Moog Music Forum

I've been running my Matriarch's Mixer output into the Mordax Data Oscilloscope to get a better sense of what happens when you overdrive the inputs. (I'm presently in unison mode, using only Osc1 for this test.)

I'm seeing a peak-to-peak signal of roughly 12 V. What I'm finding interesting is that it doesn't clip uniformly when driven to the limit. When I overdrive the inputs, the signal spans -4V to + 8V, with most of the clipping happening on the "bottom" of the wave. Is this range intentionally offset in the positive direction (and clipped on the negative)?

In contrast, OSC1 Wave Out directly to the scope appears to be 10 V, centered at 0 (-5V to + 5V).

The attached image is a pretty rough screen grab from a video, but should still illustrate what I'm seeing. The green saw is OSC1, and the red clipped saw is Mixer Output (with Osc1 Input set to maximum.) Observe the clipped "flat spot" at -4V, but the saw peak is still "pointy" at about 8V.

Also, I was under the impression that clipping should start when the input knob goes clockwise beyond 12 o'clock, but my output signal mostly matches the input at about 3 o'clock, and only clips when I get beyond that. I guess what I'm really wondering is whether the overdrive should be more aggressive.

I don’t have access to my notes right now, but your measurements all look normal to me. The CP3-inspired mixer is famously asymmetrical in clipping. This is considered a desirable sonic feature.

I don’t think there is any DC shift. Notice the zero crossings are about the same for both waveforms. The resulting average, of course, must be greater than 0V. But the non-clipped portions of the wave are more or less treated linearly without DC shift.

As for the 12 o’clock rule of thumb, your result also matches with mine. I think the rule is based on four waves all summed with knobs at 12 o’clock. A single wave should be 2Vpp or less in that setting. All four waves should be about 8Vpp. If I remember correctly, I think you will find you need a bit more than 12 o’clock to really clip. But maybe filter distortion starts to occur before the mixer clipping point.

Good idea to measure the gain structure for yourself. Lots to learn

I watched that Sonic State Q&A with Moog Engineers and they speak about this exact thing. I’ve only had my Matriarch since Monday, what a great sounding synth!