[sdiy] Tubes in Synths [ was : Harry's Nightmare! ]

[Mike Granger]

Alex:

The NE-58's are neon discharge lamps which are a glass filled with Neon 
gas and contains two electrodes separated by about an eighth of an inch. 
They are open circuits until the voltage across them exceeds the firing 
voltage (about 70 volts) and then they conduct abruptly and emit an 
orange glow. They were used for indicator lamps in many devices before 
LED's came on the scene.
In the circuit you have referred to, I believe they are used to limit 
the voltage across the plate ofthe third triode and the control grid of 
the fourth one. Thgis is similar to what you might do with two 
back-to-back zener diodes in a solid state circuit.

alex dickey wrote:

>>On a related note, I found a schematic for an old tube opamp which
>>is I think one of the first packaged opamps made.
>>http://www.themusic.net/schematics/tube-opamp.gif
>>
>
>can someone fill me in on what the NE-58's are?  i've never seen that
>symbol before.
>
>thanks,
>alex
>