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Korg Monotribe modifications thread
MUFF WIGGLER Forum Index -> General Gear Goto page Previous  1, 2, 3 ... , 37, 38, 39  Next [all]
Author Korg Monotribe modifications thread
Remork
hey

just a quick heads up to the wigglers - came upon this thread looking for a way to eliminate that 200-250Hz hum that was really bugging me.
made the whole thing useless- it was so bad it sounded like a constant ringmod with a B note.
so i did Snyder80's led matrix dehum, combined it with the sound advice of replacing R1 with 80 ohms. problem solved! great.

while the MT was open, i decided to poke around for the other mods.
so i installed the VCA declick mod (also great!).

i'm going to install HH decay and a SN noise decay on/off/on switches.
i tried marmad's way of doing the decay, but especially on HH and SN the cap you choose for longest delay time always seems to influence the circuit, so you never get back to the original sound.
i could get it to be as short, but not with the same attack in the sound.
so i'll end up just adding parallel timing caps. works for me.

Snare frame length i'm not interested in.

while trying stuff in the BD section, i accidentally f#$%^ stuff up, so i turned a problem into a challenge smile and ended up replacing R73 and R74 with a stereopot - well, kind of - and got myself a tuneable kick!
here's how that works:



this way it spans just over an octave (low E to F or something.)
of course, it's a tuned oscillator, so the length mod works more on some tunings (the middle part is closer to the ideal frequency for the circuit, i guess.) so it's all a bit interactive. but hey.
for BD decay i put in a 220R fixed resistor, parallelled with 10uF for a bit more oomph, and a 1K pot in series.
goes from original length to oscillation. on some notes. hah.

next, checked out the Clap mod someone posted - shorting snare noise out to snare frame out. it basically just alters the mix of the snare noise; normally that has a 220K mix resistor, and by connecting it to the snare frame output you run it through a 22K. big difference, and indeed more clap like. so i put that connection on a 100KA pot: now it goes from original snare to clap. which is nice.

anyway, thanks to the forum, just wanted to contribute!
zaphod betamax
Also noticed that if you use the S&H LFO mode on the Monotribe and set the speed to slowest, that when you engage the drums, the S&H changes with the beat!

This works great because I have the synch out into trigger on the S&H on the Korg MS-20K which in turn gets its S&H LFO in step with the beat.(built with pink noise as input and output to HPF Fc)
As the MS-20Ks CV and trigger are fed into the Monotribe, it also allows me to use the Monotribe as a third oscillator!
marmad
Remork wrote:
i tried marmad's way of doing the decay, but especially on HH and SN the cap you choose for longest delay time always seems to influence the circuit, so you never get back to the original sound.
i could get it to be as short, but not with the same attack in the sound.

It's true that you can't really add any capacitance or resistance to an RC filter without inevitably influencing the sound to some degree, but it's not really hard to get close to the stock Korg sounds with my circuit. But if you try to get very long decay times, the trade-off (and there's always a trade-off) is the amplitude. The bigger you make the added capacitance, the harder it is to get the original decay length at the same volume.

For example, look at the two Hi-Hat waveforms and FFTs below; they're almost identical (both with ~600Hz peak frequencies and ~80ms decays), but the second one has ~15mVpp less initial amplitude. The first is the stock Korg HH out, and the second is using my circuit with an added 22nF - which is what I've found to be a good trade-off value between slightly less volume and longest decay time.

Stock Korg HH:




Added HH decay circuit (22nF and pot near center position):

Remork
funny, i ended up with a 22nF as well.. but just plain switchable. (other cap is a 6.8nF for just a hint of extra hihat.)

i totally trust you on the analytic side of things - but it just didn't sound quite the same. seriously, i just don't get it
maybe the cap values i tried were too high? i may have given up too quickly on your method, dunno.
anyway, quite happy with what i got now.

meanwhile, also threw in the VCO mute.
midi I/O i already had.
now i just want to run a full mix drum output (don't really want the separate outputs, got other gear for that) and a firmware update - got a TRRS cable to 3x RCA on a fleamarket. think it's from an old camcorder. hope it'll work.
marmad
Remork wrote:
funny, i ended up with a 22nF as well.. but just plain switchable. (other cap is a 6.8nF for just a hint of extra hihat.)

i totally trust you on the analytic side of things - but it just didn't sound quite the same.

Well, the resistors effect the amplitude at different settings as well. I used a 22k resistor and 2k log pot for the voltage divider, and I used a 220k resistor for the discharge resistor.

With these values, you don't get quite zero sound at one end of the pot, but I couldn't hear (or see on the oscilloscope) any difference at all between the stock Korg hi-hat and when the pot was near the center position. It's possible the discharge resistor could be lowered still more without altering the stock sound too much.
Remork
hm. i tried the 47K as described for discharge R, and - iirc - a 100K with a 10K pot. i don't know, i think i understand the theory behind your method, but my implementation just didn't quite do it for me. plus i wanted to seal it back up, and i don't really have much use for separate drum mutes.. to each his own, i guess.

as for now, i did the 2.1 firmware upgrade, and it's running happily along the MS20 as a third oscillator. tracking seems fine across most of the keyboard range, up to the high G. the five keys after that just play the same high G, or slightly sharp versions of it smile
it's nice to have a third oscillator that has it's own LFO, really makes thicker sounds come alive.

need to try if, instead of playing C notes for calibration as per the manual, i could tune to something like fifths and go for chordal stuff. smile
edit: it works, but it'd probably be more succesful in v/oct mode.. if i play an F for calibration, it plays a bit short of a G when i hit a C note on the MS20. it's close enough to maybe get away with, esp with some modulation on the MT vco, but it's not quite spot on. i would expect v/oct to be more of an accurate parallel shift.
zaphod betamax
Easy fix for this. The Monotribe can not read +8V on Hi C on the MS-20.
Take the CV and divide it in 2 and then port it to the Monotribe. fixed.



Remork wrote:
hm. i tried the 47K as described for discharge R, and - iirc - a 100K with a 10K pot. i don't know, i think i understand the theory behind your method, but my implementation just didn't quite do it for me. plus i wanted to seal it back up, and i don't really have much use for separate drum mutes.. to each his own, i guess.

as for now, i did the 2.1 firmware upgrade, and it's running happily along the MS20 as a third oscillator. tracking seems fine across most of the keyboard range, up to the high G. the five keys after that just play the same high G, or slightly sharp versions of it smile
it's nice to have a third oscillator that has it's own LFO, really makes thicker sounds come alive.

need to try if, instead of playing C notes for calibration as per the manual, i could tune to something like fifths and go for chordal stuff. smile
edit: it works, but it'd probably be more succesful in v/oct mode.. if i play an F for calibration, it plays a bit short of a G when i hit a C note on the MS20. it's close enough to maybe get away with, esp with some modulation on the MT vco, but it's not quite spot on. i would expect v/oct to be more of an accurate parallel shift.
zaphod betamax
Is there a mod that will allow an external synths ADSR to control the VCA or VCF, along with trigger in?
dwnstream
Hey all! I came across the monotribe cv/gate breakout boxes posted a few years back in this thread. I really need one of those, hopefully you guys are still making them?

I tried to PM first, but the forum said I couldn't PM unless I've posted at least once. So here is a post! Altitude909, expect a PM from me shortly.
zaphod betamax
Greetings from Sarnia, Ontario!
These are fairly easy to build DIY from a TRRS 1/8" cable with the
end going to 1/4" in my case,or maybe 1/8" in your case.

Hack apart an AV cable for video, and this should do the trick!


dwnstream wrote:
Hey all! I came across the monotribe cv/gate breakout boxes posted a few years back in this thread. I really need one of those, hopefully you guys are still making them?

I tried to PM first, but the forum said I couldn't PM unless I've posted at least once. So here is a post! Altitude909, expect a PM from me shortly.
Altitude909
dwnstream wrote:
Hey all! I came across the monotribe cv/gate breakout boxes posted a few years back in this thread. I really need one of those, hopefully you guys are still making them?

I tried to PM first, but the forum said I couldn't PM unless I've posted at least once. So here is a post! Altitude909, expect a PM from me shortly.


hmm. several ppl have asked about these so maybe a small run is in the future..
zaphod betamax
mods (which require no soldering)
1)Run two Monotribes off the same CV.

2)Run the headphones out of MT #1 into audio in #2, then headphone out
on MT #2 into audio in MT #1
JayEm
zaphod betamax wrote:
mods (which require no soldering)
1)Run two Monotribes off the same CV.

2)Run the headphones out of MT #1 into audio in #2, then headphone out
on MT #2 into audio in MT #1

won't that just create a feedbackloop? assuming you're even playing both, since the audio in only works when the internal synth is playing
zaphod betamax
Ahhh, but I am playing them at the same time!
MS-20 Kit #1 CV out and trigger to MS-20 Kit #2
with Y-splitters and attenuators to both CV ins on the
Monotribe #1 and #2.

This could also be achieved with a V/octave controller keyboard
as the Monotribe speaks both Hz/V and Volt/Octave.

And I could play them in tandem without any of this....
You put #1 and #2 into Record/Play and wire as I said
previously, and yes it is a feedback loop but it
exponentially cooler than the feedback loop that one
Monotribe does as a single entity.
(surely you have routed the headphones
back into the Audio In!)
In the above mode you could (for example) have drums
and press a note on MT #1 and on MT#2 mute the drums
press a note (thus opening the filters on both MTs).
It sounds golden!

And you will note in my "mod", I note "run two Monotribes
off the same CV", which implied that they are being controlled
(played ) at the same time.
In my case it is Master MS-20Kit #1 controlling another
MS-20Kit and the two Monotribes.
Everything shares the same CV and trigger.




JayEm wrote:
zaphod betamax wrote:
mods (which require no soldering)
1)Run two Monotribes off the same CV.

2)Run the headphones out of MT #1 into audio in #2, then headphone out
on MT #2 into audio in MT #1

won't that just create a feedbackloop? assuming you're even playing both, since the audio in only works when the internal synth is playing
JayEm
Ah, misunderstood your post. I thought you were implying you could CV control via the headphone out.

zaphod betamax wrote:
Ahhh, but I am playing them at the same time!
MS-20 Kit #1 CV out and trigger to MS-20 Kit #2
with Y-splitters and attenuators to both CV ins on the
Monotribe #1 and #2.

This could also be achieved with a V/octave controller keyboard
as the Monotribe speaks both Hz/V and Volt/Octave.

And I could play them in tandem without any of this....
You put #1 and #2 into Record/Play and wire as I said
previously, and yes it is a feedback loop but it
exponentially cooler than the feedback loop that one
Monotribe does as a single entity.
(surely you have routed the headphones
back into the Audio In!)
In the above mode you could (for example) have drums
and press a note on MT #1 and on MT#2 mute the drums
press a note (thus opening the filters on both MTs).
It sounds golden!

And you will note in my "mod", I note "run two Monotribes
off the same CV", which implied that they are being controlled
(played ) at the same time.
In my case it is Master MS-20Kit #1 controlling another
MS-20Kit and the two Monotribes.
Everything shares the same CV and trigger.




JayEm wrote:
zaphod betamax wrote:
mods (which require no soldering)
1)Run two Monotribes off the same CV.

2)Run the headphones out of MT #1 into audio in #2, then headphone out
on MT #2 into audio in MT #1

won't that just create a feedbackloop? assuming you're even playing both, since the audio in only works when the internal synth is playing
zaphod betamax
May I add that I enjoy the MT when not in auto-tune mode, where keyboard mode is not selected. I get around the same thermal warmup time as my MS-20Ks.

Also, since that pesky auto tune algorythm is disabled, you get subtle mistunings from two Monotribes receiving the same CV.
(and most people have more than one monotribe?)

Only tested in hz/V. The last time I had a V/oct synths was my Moog Prodigy, and I sold that back in 1991!
maltemark
Someone should really port the monotribe oscillator into eurorack, the squarewave is so full of nice, nice character that I miss it especially.
mckenic
http://pulplogic.com/product/monotron-e/
stopthesignal
Just to offer some follow-up on the helpful de-click mods posted here, I originally did the de-click mod with a 4.7uF electrolytic capacitor. It certainly reduced the clicks, but it also introduced an odd, intermittent glitch sound when gating the VCO. It sounded something like the VCO going through its entire frequency range, low-to-high, in a very small fraction of a second. It was subtle, but definitely noticeable. I suspect it was related to the auto-tuning algorithm.

I replaced the 4.7uF electrolytic with a 2.2uF Film capacitor and now the glitch is gone (as well as the clicks, of course).
zaphod betamax
Just sort of effect did it have on WIDE and NARROW mode, where auto-tune is diabled?


stopthesignal wrote:
Just to offer some follow-up on the helpful de-click mods posted here, I originally did the de-click mod with a 4.7uF electrolytic capacitor. It certainly reduced the clicks, but it also introduced an odd, intermittent glitch sound when gating the VCO. It sounded something like the VCO going through its entire frequency range, low-to-high, in a very small fraction of a second. It was subtle, but definitely noticeable. I suspect it was related to the auto-tuning algorithm.

I replaced the 4.7uF electrolytic with a 2.2uF Film capacitor and now the glitch is gone (as well as the clicks, of course).
stopthesignal
zaphod betamax wrote:
Just sort of effect did it have on WIDE and NARROW mode, where auto-tune is diabled?

The glitch was there no matter what mode that switch was set to. I'm not really convinced that auto-tune is disabled in WIDE/NARROW when the sync in jack is set to Sync mode rather than CV/Gate mode, but I also don't know for sure that this glitch was related to the self-tuning algorithm.
zaphod betamax
Do you think the fact that a film capacitor has no polarity, unlike an electrolytic has any bearing on the glitch?
Dreamfish
Hi Muff Wigglers

been modding the hell out of my Monotribe of late thanks mainly to this thread and Daren's excellent mod kits.

I really want to integrate a small analogue delay pedal inside the MT just on the synth voice and using the internal batteries (running at 9V) for an all in one portable box of delights.

Got a cheap Joyo JF-33 which seemed ideal as I can detach the pots and surface mount them to the top of the MT's front panel (eventually).
Connecting the synths VCA output directly from the board into the pedal worked fine.
Now connecting the pedals 9V battery connectors to the +/- on the inside of the MT's battery compartment makes it turn on however with the signal from the VCA going through but no effect from the pedal even when it's LED is o

I'm no electronics expert by any stretch but wondering if there's some other way I should be connecting the pedals negative somewhere else onto the board perhaps?

Also am I right in thinking if I do get the pedal working properly from the MT's internal batteries that breaking the VCA's direct signal to the main output and feeding the pedals output from there is going to be that easy? confused

thanks in advance
InDex
Hello all, I realize this is reaching back a ways but in response to young Zaphod (who plays it safe [sorry, that'll be my one and only name joke for a while.]) there was this video for external control of the VCF envelope: https://www.youtube.com/watch?v=cDWL5MSgoq0 there was some speculation in the comments section about using it to control the VCA envelope as well but I don't think that any consensus was reached in that area. Just thought I'd put it out there.

Cool, thanks for having this community, happy to be here. Sorry if my posts are a bit sloppy at first, it's been over 1.5 decades since last I said anything on the internets.
zaphod betamax
PLEASE IGNORE: FOUND IT!
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