[sdiy] Looking for: AK Drummer (CRM-260) schematic

[David Huss]

Hi Benjamin,

thanks for your kind response. That is some useful info already.
I suspected the use of a counter and logic already based on the rhythms 
that came out of the thing and Twin-T was something I suspected based on 
the sounds. But the noise circuit would have been a hard guess.

The sounds being toy-like is somewhat of the appeal in my case (for the 
person who asked me to mod it), but I am unhappy with the undercomplex 
rhythms. This should be a matter of figuring out where to inject trigger 
signals and coming up with a control scheme for it. Since everybody and 
their dog are doing euclidian rhythms for a while now I wanted to revive 
the idea of the Relabi pattern (Relabi: Patterns of the Self-Erasing 
Pulse <https://www.johnberndt.org/relabi/Relabi_essay.htm>, John Berndt, 
August 2009) for an experiment with this. Maybe with repeatable seed 
values and potential auto-reset.

I guess I will just have to trace the circuit out then. Maybe something 
to do over the Christmas break.

Your idea of a use of the case for your own purpose sounds interesting 
as well. Should I come up with a schematic I will make sure to share it 
here as well.

Greets,

David/atoav


On 2025-11-24 12:52, Benjamin Tremblay wrote:
> I never found a schematic. But the circuit is not hard to trace.
> The ic is a 4017, producing 6-8 step sequences. The kick drum and 
> other drum circuits are very typical twin t circuits. The snare is 
> just a tom tom sound, no white noise of its own. The hi-hat/shaker 
> sound uses a coil like the Boss DR-55 to produce that whistling blue 
> noise. In my experience with 2 of these machines there is a wide range 
> of deviations between components and sound quality, and the trim pots 
> are not enough to get things sounding nice. It’s a toy basically and 
> the kick drum has no kick. I designed a pcb with some of the Monotribe 
> drum voices and room for a Xiao type microcontroller to fit in the 
> enclosure but I have not gotten around to trying it out. This is 
> because the new circuits would require a better power supply than a 9v 
> battery and it just seemed like too much love for such a low quality toy.
> But winter is coming so I may need a small project like this to keep 
> me busy.  (In particular the Monotribe kick drum sound and snare would 
> help the CRM-260. I have a mod to extend decay on the kick and add 
> swept pitch but it’s a half sine wave sound that is quite nasty.)
>
> Benjamin Tremblay
>
>> On Nov 24, 2025, at 6:02 AM, David Huss via Synth-diy 
>> <synth-diy at synth-diy.org> wrote:
>>
>> 
>>
>> Hi,
>>
>> I have a AK Drummer (CRM-260) Rhythm Machine and I am looking for a 
>> schematic.
>>
>> I searched the web high and low. I figured out that this was also 
>> sold under the names Conrad CRM‑260 or CORT CRM-260 in what seems to 
>> be identical devices (apart from the different manufacturer logo).
>>
>> I found a 10 year old youtube video 
>> <https://www.youtube.com/watch?v=9z71-mFVPcs> where someone has moded 
>> the thing, but there is no description and in a comment from 5 years 
>> ago  they say the documentation has been lost.
>>
>> Does anyone know a thing?
>>
>> All the best,
>>
>> David/atoav
>>
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