Roland TR-909 tune+decay mods, firmware upgrade

Posted by in equipment, KORN HARDCORE CUSTOMS, mods & repairs, News, Studio

Duration 10h for Mods: 700€ + parts (knobs+housing) + postage (No VAT (small business §19 (1) UStG))

Spring 2020 new full length video!

Completely reverted the previous work. NOW it feels like my very own 909. Notice that signatures from Jeff Mills and Juan Atkins that i was lucky enough to meet during gigs.

So the final list of modifications is almost endless since the great nava extra 9 project and Robin Whittle documented a lot of other stuff that i needed to try out. I was actually ok with it now to not being able to switch every mod on/off. But you can dial in the stock values still. Plus i needed that replica knobs that really look great on the machine now. Was some extra work to fit in the support boards for the d-shaft knobs but totally worth it.


Anyways, here is the list:

-BD Pitch R59 (100k lin + 10k)
-BD Tune Depth R28… (220 kB+Trim)
-BD Overdrive R52 (10 k lin + 1k)
-BD Tune Range (C9 1uF, R21 1k R57 10k paral.)
-BD Decay Range (C8 1uF parallel)


-SD Tune Range extended R284, R287 (4,7k 47k prallel)
-SD Tone Range extended (Noise Decay) R254=100k: 10k replace or 10k parallel
-SD Snappy Boost R294 (22k parallel) Trimmer: boosted the mix level of the output of the Snappy pot (13.4k instead of 47k, leading to 3.5 times the signal level, which is about 10dB)
-Switch Snare Decay exponential C68 is removed, which eliminates the 24 ms flat start to the envelope

-Tom Tune Range extended R112 10k Original parallel 4,7k and R113 68k orig parallel ca. 30k

-RIM Tune R414 (1M rev log )
-HH Tune R492 (22k lin + 6,9k)

-CLAP Tune R207 (500k lin + 13,7k)
-CLAP Noise (10k lin) TM near R494
Tune R492 (22k linear +6,9k) 50k

Cassette Slot: 
-Rim tune pot (r414) 1m log
-switch on/off
-clap tune pot 500k
-switch on/off

-BD Diodes
-Snare bleed!!! Q47 VCA (hi passed noise) almost gone, thanks Robin Whittle!!!
-Master Volume crackle => vaseline:)
-BD Tune Depth and Tune on one switch

Resources: … Matma?dl=0


Summer 2013:

Modded this little Roland TR-909 together with Claudio of discrete-audio-solutions back in the days. All mods are switchable to „stock“ sound (except clap noise).

-BD-Tune, BD-Overdrive, BD-Decay Range Extension Switch
-Clap Noise Volume
-Rimshot Pitch variations switch
-Hihat Tune


Also exchanged the eprom to the latest firmware (V4) with stable MIDI timing. Thanks to curetronic for the steady desoldering-hand:)