Not yet !
Just as load for Mosfets . . .
In the very old time, it was common to add a small light bulb in parallel with the loudspeaker to produce some "expander" behaviour !
Yves.
Just as load for Mosfets . . .
In the very old time, it was common to add a small light bulb in parallel with the loudspeaker to produce some "expander" behaviour !
Yves.
I've been thinking, the light bulb has been in and out of audio/visual electronics for more than 25 years. I first saw it as a troubleshooting tool for high voltage DC switch-mode regulators in televisions back in the late 80's. Peavy prototyped an eq that had light bulbs on each tuning frequency to show peaks in the audio signal as a tool to spot positive feedback (was changed to leds in final design because of recovery time). crossovers used one to protect horns in stage monitors (still used today, but on below 500W designs). Guitar amps from time to time have them, but they were solid state based. and I saw the zen amp designs just a few minutes ago.
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I have played with the thaught of using some GM70 tubes (filament) for a DeLite-amp...(or Zen..)
Arne K
Arne K
Not yet, but doing some back of the envelope calculations with small (10W at 220V) bulbs they may actually sort of work. At 220V a 10W has about 5k resistance, pulling 45mA. Parafeed EL84?
light bulbs where used as plate load for tube burn in . a very bright bulb would indicate a shorted tube 😀
An ideal CCS (Constant Current Source) has infinite output impedance. A small light bulb will be a few hundred ohms -- pretty darn far from ideal. So for a CCS, it's not a good candidate.
Used as a plate load for wonky distortion effects may be another story.
~Tom
Used as a plate load for wonky distortion effects may be another story.
~Tom
They are not pure resistive and are not linear...... but they were cheap! I've only seen the in class A Mosfet follower apps.
An incandescent light bulb is not a CCS, not even close. It IS a nonlinear device with a positive resistance VS current characteristic. Its resistance INCREASES with increasing current.
This characteristic can be used to advantage. In fact it is what started the Hewlett Packard company. The Hewlett patent used the ordinary incandescent light bulb to stabilize the feedback path in an audio oscillator. This allowed a very low distortion ofer the entire audio range.
Try putting a light bulb in parallel with the cathode resistor in a vacuum tube output stage. The bulb shold be sized such that it does not glow, or glows dimly. This is the range where the nonlinearity is the largest.
This characteristic can be used to advantage. In fact it is what started the Hewlett Packard company. The Hewlett patent used the ordinary incandescent light bulb to stabilize the feedback path in an audio oscillator. This allowed a very low distortion ofer the entire audio range.
Try putting a light bulb in parallel with the cathode resistor in a vacuum tube output stage. The bulb shold be sized such that it does not glow, or glows dimly. This is the range where the nonlinearity is the largest.
I've played with 240v 25 watt lightbulbs (roughly 2k ohms) in a couple of parafeed amps and I like the sound they produce. In one of the amps, a 6V6 parafeed, I have switches so that you can use 2 bulbs and one 1k resistor as the load or a single 5k resistor as the load. They do sound different and my ears can easily hear the difference.
I understand the non linear aspects of the bulbs, but they are fun and worth trying once. They even flash with the music if that is your sort of thing. But as tubelab says, the bulbs are not a ccs, just a non linear resistor.
I have a long write up about my 6V6 amp here. (it even has George's Powerdrive)
6V6 Lumiere
The thing that puzzles me is why I prefer the bulbs to the resistor. I presume there is some sort of resonance but why that should translate into a more delicate open sound intrigues me.
ray
I understand the non linear aspects of the bulbs, but they are fun and worth trying once. They even flash with the music if that is your sort of thing. But as tubelab says, the bulbs are not a ccs, just a non linear resistor.
I have a long write up about my 6V6 amp here. (it even has George's Powerdrive)
6V6 Lumiere
The thing that puzzles me is why I prefer the bulbs to the resistor. I presume there is some sort of resonance but why that should translate into a more delicate open sound intrigues me.
ray
I know the lightbulbs are non linear, and I want to see what people can up with using this unusual varistor. Especially since power tubes tend to be non-linear devices forced to comply to the circuit parameters. maybe there is a dynamic complement. On another side note, I think there might be an application in line stage world with this device too: like a beer budget comp/limiter. but this is going to have to take some serious r&d.
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