Etherwave maximum input voltage

Hi all,

I've moved back to Australia from the US (where I got my Etherwave) and forgot to order a 220V power supply before I left. I know I can order one from the US (or Evilbay), but I'm pretty sure I can make one myself, which will be much quicker.

I saw that the schematic posted here: http://www.theremin.info/-/viewpub/tid/10/pid/58 has a regulator section in the circuit. The LM78L12 and LM79L12 should be able to handle about 35V, if I'm not mistaken. I can get a 17VAC adapter with an earthed output and connect it to the correct pins on a MIDI (5-pin DIN) connector.Here's a link to the AC adapter: http://www.jaycar.com.au/productView.asp?ID=MP3022&form=CAT2&SUBCATID=1000#12

Can anyone see any glaring flaws in my thinking?

Cheers, Pat

Yes there is a glaring flaw!!!

Theoretically, these voltage regulators (78L12 and 79L12) support 35V at their inputs, but their power dissipation (Vin - Vout) * (Iout + 2mA) may not exceed 300mW. An Etherwave Standard draws 30mA, so that (Vin - Vout) must not exceed 9.357V, that means that the input peak voltage may not exceed 21.375V.

That means that the AC Voltage may not exceed 21.375 / SQRT(2) = 15.1V

That's why Moog uses a 14V transformer which gives about +/- 19VDC at the big loading capacitors. There is a logic behind everything... ;-)

BTW: You do not forcibly need an earth/ground connection. It is enough to connect the Etherwave to an earthed/grounded instrument amplifier (most are). If you provide an additional earth/ground through the theremin's power supply, you create a ground loop which will add lots of unwanted buzz to your audio signal. That's why Moog's original power supplies for Western Europe come without earth/ground.

It seems that aussies don't say "thank you" or something similar... or perhaps they ask questions without really looking for an answer... I wonder why I made the effort...

I do apologise for the delay, it's been a hectic week and I haven't been able to check the forum.

Your answer makes perfect sense, thanks very much. My amplifier is indeed grounded, so that's not a problem, but if I run the Etherwave through my effects pedals and into my DAW that may not work. It's probably easiest just to order a 240V Moog power supply and be patient :)

hi! thanks for the information, in my case i have a moog theremin 

it use 14v 200Ma and recently i lost my supply,

im in argentina now and the price to order one to moog its really expensive, 45euro.

i tough to use a 12v 500ma will be ok for the moog theremin? 

or i can try a computer supply of 14v and 500ma?

i don't want to try, i think moog theremin don't have a fuse?

im going soon in france but the price to order tu usa still expensive,

thanks a lot!

fede

hi fedexmin,

welcome here,

if you understand schematics a bit and are able to solder, you can build your own psu. cheapest way. the theremin needs 14v AC and 200mA. the mA are not so much to worry about, but you can't use 14v DC, which most psu has as output. you also need to change the plug and use a common 5 midi-plug on which you have to remove the unneeded 2pins and solder all correctly together.

 a nice picture on moogmusic forum about power plug adaptor.

if this is above your head, better check for someone who understands that or buy the original one.

thanks Xtheremin for your answer, 

here in a shop in my city i found supply of 14V and 1.4a (1400ma)

understand about the plug, there is one the two pins thats go together.

so the question is if with 1400 will be ok for the theremin, using for long hours...?

thanks again, 

have a nice day =)

fedexmin,

1400mA are seven times more than the theremin consumes. good thing, the PSU won't get hot at all. the theremin just sucks the needed 200mA.

your new adapter is 14V AC? i just ask because you did not tell about that. i  hope you know the difference of AC⚡️DC.

Hi, I'm new here and just decided to build a Etherwave theremin.

However, I don't want to pay extra 50€ for adapter and want to make it myself. Is it enough to just make a simple 230 to 14 transformer to power it or are there other catches? And if it is that simple, is there a reason why a din connector is used instead of a normal one?

Thanks in advance for anwsers :)

Hello Cros:  "And if it is that simple, is there a reason why a din connector is used instead of a normal one?"

Should you not be sleeping right now, then again hanging with Americans can be fun, at least me.

Here in the states power supplies come with earth ground. The din was a convenient three prong plug to use. To me a 230 to 14 volt AC transformer is all you need but where are you going to find one?

Thierry might chime in as he might have mentioned a transformer to use in the past?

Are you building from scratch or the kit, a kit actually arrived at my door today. This new one I am going to see if I can break it.

Christopher