[sdiy] Help with Jupiter 8 clone

[Mike Bryant]

Yes I use the those TI products a lot for low-noise mic amplifiers.

The only time you really need multi-phase and zero-crossing is when you are dealing with kW levels – either as power amps or as solar panel controllers which are two of our specialities.  Solar controllers tend to be more specialised so you usually use a DSP orientated MCU to do the timing.   Google for solar power zero-crossing and lots of paper should appear.



From: DIY DSP [mailto:diydsp at yahoo.com]
Sent: 03 August 2022 19:26
To: Josh Nursing; Mike Bryant
Cc: synth-diy at synth-diy.org
Subject: Re: [sdiy] Help with Jupiter 8 clone

>A good one using multi-phase zero-crossing switching will show none of that.

I hadn't heard of multi-phase switchers before, so I googled it and found htis nice doc I figured might interest people:
https://www.ti.com/lit/an/slva882b/slva882b.pdf

the only problem is that it doesn't reference the zero-crossing part...   I'm having less luck finding that...  have you got any good references for that?

thank you!



Noah Vawter's futuristic electronic music instrument lab: youtube.com/diydsp<https://youtube.com/diydsp>


On Tuesday, August 2, 2022 at 12:05:07 PM EDT, Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>> wrote:



I’ve been using SMPS in pro-audio equipment we design since the 1970s, as have most of the other top audio designers I know.  Some took until the late 90s to come round but from then on everybody who mattered accepted SMPS were better.



High frequency current spikes indicate a badly designed SMPS, nothing more.  A good one using multi-phase zero-crossing switching will show none of that.



Have a look inside every pro-audio product nowadays and you’ll find a SMPS.  And to be sold they have to pass mains radiated tests so there is very little mains-side noise.  Indeed it is linear supplies which often used to fail those tests as they distorted the mains signal more due to core hysteresis.



So I will submit that you have a somewhat jaundiced view.





From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org] On Behalf Of Josh Nursing via Synth-diy
Sent: 02 August 2022 16:47
To: synth-diy at synth-diy.org
Subject: Re: [sdiy] Help with Jupiter 8 clone



SMPS are the most polluting/noisy PSUs for audio purposes. Lots of high-frequency current spikes affect both downstream circuits and the mains they're connected to.



And before you start telling me about filtering the output of them, that does absolutely nothing for the mains-side noise.



Effects on audio are across the board - all audio frequencies suffer, and it's probably more noticeable in loss of bass frequencies.



On Tue, Aug 2, 2022 at 11:41 AM Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>> wrote:

How can audio suffer from putting a PSU in with 100 times better performance ?    No 50/100Hz at all and general noise almost zero.  And it’s far less heat so everything else runs cooler and better.  I think too many people see the noise from their phone charger or whatever and assume a proper SMPS is like that.





From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>] On Behalf Of Josh Nursing via Synth-diy
Sent: 02 August 2022 16:35
To: Synth DIY
Subject: Re: [sdiy] Help with Jupiter 8 clone



I really don't like the idea of replacing the linear PSU in those vintage synths with a SMPS one. Audio suffers.



On Tue, Aug 2, 2022 at 7:45 AM Adam (synthDIY) <synthdiy at adambaby.com<mailto:synthdiy at adambaby.com>> wrote:

Luís, I assume you’re aware of this



https://synthronics.de/roland-jupiter-8-new-psu/



and this guy, who has been ominously quiet of late



https://jup8restoration.wordpress.com/2019/10/22/new-power-supply-being-manufactured-for-a-jupiter-8/









A



On 2 Aug 2022, at 3:57 am, Luís Marka via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>> wrote:



Hi guys,

I am giving a serious thought about building a Jupiter 8 clone, and started to take a deeper look at the schematics (actually I already ordered some of the parts, so it looks like I will get it done eventually). In the PSU there are three GP-30G diodes tied at the -15, +15 and +5V outputs, listed as "Hi-Fi Special" both in the schematics and in the parts list. I never heard anything about a "hi-fi special" diode, any idea what that means??

Cheers!

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