Read this first - Modifications Made to PCB Board-3.04.20

1. None of the corrected holes need to be drilled or the switches installed.   S1 is eliminated S2 could be a panel mount toggle switch for mono/stereo otherwise it is not needed for single channel sound into your computer. It seems to drive the computer speaker woofer needs the ring connection. S3 is eliminated S4 is eliminated S5 is eliminated You might want to enlarge the 2200uf capacitor holes with the Mouser .040 drill bit but it will still fit in the snug holes.

2. You might want to enlarge this hole in the four TRS jacks pads between 2 & 5 with a 1/16" drill bit - the blue wire is audio out for testing - 3. Pitch Board Only: Fold the transformer mounting tabs underneath. The transformer center wires are not needed and can be cut off and it can mount in either direction. Notice how I offset the transformer to give room. Mount the big components last. Update 8.18.20                Board  3.04.20         To find a part use Ctrl-F Cut PCB copper trace before starting. see fix #1 - Hello Sage, I hate troubleshooting but I will be your Pilot - Do the best you can At the bottom of every webpage is a see through 3.04.20 board image to better understand what is connected to what. I put the power supply on the Volume Board so it fits in the EWS box, it is much better for it to be on the Pitch Board which is the board you should start with. This avoids issues with the TRS J2 board to board loose jack connection disruption in the middle of a performance. Print This List: Stuff Resistors first, then Capacitors. In order from left to right.   Stuff Sheet PDF 8.22.20 - Updated Oscillator section is the board 3" x 3" left side, Audio is the right side 5" of the board. This outstanding product keeps your solder pencil tip in perfect condition Amazon Bold parts are values changes, different than indicated on the 3.04.20 board. Underlined parts on PDF list are not on 3.04.20 board, they are specially mounted after the board is stuffed. A Part on the PCB or PDF with a Line through it is not mounted at this time unless stated. Mount board resistors: Osc: R5- 10K, R6- 10k, R15- 10K, R19- 10K, R23- 330K, R8- 3.3k, R20- 3.3k, R24- 1M, R21- 1M R25- 220 ohms, R9- 470 ohm, R30- 100 ohm Audio: R37- 1K, R7- 1K, R18- 4K7, R26- 2K2, R1- 1K, R40-1K, 1K, R41- 470 R33- 10 ohm, R14- 100K, R13- 1M, R11- 47K, R16- 100k, R12- 470k, R17- 100K R29- 22 ohms, R4- 470, R3- 100K, R10- 100K, R34- 100K see Fix #2, R2- 220k R38- 470, R31- 33K,  R27- 470 ohm, R32- 100K, R22- 2K2, R28-10K, R38-10K, R39-10K After resistors mounted, use an ohm meter to verify values. This will save you time in the long run. This image is the latest as of 8/20/20, the 3.04.20 board will need these modifications Blue is a value change, Red are parts not on 3.04.20 board, will be added later. click on image to enlarge better image to locate a part 8.22.20 That vertical gray line shows where the board could be cut apart. There is an advantage in keeping the oscillator section separate from the other parts on the board that generate heat like the regulators. The oscillator section needs shielding to block interference from Pitch Antenna feedback to the the L2 oscillator. This causes un-wanted distortion in the audio signal or prevents you from getting the deeper throaty vocal sound. Not on the 3.04.20 board but on the latest updated board are three of these. These are switch contacts that can be used or bridged with solder to complete the circuit. I will explain elsewhere in what they allow in the Phoenix theremin design. Mount board Capacitors: Update 8.20.20 Osc: C20- .1uf, C3- 100pf, C16- 47pf, C17- 10pf, C27- .1uf, C30- 47pf, C38- .1uf, C19  C13- 47pf, C23- 47pf, C31- 100pf, C7- 100pf, C18- .1uf, C22- 47pf, C8- .1uf, C36- .1uf Audio: C28- 10uf, C11- 1uf, C25- 10uf, C21- 10uf, C6- 10uf, C49- .1uf, C15- 10uf, C35- 10uf  C33- 10uf, C14- 1uf, C5- 1uf, C1- 1uf, C37- 1uf, C4- 10uf tantalum direction is markings facing 555 IC C2- .1uf, C32- 1uf, C34- 1uf, C26- 10uf (C29- 470uf, C9- 1000uf, C10- 2200uf ) <= mount these last  330uh shielded coils        View Coil orientation in board photos before mounting L1 & L2  542-8250-331K-RC       5.10 ohms     SRF=7.3 MHz     Q=65 L1 & L2  652-9250A-334-RC       6.4 ohms       SRF=6.5 MHz     Q=55 L3  3300uh   L4 & L5 3300 uh, the high current type, less than 5 ohms or it will not work. - Now go to the Oscillators to Complete and Test Them - Pot-1-  5K trimmer       D1 & D2- 1N914        D3 1N914        D4 & D5- 1N4007 Pot-1b 10k Timbre sine to vocal adjust panel mount Wave shape on the EWS, Pot-5- 10k Pre-Amp Pot-3- 1K paralleled by R9- 470 for thermal drift control, Pot-2- 50K Experimental, may  not be used. Pot-4- 1K paralleled by R25 220 ohms panel mounted or use EWS 5k. Both Pitch Null & Volume Null Mount the L1 & L2 coils after all the Oscillator parts are mounted. Pitch Board = 900 kHz & Volume Board = 750 kHz not critical. See coil mounting angles in picture. View Coils Mount the L1 coil along with the L4 & L5 choke/coils along with a 10" or 25cm antenna connecting wire for a temporary antenna. Then dial in with extra capacitance in the green terminal next to L1 until 900 kHz or close +/- 20 kHz is achieved.  Start at a higher frequency as the Pitch antenna will drag the frequency lower.  It is better to not use probes in the oscillator section. Use the extra 330 uh, similar to L1 & L2 as a sniffer coil to sense frequency connected to a frequency counter. View Pic The L2 side C19- 47pf is not used, use a felt tip pen and mark a line across it. The L2 oscillator will still work using the Var-5 variable capacitor but at a much higher frequency. Try different values of capacitors (22pf) in the green terminal on the left side of L2-330uh coil to match the L1 oscillator frequency.  Tune Var-5 the variable capacitor and see if you hit the sound of heterodyning and then Zero-Beat at ~ 900 kHz on Pitch Board.  This will need re-adjustment when the Pitch Antenna is installed. Using the 5pf variable capacitor from Amazon makes hitting Zero Beat much easier. An oscilloscope works best for monitoring the ideal audio wave shape. Take the audio signal from TP-2 or the left side wire on the transformer next to the board edge. The audio can also roughly be monitored with an "analog" AM Radio listening for the actual heterodyned signal in the static around 900 kHz. The goal on the Pitch Board is with L1 at "900 kHz" and adjust the L2 oscillator frequency using a specific capacitor value in the green terminal next to it to bring it home. The board you select to be the Volume Board has everything the same except try for 750 kHz, this freq is not critical at all as long as it does not affect the Pitch side sound. Also the Volume Board uses U2a slightly different for a pre-amp to bring up the audio signal level before the Vactrol.  8.24.20  Go to the Volume Board for more board info

The Phoenix will fit in a defective EtherWave Standard box

On the left is a $24 new meter I purchased for this project. It measures inductance, capacitance, resistance and important for thermal drift control the ability to measure hFE which might be used to reveal a transistors sensitivity to heat or room temperature change. Without touching the transistor so it remains at room temperature measure the hFE and lay them out as I want two that are identical or close. Mouser sent the transistors on an ammo strip, this is better than random grabs.

Two transistors from the same batch can seem ideal but act all squirrelly in theremin design, try two others. I believe the MPSA42 transistors I use have an advantage. Try and match their HFE number as seen below.

I plan on mounting the IC sockets for all the boards given away and give you the VTL5C1 Vactrol.

3.30.20

I packed all the envelopes, they are black on the left. Should send by way of USPS tomorrow. Funny that is USPS postal service driving by in the background.

I separate the resistors, capacitors and inductors by placing them in their own plastic baggie. As expected, missing from the parts list was the Pot-3 1k potentiometer. It is now on the parts list. 

Also seen is my $10 UV flashlight. This has several practical applications like see the silkscreen and where the cat peed.

Before anyone orders the parts list x2 it is better to let me finish stuffing the board first.

3.31.20

Stuffing the single board is about three hour project. 

Discovered the four switches have the wrong footprint. An "oh shit" moment but figured out a reasonable work around. You must drill eight holes in each board, drill bit is with the Mouser order. I ordered the switches from Jameco Electronics so I will also send those to you. The original switches have been removed from the parts list for now. View how to correct this on the Index webpage. I need to update Gerber Files and PDF Toner transfers.

Originally the footprints at .1" was correct, they were out of stock until August 2020 so I changed them.

4.01.20

Use a magnifying glass to inspect your soldering and part values.

Because of the footprint error I had to substitute switches from Jameco Electronics . Some new holes need to be drilled. I will add a .9mm drill bit to the Mouser parts list and "give" you 8 switches to adapt to the two boards if you choose.

- None of the switches are needed -

Switch S2 you might want as panel mount toggle so you can easily switch the TRS Jack next to it from mono to stereo to feed into your PC. All the other switches could be replaced with a jumper wire once you have a full build and decide what works best.

I have always considered my theremin as an experiment, that is why I use so many of the green 5mm terminals. I like to make quick changes as I develop things. Once you have a configuration you like you can use soldered solid wire connections instead of terminals which is better.

The two green terminals off the left side of the board allow me to test different Inductor behavior before they are soldered permanently into place. They also allow for a place to add extra capacitance when you want the Pitch board frequency to lower down to be a Volume Board.

I use inductor L3 to pick up the L1 & L2 magnetic fields which are mixed in the D1 diode. 

My two RF oscillators do not need buffering as they have no component connection between them, just earth ground. Between the circuits L1 & L2 magnetic fields will interact with one another. This can be controlled by the amount of current driving the coil and the L1 & L2 & L3 coil orientation to one another.

The transistor emitter current determines the strength of the oscillator RF inductive fields. Too much you could get over coupling between the oscillators which causes unwanted distortion or too strong of a heterodyned mix.

This L3 inductive approach is unique and original. It allows me to control the amplitude and mix of the magnetic fields to get the best heterodyned audio wave shape out of the D1 diode.

The D2 diode is a future experiment. This allows for a second channel using the audio section of another board and mixing it back into the final audio for possibly a much fuller or interesting sound.

4.03.20

On the left side of the board are two other types of 330 uh chokes I want to test. They mount on the left side in the green terminals. I use an original method of mixing the RF of the two oscillators using induction coupling. This avoids the need of any type of buffering to get the proper wave shape on the low end.

The board can still use 360uh IF transformers but variety allows more 330uh workable inductors.

- Right click and open the image in a new tab for a close up look -

Notice the components not stuffed on the board for this first test. No big caps, regulators or IC's.

- The fixed ferrite coils that look like big resistors in the green terminals on the left side I like so far -

The capacitor standing up from the green terminal I use as a connection point for a temporary 9 volts to the board, normally this is a 9 volt output for accessories. The green terminal directly above facing to the left is 5 volts output for accessories.

When first applying power, watch for excess current through the board, if things are good it is about 2 ma.

I wanted to change the emitter resistor from 4.7k to 2.2k to get more range at Pot-4. By accident I replaced it with a 22k so now I want to continue on and see if anything of value will be discovered by this extremely reduced emitter current, before I correct it. 

- This project is the true meaning of serendipity -

This first test we are only powering the two RF oscillators on the left side of the board. You must have the antenna properly setup and connected. Earth ground connected is a must.

Using a meter that can measure frequency, take the signal from the ungrounded end of the L3 - 3300 uh choke. The Q1/L1 side frequency should be from 850 kHz to 920 kHz. (900 kHz is ideal) Measuring the frequency anywhere else you will load down the circuit and stop oscillation. 

On the L2 oscillator wrap a 100k resistor to the tip of your red probe and measure your frequency at TP-4. 

I use an "analog" AM radio tuned to around 900 kHz and listen to the blank spots in the background static while finger touching the L1 & L2 coils. If the Q2/L2 oscillator is out of range of matching the frequency of the Q1/L1 oscillator you want to add or remove capacitance from the Q2/L2 side. One thing that can cause this mismatch is circuit variables like the 10% tolerance of the coils, etc.

Nice LC Frequency Calculator

In the picture, lower left corner, you can see I changed the yellow C19 - 47pf to the blue 39pf capacitor to raise the frequency of the Q2/L2 oscillator slightly. Now I think 33pf + 22pf variable capacitor on the L2 side with L2 choke. Always have the pitch antenna setup as it adds up to 10pf to balance the circuits.

With the L2 choke soldered in place use the L2 green terminal for capacitor substitutions.

For finding the proper L2 frequency extra capacitors are added to the list. 10pf, 22pf, 33pf, 39pf, 47pf

I will put a red circle around a few spots that are tricky with close soldering. The 10uf tantalum capacitor next to the 555 socket has a difficult to see + plus marking to get its direction correct. If backward it will short out and the larger 10 ohm resistor next to the 7805 regulator will overheat.

I use the MPSA42-AP 300 volt transistors for a slightly better sound and thermal drift control. I changed the R8 & R20 4.7k resistor to 2.2k. If you must use a 2N3909 NPN you might want to keep the 4.7k for less range with Pot 4-1k. If you need even less swing when Nulling with Pot-4 1k it can be paralleled at R25 with a 470 ohm. The fact that the MPSA42-AP reduces the Pot-4 range tells me the transistor will be less sensitive to thermal drift.

Thermal drift is reduced by the choice of transistor and matching the hFE values. Then balance the current through the two transistors using the 1k Pot-3 at the bottom of the board. At first set it half way so it matches the R9- 470 resistor value. With this method you can actually reverse the direction of drift were the Pitch can drift in the other direction.

The natural theremin sound is a wave shape as seen on the scope with the proper bends and curves here and there. It is not the mixing of saw tooth waves with sine waves and what not, that is more like mixing noise.

.5 msec/div     10 mv/div

This clean audio signal is un-amplified measured after the detector diode, taken at pin-2 of U1 LM358

My original heterodyne method allows for the ideal mix, shape and amplitude of the audio signal after the
 detector/mixer D1 diode. I can increase the raw audio signal amplitude up to 500 mv, not desirable.

Visit the Special Pitch Electrode 
Electrodeum Pitch Antenna

This gives me the ideal Pitch Field Linearity

This was my first unique theremin discovery in the beginning, I looked upward and said "are you serious"

- above these two lines is the new build progress as I go, build started 3.27.20 -

The 10 light tan capacitors on the left side oscillator section are 47pf, except C7 & C31 are 100pf, C19 22pf

Mouser Parts List
List is for a Single Board Construction

Always Check Parts List For What is Out of Stock!

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