[sdiy] Help with Jupiter 8 clone

[rburnett at richieburnett.co.uk]

There are good and bad SMPSUs.  I've been responsible for EMC compliance 
of products at several places I've worked over the years, so have seen 
examples of some very good supplies, and also some real shockers.  
Sometimes literally! (>.<)

I won't go into the details but certain supplies like flyback (wall-wart 
phone chargers) are notoriously noisy but you have to realise that they 
are made down to a target price, size and weight.  So they don't waste 
any money, space or weight on removing any more conducted and radiated 
emissions than they absolutely need to in order to achieve compliance 
whilst charging the battery in your cell phone!

One of the last bastions of the analogue linear power supply used to be 
in RF communications receivers because the harmonic spectrum of a 
high-power switcher used to put all sorts of "birdies" across the 
spectrum of a sensitive broadband radio receiver.  But these days even 
high-end radio receivers have switched-mode power supplies inside them.  
It just means that they are well designed and people have learned how to 
manage things like common-mode noise and stop it getting into the RF 
front-end or the audio output.

-Richie,


On 2022-08-02 17:50, Mattias Rickardsson wrote:
> Maybe it's possible to find some of those interference problems if you
> combine an old or unrefined SMPS design with the old original
> unshielded JP-8 PCB layout, but as a general "truth" it sounds quite
> false. :-)
> 
> /mr
> 
> Den tis 2 aug. 2022 18:23Tom Wiltshire <tom at electricdruid.net> skrev:
> 
>> +1 agree with Rob, evidence is definitely required for for such a
>> bold claim.
>> 
>> On 2 Aug 2022, at 16:51, rob hukin <rob at audiocircus.co.uk> wrote:
>> 
>> *citation required
>> 
>> rob.
>> 
>> On 2 Aug 2022, at 16:46, Josh Nursing via Synth-diy
>> <synth-diy at synth-diy.org> wrote:
>> 
>> 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> 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] 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> 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> 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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> Rob Hukin
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