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Under Construction

The Basic Board Build

- This webpage is about recapturing the original classic theremin sound -

Raw Sample.wav 
buzzy bottom then intimate, no thin whistle

 This theremin design is a beginning to be improved upon, hopefully to grab the attention of today's youth!

The theremin is about plowing through the 10,000 reason it "will not properly" work before you find success. Do not post your 9,999 non-working reasons at TW, do not clog up the google database. The theremin is a personal journey we each choose and can only hope from the start to one day find success.


Valery S starts with a better construction February 8, 2019

 


The pitch & volume boards are connected together through the J2 TRS jack. 12 volt power normally goes to the volume board first then passes a regulated 9 volts through J2 TRS jack to the pitch board. 

These are the original boards the new boards are developed from. The new are shortened from 8.2" to 200mm (7.8") and the power jack on the volume board rotated to the rear for better adaptation to the EWS box. The original black TRS jack is seen under V-Null


I noticed from this photo the wire pulled out above the F.

Ant-V volume control is very sensitive and would never be connected directly to a volume loop, use the loop more as a prop. The blue wire is maybe 8" in length and sensitive out to 24" for a very wide or narrow volume window.

A. Experimental - There are two areas that the main thermal drift originates, one is the oscillator transistor junctions and the second is the temperature change in the environment around the pitch antenna. I have observed placing the connecting wire to the B antenna in a strategic spot can offset some drift. This is about 1/4 the distance up from the base, needs more testing. When you find the ideal spot fold the spring over to spread out the loops and run the connecting wire down the center. The spring coils should move freely on the 1/4" wood stick and inside the plastic sleeve.

B. This gold cap will hide how the spring coil is suspended at the top of the tube. 

C. If you look closely you can see the 15" stick pressing the inside of the mounting end coil.

D. A small piece of the 1/4" stick is glued to the inside of the plastic sleeve to suspend the spring coil.

E. This is the L4  3.3 mh high Q choke connected directly to the base of the spring coil and earth ground. It has about 5 ohms of dc resistance, amazing it does not ground out the entire operation, instead magic happens, perfect pitch field linearity of any width.

F. I call this a 1.5" tickle wire, connected at terminal T1 B, one on each board fine tunes for the proper wave shape. The idea comes from my radio background and experimentation.

G. The b-antenna creates a stronger capacitive pitch field and this pitch side shield limits feedback to the fixed oscillator. Also it protects the L3 mixer/detector combo which is at a very high impedance from picking up 50/60 Hz hum. This method of mixing combines the inductive field from all the surrounding inductors. L1 L2 L4

H. This is the volume side 1.5" tickle wire, fold back around by L1 as seen, this will fine tune for the proper wave shape.


Seen are the four potentiometers, Pitch Null, Volume Null, Timbre, Mute adjust. These would replace the pot holes if you are using the EWS box.

The between board connecting TRS cable can be 1.5' in length if you are using the EWS box.

Having the Volume Control separate from the Pitch section allows others to design even more creative approaches.

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1.14.19 Last update

This Phoenix 2020 Theremin webpage is under construction

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