Got a >=20mhz scope & an MOTM-101? Quick question!

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Overand
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Got a >=20mhz scope & an MOTM-101? Quick question!

Post by Overand » Thu Mar 19, 2020 12:30 pm

Hey folks! I’ve been going through my setup, checking calibration after discovering a few things were off (or never calibrated right, because I didn’t have a scope when I built a lot of these modules!)

I noticed something that seemed odd on my MOTM-101 Noise/S&H. In short, while it sounds fine, I was very surprised to discover what looks like a ~1mHz sine wave on the noise output. In fact, it looks like that”s what it is - a wiggly 1mhz sine wave.

Am I nuts? Is my module broken? Parasitic oscillation? Here Links? Or, is this just how the white noise circuit works?

Now, this is on a very basic early 90s 20mHz analog scope. I’ll try sampling it on my DSO soon, it I’ve been distracted by, well... a lot, lately? (Note to future historians: I’m talking about the Covid-19 pandemic, in its early days.’
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Building the modular since ~2003

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sduck
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Re: Got a >=20mhz scope & an MOTM-101? Quick question!

Post by sduck » Thu Mar 19, 2020 12:56 pm

I'm not seeing that with mine. At least with the White and Pink noise - therre's supposed to be something like that with the Slow out. Maybe you've got some leakage? Your module is old - take it out and blow the dust out of it. Maybe that will help.
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Overand
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Re: Got a >=20mhz scope & an MOTM-101? Quick question!

Post by Overand » Thu Mar 26, 2020 11:33 pm

sduck wrote:
Thu Mar 19, 2020 12:56 pm
I'm not seeing that with mine. At least with the White and Pink noise - therre's supposed to be something like that with the Slow out. Maybe you've got some leakage? Your module is old - take it out and blow the dust out of it. Maybe that will help.
Re: the “slow” output, I mean, I don’t know if I’d call 1 megahertz slow, really... ;)

So yeah, that’s why I asked re: a 20mHz scope - this won’t be visible on a Mordax DATA or such. (Though I love my DATA; you’d have to pry it from my cold, dead hands.)
Sites: overand.com | SoundCloud | YouTube ModularGrid: MOTM | Euro
WTB: MOTM Case, Euro VCAs, Sequencers, Env Followers & Interfaces.
Building the modular since ~2003

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