Behringer Neutron sync modification

Published on Sep 1, 2018 Michael Kukat

"This week, i bought a Behringer Neutron. And i liked it so much that on the same day it arrived, i ordered a second one. The only thing i really didn't like was the oscillator sync, it sounded too "dirty" for my taste. The CEM3340 (or CoolAudio V3340 in this case) can do better.

So i had a closer look inside and decided that i will modify one of my Neutrons to "fix" this sync issue.

This video describes some background, the comparison of the 2 sync mechanisms on the scope and as audio examples, and in the second part a description how to modify it.

Please be aware that this modification is a bit difficult, you should be experienced enough with the soldering iron and have enough time and concentration. Also be aware that modifying your synth will void it's warranty and if you damage it by following my instructions, i will not buy you a new one - do what you do on your own risk! And don't panic if it doesn't work on the first try - i forgot the capacitor in the first try, so the VCO2 was totally blocked - you can see this during the power up calibration where the octave LEDs of the oscillators should flash. If one of them doesn't flash at all, you did something wrong, carefully re-check everything.

Don't ask me why i say 3240 all the time in the video instead of 3340. Maybe it was too early in the morning :)

I hope this is helpful for someone, but please understand that i will not modify your Neutron for you, i'm just a hobbyist with limited spare time. If you can't do it on your own, find someone who can do it for you, this video contains enough information for a routined electronics engineer to perform this modification.

What i forgot to mention in the video - the PNP transistor is a generic small signal PNP type, i used a BC558, i tested with a BC560 before, you can also use the corresponding 2N types, but they have a different pinout, so take care. If you use a BC558 or BC560, you can follow my instructions, for everything else, you need to check the parameters and pinout of the transistor before. BC558 and BC560 have C-B-E when looking at the flat side with the pins facing downwards."