[sdiy] Power supply for Big Briar Etherwave Theremin

[Didier Leplae]

It sounds a little like guitar amps I used to have that would have a ground lift switch. Sometimes there was less noise with and sometimes better without. 

> On Jul 6, 2022, at 11:10 AM, Mr&MrsAccount <hbissell at wowway.com> wrote:
> 
> 
> I used to have a Big Briar Theremin and often ran it on a two-wire extension cord. That obviously negates any "earth ground" on the pin.
> I never had an issue with function, so maybe there are cases where an earth ground is essential... but I didn't find one.
>  
> Harry Bissell
>  
> From: Peter <synth-diy at synth-diy.org>
> To: Roman <modular at go2.pl>
> Cc: synth-diy <synth-diy at synth-diy.org>
> Date: Wednesday, 6 July 2022 9:21 AM EDT
> Subject: Re: [sdiy] Power supply for Big Briar Etherwave Theremin
> 
> I looked at Didier's pic and yes the center pin specifically says "earth ground".  I'll admit that I got out in the weeds here, however the ebay link I had sent earlier also says GND on the center pin and has the added benefit of already being a DIN plug.
>  
> https://www.ebay.com/itm/303827582131?hash=item46bd88fcb3:g:9D0AAOSweuFf6gew
>  
> I fail to see how this is a worse option than cutting a barrel plug AC adapter and wiring it up yourself.
> 
>> On Wed, Jul 6, 2022 at 4:55 AM Roman Sowa <modular at go2.pl> wrote:
>> Exactly, it must be "grounded" in a sense of "earthed", and not 
>> "center-tap".
>> If you connect center-tap transformer there, it will not be grounded, it 
>> will be floating. And also it will be very hot, because ground pin on 
>> the socket is shorthed to one of AC pins.
>> 
>> You need a link from earth protect prong in your AC outlet to one end of 
>> your supply.
>> It all becomes so clear when you look at power input schematics on page 4
>> 
>> Do what Gordon says
>> 
>> Roman
>> 
>> W dniu 2022-07-06 o 08:05, Peter Pearson via Synth-diy pisze:
>> > https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf 
>> > <https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf>
>> > 
>> > Read page 8 of the service manual where it says - and I'm quoting here - 
>> > "*WHY IS THE POWER ADAPTER GROUNDED?*"
>> > 
>> > On Tue, Jul 5, 2022 at 7:04 AM Gordonjcp <gordonjcp at gjcp.net 
>> > <mailto:gordonjcp at gjcp.net>> wrote:
>> > 
>> >     On Thu, Jun 30, 2022 at 02:41:07PM -0400, Peter Pearson via
>> >     Synth-diy wrote:
>> >      >
>> >     https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf
>> >     <https://manuals.fdiskc.com/flat/BigBriar%20Etherwave%20Service%20Manual.pdf>
>> >      >
>> >      > The schematic is here.  A DC supply won't work.  The theremin
>> >     might be
>> >      > fussy about grounding though, so you'll definitely want a
>> >     center-tap on
>> >      > your power adapter.  I wouldn't recommend trying to cheat a
>> >     barrel jack AC
>> >      > power adapter in there.
>> > 
>> >     If you look at the power input circuit, there are only two
>> >     connections.  There's nowhere for a centre-tap to go.
>> > 
>> >     It's a simple transformer fed into a pair of half-wave rectifiers,
>> >     same as the various crappy modular PSUs that are kicking around.
>> > 
>> >     Everyone is making this waaaaaaaaaaaaaaaaaaaaaaaaaaaaaay more
>> >     complicated than it needs to be.
>> > 
>> >     A 15V transformer will be fine.  It doesn't need a centre tap. 
>> >     Anything over 200mA will be fine.
>> > 
>> >     -- 
>> >     Gordonjcp
>> > 
>> >     _______________________________________________
>> >     Synth-diy mailing list
>> >     Synth-diy at synth-diy.org <mailto:Synth-diy at synth-diy.org>
>> >     http://synth-diy.org/mailman/listinfo/synth-diy
>> >     <http://synth-diy.org/mailman/listinfo/synth-diy>
>> >     Selling or trading? Use marketplace at synth-diy.org
>> >     <mailto:marketplace at synth-diy.org>
>> > 
>> > 
>> > _______________________________________________
>> > Synth-diy mailing list
>> > Synth-diy at synth-diy.org
>> > http://synth-diy.org/mailman/listinfo/synth-diy
>> > Selling or trading? Use marketplace at synth-diy.org
>> >
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
> Selling or trading? Use marketplace at synth-diy.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20220706/420d5561/attachment.htm>