Hey I need help with the tr808 snare drum stripboard I made. I got it working for the most part, where it can make sounds when triggered and sound like a bongo or some kind of small percussion sound (sorry I don’t know percussion instruments that well!) but for some reason it doesn’t really sound like a snare when I want it to. Like the knob that is used to control the noise barely does anything and the noise is almost nonexistent when playing, even when I change the other parameters, its not really present. I’m not sure where in the stripboard the noise circuit is, or what the problem might be, can anyone help?
Oh ive seen this stripboard layout around the internet, but i havent built it. If it sounds like a bongo and not a snare, im guessing somethings wrong with the noise part of the circuit.
To help, im going to put both sides of the layout since you only included the top in a low resolution.
Credit for artwork and layout: Minus from the electro-music forum.
https://electro-music.com/forum/topic-45134.html
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That’s my assumption too. I’ve tried looking around and resoldering the bottom rightmost corner of the stripboard that is connected to the noise pot, but no luck there. There is a tiny bit of noise when I crank the pot all the way up, but it’s so little that it might as well not be there. And thanks for including the other images, I almost didn’t think to include them!
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if there is noise, but its quiet, its probably something to do with the gain on the amplification circuit.
(maybe)
Try reducing the level knob and increase the noise and see if the noise if more noticeable even if the overall sound is more quiet. The unity gain might be driving the noise level down.
I’ve built this one, and it works good for me. I just turned it on and messed with it again. I was able to duplicate your problem by having “snappy” turned all the way to one side.
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I thought it had to be something like that. I was worried it was something to do with the accent. I REALLY need to make these btw, they sound awesome.
Thank you all for the help I’ll try your suggestions and hopefully have it sounding good! one minor question though, what exactly is the accent input for or what is it used for? All I know is that to make the drum modules work, I put a constant gate/trigger signal into the input to make it work, but other than that, I don’t know anything beyond that.
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You might find your answer about accent a couple posts down here: Eric Archer TR808 modules
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So I tried adjusting the pots in different combinations as much as I can, and the noise is slightly more there, but still subtle. Like the best way to put it is that it would sort of have the noise sound, but it would be more of a “punchy” kind of sound still
Presumably the noise is produced by transistor T1. Given that you normally don’t want transistors to produce a lot of noise you have to operate one outside its usual limits to get noise, and what happens when you do can be unpredictable: Sometimes you have two nominally the same transistors and one produces lots of noise while the other produces much less or almost none. It’s possible you have a “bad” (= not noisy!) transistor.
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@analogoutput Thats what im thinking. I tried like 4 simple noise circuits before I figured out the transistor I was using was never gonna make noise
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Thats something I thought of, I know the BOM of the stripboard layout needs a PN100 for T1, but I had no luck finding any so I went for a 2n3704 instead. Problem is I know the configuration for it is different than the PN100 and just thought I can drop it in as it. Even though it’s different, would it still work even though the configuration is different or is there a work around?
Could be as simple as trying another transistor, even of the same type. You see this sorta thing with the super simple oscillator too. As @analogoutput said, its kinda exploiting some “bad” behavior to give a result that would normally be bad, but is desirable in this case. Due to manufacturing being not entirely perfect, some will have more of a defect than others, so the “ideal more noisy” transistor might take a few tries to get the one you want.
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So I just replaced the 2n3704 with a 2n3904 and it sounds amazing now! Such a shame I couldn’t use the original transistor intended for the stripboard
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