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posted by martyb on Friday September 14 2018, @08:16AM   Printer-friendly
from the a-feature-is-something-that-is-broken-in-a-useful-way dept.

That headline sounds suspect, but it is the most succinct way to explain why the Roland TR-808 drum machine has a very distinct, and difficult to replicate noise circuit. The drum machine was borne of a hack. As the Secret Life of Synthesizers explains, it was a rejected part picked up and characterized by Roland which delivers this unique auditory thumbprint.

Pictured above is the 2SC828-R, and you can still get this part. But it won't function the same as the parts found in the original 808. The little dab of paint on the top of the transistor indicates that it was a very special subset of those rejected parts (the 2SC828-RNZ). A big batch of rejects were sold to Roland back in the 1970's — which they then thinned out in a mysterious testing process. What was left went into the noise circuit that gave the 808 its magical sizzle. When the parts ran out, production ended as newer processes didn't produce the same superbly flawed parts.

Source: https://hackaday.com/2018/09/06/you-cant-build-a-roland-tr-808-because-you-dont-have-faulty-transistors/


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  • (Score: 3, Informative) by RS3 on Friday September 14 2018, @02:05PM (1 child)

    by RS3 (6367) on Friday September 14 2018, @02:05PM (#734819)

    Another thought: I haven't seen the circuit yet, so I'm speculating / theorizing, but it's possible the "faulty" transistors had a slightly worse high-frequency rolloff; IE: didn't amplify the highest frequencies as much as the lower ones in hearing range. Noise containing more amplitude of frequencies at the higher end of human hearing is generally harsher. Think: turn down the treble control a bit, but at a higher frequency than an average treble control (E.g.: 15K rather than 4K).

    Also, in that time period many people were (still) using noisy carbon resistors, and maybe occasionally using metal-film in audio circuits, so maybe that is a factor?

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  • (Score: 3, Informative) by RS3 on Friday September 14 2018, @02:08PM

    by RS3 (6367) on Friday September 14 2018, @02:08PM (#734822)

    Yeah, I just found a pic of the circuit board and I see lots of carbon resistors and no metal-film. https://www.sequencer.de/pix/roland_TR/tr808_offen_original.jpg [sequencer.de]