Etherwave Standard - Volume issue on mic stand

Hi there,

I've been playing around with a Theremini for the last few years and have been reading through this website as a helpful resource throughout. I've recently decided to get a 'proper' Theremin and have managed to source an Etherwave Standard after much searching as the model is currently listed as discontinued on all official Moog dealer websites in the UK.

I purchased the pre-assembled Etherwave Standard a few days ago and initially played the instrument on the edge of an ironing board while I sourced a microphone stand. The Theremin seemed to tune fine (roughly 12 o'clock for the pitch and 10 o'clock for the volume) and the volume antenna was fully over the edge of the board. The instrument made a constant noise even if my hand was nowhere near the volume antenna as long as I was in range of the pitch aerial.

I've since attached the Etherwave to a microphone stand and the pitch seems to tune roughly the same but the volume antenna now works in reverse (it reaches its loudest when my hand is in the centre of the antenna and is silent if my hand is around 6 inches away. Any movement of the volume dial seems to have little effect. If I place one hand just underneath the volume end of the cabinet and use the other hand on the volume antenna it works as expected again (it becomes quieter as one hand gets closer). I wondered if anyone could advise what I may be doing wrong?

-I've let the Theremin 'warm up' for 15+ minutes
-I've plugged it directly to the wall and also through a surge protector into a different socket (UK mains)
-I've tried it in the centre of the two biggest rooms in the house (I live in a small house so there's probably just over 1m clearance before any objects)
-I've plugged the output into a bass guitar amplifer connected to a surge protector (whilst the Theremin in either plugged into the wall or the same surge protector as the amp)
-I also tried headphones directly into the line-out
-I've had the Theremin for three days and the weather has become much warmer and less humid than the previous week or so

Is there an obvious thing that I haven't tried yet?

I'd be really grateful of any advice and look forward to reading through the techniques and recommendations on this forum.

Many thanks,
Danny

First, you need to ground the theremin with some wire to the water heating pipes or a large metal object. Then check all settings. They will change. Alternatively, you can use a long shielded cable to the power amplifier. If the response of the loudness antenna is reversed, it will be necessary to adjust the volume generator coil with a red screwdriver, carefully turning its core to the right or left to achieve the desired direction of flow and sensitivity.

I purchased the pre-assembled Etherwave Standard a few days ago and initially played the instrument on the edge of an ironing board while I sourced a microphone stand. The Theremin seemed to tune fine (roughly 12 o'clock for the pitch and 10 o'clock for the volume) and the volume antenna was fully over the edge of the board. The instrument made a constant noise even if my hand was nowhere near the volume antenna as long as I was in range of the pitch aerial.

By "noise" do you mean the desired sound or is it unwanted noise like interference?  The term "noise" usually refers to a bad thing in theremins...

I've since attached the Etherwave to a microphone stand and the pitch seems to tune roughly the same but the volume antenna now works in reverse (it reaches its loudest when my hand is in the centre of the antenna and is silent if my hand is around 6 inches away. Any movement of the volume dial seems to have little effect. If I place one hand just underneath the volume end of the cabinet and use the other hand on the volume antenna it works as expected again (it becomes quieter as one hand gets closer). I wondered if anyone could advise what I may be doing wrong?

Is the theremin properly grounded either through the mains power (if you have earth ground on mains where you are) or some other means?  It sounds like the volume side is functioning alright but it may be shifted in tuning a bit internally) so that it requires a little extra capacitance from your second hand.  You may not be doing anything wrong, and when you were playing on the ironing board you may have been getting a little loading (equivalent to what your second hand is doing) from the ironing board itself.

-I've let the Theremin 'warm up' for 15+ minutes
-I've plugged it directly to the wall and also through a surge protector into a different socket (UK mains)
-I've tried it in the centre of the two biggest rooms in the house (I live in a small house so there's probably just over 1m clearance before any objects)
-I've plugged the output into a bass guitar amplifer connected to a surge protector (whilst the Theremin in either plugged into the wall or the same surge protector as the amp)
-I also tried headphones directly into the line-out

These are all good diagnostic steps, so no fault there.

-I've had the Theremin for three days and the weather has become much warmer and less humid than the previous week or so

Both humidity and temperature will affect tuning somewhat but the changes should be within the tuning range for both the Pitch and Volume controls provided the theremin is/was properly tuned for average conditions in the first place.

Is there an obvious thing that I haven't tried yet?

Maybe try going back to the ironing board setup that you had initially to see if it still behaves the same way.  Is this a metal or all-wood ironing board?

I'd be really grateful of any advice and look forward to reading through the techniques and recommendations on this forum.
Many thanks,
Danny

It sounds like you aren't doing anything obviously wrong, but first retrace your steps to see if grounding is good and to convince yourself that under normal conditions the theremin wants/needs a little more capacitive loading on the volume loop side (either from your second hand, nearby metal, or even a lot of wood/fabric/padding from an ironing board top can provide this).

If you confirm this, then it would seem that you might need to tweak an internal inductance adjustment.  But first, if this was purchased new, contact Moog and describe the problem and get their blessing/advice on the adjustment.  They supply those little red tuning tools with the theremin so that you can maintain this yourself over time, but contact them anyway.  It's an easy adjustment but without equipment you need to record your adjustments so that you don't get lost.

If you bought it used then it's up to you.  Come back when you're ready and I or someone will point you to the information you need.

Thank you both for your advice!

First, you need to ground the theremin with some wire to the water heating pipes or a large metal object. Then check all settings. They will change, Alternatively, you can use a long shielded cable to the power amplifier.

I've tried looping a piece of steel wire around a radiator pipe and placing the other end against the control panel. I've also tried looping it around the lineout jack and there doesn't appear to be a noticeable change in the volume field. Would this suggest that the theremin is already grounded and internal adjustment may be required?

By "noise" do you mean the desired sound or is it unwanted noise like interference?  The term "noise" usually refers to a bad thing in theremins...

Apologies for the ambiguous terminology. Yes, it's producing the expected sound rather than 'noise'

Is the theremin properly grounded either through the mains power (if you have earth ground on mains where you are) or some other means?  It sounds like the volume side is functioning alright but it may be shifted in tuning a bit internally) so that it requires a little extra capacitance from your second hand.  You may not be doing anything wrong, and when you were playing on the ironing board you may have been getting a little loading (equivalent to what your second hand is doing) from the ironing board itself.

I'm in the UK so I believe we have the earth ground (3 pin plug)? Assuming that I followed Valery's instruction correctly, would the fact that there was no change with the steel wire suggest that it's already grounded?

Maybe try going back to the ironing board setup that you had initially to see if it still behaves the same way.  Is this a metal or all-wood ironing board?

I've tried the original setup on the metal ironing board and it seems to be working again as expected. I've noticed that it's nearly impossible to get the instrument to silence more than 1cm or so above the antenna with the volume dial turned fully anti-clockwise. At the other extreme I have to put my hand a fair distance through the loop to get it towards silence and I hit what seems to be the equivalent of the zero beat and it jolts and starts increasing again before it ever becomes completely silent

If you confirm this, then it would seem that you might need to tweak an internal inductance adjustment.  But first, if this was purchased new, contact Moog and describe the problem and get their blessing/advice on the adjustment.  They supply those little red tuning tools with the theremin so that you can maintain this yourself over time, but contact them anyway.  It's an easy adjustment but without equipment you need to record your adjustments so that you don't get lost.

I purchased it new from a shop that is closing so I will see what Moog suggest. The adjustment tool was not included in the box so I think I will need to request this from them anyway. Are there any major risks to DIY adjustments? It reminds me of the fear I felt when adjusting a guitar truss-rod for the first time haha.

Thank you again for your help!

The volume control actually adjusts the strength of the antenna's response. You need to adjust at the 12 o'clock position for a distance of 5-10 centimeters to the volume antenna. Turning to the right decreases the distance and makes the attack sharper, turning to the left increases the distance and makes the attack softer. Setting up with a plastic screwdriver is not difficult, but you need to have an original red tool. Usually new terms are sold with it.
[color=#3c4043][font=Roboto, "Helvetica Neue", Arial, sans-serif]If, when grounding with a wire, touching the metal part of the plug with your finger does not cause any changes (the tone is almost preserved), then the grounding is done correctly.[/font][/color]

Sorry for the font and symbols ...

The information below is supplied to use at your own risk, and preferably with the blessing of someone at Moog support.  They may have alternate instructions in which case you should follow them.

If you didn't get a plastic tuning tool you need to track down one of these: https://www.coilcraft.com/en-us/tuningtools/ or an equivalent.  The only part you need is the small plastic hex end that is about .075", and it doesn't have to be a Coilcraft tool.  These are generally available from most electronics distributors.  Don't buy the one on eBay for $30!

Using a metal hex (Allen) driver is not recommended because it can crack the ferrite slug easily if you tip it.  Metal also affects the tuning but with the cover off and your hands nearby you have to tune by feel anyway.  The general procedure for tuning the Etherwave involves rotating the appropriate tuning slug a fraction of a turn (like less than 1/8 turn), then replacing the cover and checking your progress.  You don't need to replace all the screws, but don't be surprised if you do see a slight change when you finally do tighten them all down.  Be aware that the presence of the cover has a huge effect on tuning, so you always need to make your final assessment with the cover on.

Quoted below is an excerpt from a volume tuning procedure that seems to work but this is intended more for tuning from scratch if you should ever get completely lost. 

Your tuning just needs a slight adjustment, so I would center the Volume knob, make a small turn to L11 (write down amount and direction), replace the cover and check your progress.  If it's worse, return the slug to the original position and then make the ~1/16 to 1/8 turn in the opposite direction, and check the results.  Always write down your changes so that you can get back to the original position or close to it if needed.
 

 If all else fails and you get lost:

Set the volume knob on the control panel to 3 o'clock. Stand as far to the right (pitch side) of the unit as possible, so you are away from the volume antenna.

With the unit powered on and hooked up to amplification, reach over with the trimmer tool and start turning L11 through its range.

Somewhere in the middle, you should hear a sound start to be audible, reach a maximum loudness, and then die off again.

Turn the lug back to the point where the sound is loudest. This should put it in the correct range, to where the sound is silent when your hand approaches the antenna and them becomes louder as you draw away; additionally the Volume knob should be set correctly such that it controls not the actual volume but rather the hardness or softness of the volume curve; meaning how quickly the sound reaches maximum loudness as you draw your hand away. At the clockwise extreme it should have a brighter, sharper attack and at counterclockwise the volume should increase smoothly and slowly as you draw your hand away from the volume antenna.

L11 is the rectangular metal can in the upper left just below the power connector.  You can see the ferrite slug with the hex hole in the top opening:

If you have to order a tool and you want to try something else while waiting for it, you might just add some aluminum foil or foil tape to the wire extending from the circuit board to the left in the picture (running to the loop antenna).  This will add a little capacitance and might bring it into a usable  tuning range.