The equivalent thermal conductance goes like T**3, so it responds hundreds of times faster at 2700K vs. 300K.
Plus the rolloff is only one-pole, and heat is generated throughout the filament at the same time, so there's not much thermal conduction delay.
Cheers
Phil Hobbs
In the hard sciences, there is a simple way: Try it yourself!
If it works, it's not lie.
GE made some silicon transistors encapsulated in a tan-colored epoxy. Not for long! (I guess not for long in tan epoxy, and not for long making transistors.)
None of the old tube giants made it into the semi business.
I did the same as a junior high-school science project. The transmitter was a flashlight bulb fed by a D-cell in series with the output of a radio. The receiver was a selenium solar cell and an amplifier. It sounded pretty good.
I've read that a car headlight can be audio modulated, but I've never tried that.
Good grief, are you proposing experimental verification of scientific theory and simulation? That's pretty radical.
It absolutely works. I did it also. I used spotlight bulbs. On one, I drilled a hole in the back and put the phototransistor at the focus of the bulb.
I did the same think around the same time. Mediocre, but it did work. IIRC "Popular Electronics" had an article describing this around this time.
On Monday, August 29, 2016 at 7:08:02 AM UTC-7, Mike Perkins wrote: ...
...
For the first few years they use a translucent gel that allowed you to use them as a phototransistor but Mullard then started using an opaque white (or blue in some cases) gel that prevented that.
Supposedly it was to stop people purchasing the OC71 at 6/6d rather than the OCP71 at ~25s.
I bought my first OC71 (maybe only?) around 1961 when I was 10 and it was filled with the translucent gel.
kevin
Well, RCA did for awhile.
Cheers
Phil Hobbs
Linear Systems (I think) has an application note which shows how to use a long-tailed pair made from one of their dual monolithic very-low-noise JFETs (the "tail" is a discrete current source) as the input section, then feeding into a low-noise op amp which provides additional gain and the RIAA equalization.
I confess to doing the same, though the distance was more 1" than 10m.
I also used a light dependent resistor rather than an photo transistor and more than a decade or so later!
I used a small 12V 2W bulb and the frequency response was indeed very limited, but sufficient to be intelligible.
Sure. So did GE and Sylvania and Transitron and Motorola. But none lasted.
GE makes good jet engines and locomotives.
Using a diff pair just adds noise. Lots of people are enamored of diff pairs for no good reason.
Wire they enamelled?
NT
On Monday, August 29, 2016 at 1:17:39 PM UTC-7, John Larkin wrote: ...
...
If the output of the amplifier is DC coupled to the speaker you need a fairly low offset voltage at the front end to avoid current through the speaker.
kevin
PA voltage gain is usually pretty low so IOS isn't generally a problem.
It might be "Gigabit Film'.
Cheers
Agreed but you couldn't tolerate the 0.7V of a single-ended input stage. I've never seen a PA with DC coupling on the output with anything other than a diff-pair at the input.
kevin
The mathematicians - theoretical physicists - like to test the internal self-consistency of a theory before they let the experimental physicists lose to spend money on experimental verification.
This is a bit more complicated than John Larkin can follow - he skipped the relevant lectures at Tulane, and doesn't seem to have learned anything useful since then.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required