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Hey,
I recently saw the use of a "magic eye" tube.
Essentially it has a section within the tube that glows green and becomes
animated when different voltages are applied to the grid:
EM71-HM71
I found this one in my tube stash and had no idea what it was for, until I read a brief mention of one at:Beavis Audio Research
(about 8 pictures up from the bottom of the page).
So here's what I've worked out:
Power/heat the tube with the power transformer in a tube amp.
Tap the high voltage AC with a 220k resistor, a diode to make it negative, and a pot to ground as a variable resistor to send 0 down to -20 volts to the grid.
Here's the fun part...
add a photocell to the 2 lugs of the pot and use a small lamp across the speaker terminals the generate pulses of light that trigger the negative voltage to shift, thus animating the tube.
There was another thread on the placement of one, is it possible to add a diode to the speaker terminal to conduct the negative voltage?
Thought I might put this one in an amp as a space age visual display. Thoughts?
-Dave
I recently saw the use of a "magic eye" tube.
Essentially it has a section within the tube that glows green and becomes
animated when different voltages are applied to the grid:
EM71-HM71
I found this one in my tube stash and had no idea what it was for, until I read a brief mention of one at:Beavis Audio Research
(about 8 pictures up from the bottom of the page).
So here's what I've worked out:
Power/heat the tube with the power transformer in a tube amp.
Tap the high voltage AC with a 220k resistor, a diode to make it negative, and a pot to ground as a variable resistor to send 0 down to -20 volts to the grid.
Here's the fun part...
add a photocell to the 2 lugs of the pot and use a small lamp across the speaker terminals the generate pulses of light that trigger the negative voltage to shift, thus animating the tube.
There was another thread on the placement of one, is it possible to add a diode to the speaker terminal to conduct the negative voltage?
Thought I might put this one in an amp as a space age visual display. Thoughts?
-Dave
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