I tried the 1uF cap between two 470k resistor, and nothing changed with the noise issue. Increased it to 47uF. Also, no change.
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Of course the one value where I couldn’t find a nice flat cap lives right next to each other in the busiest part of this busy board 
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(Hard to see with the wires in the way, but there’s a big white cap sitting on top of a smaller grey one.)
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maybee i need this style cap to fix mine? I have the pillow style ones.
Haven’t actually tried it yet, I’m just about 95% ready so hope to give it a go soon.
So I don’t know yet if its any good, but I’ve used Metallized Polyester Film Capacitor (MKT) caps.
So I’ve built this thing. It seems to work, in that nothing burns and I get a sound out of each drum when I trigger it with the keystep pro. However, none of the decay knobs seem to do anything. I’ve tried adjusting the trim pots through their complete travel, and with the decay pot either zero or full it all sounds like the same real short sound.
I’m using CD4011UBE and I did change the mentioned resistors to 470k.
I also built this one, it works pretty well, I used the CD4011AE.
Only issue I had was that I was not able to trigger the noise with any of the 8 step outputs of the #2000 sequencer, it only worked with the seperate gate/trigger output. I found out that the peak voltage of the step trigger was ~4.5V, whereas the combined gate/trigger output was peaking at ~7V. I then added a 1M resistor in parallel over R27 and got a tiny bit of noise with the 4.5V trigger. Eventually I swapped the 1M in parallel with a 680K, so my R27 is now 404K. I now get a decent noise sound with the 4.5V trigger and a loud one with the 7V trigger. Maybe I’ll change the sequencer in the future to get the same peak voltage on all outputs but for now I am considering to leave everything as is as it works fine.
Is there any harm to doing this? As said it works fine for now but don’t want to break anything.
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Quick question for anyone who has built this. Is it expected to be much quieter than other eurorack level sound sources? I probed around a few parts of the circuit and the signals all seem to be +/-2.5 volts. I have to really crank down all of my other channels to start hearing the drums.
I built two of these and their output is at “normal” levels.
what chip did you use. a common problem is the use of 4011UBE vs 4011AE (see some posts by Sam at the beginning of this thread). Both work but the UBE ones behave differently and work better with some modifications…
good luck 
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What are you using to trigger the drum module? Are you using the VCLFO? If so, message #54/55 in this thread used the VCLFO, stating it is outputting 2.5V, which seems to correspond to the output voltage you are seeing.
I haven’t finished building the 2700 Twin T Drums yet. Maybe somebody who built the 2700 Twin T Drums can chime in whether the level output of that module is input dependent?
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I have a few different 4011AE chips I’ve tried and they all output the same. Another quirk is that I’ve had to use lower resistor values for R2,17,32,47 or else the trimpots can’t stop self oscillation with the knobs above 65%.
The signals coming out of the 4011 are 0-5v, which I think is correct since it’s a 5v chip?
I’ve tried a few different triggers and they seem to be enough to get the drums to go. I’ll try some higher voltage triggers and see if that changes anything.
Well, it might be the trigger voltage! I boosted the LFO signal and it definitely makes the drums louder. I’ll have to hook up my BSP later and see how that does. Thanks for the tip, I read that comment and assumed it was only an issue with the noise.
Maybe I’ll put together a bodge to boost all of the input triggers of the normal trigger voltage aren’t enough.
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Confirmed with a beat step pro that it is indeed weak triggers making it quiet. I’ll get some transistors bodged onto the triggers tonight so even a weak triggers will get the drums singing 
I’ll let everyone know how it goes. Might be worth adding the few components if this ever becomes a eurorack or V2 of the module, @lookmumnocomputer . Could be interesting to add an intensity knob for the trigger voltage 
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If you work out a way to boost the input and you’ve got the space for a second TRIGGER jack, maybe you can give it HARD and SOFT TRIGGER inputs - two drum voices for the price of one.
Similar to this maybe?
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I like the @ShedSynth circuit. I built it on breadboard a year or so ago. Just didn’t have a spot in my rack for it. Regardless, I liked the simultaneous output of the different sounds from the same voice.
Thank you, it’s nice to hear about people building my stuff.
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It took a bit more than a transistor, but I can now trigger the drums with a lower voltage and get the full volume out! I went with the opamp buffer I found here, and used a trimpot to set the voltage for the voltage divider on the negative opamp inputs. I messed around with a few different circuits and this one is working well for me. Adjusting the trimpots adjusts the sensitivity for the input trigger, and the output trigger to each drum voice is just above 10v.
I didn’t notice much of a change to the drum sound based on it’s trigger voltage other than the sound, so I think the modification for a hard and soft hit like @ShedSynth 's circuit would be much more involved. I also have no idea what I’m doing when it comes to the circuit side of things 
Now I can get some good drum sounds at a high volume with LFOs and other lower voltage triggers. The #1008 MIDI TO TRIGGER shuld play nicely with it now as well, I think that has 5v trigger outputs.
If anyone is interested, I can try throwing a schematic together. I need the practice KiCad
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One more update. So, the gate buffer is working great. However, the drums have a transient on the falling edge of transients 
I decided to bodge my bodge and make it a gate to trigger. Super janky, but it’s working really nicely now! No transient on a falling edge, longer gates become a short pulse. You can even get a some subtle differences in tone with lower voltage gates/triggers in.
I went with Ken Stone’s circuit at the bottom of this page
The last modification I’m considering is some sort of noise gate for the noise into the mixer so it doesn’t add background interference into the mix out. That might be a bridge too far for me, though.
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When I turn the potentiometers of the Kick or LBongo 70-80% to the right, I get the infamous hum, even though the trimpotmeters are turned all the way counter clockwise.
Is there a remedy to remove the hum completely, for instance by replacing or adding a resistor somewhere?
If everything sounds OK all the way round to 69½% you could add a fixed resistor to the clockwise end of the pot to restrict the range.
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