So you shouldn't use a guitar amp?

Posted: 7/13/2005 8:37:29 PM

From: Winston-Salem, NC

Joined: 6/30/2005

I just bought one for practice - a Fender 15R.

It's a nice little amp, good looking and very portable. But I have recently heard that I should have gotten a keyboard amp. I understand that it is a problem with input levels.

How much of a problem? If I need to throttle the theremin down, I am wondering about using an effects unit of some type to do it, with the added benefit of coloring the sound to get more of a string or woodwind character. Another benefit is that I can use it with my other, larger amp - a Peavy Backstage Plus (35w).

I'm playing (sorta) on a Big Briar Etherwave ki.
Posted: 7/13/2005 9:24:49 PM
Jeff S

From: N.E. Ohio

Joined: 2/14/2005

You heard correctly. The Etherwave (and Etherwave Pro) are line level instrument and are a bit hot for guitar amps. Keyboard amps are designed to handle a hotter signal.

Is it a problem? Somewhat, but not a large one. At the very least you will have to keep the controls on your guitar amp turned way down.

Also, consider that some guitar effects can also increase the gain of the signal going into the amp. Can you control the input with the effects? Probably. I have a reverb/delay unit I may have damaged by running my Etherwave Pro through it.

If you're going to use guitar amps and effects it might be worth it to consider cutting the output of the Etherwave itself as described in the Hot-Rodding manual you may have received with your unit. It involves simply replacing the 4.7k resistor (R33) with a 47k resistor. It occurred to me that you could even install a switch so you could switch between the two resistors and have a high and low level output. The best of both worlds!
Posted: 7/13/2005 11:05:34 PM

From: Winston-Salem, NC

Joined: 6/30/2005

Right! RTFM!

I had forgotten about the hot-rod manual. I couldn't find it, so I downloaded it from the Moog site. I think I'll take your advice and set up a switch on it. I think if I keep the leads as straight and short as possible, I won't have problems. I'll probably also need to keep everything well away from the antenna ends of the instrument.

Posted: 7/14/2005 12:11:25 AM

From: Hillsborough, NC (USA)

Joined: 2/13/2005

So, related to this... what about running a theremin through an effects pedal designed for a guitar? Any problem with that?

Pardon my ignorance ;) I don't use effects, so I don't have much experience in this department.
Posted: 7/14/2005 9:32:50 AM

From: Winston-Salem, NC

Joined: 6/30/2005

Using an effects pedal was one of the tricks that I was thinking about - I'm sure some of the Moog effects units have been tried before. I ran my theremin through an equilizer last night and was able to color the tone somewhat, but the cord I was using had a short in it, causing a buzz, so I didn't leave it hooked up long.

I'm thinking now that, rather than modifying my circuit board, I could make an adapter plug to go on the end of my guitar cord with the extra resistance in-line with it. I'll need around 42 ohms.

If I can't find something close enough to that value in fixed resistors, maybe I'll try a small pot. The value probably isn't critical, but I don't want to cut the voltage back too much. I'm stopping by Radio Shack on the way home today....
Posted: 7/15/2005 9:22:03 AM
Charlie D

From: England

Joined: 2/28/2005

A good guitar amplifier will suffice for low-volume practice and performance, but if you want to crank up the volume and perform onstage then you really need a PA speaker/amplifier or a keyboard amplifier.
The main advantage with guitar amps is that they usually have reverb built in- and this can strengthen the sound of the theremin, which can sometimes be quite weak and thin.
Posted: 7/15/2005 7:01:10 PM

From: Undisclosed location without Dick Cheney

Joined: 2/21/2005

I didn't know what I was doing when I bought my amp, so I bought a guitar amp.

My experience with it is, it works, although I need to keep the volume on the amp set very very low. Also, the Theremin overdrives it very easily... what this means is that my volume control isn't nearly as expressive as it should be: instead of a full range of possible volume, it's more sort of on-or-off.

My guitar amp also makes it sound a bit shrill.

In contrast, I brought the Etherwave to a friend's place, who is a professional musician who knows what he's doing, and he hooked it up to his amp. Wow, it sounded so rich and vibrant! And the volume control was so *expressive*! A good amp made a world of difference.
Posted: 7/16/2005 12:31:32 PM
mike j

From: long beach california

Joined: 7/16/2005

I got an etherwave 2 weeks ago and have been playin thru a fender 15 watt bass amp.I could not get decent sound or range with it.I just last night got a roland kc60 keyboard amp. WOW now my theremin is a whole new instrument. I can now find 6 octives and play basic scales.I hope to get halfway decent with it someday.Not an easy instument,but a very exciting one.
Posted: 7/16/2005 6:11:25 PM

From: Winston-Salem, NC

Joined: 6/30/2005

Well, put the extra resistance in the cord, but I don't think it has changed the situation much - I still can't turn it up very much. I may not have read the schematic right.

So, as much as I like this beautiful Fender amp, I'm going back to the music store on Monday to see if I can swap for a Peavey KB-1. I think I'll take the Theremin with me this time (probably have to put on a show - REALLY not ready for that!) and try it out first.

And I'll have to buy a new cord, also,,,,
Posted: 7/16/2005 8:09:52 PM
RS Theremin

From: 60 mi. N of San Diego CA

Joined: 2/15/2005

Hello User,

"Well, put the extra resistance in the cord, but I don't think it has changed the situation much - I still can't turn it up very much."

You need two resistors as a voltage divider configuration. Before you void your warranty go buy and try this 6.5' Attenuating Dubbing Cord for $4.29.

You probably need 1/8” to 1/4” plug adaptors.

Radio Shack

Record from a line-level output! Connects earphone jack from radio, cassette or CD to recorder's input or mic jack 1/8" phone ...

User, this may reduce the signal level more than desired and put you on the quiet side. I don’t know what a guitar amplifier requires for a voltage input but it should work, if it does let us know!

Good Luck,


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