Analogue Triggers?

[ewanmathers]

Hi there, I used to have a DR-55 years ago and now regret selling it as a poor student!  Anyway I was interested in building the CB-55 and reliving my youth!  What I don;'t quite get is how this board gets triggered.  I recently built a simple sequencer using the Velemann MK-107 kit (as in https://youtu.be/pJ35ShtB8XI?list=FLm9fvbTAOmPkcOHQtr_Ej1g ) and integrated this with a Korg Monotron and Monotron Duo in  a big box with lots of mods, delays etc.  All works fine.

So I am thinking about adding in some drum sounds and had been thinking about the old DR-55 and its triggers.  Then I cam across your CB-55 and thought I can build that and mod it without having to buy a expensive piece of history and then mess it up. 

My question is all about the triggering.  Will the MK-107 and its outputs trigger the CB-55?  I think it will but as it steps through 8 steps at differing voltages what would I actually hear - I suspect just one sound 8 times?

So is there a way so trigger the CB-55 using just voltage triggers 0-5V that will give some sort of drum sounds that make sense.  Even if I was just able to add in an 8-step sequence of percussion sounds to the 8-step notes I am generating would be something.

As for midi where do I begin!?  Is there anyway, for example, to hook up a Mac and Garage Band through a device to the CB-55 and program the drum sounds on the Mac?

Any help would be appreciated.

[Circuitbenders]

I think i'd advise doing some research into the fundamentals of how triggers and gates work in analogue drum machines and modular synths.

As that MK107 only has a single output, you would only be able to use it to drive one CB55 sound at a time, so you'd need 5 of them running alongside each other to trigger all four CB55 sounds and the accent. Its not an uncommon DIY approach.
You need a 5v trigger pulse to trigger the CB55 sounds properly so you'd have to turn up the pots to maximum for a trigger step, and down to zero for a non triggered step, although personally i'd just replace the pots with on/off step switches for a drum sequencer.

The problem you are probably going to have is that unless you can shorten the length of the pulse on each step, you'll just see a variable voltage at the output with no gaps. This probably isn't going to trigger the CB55.
Normal trigger pulses might be 10ms or more long, but however log they are, there will be a 0v gap before the next pulse or the sound won't retrigger. The CB55 triggers on the rising edge of the pulse, but if theres no gaps between pulses, there won't be any rising edges.

To drive the CB55 with midi you'll need a midi to trigger converter. You can buy these at various places around the net. Alternatively you could just get some kind of machine with trigger outputs built in.

[ewanmathers]

Thanks for the reply.  I had worked out needing 5 sequencers to do the triggers but was thinking that the trigger length might be an issue.  I was visualising a set up with 5 rows of switches that could be manipulated in real time to trigger on an off the sounds.  I'm not really keen to get into midi programming as I like the hands on approach.  I will have a few experiments and do a bit more research to see what I can come up with.

[ewanmathers]

Just found Mutable Instruments Grid Topographic Drum Sequencer - http://mutable-instruments.net/modules/grids/manual would this do it?  I realise it only has 3 triggers but I think that would be fine.

Any experience with this?

[Circuitbenders]

no, the triggers are too short at 1ms.

As it says in the CB55 build manual, you need triggers of 10ms or more, like the vast majority of machine use.
A 1ms trigger will work, but it won't sound right. although it wouldn't be too hard to extend them with a couple of caps and a 40106.
http://www.musicfromouterspace.com/analogsynth_new/ELECTRONICS/mickeymouselogic.html

[Dr_sax]

Anyone try a beat step pro from Arturia to trigger a CB55? Thinking of building a CB55.

[Circuitbenders]

https://www.youtube.com/watch?v=vLdxcMWlW6U&ab_channel=JasonHotchkiss

although it does kind of sound like his triggers might be double triggering the snare somehow.

[sirgavalot]

Anyone try a beat step pro from Arturia to trigger a CB55? Thinking of building a CB55.

I'm trying! The voltage attenuators I've made to reduce the BSP trigger outputs from 12v to approx 5v as specified are the only things that are currently working properly

[NoellEagan]

Hi..i am a new user here. As per my knowledge you should shorten the length of the pulse on each step, you'll just see a variable voltage at the output with no gaps. This probably isn't going to trigger the CB55.Normal trigger pulses might be 10ms or more long, but however log they are, there will be a 0v gap before the next pulse or the sound won't retrigger. The CB55 triggers on the rising edge of the pulse, but if theres no gaps between pulses, there won't be any rising edges.

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