Twin T Drums (Practical Electronics 1978)

For people who haven’t seen it, and also I think opening a thread about this was interesting.

4 analog drum sounds : Bass Drum / high Bongo / low Bongo / Claves

The stripboard version (bad screenshot, sorry :slight_smile: )

PART 2 :

Related topic


the March and April 1974 Rhythm generator project is IC based with SN7489"s and such and much more difficult put togetherness. and a very large parts lists . Yet what it does is have separate drum circuits into one setup , kinda like Sam did in patreon. and it looks good as a project, the ic’s themselves go for about $4 usd a pop.

In the 1978 version there is no talk about how you are supposed to use the DIN jack and 3.5mm jack and The Din jack looks like it is wired to screen wire ground , straight down the jack and the signal end is soldered to the next 2 pins as one? does that sound right ? This diagram is in the Feb 78 2nd part . So if someone could pdf that here in out forum, also the author changed some part numbers . ie: C31 0.1uf is now polyrad not electrolytic. R61 is 33 ohms not 33k and VR2 is 25k LOG not linear.

So there are 5 pins on this style DIN and am I right that the bottom is the ground connection and that the signal wire is attached to BOTH of those 2 pins?

To me it looks like that…
That’s pin 1 and 4 which are shorted, if I’m not mistaken, and that should be left and right out.

It depends what you will connect it to…
The Audio DIN pinouts are somewhat… special…

Just put a 6.35mm jack in place of that DIN :slight_smile:

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thanks Eric , that"s what I thought about too, Its just this project says that DIN is to go to an external amp and I pondered then said , why shouldn"t it be a 6.35mm jack too. Buzzer in mind went off !!

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EDIT: this message used to say “AD4011” instead of “CD4011”. This was a typo, which is why the below messages are talking about that. apologies for the confusion

Yo, so I want to make one of these per Sam’s stripboard layout. I’m just wondering about that chip, the CD4011. In the video, I zoomed in and Sam seems to be using the CD4011AE: image
I’ve looked on ebay, and I’ve found a pack of 10 CD4011BE’s for 4 quid (here if you’re interested: 10 pcs CD4011BE | eBay) so I was wondering, is the difference between the chips crucial, or will the CD4011BE work just fine?

What’s “LMNK”? tiny

Anyway, AD4011 is an entirely different part from CD4011. Between CD4011A and CD4011B, the datasheets are your friends. I haven’t compared them in great detail but it looks like the main differences are quiescent current and speed, neither of which is critical, so I think either should work. The final E just refers to the packaging, PDIP as opposed to CDIP or SOIC or whatever.


B means buffered, with electrical characteristics according to a JEDEC standard from the late seventies, and properties like “output characteristics shouldn’t depend on current or previous inputs” and “interoperability is a good thing”. A is whatever they did before this standard. UB is mostly B specs but unbuffered. They kind of stopped making A when they started making B and UB, afaik.

The only new CD4011A I can find today is mil speced CDIP from Texas Instruments for $50/ea (plus $600 if you want one newer than 5 years) and Rochester (who packages old wafers from other manufacturers) for $20/ea.

EDIT: For $2500 Texas lets you pick a date code, and they offer 2013 and 2020 so I guess they’re still made. Or at least packaged, date is when “package was sealed”.


Sans titre

it seems to be a CD not AD … 4011 :slight_smile:


RCA went bust in the early eighties, so god knows where @lookmumnocomputer got those :grinning:

I randomly stumbled upon an RCA COS/MOS (sic!) catalog from 1975 where they discuss the difference between A and B (see page 25, main difference appears to be supply voltage) but this predates the JEDEC standard, so their B isn’t necessarily the same as today’s B:

See page 63 for CD4011AE details.


I recently watched Tech connection’s video series about the CED which also covered RCA’s downfall. What a wild thing.

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Like those boxes and boxes of electronic components that someone gifted him…

interesting! I must be honest I can’t remember where I got those. it might have been in my drawers already will try with B’s before the next vid.

That’s a fascinating examination of a product that vanished into the early 1980s video player market without a ripple. Rock solid research backing up highly focussed presentation.

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Ah, sorry, I was using LMNK as an acronym for Look Mum No Computer, maybe I should just say Sam, lol. Also, that was a typo, I meant to type CD4011. I’ve edited it now. And thank you for those datasheets!


That’d be LMNC, not LMNK


oh dear :rofl: very true, sorry about that



EDIT : deleted the stripboard pic with some mistake.


The big black condensator 100mH ?
someone can explain this value plz ?

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