Boss RDD-10/20 Delay time mods

[ambulancevoice]

Hello everyone

Well after getting my hands on a Boss RDD-10 digital delay, I only realised after I bought it that compared to other Boss delays it had a rather limited delay range (same goes for the RDD-20). Even other digital delays from Boss's product line at least has 800ms if delay time, so I figured surely there would be a way to modify it for a much more useable delay range.

After reviewing the schematic and examining other boss delays from the same era, I noted the "clock low" trim pot (RT4 on the board) would set the max long delay time. I cracked open the unit and tweaked it (clearly it had been set for the max 400ms) and managed to get approx 500+ms. I noticed on other boss delays the resistor from the 5v+ line was much larger on these compared to others. That resistor is R116 (not R16 as the schematic says) and is 10k, I desoldered it and replaced it with a 2.4k (no real reason behind that value it was what I had on me).

After I put it back together and tested it, the delay time was massive. Possibly over a second without any serious loss of quality. The long delays combined with the modulation and tone control definitely yields some tape like sounds. The very good sounding "tape echo" mod for the DD-2/DD-3 is possible on these as well, simply replace
R41 10k
R34 22k
C21 10n

Here are some screen grabs of where to find the components to adjust the delay time.





Enjoy!