Marbles: gate outputs' shape

Dear Marblelers and MI :slight_smile:

I´m trying to strike a passive LPG with Marbles´s t-outs (any of them) through a passive gate-to-trigger module.
The setup works great with gates coming from ex. PNW or any square LFO. But there´s something about the character (or waveform) of the gate coming from Marbles´s t-out, that makes the setup work only very vaguely. I´ve monitored the Marbles gate-waveform on a scope and it looks like a kind of shark-fin like envelope (exponential, I suppose) with a relatively long release. Is there a way the gates can be altered into a more clean square-waveform? - that seems to be the issue here. (I´ve tried with different gate lenght on Marbles with no luck)

Thanks a lot for an awesome module, by the way :slight_smile:

You can adjust gate length on Marbles. Details are in the manual.

Are you sure your scope was DC-coupled and not AC-coupled? Which oscilloscope is it? What you describe is the normal shape of a low frequency square signal passed through an AC-coupling (high-pass) filter. Here’s another post about this (non-) problem: Module Tester clock signal issues . It is also worth mentioning that software oscilloscope with an AC / DC coupling option are only running (or not) a software filter on the signal – if your input is AC-coupled, it won’t change a thing!

Marbles’ gate output are nothing more than gates – they are generated by a digital output which can only have two levels (0V and 3.3V), then passed through an op-amp with a gain of 2.4 to reach the nominal 8V level.

Your problem is related to something else (maybe the gate being too short - in which case this can be adjusted using the procedure described in the previous post).

Thank you very much for the swift and thorough answer.
You might be right concerning the AC/DC-coupling of my scope. I´m using a Zeroscope, but I did not take notice of the couplling.
I tried altering the gate length on Marbles, but the passive gate-to-trigger/Passive LPG setup is still not responding very well compared to other gates sources.
I noticed that sending the Marbles gate outputs through a Frap Tools 321 active attenuator with gain x1 (no offset) solves the issue. Do you have any idea what can be the case here?
Can it have something to do with currency level or something like that?
(I´m not a complete electronics-Pro, as you might have guessed :slight_smile: )

Many thanks and best wishes

Marbles’ gate outputs have a 1k protection resistor that prevent damage to the module when these outputs are patched by mistake into another output. This might explain a difference in level when they are patched into a passive module with a low input impedance.

Note that these resistors have a negligible effect (a 80mV drop of amplitude) when the signal is patched into a regular active module (with a 100k input impedance).

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