Simple Twin-T Kick Drum

[juggle]

@eric

You should put the TL072 Unit C symbol and connect it to +/-12V.

That’s how I’ve ususally done it…but I learned more about power nets a board or two back and was able to just use PWR_FLAG’s to identify them so it automatically hooked that up behind the scenes. Not sure why it’s not doing that on this one. But I was getting pretty tired last night and didn’t try to think it though - was just trying to get all the components down

@Jos

Any idea what the transistor in the top right is for?

I don’t fully understand how that part of the circuit works either. It comes from the dogsnakes noisedrum (which I really like as a hi-hat) and it works…I’m just not clear on why/how.

@Dud

maybe before it is tested put some where “Not verified” for the moment, if someone find it on a google search

Good idea…I’ll try and do that a little later.

[Bitnik]

@Jos

Any idea what the transistor in the top right is for? The fact that there is no connection to some positive voltage on its collector puzzles me

I think this is the noise generator as discussed elsewhere in this thread. It’s advisable to cut that unused collector leg very short so as to eliminate unwanted RF interference.

[Dud]

the transistor with no connection at all on collector ?
i think it’s the master piece for create the white noise

[eric]

@juggle

and was able to just use PWR_FLAG’s to identify them so it automatically hooked that up behind the scenes.

I guess now that you have +5V and +12V power nets, kicad just chooses one… by some arcane algorithm…
Did you have both in your previous design(s) where it worked ?

I never trust software… I know why, after all, I’m a software developer

[juggle]

Yeah, The ones I’ve used that method in before didn’t have +5. But it didn’t pick up the -12 either.

But…I’ve also only used it with TL074’s and this one is a TL072 so it could be a difference in how the part is defined in kicad as well.

[eric]

I guess it knows which pin of the IC should be positive and which negative, but by no means can it know which voltage.
I never designed a symbol in kicad, so maybe I’m wrong… what attributes can you set on power pins ?

[Dud]

In the video, his module (Twin T kick) have an Attack select switch, it’s not in the schematic and i really don’t understand his explaination about it.
Some one can help me plz ? what’s he saying ?

[CTorp]

He says these diodes are connected to the switch to provide two attack responses but yeah it doesn’t show how…but I imagine the switch would break the path going thru both diodes

[Farabide]

As far as I can see it’s just switching between two cap values to give you different lengths of decay…like sso pitch ranges. Or did I miss something?
Edit: yeah I missed that. Im off to sleep

[Dud]

yes i think it’s between the 2 diodes and GND like you said, thx

[Krakenpine]

Yeah, simple switch connecting the diodes to ground or just to leave them hanging in the air.

I must say, I got surprised find a thread about this in here
Also, “lovely Finnish accent”. What

Maybe I’ll make more videos like this, with better explanations.

[BlackDeath]

Tervetuloa!

[Dud]

thanks a lot for explain @Krakenpine

[Dud]

what name i put for the “Original schematic by …” in my stripboard layout version plz ?
I would also add the Attack switch.

[Dud]

I build it, here my Twin T Kick Drum stripboard version verified

Verified Stripboard Layouts!

Here’s my version of the TWIN T Kick Drum stripboard [twin T kick drum layout by sound bender] [twin T kick drum layout by sound bender - Copie] see here (pics and sound) schematic [image] EDIT : i put the stripboard version with Attack switch

[Plop]

Hi, I made the Twin-T kick Drum on a stripboard, but I have a problem with the trigger input, it only works when I send a negative gate, the craziest thing is that it worked normally last night, I double checked and reflowed all my connections (from the krakenpine schematic and the stripboard layout), it’s driving me crazy and having only a first price multimeter at my disposal I don’t know what to do to debug it since I have no point of comparison.

Do you have any leads, tips or values that I’m supposed to have on certain components?
For example, what voltage am I supposed to have between the 0v line and the different legs of the OP-Amp?
Also I noticed that I have a few millivolts between R1 and GND but it seems normal to me from the schematic

Thank you, for your time

[Dud]

Hi to you, sorry I suck in theory (other here could help you better), I just made a stripboard from the diagram and everything worked on the first try. Check your circuit again, there is bound to be an error somewhere . Maybe show us pictures.

[Plop]

I’m sure that the problem is on my side since it worked briefly, I’m changing all the capacitors, since I can’t test them with a multimeter, here are some pictures.

The full view :

Zoom

Zoom

Part A

Part B

Part C

PS :
For part B the two resitors solder to each other are just 1k and 2k put together to get a 3k resistor

For the part C i juste moove part to the center to have some space for when i will do the led driver (the rectangle on the right)

The two rectangles with a hole on the left are for the monting brackets.

The big horizontal line is GND, +12 on top, -12 on the botom and vertical black lines are the paths wihch i cut

[Plop]

I’m re-building it from the begining, it’s not like it’s a lot of part, and i can re-use jack, pot and the op-amp, i think it will be easier this way.

[Plop]

Ah ah, i’ve got the same probleme with the new build so i think it’s come from the part i change I will post the modified layout.