[sdiy] Power supply for Big Briar Etherwave Theremin

Didier Leplae didierleplae at yahoo.com
Thu Jun 30 22:23:51 CEST 2022


 So, now I've opened up the theremin and it does indeed seem that pins 2&3 are connected to ground as indicated in the schematic from Fdiskc. 

The 14VAC is being converted to +12VDC and -12VDC with voltage regulators 78L12 & 79L12. So, I'd imagine going a little higher, to a 15VAC power supply wouldn't hurt anything.
   On Thursday, June 30, 2022, 2:25:14 PM CDT, Peter Pearson via Synth-diy <synth-diy at synth-diy.org> wrote:  
 
 Those are all DC supplies from the looks of it.  They're also barrel plug without a center tap.  You'll want a center tap.
And yes, you're basically looking at a transformer that plugs in the wall on one end and has a cable going to your synth on the other.  If you've ever cracked one open, you'll see that that's what's inside the box part.
https://www.youtube.com/watch?v=ue1-lnHVkpQ&ab_channel=FRY524

On Thu, Jun 30, 2022 at 3:11 PM brianw <brianw at audiobanshee.com> wrote:

Yes, they're still making them. Look for Triad Magnetics on Mouser.com
https://www.mouser.com/c/power/power-supplies/plug-in-ac-adapters/wall-mount-ac-adapters/?m=Triad%20Magnetics&number%20of%20outputs=1%20Output&output%20voltage-channel%201=13.5%20V~~15%20V&instock=y&rp=power%2Fpower-supplies%2Fplug-in-ac-adapters%2Fwall-mount-ac-adapters%7C~Output%20Voltage-Channel%201

I recently designed a phono (turntable) preamp, and I wanted to have a bipolar supply while avoiding 120 VAC. The AC output Triad Magnetics products work well. They have a wide variety of output voltages, and I bought an assortment to use with power supply design variations.
They don't seem to have 14 VAC exactly ... only 13.5 VAC and 15 VAC. You'd have to look at the specific components in the Theremin to see whether either would be compatible (e.g. maximum voltage ratings, potential consequences of under-voltage, etc.).
Brian Willoughby


On Jun 30, 2022, at 11:58 AM, Tom Wiltshire <tom at electricdruid.net> wrote:
+1 agree. An "AC supply" in this case is called a "transformer", surely?
I know they're a bit out of fashion, but I *think* they're still making them, so it can't be that hard to find one that'll get you from your local mains voltage to 14VAC. 200mA is basically nothing, so that's not going to be the hard bit. It looks like it needs a centre-tapped output, but those are common too, so it isn't difficult.
HTH,Tom

On 30 Jun 2022, at 18:56, brianw <brianw at audiobanshee.com> wrote:
I may be oversimplifying, but the vast majority of AC output "supplies" are nothing more than a transformer.
If you live in the 220 VAC 50 Hz part of the world, then you'll need a transformer rated for 200 mA that can convert 220 VAC to 14 VAC.
If you live in the 120 VAC 60 Hz part of the world, then you'll need a transformer rated for 200 mA that can convert 120 VAC to 14 VAC.
It's possible to design a power supply circuit that actually generates a 14 VAC sine wave at the proper frequency, with 3 W of output power, but I somehow find it doubtful that Big Briar did that. The Apple II power supply was renowned for synthesizing a 60 Hz wave, with feedback to increase or decrease the frequency depending upon the correct output voltage. This is why the Apple II made an audible chirp when the power switch was flipped. But that power supply was a lot larger than the Etherwave, and certainly more expensive.
Brian

On Jun 30, 2022, at 10:10 AM, Didier Leplae wrote:
I would imagine what’s indicated on your power supply must be correct. I also found another image online of a power supply and it had the same pinout. Perhaps the schematic has an error or perhaps there was another version. I should be able to open up the theremin and see if pins 2 and 3 are both connected to ground.
Now, does anyone have a suggestion for building a 14vac 200ma power supply? Or if I could find something with those specs I could put a 5pin din connector on it




On Jun 30, 2022, at 11:33 AM, Ben Stuyts <ben at stuyts.nl> wrote:


Oh bummer. Let me know if you want me to actually measure it. 

Ben










On 30 Jun 2022, at 18:00, Didier Leplae <didierleplae at yahoo.com> wrote:




Interesting because the pinout shown on your power supply is different than indicated in the schematic in the manual on fdiskc. There pin 1 is connected to power and pin 2&3 are connected to ground. I wonder if that means there were different versions?


















On Jun 30, 2022, at 10:43 AM, Ben Stuyts <ben at stuyts.nl> wrote:






Here’s a photo of mine. Funny, the MIDI warning on the label.
The connector on my Etherwave is a 5-pin connector, so the power plug can be either 3-pin or 5-pin.

Ben
<PSU_Etherwave.jpeg>




























On 29 Jun 2022, at 22:46, Didier Leplae via Synth-diy <synth-diy at synth-diy.org> wrote:








I have an opportunity to buy a Big Briar Etherwave Theremin from a friend for cheap. The only problem is it is missing the power supply. Searching online, I find a lot of Moog Etherwave power supplies.Does anyone happen to know if these are compatible?The power plug on the Big Briar unit is a 5-pin midi style plug. Pictures of the Moog power supply look like 3 pins. https://www.bigcitymusic.com/products/power-supply-115v-us-for-etherwave-theremin
I’m wondering if they just simply removed two pins and the three fit in the midi style plug. If not compatible, does anyone know where to get a hold of the Big Briar supply?





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