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Hi Guys
New to the forum, thanks for having me.
New to tubes as well, and really enjoying the whole thing.
I've been doing quite a bit of reading online of how tubes work.
I think I have the technical basics down but still don't fully understand how different tubes can affect an LP's sound.
I'd love to study a diagram that shows in layman's terms the journey of the sound signal from needle to speakers. Has anyone done this?
For instance, when the music signal hits the tubes, how is the signal affected, to sound warm or harsh or whatever?
A few of the lengthy papers I've read have summed it up as "magic" and a "mystery" at how it all works out. If that's the truth, then I have no problem with it. Just curious.
Thanks C
Follow Ups:
Simple: Electrons passing through a vacuum rather than silicon sounds better. I liken silicon to the sound of a ceramic capacitor-BAD.
They have never shown much interest in SS, but tubes are another story?
Steve
Two very good books that can help you are:Theory and Application of Vacuum Tubes, Reich
www.tubebooks.org/Books/reich.pdf
Materials and Techniques for Vacuum Tubes, Kohl
http://www.tubebooks.org/Books/Atwood/Kohl%201960%20Materials%20and%20Techniques%20for%20Electron%20Tubes.pdf
Both have understandable explanations of actions of electrons in tubes, various materials, etc.
I've read several chapters many times. I'm getting there. Where, who knows. I question why I enjoy reading this stuff. I generally do not like to sit and read.
"I can't compete with the dead" (Buck W. 2010)
"It would take me forever. I don't think I have forever" (Byrd 2015)
Edits: 04/18/16
Byrd, I totally know what you mean. Not completely sure why this stuff interests me. I think its because there is magic and mystery and the end result is something beautiful and worthwhile.
"I'd love to study a diagram that shows in layman's terms the journey of the sound signal from needle to speakers. Has anyone done this?For instance, when the music signal hits the tubes, how is the signal affected, to sound warm or harsh or whatever?"
Well, to start with the music signal from the phono cartridge goes to ground across the grid resistor of the first tube. That's it, it's done.
That AC music signal voltage is present on the grid of the tube and that causes the current that's flowing in that first tube to increase (on the positive half of the music signal) and decrease (on the negative half of the music signal). You can think of it this way, the music signal on the grid of a tube is constantly changing the bias of condition of the tube causing the current that's flowing through the tube to increase and decrease.
When the current flowing through the first tube increases, the voltage drop across the plate resistor (the resistor between the plate of the tube and the power supply) increases so there is less voltage at the plate of the tube. When the current through the tube decreases there is less voltage drop across the plate resistor so there is more voltage at the plate of the tube.
When we strip away the DC voltage (by using a coupling cap) what's left is an AC signal that is like the signal that came from the cartridge but at a higher AC voltage. (this is amplification).
That larger signal will also go to ground across the grid resistor of the next stage (the next tube in the circuit) and cause that tube to change it's current draw across it's plate resistor.
So each stage recreates the input signal that it "sees" at it's grid.
The first stage "sees" the signal from the source (cartridge, CD player, ect.) but the second stage "sees" the signal that the first stage created caused by the source signal being present on the grid of the first stage and so on and so on.
The output signal of a stage will look very much like the input signal (only larger) if the tube is linear and if the tube is being 'operated' in a linear way. The "operating condition" of a tube includes the voltage from the plate to the cathode, the current running through the tube at idle and the total impedance* that the tube is playing into (* the value of the plate resistor in parallel with the grid resistor of the next stage.
When we get to the output stage of a circuit the plate load is an output transformer instead of a plate resistor and the output stage's job is to increase the current delivery capability so you can drive a loud speaker (current amplifier stage vs. a voltage amplifier stage).
If you get all the operating conditions of all the stages correct then the output of the circuit as a whole can look very much like the original input signal to the first stage (low harmonic distortion, little or no loss or exaggerations of the frequency extremes, etc.).
That was a very brief version of a very long story.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/17/16 04/17/16 04/17/16
Tube Acolyte and Tre', thank you for the replies. I'm going to have to re-read them a few times, to get my head around it, but it seems very clear. I'll follow up on your info suggestions, looking fwd to it. Really great, thanks guys!
As to why, or how two identically functioning tubes affect music, don't think any one knows? but that they do is undeniable!
I suspect, since I lack an adequate understanding of it, that the root of the conundrum is our concept of what "an" electron is? Is it a nice finite little corpuscle of energy? One concept of light has that view.
Of course, the problem could be rooted in how an electrical signal jumps the synapse in my brain cells?
Tin Man bob
Never assume anything I post is accurate.
Well, to have a gander at the question(s), you're biting off a lot. But, if you have time to chew, you'll get through it.
When it comes to the "magic", there's a lot going on. Mainly, from what I've read and experienced, it boils down to a few distinct features of tube amplifiers:
-They're fully analog devices. Transistors react differently. For X in, you get Y out in each case, but tubes are "on all the time, ready for a change" whereas transistors operate at a set frequency (not sure, but I think it's in the MHz range). While that switching speed is REALLY fast, a pure analog signal gets parted and blocked into millions of pieces every second, instead of playing in one smooth motion in a tube.
-While it depends on the circuit, tube amps often lend to even-order harmonic distortion. This works out into that "magic", the "warmth", and the "life" a lot of people talk about.
-Once you've done a little reading and digging, you'll run across something called "grid current". Grids are that essential piece to any audio tube, and the control grid (grid 1) is essentially for setting a tube's "bias". In small signal tubes like AX7, AU7, and AT7 types, this can vary from -2 to -10 volts. For a given input signal into a tube's grid, there's a point where the peaks will cause the grid's voltage to approach zero volts. In most cases, the grid never actually reaches 0V as the grid resistor effectively eats the extra signal. In oldschool guitar amps, this translates into overdrive. In hifi, you get a natural form of compression. Throwing around some arbitrary numbers, with a bias set at -2, a perfect 1.6V AC signal into the grid would cause the grid to see swings between -0.4V to -3.6V. A song can most generally float around 1.6V, but it may contain transients going up to 2 volts. Those transients don't disappear or squarewave like in a transistor amp, they compress and remain apparent in the sound.
As good starter material, find these readings - it's mostly free on the net:
-Spangenberg - Vacuum Tubes
-Crowhurst - Basic Audio Vol 1, 2 and 3
-RCA - Radiotron Designer's Handbook
-Valve Wizard (great web resource, taught me tons) - http://www.valvewizard.co.uk/
-Youtube - there are plenty of folk who video-document tests, benchmarks, and diagnostic methodologies. Start with ElPaso TubeAmps, Uncle Doug, Mr Carlson's Lab, and EEVBlog (this last one is for mainly modern stuff). There are more, I just can't find them right now haha
Hope that helps!
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
May your tubes be lively, warm, and long-lasting. Holy be thy heater.
since anyone can post a blog and state their opinions. It is best to take it with a grain of salt if it is online. The classic books as mentioned by Palustris and simpler books like the RCA Receiving tube manual or the Radio Amateurs Handbook provide a more basic and factual approach to tubes. Of course nothing beats hands on experience like building your own or rebuilding a classic tube amp. cheers, Dak
that affects the sound. Different structures, designs, metallurgy, etc impacts the flow of those electrons from "C"athode to "A"node.
That's the simple explanation.
Some good books recommended.
Welcome to the Asylum!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Hi Jonesy, thank you for the welcome.That's amazing, I've never heard it put quite that way in anything I've read yet. Thanks!
So is the signal from the turntable "flowing" through the tubes, in & out? And once the signal hits the tubes, it activates the electrons? Or are the electrons the signal?
Edits: 04/17/16
In a tube that has voltage at the plate and the cathode is hot and the cathode is connected to ground (usually through a resistor)......electrons from the power supply are flowing from ground to the cathode, past the control grid to the plate, across the plate resistor to the power supply and then back to ground even when there is no signal from the turntable.
When there is music signal from the turntable present at the grid, the electron flow in the tube increases and decreases according to the music signal from the turntable.
The electron flow in the tube is not the electrons from the turntable. They are electrons from the power supply that are being controlled by the electrons from the turntable.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
In my "simplified" example the tubes are used to "amplify" the signal. So the signal arrives at the cathode in the tube. The electrons then "jump" to the anode. Now the signal has become "louder" and travels through wires to the speakers. As you turn the volume control up, it results in a larger quantity of electrons making the "jump" further amplifying the original signal.
Cheers!
Jonesy
"I know just enough to get into trouble. But not enough to get out of it."
Another good one is Beginners Guide to Tube Audio Design by Bruce Rosenblit.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
Great, thank you WW.
If you want to get above the "mystery" and "magic" level of understanding, a simple high school physics book will review elementary AC and DC circuit theory. From there, a good path for real understanding is "Valve Amplifiers" by Morgan Jones. Mr. Jones goes into AC and DC circuit theory as well as introducing the basic building blocks of amplification and how these individual components work together to make up a complete amplifier. There's much more to the book, naturally, so MJ is a great way to cast off the chains of mystery and magic and allow some basic concepts of physics to expand your understanding of how electronics work.
Thanks Palustris, I'll follow up on your suggestions.
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