[sdiy] Help with Jupiter 8 clone

Wed Aug 3 11:11:57 CEST 2022

Here we go again. I have a Huge mixing board in my studio, a Soundcraft Vienna 40 channels. It was a touring FOH board in the 90s that cost 10s of thousands and I bought it for €800 a couple of years ago. It has 2 massive power supplies. One is a CPS 550, a 2 rack space unit that puts out a pair of +/-17v rails. The other is CPS 750, a 4 rack space monstrosity that puts out -17, +17, -7.5, +7.5, +48, +24, +24. Together they weigh like 50kg. The rails are something huge like 5A or more each. If I switch them on at the same time the breaker in the room blows. I could cook eggs on top of them. Naturally, I looked into the idea of replacing them with something modern and down the rabbit hole I went. There is a whole scene for guys with SSL, Neve, etc. replacing the power supplies (which if you have never seen them are 20 rack spaces 50cm deep or something) with hip, small, efficient, expensive supplies like this https://www.atomicinstrument.com/ <https://www.atomicinstrument.com/>
The website from Atomic Instruments is filled with celebrity engineer testimonials about how much better the SSL sounds now because of this great supply and how finally the owners can turn off their boards at night, saving untold fortunes in electricity. What’s missing from the discussion is the fact that these are obviously switching supplies. Do you think that if the snake oil salesmen would mention this that the noisefloor would suddenly get higher and the bass would suffer?

Incidentally, I couldn’t get anyone to supply me a simple replacement for my supplies and still live in fear f turning them on. I guess I could build something from SMPS units, but I don’t know much about it. Maybe the only thing separating the Atomic supplies form the off the shelf units is the connector and the LED displays on the front. Do you think the display is reading the voltage at the board or in the rack? ;)

Mark

> On Aug 2, 2022, at 5:56 PM, Mike Bryant <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/ <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/ <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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