12/17/2005 Joe Fox has a video of his neon still in the box working perfectly with a circuit he designed.
Video is here.
Circuit design is detailed below.
Joe writes
Here is the diagram for the neon. It is simple and reliable.
The neon is not blindingly bright. (which I consider a plus)
I have not experienced any beading problems. Current draw is about 200mA standby and 2-1/2 Amps lit.
I don't like the addition of diodes to the neon circuit. They WILL shorten the life of the neon.
The electrode at each end of the tubes is a combination cathode/anode
On D.C. one electrode is always the cathode and the other is always the anode. This depletes the emissive material from the cathode twice as fast.
This circuit is A.C. so each electrode is a cathode 50% of the time. The circuit has very high strike voltage and limited current so your neon should last virtually forever.
I worked in lamp engineering for a number of years including cold cathode types such as neon, HID, and xenon flash.
I would NOT recommend the circuit for direct 120Vac operation.
During testing I discovered that only ONE of the ignition coils tested would work in the circuit when used on regular 120 Vac house current. (without the inverter)
ALL ignition coils tried (4 of various makes and ages) worked FINE when used with the 12-to-120 Volt inverter. I even tested several different wattage inverters. (95, 120, 400)
I was not satisfied until I found out why? An investigation with the oscilloscope revealed the answer.
Normal household current (out of the wall) is a pure sine wave.
Current provided by low cost inverters is invariably "Modified sine wave" The fast rise time and high peak voltage excites the ignition coil more efficiently.
If constructed as shown and used with an inverter the circuit is foolproof and reliable.
12/21/2005 James Collins offers his version 
A few months ago I said I would let everyone know how I was going to wire my neon mouth light. Well I have finished and I can send anyone interested a PDF drawing of what I wound up doing. Which wound up being close to what Craig Reinbrecht is doing.
My goal was simple. To have the neon light flash well with Dick Tufeld's modified voice. Very little or no neon beading effect. Work well at low and loud speaker volume settings. I used the Tech22 music adapter and the model 8000 power supply (like it seams most everyone else is using).
In examining the music adapter, I learned the following things
1) The output impedance is only 3000 ohms, which is a little weak for driving the TTL like input of the model 8000 power supply. This is almost a design error.
2) The output is also pulse width modulated (at low audio levels it gives a short full power pulse and at high levels it is on most of the time) and it has a gain control that permits the switching point to be set at low levels if needed and it comes from the factory set so that a very large audio signal is needed to activate it.
3) The robots voice is centered at about 250-300 Hz and the bass output is centered at 150 Hz and the mid-range is centered at 1,000 Hz. This means that for good activation for all words, not just the "BBBB" or "SSSS" sounds, the two outputs (bass & mid-range) would have to be mixed together.
First what I did was to adjust the gain control on the music adapter so that the unit switched full-on at 3 Volts RMS at 150 & 1,000 Hz. This means that when using an audio system driving a 8 ohm speaker, the light will come on at any level 1 watt or more. Then I used the schematic shown to lower the impedance and mix the two outputs together for driving the power supply. Then adding one or two 62 Volt zener diodes to remove any
beading effect and the system seams to work very well.
Thanks
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