11–20 of 75 posts
This is an interesting topic, but the ads overlaying the content make this very hard to read :( * Please don't suggest I install an Ad blocker.
That's a cute little article. The key diagram is the one that shows the signal path through the amplifier. Input feeds grid, plate feeds next grid, final output is from plate. Everything else is supporting circuitry. Note that between each stage there's a capacitor in the signal path. That's to block DC. If you want an amp that amplifies DC, each stage has to run at a higher voltage than the previous stage. The plate…
You can also stick a voltage divider (and probably some diode clamping) in there to pull the signal off of the plate down to a grid compatible voltage for the next stage if you're just doing digital computing. That was the most common setup I've seen in tube based computing. They tended to play pretty nice with the resistors needed for the plate current anyway so it wasn't that much extra RC constant delay.
it's a bit weird that I never thought about it before this, when I already had the facts in my head: the triode tube amplifier was invented by Lee de Forest, but he had no idea how it worked or even what it was capable of. then 45 years later, the solid state transistor amplifier was invented, and they had no idea how it worked either. for people who have not had much EE education, what is important about triodes and…
> he solid state transistor amplifier was invented, and they had no idea how it worked either. That cannot possibly be true. Not knowing what exactly is going on with the charge carriers at the subatomic and quantum levels is not the same as not knowing how the amplifier works: like if we fiddle with the voltage at the base, we can influence the collector current, and all the rest. What is true is that some early tra…
That's a cute little article. The key diagram is the one that shows the signal path through the amplifier. Input feeds grid, plate feeds next grid, final output is from plate. Everything else is supporting circuitry. Note that between each stage there's a capacitor in the signal path. That's to block DC. If you want an amp that amplifies DC, each stage has to run at a higher voltage than the previous stage. The plate…
> Note that between each stage there's a capacitor in the signal path. That's to block DC. If you want an amp that amplifies DC, each stage has to run at a higher voltage than the previous stage. The plate must be above the grid in voltage. This was a huge headache in tube computers, both analog and digital. You can also stick a voltage divider (and probably some diode clamping) in there to pull the signal off of the…
Earlier quoted context omitted.
> Note that between each stage there's a capacitor in the signal path. That's to block DC. If you want an amp that amplifies DC, each stage has to run at a higher voltage than the previous stage. The plate must be above the grid in voltage. This was a huge headache in tube computers, both analog and digital. You can also stick a voltage divider (and probably some diode clamping) in there to pull the signal off of the…
That won't help with the power consumption though, I guess. (Or is that a rounding error compared to everything else?)
I'm trying to keep my tube computer I'm building down to ~3KW, and that's probably the biggest actual constraint on design complexity.
Earlier quoted context omitted.
> he solid state transistor amplifier was invented, and they had no idea how it worked either. That cannot possibly be true. Not knowing what exactly is going on with the charge carriers at the subatomic and quantum levels is not the same as not knowing how the amplifier works: like if we fiddle with the voltage at the base, we can influence the collector current, and all the rest. What is true is that some early tra…
Radio Shack sold PA amplifiers with an output transformer well past the age of the tube, like the MPA series, e.g. MPA-40, a 20 W mplifier. On that thing you can obtain the raw amplifier output using the "70V" terminal. Then it has a number of through-the-trafo outputs labelled with nominal ohmages of speakers. The Owner's manual extols the advantages of using transformers for speakers and describes how to use the 70…
https://www.atlasied.com/speech-privacy-speakers?srsltid=Afm...
I had a 1971 Marshall tube amp land in my lap, for free. I'm not a guitar player, but wanted to get it fixed it up before either selling it or learning guitar. There's a lot of "magic" there - the amp guy asked if I wanted to swap the tubes for some "more authentic" tubes that were used in England at the time. Pro tip - don't ask the internet for advice for making your tube amp sound nice, you'll get every opinion po…
Earlier quoted context omitted.
Radio Shack sold PA amplifiers with an output transformer well past the age of the tube, like the MPA series, e.g. MPA-40, a 20 W mplifier. On that thing you can obtain the raw amplifier output using the "70V" terminal. Then it has a number of through-the-trafo outputs labelled with nominal ohmages of speakers. The Owner's manual extols the advantages of using transformers for speakers and describes how to use the 70…
Sound masking systems still use 70V audio output with output transformers at each speaker, voltage drop is rough when your signal is only a few volts and you’re using small conductors. Last time I sold a sound masking install we used 14/2 cable for the 70V audio signal. https://www.atlasied.com/speech-privacy-speakers?srsltid=Afm...
The cost is fidelity. Full-range audio transformers aren't cheap, so these systems usually make some compromises because your announcements or smooth jazz over the pasta aisle don't need to be true hi-fi.
Its cool technology. Most of the speakers have variable power taps, so you can run a bunch of them in parallel on a single line and control the actual volume as-needed based on where the speaker is deployed by varying the transformer tap on each speaker.
Just his list of 5E3 mods (Fender Deluxe) is awesome: