>
>Should I expect to be able to trim the MOTM-110 ring modulator to absolute
>silence with one input zeroed?  I feed a high-C sine wave into X IN with X
>LEVEL at 10, Y LEVEL at 0, X and Y both AC-coupled, Y IN unconnected.  By
>turning the X trimpot I can render the original sine wave nearly
>inaudible, but a frequency-doubled version appears at the output and
>cannot be trimmed away.  Exchange X and Y, and the doubled wave is much
>louder (clearly audible at "reasonable" volume levels).  In addition the
>output clips if I turn Y LEVEL past 9, but I guess this is to be expected
>(driving from a 300).

Again, this subject has re-appeared again, so I will reiterate.

1) The MOTM-110 is specifically designed for LARGE signals. NOT guitars, NOT
the output
jacks of synths.

2) The best way to boost signals to be '110 happy are:

a) use the headphone output
b) use the SEND buss of a mixer
c) use a 'direct box'
d) gnash teeth while waiting for 1U triple pre-amp

3) ALL ring-mods have carrier leakage. The carrier "nulling" is input
amplitude *dependent*.
If you adjust the 2 trims pots at one level (say 2V pk-pk) then if you input
8V pk-pk the null
is greatly reduced. So, Rule #1 when setting the trimpots: use the largest
signal you plan to see.
Like, VCO outputs.

Also, the null amount is basically *not* all that great: say 30-35 dB down.
You *will* be able to hear that.
But, in general a good null point, coupled with enveloping BOTH X & Y
inputs, will keep the
*perceived* leakage to a minimum.

Of course, the UNBAlance control *adds* leakage!

4) Remember: the best RM sounds use a SINE or TRI wave for Y and the "audio"
into X. Shoving 2
presets into X & Y will get noisy fast! In fact, you may HEAR "extra noise"
coming out of the '110
which is the by-product of the RM.

5) The '110 has a *built-in* gain REDUCTION of 5. The reason: if you put in
2 5V pk signals, 5 * 5 /5 = 5V out
which is what we want.

You put in 2 1Vpk-pk signals, like the OUT of a synth, and you get out
(.5)(.5)/5 = 50mv = not much there!!!

Careful level adjustments plus proper nulling using the trimmers will get
you some great effects!

POP QUIZ!!!

Why is Chris seeing a "doubled" waveform??

Paul S.

>From: "Paul Schreiber" <synth1@...>
>POP QUIZ!!!
>Why is Chris seeing a "doubled" waveform??

A) Chris drinks too much and therefore often sees double!

B) Proof by contraception:

1) Assume sine present at INPUT X.
2) Assume no input at Y
3) Assume small leakage between X and Y

Since the signal, X, is also present at Y, and since the RM OUTPUT is defined 
as the sum frequency and difference frequency of the SINE wave inputs at X 
and Y we see that the sum of (X + Y leakage) is equal to the sum of X + X = 
2X which is one octave above X. While the difference (X - Y leakage) = (X - 
X) = 0.

QED

But please don't call me POP.
JB