Moog One Output Signal Distorted

Polyphonic Analog Synthesizer
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ZaphodB
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Joined: Fri Dec 27, 2019 12:06 pm

Moog One Output Signal Distorted

Post by ZaphodB » Fri Jan 17, 2020 6:50 pm

As soon as I turn the output level past 8, the signal of my Moog One is distorted.

I have attachted a picture with a digital oscilloscope. Although the picture is not perfect, it is clearly visible that the signal is flattened as if it is hitting the amplifiers max/min voltage level. This does not happen when the output volume is lower than 8 and it never happens to the headphone output, not even at high levels (see other picture). The patch I'm playing here is stock E-4.

Any clues to what is happening? Is there something I can do about this or do I need to sent the synth in for repair?
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Iaamusic
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Re: Moog One Output Signal Distorted

Post by Iaamusic » Sat Jan 18, 2020 12:36 pm

Check this thread.
In short, don’t turn master volume above 1 o’clock. Use VCA and Oscillator volumes to get gain sorted.

https://forum.moogmusic.com/viewtopic.php?f=22&t=32884

ZaphodB
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Re: Moog One Output Signal Distorted

Post by ZaphodB » Sat Jan 18, 2020 3:35 pm

@y Iaamusic

What you suggest may be a work around, but anyone who knows how amplifiers work, will recognize the distortion as a matter of overloading the amplifier. I'm not speaking about noise as is being spoken about in the thread you mention, this is unwanted distortion of the otherwise clean signal. And mind you, why does the headphone signal not distort at high levels? That signifies that the headphone amplifier had either more headroom or is not overloaded. This is either a fault in my synth's amplifier or a design issue. I'm curious whether anyone else has taken a look at the signal at high levels and has witnessed this typical flattening of the waveform at high levels ?

ZaphodB
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Re: Moog One Output Signal Distorted

Post by ZaphodB » Sun Jan 19, 2020 2:57 pm

Wherever in my previous posts I speak of 'overloading' or 'flattened' I mean 'clipped'. I realized only just a minute ago that that was the word I was looking for. The signal is clipped and that is not what I would expect.

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hieronymous
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Re: Moog One Output Signal Distorted

Post by hieronymous » Mon Jan 20, 2020 9:12 pm

Did you see this post in the thread that laamusic posted?

viewtopic.php?f=22&t=32884&start=15#p175508

In your original post you say you have the volume on 8 - this would be approximately 3:00. The statement from Moog referenced in the link states: "Their claim is that 12 o'clock on the master volume knob is unity gain, and anything above that is additive. The VCA & master volume are purposely voiced high to allow for distorted sounds in lieu of a dedicated overdrive circuit." Distorted sound can look like a square wave, correct? Perhaps resembling the clipped signal you are seeing?

I could be wrong, but I think you need to consider this as a possibility.

DISCLAIMER: I don't have a Moog One as I mentioned in the thread I quoted, but recent Moog stuff seems to be built like this, including the Sirin which I do own (though I haven't gotten much distortion out of my Sirin)

ZaphodB
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Re: Moog One Output Signal Distorted

Post by ZaphodB » Fri Jan 24, 2020 5:38 pm

I did not know about this statement, but that explains everything. The distorted sound will be clipped and given the right basic waveform will resemble a square wave. Phew, so the machine is not broken, this is by design. That's a relief. But I find the concept of creating distortion this way a bit weird. There are far more creative ways to make distortion that even sounds good. This clipping does not do that so much (for me).

Iaamusic
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Re: Moog One Output Signal Distorted

Post by Iaamusic » Sat Jan 25, 2020 4:35 am

But I find the concept of creating distortion this way a bit weird
On that, you’re not alone......

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