MB-808: additional Triggers, 15V to trigger SH-101

[mokkinger]

hello folks,

does anybody know how to route 3 additional Trigger signals out of the MB-808 Sequencer?

There are 12 Instrument Trigger plus the Accent, so I guess I have 3 tracks left that could trigger external Instruments without having to use an MB-808 Instrument - is this possible?

Another Problem I have is the voltage of the Triggers; Is there any possibility to get a 15 V Trigger out of the Seq so I could trigger my SH-101? the 12 Instrument trigger only have about 5 V, which isn´t enough to trigger the seqeuncer of the 101...

does the Accent trigger have 15 V when fully turned on? and where on the PCB would I find the Accent trigger output?

thanks & cheers,

mark

[creekree]

there are 3 more trigger lines, called ext1 to ext 3... use those.

as for 15v level, copy the accent circuit from the mb808 pcb (you'll find it documented in the eight-oh-eight forums) 3 times and hook them up to the DOUT pins for ext 1 to ext 3 (specified in your configuration file).

thats it. i know it works, because i did the same ;)

please note that i do NOT own an original mb808 pcb, so i do not know if there are pins on the DOUT shift registers free or if they have all been used. in the worst case you might have to add another shift register.

[mokkinger]

ok cool. so first of all I should edit the config file to activate the 3 ext triggers, right?

and after that I guess I could find these trigger signals on the shift registers by checking for the voltage, right? I thnik I saw empty pins at the shift register, but I´m not shure if theses are the right ones...

and do I understand you right, I need to build the accent-circuit 3 times? cant I just use the accent circuit thats already on the PCB? or why do you built a new one?

thanks for your help!

[creekree]

the three triggers are already defined in setup_808_default.asm

you dont have to probe for voltages to find where the signals "come out", look for

DEFAULT_TRKINFO MACRO

and read the annotations. you get to see which track hangs off which pin on which shift register (and you can change it). just be sure not to mess up things up to badly, or your conga might sound when in fact you programmed a bassdrum; or a LED might light up instead of a snare sounding ;)

you need the accent circuit three times because the mb808 only has a global accent - one accent track for all voices at the same time.

if you just used the one that is already on the pcb it would trigger 1) whenever an accented step is set,  and 2) programming your ext trigger would fire the accent as well; not something you want to have.

if i understood you correctly, you want one (or three) dedicated trigger outs for your sh-101 (or modular synth stuff) peaking at 15v.

you need separate accent circuitry for each of your "ext" tracks - it does nothing more than shift the trigger voltage from 5v to 15v -

which is exactly what you want

uhm, btw: you can rename the tracks to something more appropriate, like "SH-101 " or so, as long as it is exactly 6 characters long.

[mokkinger]

ok, so i could also just build an OpAmp that drives the 5 v up to 15 V, right? Im not shure what the accent section of the MB-808 does, but as I remember it is a little more complicated than just an OpAmp...

[TK.]

You could also use two transistors instead of an OP Amp:

http://www.elektronik-kompendium.de/sites/praxis/bausatz_pegelwandler-mit-transistoren.htm

Best Regards, Thorsten.

[mokkinger]

ok, so that would convert the trigger to +15 V so it can trigger an external Instrument like the 101?

I just built an OpAmp with a 4558D, and now I have +13,88 V on the trigger out, but this doesn´t work. :-( also with this OpAmp turned on I can´t hear any trigger sound on the headphone anymore... i will try to activate the Ext. triggers now, and connect one with the two transistor schema, hopefully that will work;

what I am not sure about is the assignment of the shift register pins to the Ext Triggers. The default.asm says that Shift Register 1, 4 and 7 (for th accent only) are used, and on Shift register 4 there are some Pins not used (pin 2 and 6) . I guess there could be some spare pin for the Ext 1 and 2 to fit... ? and do I have to compile a new hex-file after this? never done that kind of stuff before - help is really really apreciated!! :-)

and where to go with the output of these pins? they go directly into R1 of the transistor scheme that TK posted?

and the output is the trigger to go to the 6,3 mm jack?

sorry for asking these noob questions, but I am still beginning with all this, and this seems to be really complicatd to me... i´m still not sure if I can handle all this...

thanks for reply on this!

mark

[creekree]

check your PM..