Let's say you're building a modern SS preamp and styling it with vintage looks. Hammered paint finish, NOS bakelite knobs, neon pilot lamp etc. It occurred to me the ultimate vintage look would have a couple tubes sticking out the top of the chassis or visible through a window. Their only purpose would be to glow romantically as tubes do; they'd not be part of the audio circuit whatsoever. Consider them the "power on" indicator 😛
Cheap to purchase and implement are important as these only need to glow; sonics won't matter. Are rectifier tubes what I should look at? I'm assuming they would be simplest in this application as AC power for the filaments could come from a suitable transformer? Powering the filaments only and ignoring the other pins will provide the desired look?
Since the tubes are only heated and not driving anything I wouldn't generate any noise into the environment of the SS preamp circuit, correct?
What ideas do you have?
Cheap to purchase and implement are important as these only need to glow; sonics won't matter. Are rectifier tubes what I should look at? I'm assuming they would be simplest in this application as AC power for the filaments could come from a suitable transformer? Powering the filaments only and ignoring the other pins will provide the desired look?
Since the tubes are only heated and not driving anything I wouldn't generate any noise into the environment of the SS preamp circuit, correct?
What ideas do you have?
Just saw the other day, a Dayton amp where the tubes were illuminated from the bottom with orange colored LEDs.
That's nasty. Especially blue led below tubes. Or green mcintosh, blah.
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Behringer was heavily critized for putting orange led behind mic tube pre. Lots of people disliked the gimic.
This would be cheap and easy as I could use dead tubes, but I really want the heaters themselves to glow as opposed to an LED in the base.
6AS7 and 5U4GB seem to be good choices thus far as they're relatively cheap with heater voltage of 5-6V.
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In 1930's ... 1960's equipment the valves are usually not sticking out, you only see them through the ventilation holes or slots. They do stick out in 1920's battery-powered radios with directly heated bright emitter valves, but it would be a waste to use those.
Remember, whether 6 or 12 volt, you may have to have 500-600 ma of current, depending on tube. LED, not so much.
I used to have big russian rectifier tube on my headphone amp, i believe 5u4g, where you could nicely see glowing heater wires going up and down.
Nice to look at, lava red hot.
Nice to look at, lava red hot.
My favorite is the OD3 gas, Shoulder glass envelope version. Purple glow.
One resistor, one series diode, one OD3. Simple & pretty.
You can even use it to provide regulated 150V to a low plate voltage tube, cathode follower, or a medium voltage pentode screen.
Since this is for a solid state preamp, there probably is not enough voltage to run the OD3 . . . Unless you use a series resistor, series diode, and OD3 from the power mains (220VAC will work; 120VAC probably will not be enough (170V peak).
For a different look, try some of the lower power direct heated RF transmitting tubes that use Thoriated filaments.
One resistor, one series diode, one OD3. Simple & pretty.
You can even use it to provide regulated 150V to a low plate voltage tube, cathode follower, or a medium voltage pentode screen.
Since this is for a solid state preamp, there probably is not enough voltage to run the OD3 . . . Unless you use a series resistor, series diode, and OD3 from the power mains (220VAC will work; 120VAC probably will not be enough (170V peak).
For a different look, try some of the lower power direct heated RF transmitting tubes that use Thoriated filaments.
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I also really like the voltage regulator but I believe you won’t get any glow from the internal gas if only the 6.3V are powered.
I could be wrong though. Talking about transmitting tubes, here’s the 807 😀 in total darkness.
I could be wrong though. Talking about transmitting tubes, here’s the 807 😀 in total darkness.
e-fortier,
Float the series resistor, diode, and OD3 across the 220V mains power input, not the DC power supply.
It will flicker at the mains power rate.
Add a full wave diode bridge, capacitor, and get DC Volts; eliminate the flicker.
You will only get shocked if you grab the tube, break the glass, grab the metal, and . . . you are grounded
Float the series resistor, diode, and OD3 across the 220V mains power input, not the DC power supply.
It will flicker at the mains power rate.
Add a full wave diode bridge, capacitor, and get DC Volts; eliminate the flicker.
You will only get shocked if you grab the tube, break the glass, grab the metal, and . . . you are grounded
So remember>> Never leave the amp on (using an extension cord of course) and attempt to run down a dark stairway. You may get shocked.<<<
6AS7 has visible heater, but needs 6.3V @ 2.5A - an extra 16 watts plus transformer losses. For small tubes, 6J6 has exposed heater and uses a fraction of the power at 0.4A each. But I like the idea of VR tubes - can run directly off-line with a capacitor as current limiter and full-wave bridge for no extra heat generation.
Great ideas guys but keep in mind the basic needs are: CHEAP to implement, robust and GLOW. These tubes would function as nothing more than lightbulbs so the cost of the tubes themselves and the circuit required to run their heaters are the most important factors. At the same time for this project my conscience won't let me put hours on any tube that someone else in the world needs to place in their project and make sing. I'm considering widely available affordable types only.
So far 6J6 is the front runner as it's common, will glow and has small current requirements for the heater and thus a far smaller transformer needed to power the heaters= CHEAP.
You tube amp guys already know the cost is always in the iron and the glass.
So far 6J6 is the front runner as it's common, will glow and has small current requirements for the heater and thus a far smaller transformer needed to power the heaters= CHEAP.
You tube amp guys already know the cost is always in the iron and the glass.