[sdiy] Power supply of a 19" rack

Frédéric (Opensource) marzacdev at gmail.com
Wed May 15 16:28:41 CEST 2019

Hi Rutger.

 >> I was touring as a musician I absolutely hated wall warts.

I totally get this, also their (cheap) cords tend to break at
the jack connector or at the junction with the wart.

I also experienced poor wart designs which are a real fire
hazard (just open a Mackie VLZ2 wart for great fun) which
consist in an unprotected (or merely protected) transformer
and wires. Short them, they heat up and burn their isolation.

I have some rack (old alesis reverbs / waldorf gear) using
warts and I haven't heard much complaint.

>> and plugging them into a socket may not be enough

I can provide a "Roland style" cable hook for this purpose.

>> You can design the rack unit for sufficient isolation from the PSU

That's true.

Funny you mentioned the Streichfett, I made the electronic
board and some of the DSP of it ;-)

Thanks for your feedback.

Le 15/05/2019 à 12:08, Rutger Vlek a écrit :
> Hi Frederic,
> When I was touring as a musician I absolutely hated wall warts. They get lost, damaged or unplug at the wrong moments. But my hate is specifically turned towards wall warts for instruments that get packed/unpacked frequently and sit quite prominently on stage. In that sense a 19” rack is different. My 19” rack is rather static, I don’t change it much and certainly don’t make changes while on the road. Also, the back side and power-supply (in whatever form) is well protected by the case the units are mounted in. So in that situation, I’m relatively okay with wall-warts, though there are a few considerations in 19” world:
> - some wall warts are heavy and plugging them into a socket may not be enough to keep them there during transport. As soon as they get on the loose inside a 19” case, they might cause problems/damage/unreliability.
> - radiation from wall warts…. I’ve always had some worries about interference between wall warts and sensitive cables or devices in my rack. I try to keep them as far as possible from each other. Of course you have the same with internal power supplies, but then you have a more controlled situation. You can design the rack unit for sufficient isolation from the PSU and you the casing can assure radiation will not leak to the outside world.
> All together I keep preferring a mains input, though for some devices (desktop units, e.g. a Waldorf Streichfett) it just doesn’t make sense.
> Rutger
>> On 14 May 2019, at 10:15, Frédéric (Opensource) <marzacdev at gmail.com> wrote:
>> Hi everyone.
>> I have not written here for a long time but I keep reading
>> the list because of the interest of the topics.
>> I am shared between two concepts for the power supply
>> of a 19" rack and I would like to hear your opinion both as
>> musicians and as instruments makers.
>> _Option A: mains_
>> Offering a regular 220V / 110V / 100V C14 input at the rack.
>> Inside:
>> pre-certified switched mode power supply (which adapt for all countries)
>> Pros:
>> * C13 cables are common and available
>> * No need for an external wall adapter
>> * Musicians seem to like this (my impression)
>> Cons:
>> * Certification process (more complex and costly)
>> * Design risks (mains inside / grounding / security for users and technicians)
>> * Big additional cost
>> _Option B: all in_
>> Offering a regular 2.1mm DC jack connector that can accept ANYTHING
>> like DC/AC from 6V to 16V.
>> Inside:
>> rectifier + small DC/DC converter or linear regulation
>> (depending on the consumption and dissipation of the circuits)
>> Pros:
>> * Everyone owns needless adapters that could be reused
>>     (= environment friendly / less e-waste)
>> * Less design complexity
>> * No mains inside the rack
>> * Simplified certification process
>> Cons:
>> * Need an external power adapter
>> * Need a power adapter that works for the region where the machine is used
>>     (simple wall transformers often cannot travel)
>> * Musicians don't seem to like it (my impression)
>> Question:
>> What would you prefer?
>> Fred.
>> PS: By the way, last hours for the Buzzzy! on Kickstarter:
>> https://www.kickstarter.com/projects/1304489933/buzzzy-the-digital-polysynth
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