[sdiy] OT - looking for roland JX10 chorus details

[Dave Kendall]

Hi Richie.

Thanks VERY much - that's a real goldmine of precise info :-)

Most amplitude/time parameters in Kurzweil synths are presented in 
terms of dB and in seconds, so it should be relatively straightforward 
to get close to the effect quite quickly.
I've played with a bare saw in the JX into chorus, but hadn't thought 
to view the results of on/off in a waveform editor. Nice!
The EQ details will really help too. As the Kurz is so clean, I should 
probably inject some low-level white noise in to get the correct 
effect. The JX's chorus is subjectively quite dark-sounding, and that 
was a part I have't got right yet. Nice one.

Many thanks to all for the help. It's going to be a productive 
sunday.....  ;-)

cheers,
Dave

On Apr 21, 2012, at 20:19, Richie Burnett wrote:

> 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....
>
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