James Jacobson's Theremax Mods

Hi all

Does anyone have any information on the modifications that James Jacobson made to the Theremax? http://www.thereminworld.com/gal_jamesjacobson.asp

I am building the theremax currently and I would like to increase the pitch liniarity.

After reading what James wrote (below) i think the mods would be very helpfull to find out what he did.

[i]I didn't care for the Paia case or antennae, so I decided to make my own. As you can see from the photos, I made the top of the case hinged for easy access to the tuning coils. Also visible in the photos are the Etherwave-type sled feet, and a microphone stand on the underside.

I modified the circuit to suit my particular taste. The original circuit gives the Theremax around 9-10 octaves in a short control range - this makes it very difficult to accurately play notes, and the extreme upper register is fairly unmusical. So I changed the operating frequency in order to decrease the operating range to approximately 5 octaves. This has a positive effect on playability. Furthermore, I added a inductance coil in series with the pitch antenna in order to get a linear pitch response. In addition, I replaced the Paia wire pitch antennas with rod-type to further improve the control ranges.

I also changed the values in the low-pass filter and timbre control, and added coupling to the LC ciruits in order to tweak the sound.

I am happy to report that the Theremax is now very playable, and has a better linear response than a standard Etherwave, although it is not as linear as my Etherwave pro, unfortunately. [/i]

Regards

Tim

I am in the early stages of building a Theremax too. I plan to put a large induction coil with multiple taps connected to the pitch antenna through a rotary switch, and use a friend's oscilloscope to discover what the various settings will do for linearity (and maybe frequency). Hoping for the best, but will have to wait and see. I bent antennae out of 3/8 inch aluminum tubing, 0.035 inch wall thickness that turned out pretty well, I think. Plan to start on the box next.

JAMES! HELLO-O-O-O! JAMES JACOBSON?! ARE YOU OUT THERE?
Personally, as aTheremax owner, I think that the 'extra' inductance,(coil), that JAMES JACOBSON,(?!), built into his T-Max probably was too large and kept the Theremin from being properly tuned.
The standard tune range that is playable is about five octave without all of JAMES JACOBSON's 'I'm special' electronic postering. Did you ever find any soundfiles from JJ on Theremin World? When was JJ's last post?
I guess I'll have to look!

Good Luck!

teslatheremin

I tried looking for posts made by James but it seems there is none. The main reason I was impressed by what James had done was the statement he made saying that the theremax was now more linear than his Etherwave Standard. I suppose all we can do is just some trial and error with the a Pitch linearisation coil. Since i'm terrible at mathematics and most electrical theory I'll just experiment

Tim

I was rather suspicious of what JJ said about the original range of his Theremax--it just didn't sound right. I'm going to experiment too. BTW, I found an "easy touch" on/off push button at Radio Shack last night that fits into the hole for the mute jack; I think a mute push button will be much more to my taste than another cable coming out of the panel for a foot switch (and cheaper too).

Alan...
The only backside of placing a switch in the T-Max mute jack hole, would be the lack of speed to silence the Theremin. One, would have to hold their volume hand in the 'silence' position on the volume antennae,(or rod, as some Thereminists point out), and use the pitch hand to depress the mute switch.
The mute pedal is just a switch housed in a box wired to a length of phone cable with a phone plug at it's terminus. The cost to make such a device cannot be that much more than the 'Soft Switch' available at RS.
But, to each his own; one could incorporate the mute switch into the front panel of the T-Max and see if it fits his needs. One, can always change the configuration of the T-Max as is necessary. That is the PAiA T-Max Theremin's ultimate strength.

Good Luck!

teslatheremin

Tesla--I was thinking of using the mute only when not playing, e.g. during warmup or standby You seem to be thinking of another purpose that is rather unclear to me. An alternative suggested to me by the folks at PAIA was a plug with a microswitch in it, but with the only parts I could find, that would be rather obtrusive.

My goodness, this is an old thread.

I can't remember the values of the mods offhand, I will see if I can hunt them up.

Hello!
Is this James Jacobson?
Good Luck!
TT

Ummm, "good luck" with what exactly?