Gate leaks from stillson

Having some troubles with my stillson hammer mk2 and 301. When I try to create a synth in the 301 I want to send the gate to the vca. But when I raise the gain (next to bias) it leaks through. It acts the same if I unplug the cable from the stillson. It’s quiet if I plug it in my gate out on the 101. Does anyone know why this happens?


I think we can safely take the Stillson out of the equation if that is the case? If the bias on the VCA is 0, then there should be no sound at all when Gate is low. From your description however I can’t tell what’s going wrong. Maybe take a screenshot, make a video, or take another stab at describing your exact settings and situation so we can help you out.


You have encountered the common situation where an external gate has a slight positive voltage when it is low. To be clear, a gate does not have to be exactly 0V to be considered ‘low’. A low gate just has to be below some agreed on threshold (e.g. below 0.05V for 5V CMOS logic and anything below 0.5V for 5V TTL logic).

The solution is to use a unipolar VCA with a slightly negative bias. The unipolar aspect causes the VCA to ignore negative control voltages. The slight negative bias will cause the VCA to close completely for a range rather than just at 0V.


thank you for your answer @Bparticle

@odevices should/could this happen even though the cable isn’t plugged in on the other end? I have it plugged in to the a-d jacks, maybe that could have something to do with it? It doesn’t happen on the G inputs.

Absolutely. If you have a cable plugged in on only one end then this defeats the normalization to ground inside the jack and you are left with a floating connection that could fluctuate quite a bit. The G inputs are unipolar by the way.

Ok so the jacks on the stillson gate outs are not grounded I suppose?


I never said that. :thinking:

No i’m asking :slight_smile:

I guess I don’t understand why you are asking that. So I’m wondering if we are failing to communicate.

Anyway, the ring connection of all jacks in eurorack are connected to ground. Based on what you have reported, I have no reason to believe that isn’t true for your Stillson. Everything is behaving as expected.

probably Brian means that when it is patched to the stillson, maybe the stillson doesnt go exactly at 0v when on Gate Low , so this might be the reason for the odd behaviour when patched to the Stillson, the grounding is not an issue, the fact it didn’t probably close at perfectly 0v is. (tip: maybe it can be calibrated with trimmers! a lot of modules , example: analog envelope generators, don’t close perfectly at 0v, usually with analog devices this might not be a problem because there are tolerances, but with a very precise machine such as er-301 this might become noticeable)

but when you unpatch from the stillson and leave the cable patched only on one end to the 301, it is normal to have some voltage going on! so this is the reason for this behaviour, and has nothing to do with the other behaviour.

same result, different reasons :slight_smile:

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@odevices I’m just trying to understand what’s going on :slight_smile: that’s why I’m asking what might seem to be stupid questions.

thank you both for your elaborate answers!

You are very welcome but did any of it make sense? We’re we successful? :ear:

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I’m gonna conduct a couple of tests. Will report back :slight_smile:

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