Neutron The New Behringer Semi-Modular Synthesizer

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Biff
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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Biff » Mon Mar 16, 2020 11:00 am

Does anyone own two of these? I’m debating whether getting a second one would open up a lot or if the money would be better spent on a small eurorack expander for it (the former being much cheaper).

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Nightly Closures » Mon Mar 16, 2020 3:45 pm

I have one. I think getting other modules to compliment it would be the better solution. Something like a quadrax really sets it off right.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by bitSmasher » Tue Mar 17, 2020 5:46 am

Biff wrote:
Mon Mar 16, 2020 11:00 am
Does anyone own two of these?
I bought two at once, and they're great fun together.
I do see the need for a bunch of mults, VCAs and mixers to make it all gel... so maybe factor some cheap utilities in to your budget.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue Mar 17, 2020 8:18 am

I've found the main thing the Neutron benefits from, is having a few more attenuators available (home made passive ones are fine), and an extra multi or two (passive, home made or otherwise, also fine).

Another useful one is a preamp to boost from line level to modular level.

Any split rail preamp running on at least +/-12V, or +/- 9V (at a stretch) is useful, relatively simple to make, and remains relatively cheap to buy - but harder to source without hassle than it once was.

The 1/4" rear Audio In connection has no level boost, or other control, and is patched out too easily - the routing to the filter input is "normaled" (insert own spelling) via a switched 3.5mm jack socket.

If you patch an attenuator (recommended) or another module (e.g. the overdrive section) between the oscillators and the filter input, you lose Audio In - and it's inadequate for that purpose. It' actually a 1/4" modular level In, wired to a the switched or "normal" pin of the 3.5mm socket, IIRC.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Archimboldi » Sun Apr 19, 2020 1:14 pm

Quick: How to isolate LFO?

Hey all, I might have missed this... but I'd like to isolate the LFO (to use with other modules) w/out losing the ability to modulate the PW w/Att 2 on the Neutron. Is this possible? Thanks.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Dave Peck » Sun Apr 19, 2020 3:18 pm

Archimboldi wrote:
Sun Apr 19, 2020 1:14 pm
Quick: How to isolate LFO?

Hey all, I might have missed this... but I'd like to isolate the LFO (to use with other modules) w/out losing the ability to modulate the PW w/Att 2 on the Neutron. Is this possible? Thanks.
What do you mean "isolate"? If you just want the LFO output so you can use it elsewhere, there is an LFO OUT jack in the patch panel. If you want to also use the LFO to modulate the PW at the same time, you can do that just by sending the LFO OUT through a MULT or "Y" cable.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Archimboldi » Sun Apr 19, 2020 4:12 pm

Dave Peck wrote:
Sun Apr 19, 2020 3:18 pm
Archimboldi wrote:
Sun Apr 19, 2020 1:14 pm
Quick: How to isolate LFO?

Hey all, I might have missed this... but I'd like to isolate the LFO (to use with other modules) w/out losing the ability to modulate the PW w/Att 2 on the Neutron. Is this possible? Thanks.
What do you mean "isolate"? If you just want the LFO output so you can use it elsewhere, there is an LFO OUT jack in the patch panel. If you want to also use the LFO to modulate the PW at the same time, you can do that just by sending the LFO OUT through a MULT or "Y" cable.
Thanks for the quick reply. I realize that my post was not clear - I'd like to use the LFO OUT (to send to an external module) AND bypass/disconnect the LFO's impact on the Neutron's VCF and ATT 2. It's probably a simple patch step I'm missing. Hope this helps clarify. Thanks.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by racooniac » Sun Apr 19, 2020 5:12 pm

Archimboldi wrote:
Sun Apr 19, 2020 4:12 pm
I'd like to use the LFO OUT (to send to an external module) AND bypass/disconnect the LFO's impact on the Neutron's VCF and ATT 2.
if you plug something into ATT 2 IN it disconnects the internal normalisation.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Dave Peck » Sun Apr 19, 2020 6:28 pm

racooniac wrote:
Sun Apr 19, 2020 5:12 pm
Archimboldi wrote:
Sun Apr 19, 2020 4:12 pm
I'd like to use the LFO OUT (to send to an external module) AND bypass/disconnect the LFO's impact on the Neutron's VCF and ATT 2.
if you plug something into ATT 2 IN it disconnects the internal normalisation.
..And for the filter, just don't turn up the filter MOD control, or plug something else into the VCF freq mod IN jack to override the LFO connection to the filter.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Archimboldi » Sun Apr 19, 2020 6:33 pm

racooniac wrote:
Sun Apr 19, 2020 5:12 pm
Archimboldi wrote:
Sun Apr 19, 2020 4:12 pm
I'd like to use the LFO OUT (to send to an external module) AND bypass/disconnect the LFO's impact on the Neutron's VCF and ATT 2.
if you plug something into ATT 2 IN it disconnects the internal normalisation.
Thanks... perfect. I did that + patched the Freq. Mod IN (no OUT) - mission accomplished. 8-)

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by latrohexus » Mon May 11, 2020 1:01 pm

Hey all, I've discovered a quirk (or busted my Neutron). I threw an LED across the ENV2 output and it acted like the sustain knob was set to full, and I see the same behavior now if I run it directly to the CV input of a DPLPG. If I run ENV2 through an attenuator first, it acts normally (and triggers the DPLPG) until the knob is nearly fully clockwise, at which point the envelope goes high. I don't have an oscilloscope or anything to show exactly what's going on at the output, but I can try Multing it into my DC coupled audio interface to see if I can record the function directly. (edit: if I run the ENV2 output to a mult, and then from the Mult to the LED, the behavior goes away and it operates normally.)

The diode isn't just affecting the output, since I can hear the affect even when nothing else on the Neutron is patched. Is this normal behavior, or did I burn something out by messing with an LED without a serial resistor directly on the patch cable?

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Mon May 11, 2020 1:58 pm

latrohexus, have you put a resistor in series with the LED?

If not, you are clamping the output to around 1.5V-1.7V, which is the Vf of the LED.

It should be like this:

Out -> Current limiting resistor -> LED

Not

Out -> LED

- that would be limiting the current only by the presence of a safety resistor before the output, but the voltage at the output could not exceed 1.7V or so (depending on the characteristics of the LED).

If you add the resistor before the LED, the output voltage may still be dragged down a little, but it will not be clamped by the LED Vf or turn-on voltage.

If you assume the envelope output is 10V peak, and you ignore any safety resistance built into the output (after an op amp, usually), the LED current is then approximately:

(10V - 1.6V) / R

where R is the resistor you've added.

So, for example if you use a 1k resistor for R, you will get 8.4V / 1k Ohms = 8.4mA, which is enough to brightly light most 5mm LEDs.

If all you need is an indicator for a dark room, a 10k resistor will usually be fine, so that's 0.84mA, or you could go with a smaller value resistor, for a bigger current. Some 2mm LEDs are only rated for 2mA, and are still quite bright, so 1mA or similar is enough, unless you need to see the LED in bright lighting conditions.

By using an attenuator, you've effectively done the same, but what you should do is add a fixed value LED. If you start with a largish value, you can make it brighter by soldering another one in parallel, without needing to cut anything - so try 10k, or 4k7, or similar.

Choose a 1/4W resistor, so it doesn't overheat. For a couple of quid / euros / dollars, you can get an assortment of values on ebay.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by latrohexus » Mon May 11, 2020 3:18 pm

Thanks for the info. I wasn't planning on making an indicator light or anything, just experimenting with bare components. The current limiting stuff makes sense, but what I'm curious about specifically is why the ENV2 envelope behavior itself changes in response to the presence of the bare diode, but not the current limited diode. I haven't pulled out the DPLPG to see what the schematic is like, but I don't see the same results from ENV1 when patched directly into the CV input, even if ENV1 and ENV2 have the same knob settings, nor does ENV2 act up when there's a buffer between it and the DPLPG CV input. I would have assumed ENV1 and ENV2 are identical circuits, which makes me wonder if I somehow damaged ENV2 with the bare diode.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Mon May 11, 2020 6:32 pm

You're welcome, latrohexus.

My guess is you didn't damage it, but ENV1 and ENV2 have different circuits. Unfortunately, there are no schematics to refer to that I'm aware of.

The bare diode would not be much different to shorting the output to ground, but they seem to have allowed for that, or there would have been more people accidentally damaging it. I've followed the main Neutron thread on GS for quite a while, and people seem to get away with all sorts of accidental abuse.

If it still does it's job with nothing connected to ENV2 Out, or with that buffered before connecting to anything else, I'd guess it's fine. They probably put in a small value limiting resistor, otherwise the current through your LED would have been high enough to burn it out.

There are some peculiarities. The Resonance CV Input can't be driven by a Yomo dual Attenuverter, for example - or at least, it doesn't make any difference that I can hear. For some odd reason, those are made with a stupidly high output impedance so it can't drive the Resonance CV directly, but can via the active buffered Multi. The same attenuverter can drive other CV In's though, so the Resonance one just needs a relatively low output impedance source to drive it.

Perhaps ENV2 is designed differently to ENV1, due to what it's normally wired up to having different input requirements.

Op amp circuits often use negative feedback resistors from the output of an op amp to it's inverting input. Normal behaviour assumes the output isn't shorted, or clamped so that it can't exceed a certain voltage - so doing that changes the behaviour, and it changes the voltage at the inverting input of the last stage op amp which drives the output.

One envelope might have a buffer before the output, so that it could drive a lower impedance, for example. Maybe ENV2 wasn't thought to need the buffer because it normally drives a higher impedance.

Either way, if it still works as it used to, when you're not trying to drive an LED with no current limiting resistor, I'd say it's fine. Most op amps are current limited anyway. The problem with relying on that is that it might provide more current than the tracks can handle, in which case you'd probably have a burned track and it wouldn't work at all, any more.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by latrohexus » Mon May 11, 2020 11:24 pm

Thanks again, it's really too bad that there are no schematics for the thing. Next time I rearrange the case I'll probably take a close look at the board, but given that the envelope does seem to work normally in every other circumstance, I'll quit worrying about it 'til I'm in the guts. I'm still learning about op amps (going down the DIY rabbit hole but haven't made any active modules yet) but even with my limited knowledge the idea that modifying the output conditions would affect the amp does make general sense to me. I've got some opamps coming in the mail tomorrow so I may try to breadboard some envelopes and see if I can replicate it. Either way, good food for thought and I'm definitely gonna do some more research on input and output impedance, too. Thanks for taking the time to respond in such detail, I'm learning a lot here.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Mark_Lewis » Mon May 11, 2020 11:54 pm

Would it be possible to cut the normalled connections?

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue May 12, 2020 6:11 am

latrohexus wrote:
Mon May 11, 2020 11:24 pm
Thanks for taking the time to respond in such detail, I'm learning a lot here.
You're welcome, latrohexus.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue May 12, 2020 6:22 am

Mark_Lewis wrote:
Mon May 11, 2020 11:54 pm
Would it be possible to cut the normalled connections?
You probably can, by cutting tracks close to the sockets, but you'd need to look out for tracks that go to the normal pin of a socket, then go somewhere else.

I've cut around the normal pins on a couple of Yomo attenuators, because I didn't want them grounded. I used a tungsten carbide scriber, to scratch away the copper around the pins. It wasn't easy though because those pins connected to the ground plane, which covers most of the underside of the PCB.

In the case of the Neutron, there are probably fairly thin tracks to each pin, so that should be easier, but if the track goes on from there to somewhere else, you might have to add a wire to bypass the part where you make a cut.

You can check which is the normal pin by using a patch cable and a multimeter, set to measure resistance (on the lowest value scale) or continuity. Plugging the cable in pushes a spring contact away form the normal pin, disconnecting it from the "tip" pin.

The ground pins should be easy to spot. On most sockets like those, the ground pin is exposed on the outside of the socket, on one side. They always connect to the ground plane, or to a large thick track that connects all the ground pins of all sockets.

The normal pin and tip pin of a socket are usually very close together - like 0.1" or less apart.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Mark_Lewis » Tue May 12, 2020 10:52 am

AndyHornBlower wrote:
Tue May 12, 2020 6:22 am
Mark_Lewis wrote:
Mon May 11, 2020 11:54 pm
Would it be possible to cut the normalled connections?
You can check which is the normal pin by using a patch cable and a multimeter, set to measure resistance (on the lowest value scale) or continuity. Plugging the cable in pushes a spring contact away form the normal pin, disconnecting it from the "tip" pin.
Thanks for the advice!

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue May 12, 2020 11:49 am

You're welcome, Mark.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Mark_Lewis » Tue May 12, 2020 11:56 am

Also, you could just buy some 3.5mm male to female port extenders and leave them in the normalled jacks.
Last edited by Mark_Lewis on Tue May 12, 2020 10:08 pm, edited 1 time in total.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue May 12, 2020 2:28 pm

Agreed, Mark. I'd go with that solution, personally.

I found a common size of UK double mains socket back plate (open fronted metal box) fits onto the two bolts, holding on the right end cheek, so mine has one of those permanently attached, with a piece of cardboard from a bar of chocolate, used as insulation.

I just took the top two bolts out, fed them through two holes in the back plate, and screwed them back in. At worst, you'd have to drill one more hole, if they didn't line up as well as mine does.

I also wrapped velcro loop around it, before bolting it on, mostly to avoid scratching the end cheek, but it could be useful for tidying cables too.

That sort of back plate is a good size for taking passive Eurorack modules, so you could have a passive multi and some passive attenuators mounted like that, and left permanently cabled up with short patch cables - preferably right angled ones.

To do a tidier job than I have, you should also cut two small pieces of wood and glue them in to take mounting screws, in place of rails.
P1020040.JPG
P1020042.JPG
P1020044.JPG
IMIHO, the first thing the Neutron benefits from is a few more passive attenuators, and a couple of passive multis, in that order. Here, mine's modelling a Yomo 4AT quad passive attenuator, but this is one of the ones I cut around the normal pins on - I wasn't happy that the design allowed me to use it to short out outputs, if I plugged them in to the wrong socket, with the knob all the way to one extreme.

Better passive attenuators are available, and it's easy enough to make your own. If you do, I suggest adding a 1k safety resistor between the wiper of each pot and the tip pin of the output socket, just in case you use a module that doesn't have one, and relies on the op amp to limit the short circuit current (rarely a good idea).
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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by latrohexus » Tue May 12, 2020 5:37 pm

The side-mounted expander is a great idea. I bought a powered case a while ago with a janky power supply, so I've been using it unpowered for a while. I just pulled the I/O PCBs out of the stock cases for my Neutron and M32 and let them float in the case, daisychained with a wall wart power supply for the time being, and the case came with some blank panels so I just started putting together passive modules with those last week.

Atts have been the biggest game changer for me. Is the serial resistor just for when the pot is set high when you're inserting a jack?

I also wired up a passive mixer, some mults, and a couple 1/8"->1/4" converters, which have convinced me that I don't need to drop $100+ on an output module to get to my interface. Semimodular stuff coupled with DIY is turning out to be a pretty cheap way to get to a powerful modular, when I originally thought I was gonna have to dump $3000 into the case to end up with something useful.

P_20200512_173023.jpg

The other end of the M32 and Neutron, and the whole bottom row, are just gaping holes at the moment. The project this week is installing power so I can delete the floating I/O PCBs, moving my Boog into the bottom row, and building some active stuff to fill the remaining 36hp so it finally looks like a real instrument and not just a mess of cables and danger.
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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by AndyHornBlower » Tue May 12, 2020 6:55 pm

That looks good, latrohexus.

Yes, the output safety resistor is mostly for when the pot is turned all the way up, which connects the input socket directly to the output socket, otherwise.

If the normal pin of the output socket is grounded, you then have a short to ground, via the wiper of the pot. One consideration there is that normal pots are not built to take more than a few mA through the wiper.

You'd also have a problem with momentary shorts if you then plugged a patch lead into the output, then plugged it in somewhere else, but touched the tip of the cable against the ring of a socket, or a metal plate that a socket was mounted on.

Ideally you should plug cables into the input they're going to first, then the output they're coming from, but we're bound to forget, even if we try to adopt that policy.

Then there's the problem of accidentally plugging the output of a module into the output socket of a passive attenuator, with the pot turned all the way down. We physically can do that, so sooner or later we will. There's then a path to ground from the output socket, via the wiper of the pot, unless we add the safety resistor.

Active Eurorack modules are supposed to have a safety resistor on their outputs, but it's better to assume that they don't, especially since most of the manufacturers don't publish schematics.

Passive multis are another problem, especially for momentary shorts. My take on those is that it's best to patch them while the synth is turned off, but failing that, try to remember to plug the patch lead into the output it's going to, then into the multi, or if it's coming from an output, plug it into the multi first, then the output.

For something like the Neutron, without a schematic available, it doesn't hurt to assume that output protection is inadequate. 1/4W fixed resistors cost a few pennies each, and often less if you're buying a hundred at a time. It's worth it just for the peace of mind.

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Re: Neutron The New Behringer Semi-Modular Synthesizer

Post by Mark_Lewis » Tue May 12, 2020 10:22 pm

:yay: Love the hack.
AndyHornBlower wrote:
Tue May 12, 2020 2:28 pm
Agreed, Mark. I'd go with that solution, personally.

I found a common size of UK double mains socket back plate (open fronted metal box) fits onto the two bolts, holding on the right end cheek, so mine has one of those permanently attached, with a piece of cardboard from a bar of chocolate, used as insulation.

I just took the top two bolts out, fed them through two holes in the back plate, and screwed them back in. At worst, you'd have to drill one more hole, if they didn't line up as well as mine does.

I also wrapped velcro loop around it, before bolting it on, mostly to avoid scratching the end cheek, but it could be useful for tidying cables too.

That sort of back plate is a good size for taking passive Eurorack modules, so you could have a passive multi and some passive attenuators mounted like that, and left permanently cabled up with short patch cables - preferably right angled ones.

To do a tidier job than I have, you should also cut two small pieces of wood and glue them in to take mounting screws, in place of rails.

P1020040.JPG
P1020042.JPG
P1020044.JPG

IMIHO, the first thing the Neutron benefits from is a few more passive attenuators, and a couple of passive multis, in that order. Here, mine's modelling a Yomo 4AT quad passive attenuator, but this is one of the ones I cut around the normal pins on - I wasn't happy that the design allowed me to use it to short out outputs, if I plugged them in to the wrong socket, with the knob all the way to one extreme.

Better passive attenuators are available, and it's easy enough to make your own. If you do, I suggest adding a 1k safety resistor between the wiper of each pot and the tip pin of the output socket, just in case you use a module that doesn't have one, and relies on the op amp to limit the short circuit current (rarely a good idea).

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