[sdiy] Roland/Boss "long chip" RDD63H101

Sean Ellis tensiontype at hotmail.com
Thu Jun 6 13:21:41 CEST 2019

About the Boss 'sampler', I had an RSD-10 and while it could do the things it said on the box there were a lot of limitations in terms of expected input ranges. From memory the controls didn't work in some modes and getting any consistent tracking was hard. They have a bit of a cult status that is not really deserved IMO.

From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Adam Inglis <21pointy at tpg.com.au>
Sent: Thursday, 6 June 2019 12:55 AM
To: Synth DIY
Subject: [sdiy] Roland/Boss "long chip" RDD63H101

A question for the tinkerers...

In the early eighties, Roland produced their first rack mount effects unit, the SDE-2000 digital delay. This was based on a 12 bit SAR chip (AM2504) and 12 1-bit DRAM chips, a bit like the Korg SDD-3000.
Sometime after that, they designed a custom chip, the RDD63H101, a 64 pin CMOS gate array (as it was described).
It certainly seems like they attempted to get a good return on such an investment - it was used in many Roland and Boss products that followed:

Roland SDE-1000 and SDE-3000 rack mount digital delays, and the later SDE-2500
Boss DE-200 rack mount digital delay
Boss ‘half rack’ digital delay RDD-10 and 20
the Boss pedal versions of the above, the DD-2 and 3
Boss half rack delay/sampler RSD-10
the Boss pedal version of the above, the DSD-2

There could well have been more.
This chip has come to be known in stompbox circles as “the long chip”, as it runs almost the length of a Boss pedal.
It was used for delay and time-modulation purposes, but around 1986 they used it for simple monophonic sampling. An interesting implementation was in the RSD-10, where a monophonic audio signal say from a keyboard could determine pitch, dynamics and gate time of the sample playback, using peripherals such as a 4046 phase locked loop, a compander, and a 15-bit counter. There was no midi. There were also trigger and drum pad inputs. Looks to me potentially to be a fun, real-time sound-mangler.

There’s not much on the interwebs about these RSD units and they rarely come up for sale, but the pedal versions (which lack the pitch, dynamics and gate) are easier to find. I’m thinking that one should be able to modify (extra chips and PCB, re-house it) the pedal to give the same functionality as the rack - has anyone tried it?

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