(No) Danger, low voltage!

I am stumped, i have an issue that is presently beyond my understanding and i’m desperately searching for clues from anyone with insights or potential leads on where i might focus some attention - it could be that some experience of related issues from the general Modular user community will point me to the origin of this puzzler …

I have an smallish assortment of semi-modular gear by different brands, but enough to have tried much of it to sanity check my thinking by swapping out one bit of gear for another - i’ve utilised the flexibility of the A4 cv sequencing to act as a substitute for a bit of gear but it all leaves me with an issue which only manifests between two pieces in particular, and only one way …

… ironically between two ostensibly similar Behringers, my Pro-1 and Neutron ! This issue pans out in that i cannot CV sequence the Neutron from the Pro-1, whether by the Pro-1’s sequencer or using the same CV/gate derived from midi incoming to Pro-1 MIDI - both are up to date, (1.29 P1, 2.02 Neu) and i have swapped their PSUs etc etc, no stone unturned

The Pro-1 will properly sequence a Doepfer Dark Energy Mk1 (v2 of that board) an Arturia or happily drive the clock in an SQ1 … i ended up establishing the (apparent) working voltage from the Gate out … now, when hooked to a voltmeter it showed 0.03 > 5.08V yet when I instead used the gate as a pitch CV source and swapped between that and the LFO out and Amp Env out (gate shape) it was clear that the Gate out was the lowest voltage, then the square LFO (monopolar btw, only the tri is bi) and then the Amp Env, the signal from the Amp Env with sustain at Max is highest, the sustain at a smidge over 7 equates to the level from the LFO and a smidge under 7 equates to the level from the gate, the voltmeter shows -0.01 > 5.04 for the (max sustain) Env and 0.00 > 3.79 for the LFO

I’d noted that the equivalent pitch Mod from the A4 CV (using value lin and varying permissible voltage range) to achieve the same pitch range as the P1 Gate signal into the Neutron was 0.06 to 3.59, so this tallies well with all observations

Now if you set the range of A4 CV to find the tipping point for opening/closing the Neutron gate it’s in the range 1.38-1.45 … i.e. a signal falling below 1.38 will close teh gate and any signal above 1.45 will open the gate until it falls below 1.38, if it’s below 1.38 it will not open

Here’s the problem - without triggering the gate i set the Neutron VCA bias to drone and feed the P1 Gate and alternately the equivalent A4 CV signal to the Neutron Pitch Mod and they sound identical to within a few cents … when i swap the inputs from Neutron Pitch CV to Gate CV (or e.g. SmpHld Clock) then the (identical?) A4 voltage still works in both cases, but the Pro-1 will not gate the Neutron, this means that the voltage is somehow not exceeding 1.45, yet it’s the very same signal that moments before was sending 3.6ish to Pitch CV … deeply puzzling !!

Every which way i had tried to wrap my head around this i could not make progress, no googling helped, i updated both (again) - i tried and tried and considered all sorts, swapped cables etc, but right at the end i made a lucky observation, i am wondering if it may help pinpoint what is somehow happening internally here - if i take the P1 Gate out in via the Neutron Mult (with no other cables attached to the patchbay) and then take one of the Mult outs into the Gate it works !!

What gives ? What’s rendering this seemingly adequate voltage from this one source only as insufficient, what has happened to the voltage at that port that isn’t happening when seemingly identical voltages arrive from other sources - it’s clear that the gate voltage isn’t being met, so that voltage is somehow not arriving whereas gates from every other device does - I genuinely cannot pinpoint where my attention should turn, because both behave impeccably with every other bit of gear, so it’s not too clear - my initial fear was that this was something i hadn’t picked up on from the s/h purchase of the mint Pro-1 - i’d genuinely never attempted to drive anything from its seq, it’s rudimentary, but i’d actually wanted to use its sequenced (at LFO rate) gate to clock the Neutron Sample and Hold and was puzzled it didn’t fly … then tried the regular sequencing etc, and many hours later i am stumped.

I wonder if i will have joy at Behringer support, but i thought i’d field the electronics question to any folk with a hunch about what may be occurring here … i’m also going to ask users of either device if they can possibly connect the other in a simple cv/gate sequence test to see if this is restricted to my hardware or a general issue … the Pro-1 has digital envelopes so the scope that this is related to firmware is a possibility, but it doesn’t explain why seemingly similar signals are giving different results

Why is the Voltmeter showing a higher voltage from the Pro-1 gate ? Why does the Pro 1 gate play ball with all other gear and just not the Neutron and why do the gate signals from all other gear get spared this issue ? Why might the Neutron Mult fix the apparent issue between this pair ? What’s occurin’, i’m looking for clues ?

PS if you know a friend with both it and you’re inclined to ask it ought to be a quick experiment to CV seq the neutron from the Pro-1 and relay the success or not … this might not just be me affected !

PPS To trigger both the Neutron Envs you feed the Pro-1 gate to input [ E. Gate 1 ] and the Pro-1 KYBD CV (Pitch) goes to input [ Osc 1+2 ]

I haven’t read your post carefully (not much time yet), but I guess the main point is: why it works via a mult and not directly, right?

From an electronics point of view it looks like that the gate input draws more current than the gate out can deliver. This probably results in the gate out voltage unintentionally going/breaking down and can’t be detected correctly.

IMHO this smells like a design problem: either the gate out not delivering much current or the gate in drawing too much.

(the mult in between acts like a buffer providing enough current)


Thanks for the thought, seems like a plausible theory … This is making me lean towards the main issue residing with Neutron, i declined to mention something that i had noticed elsewhere on its patchbay (because i have forgotten) but it was also something that would have been resolved if a signal was being buffered (but instead it was displaying a voltage drop) - i don’t recall but i’m imagining it ironically relates to the mults not delivering what was expected whereas in this instance it appears that the mult is part of a solution for an underlying issue that may originate from either end - i’m still near 50/50 wrt which unit might be the one bringing the issue here although it only manifests between these two particular devices in that one connection mode - i’m mostly anxious that i may have inherited a
faulty/damaged Pro-1 although i won’t be best pleased to establish it is indeed a design issue which is indeed smelling more likely as i have observed and read some things wrt the Neutron that hinted at a little lack of finesse in other areas

Yeah seems like impedance mismatch.

I remember the SCI Pro One having fussy gates, so if they literally just copied it that could be why.


If it was down to the Pro-1 design, i’d have expected some internet chatter and might have expected issues with my other gear - but everything else has been fien - i just can’t get my head around how the same output can give equal results when fed into the Pitch CV but fails to work when moved to the Gate input - it makes me more suspicious about the Neutron

I vaguely recall being able to send an even lower voltage from the Amp Envelope (much lower sustain, so lower gate pulse, somewhere round about 2 or 3 on sustain) … even adding attack and decay to this did not prevent the Neutron opening its gate

For some electronics reason - that apparently high enough voltage is working in one input but is failing to materialise in another input port - it sorta fries my brain still - i’m trying to understand teh processes that may be at play because it may point to a hardware issue - i’m especially curious about how teh voltmeter can report a higher voltage (5.1) than it can apparently serve used as a Pitch source (3.6) and for it to fail to deliver enough to exceed 1.45v to only that particular gate input

Beefier quality PSUs made no difference

Did you measure the current on the Pro One gate output and compare it to the other outputs from gear that reliably triggers it?

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I have experienced the same gate issue with some gear a while back. I think it was the Arturia Microbrute. I always had to run it through a buffered multiple. (Or something else that was buffered on my modular)

I would guess that the neutron has a “buffered” input on the cv, but not the gate. And that the gate output on the Pro-1 is not buffered. As voltage drop on a cv input would be more noticeable. (Expect in your case, as you cant trigger the gate at all.)

I can see if i have problems triggering stuff on my modular with my Pro-1, but i dont have a Neutron to test with.

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I just made a 3.5 mono to 3.5 mono where i sliced the tip wire cable half way and popped on some banana plugs either side of that split mid-way - so the circuit is only completed once the meter is connected

my assumption being this was the way to test the current draw (presumably without interrupting) normal business by adding the voltmeter - i double checked i was in the right socket for the amp reading and set to a variety of mA but no dice - nothing on the meter - even for connections where the behaviour was all good

i guess my cable isn’t fir for purpose - it’s sound, but in terms of doing the measuring

so what have i missed here - this is me doing the test with both devices powered at either end of that mono cable ?

It’s all about the impedances involved. A voltmeter, for example, has a very, very high input impedance. When you connect the voltmeter to the output its almost like connecting an isolator: no current (well, only a tiny, tiny bit) gets drawn by the voltmeter and the measurement point will stay at its previous voltage.

As soon as you connect something which hasn’t a very, very high impedance the voltage at the output will definitely drop. How much it drops depends on the input and output impedance.

In the worst case when you connect the output directly to ground (input impedance=0), the voltage at the output also drop to ground level (0V).

So it doesn’t matter what you measure with your voltmeter. That will tell you nothing about what is going on when you connect something. It’s just an initial value which will drop as soon as current gets drawn.


That would be appreciated, it may be interesting to compare the level of your Gate as a Pitch CV source compared to the Square LFO and full sustain Amp Env

If these are in broad alignment with my observation it starts to fill in the gaps and give me some re-assurance that this s/h device was sound and no different to other Pro-1s in the field

I couldn’t get the gate to fail to trigger anything, except the Neutron - but every other bit of gear successfully triggered its gate (Neutron) (and the Pro-1 did but only via the Mult)

Flabbergasted that Behringer didn’t answer my technical support query, but instead quietly closed it without warning after thanking me for such a thorough and clear question. wut !

I’m still struggling to get my head around why this might be happening - one thing i noted was that all the working CV out sockets were more isolated from the Key CV/Gate out

with nothing plugged in, not even Pro-1 power, if i take a pure sin on the Neutron and Pitch mod that with a patch cable and touch the tip you get some familiar warbling/interference modulation - taking teh tip to the shields of all teh Neutron outs shows the ones which are connected

OscCV(IN) KYBdCV(OUT) GATE(OUT) Mixer(OUT) Phones(OUT) or Screws or USB shield Chassis etc

I’m wondering if this can point to some corner cutting or design issues and it may help explain why the lower voltage LFO signal works a treat

Still a bit of a puzzler that everything is ticketiboo except the Pro-1 to the Neutron

Having my case closed unanswered is seriously bad form, that leaves a really bad taste … if the support rep has no access to those units then the case should be forwarded to someone who does - this response from support has really put me off looking out for a crave

I genuinely have no idea if there’s a design fault or a hardware issue and reaching out to Behringer Technical support should have resolved that

Still keen for things to investigate to better understand what’s going wrong here … might (as a last resort) modding a buffered gate out be a way forward etc or is the design issue more likely at the Neutron end ?


It appears (just confirmed by MusicTribe) to be a repeatable incompatibility between all Pro-1s and Neutrons and the culprit appears to be the Neutron. It might be something that firmware can address, but it’s mostly a relief to know that the Pro-1 is sound and the Mult is still an inconvenient workaround for some scenarios

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