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Re: [sdiy] JX-3P question

Re: [sdiy] JX-3P question

2026-01-18 by Richie Burnett

Thanks for the confirmation everyone.

It just seemed like a strange thing to include what must have been an 
expensive BA662 OTA device at the time, instead of using yet another 
trim-pot to calibrate the noise level.

Obviously the AGC approach would try to correct for long-term drift of the 
noise level and possible variation with temperature, but that can't account 
for that much amplitude variation, and the user can adjust the level of 
noise in the mix anyway!  I would have thought the AGC circuit would need to 
measure the RMS of the noise in order to accurately control its perceived 
loudness anyway?

It's interesting that it's used in other synths of the era like the Juno 6 & 
60 and a variant in the Jupiter 6, but the Juno 106 design went back to 
using a trim-pot again (VR32).  (See attached.)

JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise sources!

-Richie,
Show quoted textHide quoted text
-----Original Message----- 
From: Florian Anwander via Synth-diy
Sent: Sunday, January 18, 2026 6:15 PM
To: synth-diy mailing list
Subject: Re: [sdiy] JX-3P question



Hello Richie

Am 18.01.26 um 18:13 schrieb Richie Burnett:
but on closer inspection it looks like the OTA is in some sort of local 
feedback loop, intended to keep the noise amplitude constant, maybe?

I never investigated deeper on this circuit, but that is my impression too. 
Roland used that in the JX3P and in the Juno6/60. A similar circuit was used 
in the Jupiter6:






I don't remember the JP8.

Florian





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Re: [sdiy] JX-3P question

2026-01-18 by Adam (synthDIY)

I wonder if it has something to do with the noise modulation option in the JX3P, rather than just the use of noise as part of the patch mix?

Noise modulation is available from the front panel but not from the PG-200

A
Show quoted textHide quoted text
> On 19 Jan 2026, at 05:47, Richie Burnett <rburnett@richieburnett.co.uk> wrote:
> 
> Thanks for the confirmation everyone.
> 
> It just seemed like a strange thing to include what must have been an expensive BA662 OTA device at the time, instead of using yet another trim-pot to calibrate the noise level.
> 
> Obviously the AGC approach would try to correct for long-term drift of the noise level and possible variation with temperature, but that can't account for that much amplitude variation, and the user can adjust the level of noise in the mix anyway!  I would have thought the AGC circuit would need to measure the RMS of the noise in order to accurately control its perceived loudness anyway?
> 
> It's interesting that it's used in other synths of the era like the Juno 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design went back to using a trim-pot again (VR32).  (See attached.)
> 
> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise sources!
> 
> -Richie,
> 
> 
> 
> -----Original Message----- From: Florian Anwander via Synth-diy
> Sent: Sunday, January 18, 2026 6:15 PM
> To: synth-diy mailing list
> Subject: Re: [sdiy] JX-3P question
> 
> 
> 
> Hello Richie
> 
> Am 18.01.26 um 18:13 schrieb Richie Burnett:
> but on closer inspection it looks like the OTA is in some sort of local feedback loop, intended to keep the noise amplitude constant, maybe?
> 
> I never investigated deeper on this circuit, but that is my impression too. Roland used that in the JX3P and in the Juno6/60. A similar circuit was used in the Jupiter6:
> 
> 
> 
> 
> 
> 
> I don't remember the JP8.
> 
> Florian
> 
> 
> 
> 
> 
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
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> 
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Re: [sdiy] JX-3P question

2026-01-19 by synth@schmitzbits.de

That. You see the buffers and S&H caps on the left, there is a DC under control of the processor.
With VR32 you even out the variations in amplitude of the noise transistor, by changing the control sensitivity.

Cheers,
René
Von: Synth-diy im Auftrag von Adam (synthDIY)
Gesendet: Sonntag, 18. Januar 2026 22:52
An: Richie Burnett
Cc: synth-diy mailing list
Betreff: Re: [sdiy] JX-3P question
I wonder if it has something to do with the noise modulation option in the JX3P, rather than just the use of noise as part of the patch mix?

Noise modulation is available from the front panel but not from the PG-200

A

> On 19 Jan 2026, at 05:47, Richie Burnett wrote:
>
> Thanks for the confirmation everyone.
>
> It just seemed like a strange thing to include what must have been an expensive BA662 OTA device at the time, instead of using yet another trim-pot to calibrate the noise level.
>
> Obviously the AGC approach would try to correct for long-term drift of the noise level and possible variation with temperature, but that can't account for that much amplitude variation, and the user can adjust the level of noise in the mix anyway! I would have thought the AGC circuit would need to measure the RMS of the noise in order to accurately control its perceived loudness anyway?
>
> It's interesting that it's used in other synths of the era like the Juno 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design went back to using a trim-pot again (VR32). (See attached.)
>
> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise sources!
>
> -Richie,
>
>
>
> -----Original Message----- From: Florian Anwander via Synth-diy
> Sent: Sunday, January 18, 2026 6:15 PM
> To: synth-diy mailing list
> Subject: Re: [sdiy] JX-3P question
>
>
>
> Hello Richie
>
> Am 18.01.26 um 18:13 schrieb Richie Burnett:
> but on closer inspection it looks like the OTA is in some sort of local feedback loop, intended to keep the noise amplitude constant, maybe?
>
> I never investigated deeper on this circuit, but that is my impression too. Roland used that in the JX3P and in the Juno6/60. A similar circuit was used in the Jupiter6:
>
>
>
>
>
>
> I don't remember the JP8.
>
> Florian
>
>
>
>
>
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace@synth-diy.org
>
> --
> This email has been checked for viruses by AVG antivirus software.
> www.avg.com________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace@synth-diy.org


________________________________________________________
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Submit email to: Synth-diy@synth-diy.org
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Re: [sdiy] JX-3P question

2026-01-19 by rburnett@richieburnett.co.uk

That's interesting Adam. I didn't know the JX-3P could do that!

I don't see a modulation path from the analogue noise source to the DCOs 
though, so I guess the noise modulation you mention must be done 
digitally by the micro?

-Richie,
Show quoted textHide quoted text
On 2026-01-18 21:52, Adam (synthDIY) wrote:
> I wonder if it has something to do with the noise modulation option in 
> the JX3P, rather than just the use of noise as part of the patch mix?
> 
> Noise modulation is available from the front panel but not from the 
> PG-200
> 
> A
> 
>> On 19 Jan 2026, at 05:47, Richie Burnett 
>> <rburnett@richieburnett.co.uk> wrote:
>> 
>> Thanks for the confirmation everyone.
>> 
>> It just seemed like a strange thing to include what must have been an 
>> expensive BA662 OTA device at the time, instead of using yet another 
>> trim-pot to calibrate the noise level.
>> 
>> Obviously the AGC approach would try to correct for long-term drift of 
>> the noise level and possible variation with temperature, but that 
>> can't account for that much amplitude variation, and the user can 
>> adjust the level of noise in the mix anyway!  I would have thought the 
>> AGC circuit would need to measure the RMS of the noise in order to 
>> accurately control its perceived loudness anyway?
>> 
>> It's interesting that it's used in other synths of the era like the 
>> Juno 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design 
>> went back to using a trim-pot again (VR32).  (See attached.)
>> 
>> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise 
>> sources!
>> 
>> -Richie,
>> 
>> 
>> 
>> -----Original Message----- From: Florian Anwander via Synth-diy
>> Sent: Sunday, January 18, 2026 6:15 PM
>> To: synth-diy mailing list
>> Subject: Re: [sdiy] JX-3P question
>> 
>> 
>> 
>> Hello Richie
>> 
>> Am 18.01.26 um 18:13 schrieb Richie Burnett:
>> but on closer inspection it looks like the OTA is in some sort of 
>> local feedback loop, intended to keep the noise amplitude constant, 
>> maybe?
>> 
>> I never investigated deeper on this circuit, but that is my impression 
>> too. Roland used that in the JX3P and in the Juno6/60. A similar 
>> circuit was used in the Jupiter6:
>> 
>> 
>> 
>> 
>> 
>> 
>> I don't remember the JP8.
>> 
>> Florian
>> 
>> 
>> 
>> 
>> 
>> ________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy@synth-diy.org
>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>> Check your settings at: 
>> https://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace@synth-diy.org
>> 
>> --
>> This email has been checked for viruses by AVG antivirus software.
>> www.avg.com<Juno106-Noise.PNG>________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy@synth-diy.org
>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>> Check your settings at: 
>> https://synth-diy.org/mailman/listinfo/synth-diy
>> Selling or trading? Use marketplace@synth-diy.org

Re: [sdiy] JX-3P question

2026-01-19 by Adam (synthDIY)

It's an undocumented feature.
In the manual, it would appear that LFO modulation is restricted to sine, square or random (Edit group B, option 10, buttons A B or C). However, if you hit the fourth button "D" you get a noise source modulation that can affect both the oscillators and filter, depending of course how much mod you have dialled in for these areas.
(Side note: the LFO Delay function also works on this noise source, for those times where you want your delicate synth-brass sound to be slowly taken over by short-wave radio hash... erm..)

But, no, I don't know the actual source of that noise modulation....
I do know I'm gonna need another coffee before I open the service manual though...

A
Show quoted textHide quoted text
> On 20 Jan 2026, at 07:31, rburnett@richieburnett.co.uk wrote:
> 
> That's interesting Adam. I didn't know the JX-3P could do that!
> 
> I don't see a modulation path from the analogue noise source to the DCOs though, so I guess the noise modulation you mention must be done digitally by the micro?
> 
> -Richie,
> 
> 
> On 2026-01-18 21:52, Adam (synthDIY) wrote:
>> I wonder if it has something to do with the noise modulation option in the JX3P, rather than just the use of noise as part of the patch mix?
>> Noise modulation is available from the front panel but not from the PG-200
>> A
>>> On 19 Jan 2026, at 05:47, Richie Burnett <rburnett@richieburnett.co.uk> wrote:
>>> Thanks for the confirmation everyone.
>>> It just seemed like a strange thing to include what must have been an expensive BA662 OTA device at the time, instead of using yet another trim-pot to calibrate the noise level.
>>> Obviously the AGC approach would try to correct for long-term drift of the noise level and possible variation with temperature, but that can't account for that much amplitude variation, and the user can adjust the level of noise in the mix anyway!  I would have thought the AGC circuit would need to measure the RMS of the noise in order to accurately control its perceived loudness anyway?
>>> It's interesting that it's used in other synths of the era like the Juno 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design went back to using a trim-pot again (VR32).  (See attached.)
>>> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise sources!
>>> -Richie,
>>> -----Original Message----- From: Florian Anwander via Synth-diy
>>> Sent: Sunday, January 18, 2026 6:15 PM
>>> To: synth-diy mailing list
>>> Subject: Re: [sdiy] JX-3P question
>>> Hello Richie
>>> Am 18.01.26 um 18:13 schrieb Richie Burnett:
>>> but on closer inspection it looks like the OTA is in some sort of local feedback loop, intended to keep the noise amplitude constant, maybe?
>>> I never investigated deeper on this circuit, but that is my impression too. Roland used that in the JX3P and in the Juno6/60. A similar circuit was used in the Jupiter6:
>>> I don't remember the JP8.
>>> Florian
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
>>> --
>>> This email has been checked for viruses by AVG antivirus software.
>>> www.avg.com<Juno106-Noise.PNG>________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace@synth-diy.org

Re: [sdiy] JX-3P question

2026-01-20 by Adam (synthDIY)

Thanks René!

Richie
2 coffees down and page 6 of the SM tells me you are probably right:

LFO (as well as ADSR) are software-generated, so almost certainly given the modulation architecture, the noise source is too



Show quoted textHide quoted text
> On 20 Jan 2026, at 07:31, rburnett@richieburnett.co.uk wrote:
> 
> That's interesting Adam. I didn't know the JX-3P could do that!
> 
> I don't see a modulation path from the analogue noise source to the DCOs though, so I guess the noise modulation you mention must be done digitally by the micro?
> 
> -Richie,
> 
> 
> On 2026-01-18 21:52, Adam (synthDIY) wrote:
>> I wonder if it has something to do with the noise modulation option in the JX3P, rather than just the use of noise as part of the patch mix?
>> Noise modulation is available from the front panel but not from the PG-200
>> A
>>> On 19 Jan 2026, at 05:47, Richie Burnett <rburnett@richieburnett.co.uk> wrote:
>>> Thanks for the confirmation everyone.
>>> It just seemed like a strange thing to include what must have been an expensive BA662 OTA device at the time, instead of using yet another trim-pot to calibrate the noise level.
>>> Obviously the AGC approach would try to correct for long-term drift of the noise level and possible variation with temperature, but that can't account for that much amplitude variation, and the user can adjust the level of noise in the mix anyway!  I would have thought the AGC circuit would need to measure the RMS of the noise in order to accurately control its perceived loudness anyway?
>>> It's interesting that it's used in other synths of the era like the Juno 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design went back to using a trim-pot again (VR32).  (See attached.)
>>> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise sources!
>>> -Richie,
>>> -----Original Message----- From: Florian Anwander via Synth-diy
>>> Sent: Sunday, January 18, 2026 6:15 PM
>>> To: synth-diy mailing list
>>> Subject: Re: [sdiy] JX-3P question
>>> Hello Richie
>>> Am 18.01.26 um 18:13 schrieb Richie Burnett:
>>> but on closer inspection it looks like the OTA is in some sort of local feedback loop, intended to keep the noise amplitude constant, maybe?
>>> I never investigated deeper on this circuit, but that is my impression too. Roland used that in the JX3P and in the Juno6/60. A similar circuit was used in the Jupiter6:
>>> I don't remember the JP8.
>>> Florian
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
>>> --
>>> This email has been checked for viruses by AVG antivirus software.
>>> www.avg.com<Juno106-Noise.PNG>________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace@synth-diy.org

Re: [sdiy] JX-3P question

2026-01-20 by Richie Burnett

That sounds cool.  Thanks Adam.  I definitely need to give this a try when I 
get my JX-3P put back together :-)

-Richie,

-----Original Message----- 
From: Adam (synthDIY)
Sent: Monday, January 19, 2026 10:17 PM
To: rburnett@richieburnett.co.uk
Cc: synth-diy mailing list
Subject: Re: [sdiy] JX-3P question

It's an undocumented feature.
In the manual, it would appear that LFO modulation is restricted to sine, 
square or random (Edit group B, option 10, buttons A B or C). However, if 
you hit the fourth button "D" you get a noise source modulation that can 
affect both the oscillators and filter, depending of course how much mod you 
have dialled in for these areas.
(Side note: the LFO Delay function also works on this noise source, for 
those times where you want your delicate synth-brass sound to be slowly 
taken over by short-wave radio hash... erm..)

But, no, I don't know the actual source of that noise modulation....
I do know I'm gonna need another coffee before I open the service manual 
though...

A
Show quoted textHide quoted text
> On 20 Jan 2026, at 07:31, rburnett@richieburnett.co.uk wrote:
>
> That's interesting Adam. I didn't know the JX-3P could do that!
>
> I don't see a modulation path from the analogue noise source to the DCOs 
> though, so I guess the noise modulation you mention must be done digitally 
> by the micro?
>
> -Richie,
>
>
> On 2026-01-18 21:52, Adam (synthDIY) wrote:
>> I wonder if it has something to do with the noise modulation option in 
>> the JX3P, rather than just the use of noise as part of the patch mix?
>> Noise modulation is available from the front panel but not from the 
>> PG-200
>> A
>>> On 19 Jan 2026, at 05:47, Richie Burnett <rburnett@richieburnett.co.uk> 
>>> wrote:
>>> Thanks for the confirmation everyone.
>>> It just seemed like a strange thing to include what must have been an 
>>> expensive BA662 OTA device at the time, instead of using yet another 
>>> trim-pot to calibrate the noise level.
>>> Obviously the AGC approach would try to correct for long-term drift of 
>>> the noise level and possible variation with temperature, but that can't 
>>> account for that much amplitude variation, and the user can adjust the 
>>> level of noise in the mix anyway!  I would have thought the AGC circuit 
>>> would need to measure the RMS of the noise in order to accurately 
>>> control its perceived loudness anyway?
>>> It's interesting that it's used in other synths of the era like the Juno 
>>> 6 & 60 and a variant in the Jupiter 6, but the Juno 106 design went back 
>>> to using a trim-pot again (VR32).  (See attached.)
>>> JX-8P and the Alpha Juno / MKS50 got the luxury of digital noise 
>>> sources!
>>> -Richie,
>>> -----Original Message----- From: Florian Anwander via Synth-diy
>>> Sent: Sunday, January 18, 2026 6:15 PM
>>> To: synth-diy mailing list
>>> Subject: Re: [sdiy] JX-3P question
>>> Hello Richie
>>> Am 18.01.26 um 18:13 schrieb Richie Burnett:
>>> but on closer inspection it looks like the OTA is in some sort of local 
>>> feedback loop, intended to keep the noise amplitude constant, maybe?
>>> I never investigated deeper on this circuit, but that is my impression 
>>> too. Roland used that in the JX3P and in the Juno6/60. A similar circuit 
>>> was used in the Jupiter6:
>>> I don't remember the JP8.
>>> Florian
>>> ________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
>>> --
>>> This email has been checked for viruses by AVG antivirus software.
>>> www.avg.com<Juno106-Noise.PNG>________________________________________________________
>>> This is the Synth-diy mailing list
>>> Submit email to: Synth-diy@synth-diy.org
>>> View archive at: https://synth-diy.org/pipermail/synth-diy/
>>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
>>> Selling or trading? Use marketplace@synth-diy.org
> ________________________________________________________
> This is the Synth-diy mailing list
> Submit email to: Synth-diy@synth-diy.org
> View archive at: https://synth-diy.org/pipermail/synth-diy/
> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
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