From mymoog@ix.netcom.com Fri Jan 02 17:35:00 1998 Return-Path: by taz.hyperreal.org with SMTP; 2 Jan 1998 17:34:59 -0000 2 Jan 98 12:34:55 -0500 1 Jan 98 06:56:57 -0500 by mailhost.bpa.nl (8.8.8/8.8.7) id LAA24931 for synth-diy-outgoing; Thu, 1 Jan 1998 11:45:51 +0100 (MET) by mailhost.bpa.nl (8.8.8/8.8.7) with ESMTP id LAA24926 for ; Thu, 1 Jan 1998 11:45:48 +0100 (MET) id xma028542; Thu, 1 Jan 98 02:45:06 -0800 From: "nc0839" Cc: Subject: Mod for DR55 that provides trigger in's Date: Thu, 1 Jan 1998 04:49:38 -0600 X-MSMail-Priority: Normal X-Priority: 3 MIME-Version: 1.0 I got the schematics for the DR55 this week. In looking over them it appears that a modification to allow a device like the MAP ADV-MIDI, PAIA MIDI2CV8 and TR series drum machines to trigger the DR55's voices via trigger pulses is possible. In bouncing back and forth between the PCB sheet and the schematic I discovered the pins on the "Logic" chip that control the firing of voices. I used an analog VOM to verify I had the correct pins (these being 12, 14, and 16). The meter being analog made it difficult to pin down the actual voltage of the spike and if the spike is positively or negatively biased. Another piece of luck developed when I discovered that the trigger lines on the board pass thru jumper wires just after the chip (a good 3cm of exposed jumper). This would make lifting the trigger lines from the chip and providing trigger in jacks instead pretty easy. I tride the whole thing with a crudely fasioned trigger cable which seemed to actually work. For this test I made a trigger cable with a 1/8" phone plug on one end and an alligator clip on the ground and a wire probe on the lead for the other. I plugged the 1/8" phone plug into my TR606 trigger out and clipped the ground to the DR55's shell. I then played a pattern on the 606 that would fire it's trigger output and touched the prob wire to one of the three jumpers inside the DR55. Every time a TR606 trigger would fire it would trigger whatever voice I was messing with. This seems to suggest that using the DM55 in a setup with a MIDI/Trigger interface or a Roland TR type drum machine is possible. The only thing I am not sure of is if the TR trigger is a negative pulse and if the DR55's internal triggers are biased the same direction? I wish I had a scope so I could see the pulses from the two machines for comparision. Analog solutions does a mod for TR/CR drum machines to allow the internal drum voices to be triggered via jacks. Has anyone ever attempted a mod like this on a TR? What is the trigger voltage/shape used in these machines to control the firing of voices? If I could get the pinout of the "Logic" chip I might be possible to modify the DR55 to sync to an external source. Say DIN or 24ppq pulses. The "Logic" chip appears to get it's timing from another IC (IC2 in the schematics). If it were possible to prevent the timer from advancing until a pulse occures on a curtian pin, one might be able to make the DR55 accept external sync (In theory). P.S. I tried the decay mod for the Kick. It makes a very 808'ish sound when the resistor is bridged. David