Etherwave Plus Power Adaptor - Grounded or Not?

Posted: 6/7/2010 5:02:34 PM

From: Dundee, Scotland

Joined: 6/7/2010

Hi all,

Have just received my first Theremin - Etherwave Plus - and am still trying to get the hang of setting it up.

The manual seems to make a big thing out of the fact that the power adaptor is grounded and labours the point that if you plug it into an extension, it has to be "a three-wire extension cord which provides a good ground connection" for "the ground connection stabilizes the ETHERWAVE's operation."

What is confusing me is that the adaptor that came with the unit has a plastic prong for the earth and the pin-diagram on the label shows the middle pin as 'nc' which I thought meant 'no connection.'

Reason for my concern is that I am hearing a definite mains hum when I am listening through the headphone socket, although it's not obvious when connected to active computer speakers.

I am also hearing a distinct sub-harmonic through both outputs, which I'm sure has been mentioned before in the forum and linked to earth connections - although I can't find the thread now that I need it.

Should I be using an earthed power supply, or is it no longer required for the EW-Plus?
Posted: 6/7/2010 9:55:36 PM

From: Brooklyn,NY

Joined: 12/1/2009

The way it works with with the EW clones Ive built is if the theremin is properly grounded through the amp, using a grounded (3rd pronged) EW supply creates interference, a ground loop i guess.( as long as they are both recieving power from the same circuit, like plugged into the same outlet.) If you have an older ungrounded amp the grounded EW power supply is necessary to provide a path to true ground or else the theremin behaves strangely, out of tune, wierd harmonics, etc.
I've never tried, but I think many have trouble when playing through a computer, but I guess it works better that way for you.
When you play through the amp maybe try to plug the power supply (or the amp) into a ground-to-ungrounded electrical adaptor that accepts 3 prongs but just has two prongs on the male side.
Posted: 6/8/2010 7:12:43 AM

From: Colmar, France

Joined: 12/31/2007

They pretend that there should theoretically be enough "indirect" grounding through capacitive coupling between the mains transformer's windings. This is right in most but not in all cases. If the plug of your power supply allows it (different from country to country) you may try to reverse it in the wall plug in order to see if that changes already something since the "cold" side of the primary winding may so come more or less closer to the secondary winding.

When you are connected to a grounded amp you tell there was no hum. So you might try if hum on the headphone output persists if you stay connected to the (switched off but connected to mains) amp through the audio cable.

Finally one must admit that the headphone output of the plus kit is kind of an orphan, that means it is realized in a very simple and cheap way (as it is also on the much more expensive Etherwave Pro) and you should perhaps not insist too much on its qualities... ;-)
Posted: 6/8/2010 6:38:51 PM

From: Dundee, Scotland

Joined: 6/7/2010

Both - thanks for the responses. So I wasn't sent the wrong power adaptor then! Unfortunately both headphones and speakers I'm using have 3.5mm jacks and I only have one jack adaptor, so I can't try them both connected at the same time.

I'm just using speakers for now as I can't tune the pitch field wide enough with the headphones in - perhaps the cord is interfering? In any case I've decided to just live with it. Will probably turn it into a pitch preview at a later stage.

Thanks again.

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