Nord Modular - DC coupled outputs

mush · Posted: Wed Jun 14, 2017 8:32 am Post subject: Nord Modular - DC coupled outputs

Hi guys.

A year ago I modded my G2 to have DC-coupled outputs with modular levels that I adjusted so that the straight output from a note module to the outputs gave 1v/oct at full volume:
http://electro-music.com/forum/topic-67269.html

Well. I recently picked up a NM G1 keyboard that was in kind of a sad shape. It was stripped of colour and the buttons and screen glitched a bit. I sanded it down and fixed the problems and painted it black and as a final touch I modded the synth with 4 minijack outputs with DC-coupled CV with a voltage swing from -4.9v to +4.9v. As the G1 power supply uses +5v, -5v and +3v I had to use a rail-to-rail opamp and I found that the signal the G1 puts out is actually inverted - so I went with a traditional inverting amplifier setup for the CV-outputs. I also saw that the DC-offset was quite big, so I added a trimpot on each output to adjust offset - and another one of course to trim the output to 1v/oct.

It all works nice.

The mod on the back:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

First try after trimming it to 1v/oct on the test-modular in the bedroom (my studio is not at home, so I have a small modular to test the modules I build):

There is a schematic on this page I posted on a Swedish forum:
http://www.99musik.se/showthread.php?344164-Nord-Modular-CV-ut-modd

It is really a great addition to the G1 (well the G2 as well) - as it makes it easier to integrate it and use it as a swiss army tool in a modular setup. I use the G2 a lot to prototype ideas for modules to see if it is worth making them in hardware. The G1, while lacking some of the modules I really love in the G2 will probably come in handy too.

Best regards

Rasmus[/img]

nuts · Joined: Aug 21, 2006 Posts: 16 Location: FR

This is really cool, thanks for the infos.

Had a G2 engine yers ago. I'm about to buy a NM rack1 and I guess even with mods it still cannot output notes data, right ?

mush · Posted: Sat Nov 18, 2017 7:21 am Post subject:

Redline · Joined: Nov 07, 2013 Posts: 33 Location: UK

Maybe a silly question, but would it be possible to make an external breakout box that plugs into and converts the factory G1 outputs to being DC coupled?

Just so that you can have the outputs DC coupled if you want to, but you're not drilling into and modding the actual unit?

blue hell · Posted: Thu Nov 23, 2017 5:46 am Post subject:

Not directly.. once the DC is gone you have no way to restore it externally.

Still it could be done with an external box, but that would have some drawbacks.

You could send out an amplitude modulated oscillator signal, which is AC so would pass the capacitors. You would then need an external envelope follower to to get the amplitude from that signal to convert it to DC again.

Drawbacks are that you need to do something special in the patch (multiply the oscillator signal by the wanted CV signal) and that, due to inherent lag on AM demodulation, it may get a bit sluggish .. depending on the oscillator frequency used.

nuts · Joined: Aug 21, 2006 Posts: 16 Location: FR

ersatzplanet · Joined: Jul 24, 2005 Posts: 65 Location: Seattle, WA, USA

This is an old thread of course, so many looking here may already know this, but some may not. The standard Nord Modular line all have DC coupled outputs already - the Headphone outs are DC coupled standard. I have always found this to be a bit weird because headphones are much more easily destroyed by DC voltages than most mixer inputs. You can try out using DC outs without modifying anything. If you like the results, than the mods will give you 2 more outs.