The nice thing about having a second instance of a circuit is that you can compare them by measuring voltages left and right with a multimeter or scope and then when you find a discrepancy this may lead you to find a solution. Make sure to give them the same input signals and settings before you try comparing them.
3 Likes
Maybe start by looking here
Do you have any pictures of your build ?
itās from my stripboard version ? schem ?
3 Likes
Yeah sorry have been too busy to post! It is based on your stripboard layout and schematic! Here are some photos of my build!
2 Likes
For me the face with the location of the components looks good,
have you checked the resistors values ?
tried another IC ?
pass a knife or cutter between the lines of the stripboard to avoid any possible short circuit between the lines ?
here for example it is not very clear in the photo but can be suspicious for me (and sometimes itās not visible to the eye)
2 Likes
Yeah I did follow your advice and using an exacto knife I carved between every trace to cut potentially any unwanted bridges and touches up almost all solder points, and the progress so far is that I kind of hear the faint sound of what sounds like the gate signal going through but not really a coherent drum sound. At some point it sounded like one of the potentiometers was affecting something when moving it, but then I lost it.
Hi,
Are you 100% sure that your TL074 (opamp) is working ? Or genuine ? Just saying this as I cant see any printing on it.
1 Like
if itās better, maybe there is also a not very effective soldering point, redo some soldering
and also
have you
ā¦
1 Like
I always use one of these to check ALL soldering joints:
1 Like
So I did swap out the TL074 on it the other day with others I had lying around and it output noise and the potentiometers seemed to actually work, turning them would change some of the tone of what is being output. It is outputting a type of noise, though nothing that resembles a kick drum sound. And it does seem that the gate signal is going through, whenever I touch the tip of the cable on the input, I do hear the noise being affected by it and when there is a gate signal going through, it can also be heard. It does sound like it is trying its hardest to output sound, it can only go so far. Iāve been double checking solder points and wires and have barely gotten any desired results. Iām not sure if it is the TL074s that I am using as they seem to have always worked and I even bought them off of tayda electronics, but I had a similar problem with a colored noise circuit I made where both the protoboard and PCB versions of the same circuit encountered a similar problem.
you are talking about Gate signal, but for this type of module (to have a short kick sound) it is a Trigger signal that must be sent
what are you testing with ?
btw if by changing the 74, the potentiometers work there is already some progress 
The trigger conditioning circuit actually turns gate signal into a trigger signal, unless the gate signal is way too long and gap between gates is short. But 50% on and 50% off gate signal with any sane tempo should work here.
1 Like
Yes I confirm that resonant twin-t networks are very noisy and really sensitive to external interferences. I never had exactly the same results for 2 identicals circuits.
Iām experimenting this type of drum circuits for a long time now, so I have noted several important details to troubleshoot them:
First it is really important to verify your wiring!
(more than 70% of problems I had with these circuits come from here);
Some poorly laid cables can quickly act as an antenna; if your circuit doesnāt work right away, delicately and carefully fiddling around with the wiring until you hear a sound, can often help to determine where the source of the problem is.
Also, I noticed that it is very recurring that the problem comes of the decay/resonance pot; either by too long or badly insulated wiring between the pot and the pcb, or else because of bad solder joints on the legs of the potentiometer. Verify connections of frequency tuning pot too, donāt forget that here the two potentiometers act on each other !
The best design choice would be to use through-hole components for pot/socket, soldered directly to the pcb, like for a āsandwich-mountingā. It eliminates a lot of problems related to āspagethiā type of wiringā¦ But it necessite to design your own PCB (in CAO)
Sometimes, the strange behavior of Twin-t filters makes them really esotericā¦ but when they work they become very satisfying!!
Currently I am studying resonator gamelan circuits, which are very similar to twin-t in design, and their are enough sensitive tooā¦ but they produce a really interesting and nice drum sounds ! (cf the Tinkle drum module by NLC, inspired by a 70ās concept of Paul DeMarinis, used for his Pygmy Gamelan synth)
I hope this information will be useful to you, keep me informed and above all donāt give up, the result will be worth your effort ! Have fun !
1 Like
So, I am experimenting with this circuit, planning to build it using @plopās PCB schematic (but not the PCB itself), and Iām not sure if Iām actually getting it to work!
Iām building it step by step on breadboard first, and building the Twin-T core, it seems the decay section has no effect? I canāt see or hear any effectā¦ I just get a pop. I can alter the frequency a little if I build the other āTā however. I donāt really understand this circuit, maybe I need to build the distortion and output section before it works?
I tried to build it twice on breadboard, once the full core, once just the decay section and the 1M resistor. Iām using TL072ās (known good supplier) to split it on multiple boards.
I know I experimented with Twin-T drums with CMOS chips a few months ago and the circuit was super fiddly too.
I added a manual trigger but itās otherwise (intended to be) almost identical to the original circuit, this is my WIP redraw (I like to redraw things to understand them better and make them fit on printouts)
1 Like
Hello, i take a look at what you redraw, the two resistors in series in the decay path are 470k.
It should work just fine with CMOS as R1 and C5 act as a high pass filter and should convert any gate to a short pulse (you can try different value for C5 to vary the pulse length).
here is a link to a workshop i followed while building it (the decay path is explained) ā here =)
Also i just finish a newer version of this design, iāll post the link for the schem/pcb/thing here as soon as the upload is finish =)
Here we go, the old Drum-k is in the āOLDā github repo and here is the new one
There are few adjustments that can be done itās being too loud and have too much low end for my taste, also the pin header positions are not the best and the accent level could not fit on the I/O board because of them so itās just a fix 10k resistor for now.
There are all quite simple fix it will be better in the next batch =)
Also because i use the sandwich way, it could be done easily in Kosmo format
Thanks, since then I have rebuilt the circuit a few times and never got it to work yet, I tried multiple resistor values (i was cross-referencing multiple circuits). Iāll take a look at this version next time I try it out.
hey folks, i built the twin-t bass drum from duds layout and it works great with a gate from my sq-1 @ 5v
however i canāt get it to trigger from an lfo like i can with the rest of my percussion modules.
is this where the āgate to triggerā circuit should step in or am i not understanding correctly?
simply can i achieve this with some minor tinkering?
1 Like
The gate to trigger is here:
Presumably your LFO either is too low amplitude or too slow rise time to make a trigger. You could try increasing the value of R2, or maybe increasing C1. Swapping R2 for a 20k pot would allow a front panel trigger sensitivity knob.
2 Likes
Thanks man I will try that.