[sdiy] OT - looking for roland JX10 chorus details

[Richie Burnett]

Hi Dave,

I don't have a JX10 to check, but I can give you the chorus details for my 
factory standard JX-3P:

The voice mix is fed to two independently variable BBDs with 3.53ms average 
delay and +/- 1.91ms of modulation.
The two BBDs outputs are panned hard left and hard right and mixed with the 
original voice mix.
Each delay is swept between 1.62ms and 5.44ms by a triangle LFO wave.  The 
LFO triangle wave modulates BBD1 delay directly, and is inverted before 
modulating BBD2.
When the BBD for the left channel is at maximum delay, the BBD for the right 
channel is at minimum delay, and vice versa.
LFO period on my JX-3P measured at 2.2 seconds and is fixed.

The wet chorused signals from the BBDs are lowpass filtered at about 5kHz 
with a 2nd order rolloff that takes a bit off the top end of the BBD delayed 
wet signals.
If you can do it, you could also put a 1st order highpass at around 100Hz on 
the wet only.  There's also quite a bit of swooshing noise added too!

As far as I know the Juno and JX series synths all use the same basic chorus 
setup, except for slight variations in the modulation.  The JX-3P chorus 
certainly sounds very close to the Juno-106 chorus, and very like the 
alpha-juno chorus too when it's set to it's more sane speeds!

If you try these parameters and it sounds right then i'd say you've nailed 
it.  If it doesn't sound exactly right, then I doubt you would have to tweak 
the parameters too far to get the JX-10 sound.  If you still have the JX-10 
then it's not hard to record a low pitch sawtooth tone with the filter wide 
open and switch the chorus on and off.  You can then easily see the delayed 
edges from the chorus appear in a wave editor and work out the delay ranges 
for the left and right BBD channels.  (Thats what I did when analysing the 
JX-3P, 106 and alpha-juno.)

I hope this helps,

-Richie

> I'm looking for clues as to mod depth, delay, LFO shape and rate - that 
> sort
> of thing. If there is any EQ in there (a la Dimension D) it would be good 
> to
> know too. I've got some way along the road, but any details would really
> help.
> FWIW, the JX10 appears to be two JX8P main boards shoved in a long box 
> with
> a keyboard. It's rather cramped in there....