If you are talking about a standard 19" rack, you can always put a blank panel
above the unit and drill a hole in the panel so you can run a midi cable out to
the synth.

The Neutron isn't fully 19" wide. I guess you could drill holes wide enough in the 19" flaps they sell.

Masi

I want to see a 5 tier rack like patrick did in one of those vids!

I want a 4 tier one. Like the 3 tier, but the 3rd is large enough for the B2600
The top tier looks downwards again.

Masi

Hey, im a new user here and i hope this hasn't been asked before, though i have searched extensively and couldn't find a fix yet.
The slew limiter on my neutron seems very off, as in it's basically unusable. It completely messes up the tracking. This happens both with the internal, and with external oscillators, so it's not some kind of internal offset. When played with midi, the porta time works fine, but i assume this is because it's a completely seperate circuit. I've seen that some users reported similar behaviour, but so far i haven't found a fix for this problem. Can the slew limiter be calibrated in some way, or is there a hardware fix that i can perform, that would solve this problem?

Yes, this is a known issue with the slew limiter. I know some people have modded the sample&hold, but I don't know offhand if anyone has done any mods to the slew limiter, or if it can be modded. It's not really suitable for pitch as it stands. I'm guessing the gain of the buffer op amp needs to be tweaked to get proper tracking, which would require changing resistor values.

The portamento is handled digitally in the midi to CV conversion process, it's not a hardware slew limiter in itself.

Are there any slew limiters around designed for wave shaping in the audio range?

The Eurorack modules I know of clearly aim at CV signals.

Masi

Isn't that what a low pass filter does?

Hm.

If I feed a square wave into a slew limiter it will end up in a trapezoid or triangle form depending on the amplitude and the slew rate. The sound will have less overtones than before. So the slew limiter has an effect like a LP filter. I assume it depends on the input waveform and it's amplitude which of the higher frequencies will be filtered out.

But I don't think that it's safe to say that the reverse is true.

Masi

The simplest low pass filter is a capacitor, charging or discharging through a resistor.

That also behaves like a slew in that the capacitor can only charge or discharge so fast (depending on the resistor and capacitor values, and the input signal amplitude), but it does that with an exponential curve.

If you had a slew that had a linear rise and fall, like a triangle wave, that would do different things, I guess.

I can't quite picture how that could be done with analog components, but no doubt there's a way.

yep, hadn't checked this before but slew on mine reduces cv spread, so across four octaves the upper note falls almost a semitone flat...

seems to be a mismatch in the op-amp feedback path - have not checked yet for the correponding circuit inside but what you suggest would the the trick, I think

Yes, in fact I used to use the slew limiter on my dotcom as a makeshift filter sometimes.

A slew limiter is essentially a simple LPF designed to work with DC/low frequency signals. It's just a resistor (potentiometer to adjust the rate), a capacitor, and a buffer (op amp).

Audio LPFs have higher cutoffs since they need to filter audio rate signals and are usually AC coupled, plus ones used in synths have resonance, and CV control of cutoff and possibly resonance.

Hey!

Had a look and fixed it - you do need to access the PCB back - just bridge R590 and C588 with some wire (in the pic below, I took both components out but tracking is good if you just bridge them too)

in the mp3 attached first unbridged, then bridged (note that tracking is still not 100% accurate in that example but that's on my dominion1 cv out, not the neutron)

Cool, thanx.

But why would I then use a slew limiter on audio? Ok, it's fun and all, but why complain that it doesn't track? If you need a second LPF bite the bullet and buy one.

Masi

You wouldn't normally. But the original issue isn't due to running audio through the slew limiter, it's running pitch CV through it, presumably to add glide when using CV/gate from an external source. The overall gain is not unity so tracking gets thrown off as the output CV doesn't match the input CV over the range.

From the top of my head, without double checking, just brainstorming: I would add current source charging capacitor. By definition current sources give constant current, therefore capacitor should be charged in linear manner. Then, since ideal current sources don't exist and ideal should be stopped before earth explodes, I would add some comparing mechanism that would switch off my current, when capacitor reaches same value as input. I would need two sources to drain (puns intended) from +Vcc and -Vcc. So you would need two or four (probably four) MOSFETs.

That sounds promising. I've found an article about a pair of MOSFETs as a current source:

https://www.allaboutcircuits.com/tec...urrent-source/

Op amps or comparators are pretty much ideal for reacting to two voltages being equal or not, so maybe using those would simplify that part.

If this is such a simple fix, why don’t Behringer modify the boards at design level and resume manufacturing with the modification? Is there some other consequence of this change?

didn't notice a side effect so far

(almost?) all i/O in the neutron have a resistor for protection and a cap, so i guess these were design decisions directed more by clean and porpoer style audio engineering than musical application

and yep, this, larger s&H cap and lower vco square levels could well be done without board redesign just by placing components of different values

Hi there,

I’m trying to connect midi out of my MPC1000 into the Neutron and then trying to use the CV out to change pitch and gate on Rings. Gate is working but I can’t seem to work out how to get pitch to work.

I’ve tried changing the Assign destination in the synth but there’s no change, just the same note each time even though there’s an arpeggio playing via MIDI. The MIDIGATE works perfectly.

Any help suggestions appreciated. I did read vast chunks of the thread

Have you connected Assign on the Neutron (bottom right on the patch bay) to V/Oct on the Rings?

Have you checked that Rings is responding to a CV source, plugged into V/OCT? I think it's meant to trigger if you change the CV enough, so gate shouldn't matter.

Thank you for your response

I tried “Assign” straight into the vOct on Rings without MIDIGATE. And nothing happens.

When I cycle through the “OSC SYNC” options and press a key on my midi device I get the same note on all options except on the middle “ramp” option where I get something like a sample and hold different pitch each time I hit the same note.

One thing I noticed is that when I plug my cable in and out of the Neutron “Assign” I can hear the pitch change in Rings by about an octave.

Ran the MPC through my Minibrute 2S and it works fine. Must be just my Neutron.

That does sound like it might be faulty. The middle one is velocity, so it should respond differently to how hard you hit the key, but the others not doing anything seems wrong... The options are:

OSC 1 CV
OSC 2 CV
“Note On” velocity
Modwheel
Aftertouch

Does it respond to the Mod wheel?

You could try the Assign Out Calibration, I suppose (section 7.2 in the manual). Maybe it can be so off that it just gives one voltage for any note. The manual says "This calibration has been carried out by the factory at the manufacturing stage", which means there's scope for human error, or missing a few out.

You're supposed to use a good quality volt meter, but you could just use your Rings and a tuner instead. The idea is to tweak values for 1V and 4V, but you could start be trying to get any sort of response at all, then aim for notes 3 octave apart. You can always do it properly later, if you get it to roughly work.

The octave jump from plugging it in suggests you're getting 1V, so you could try increasing the 4V calibration first.

In the interests of my sanity and your thoughtful perseverance I’ll give it a go tomorrow. Thanks again.

No problem. Good luck.

Have you tried running the Assign out of your Neutron to something else like your Minibrute 2S to see if pitch CV works there?

Also, have you tried running pitch CV from the 2S to Rings to see if that works?

I would think if the "velocity" setting gave you "random" pitches on Rings, that the CV is working at least, though it's actually based on the velocity of the notes you played.

Another thing to try are different CV outs from the Neutron to see if those work on the Rings, like the LFO or envelope.

Standard "process of elimination" stuff.

Are you on the latest Neutron firmware?