What goes on inside the amplifier?

[Ampster]

This thread might look funny to someone, but since I'm not familiar of tube amp mechanics or electronics what so ever, I don't know about these things.
So I ask and I try to learn.

So, what I'd like to clear out is that what master volume and gain/pre-amp knobs actually do "electronically".

So, the questions:

We all know that turning master volume up increases the volume level coming from the speakers and turning it down decreases volume level.
And the more you turn the master volume up the more you will get power-tube distortion (why this happens?).


And I also know that turning gain/pre-amp up gives you more distortion (and volume) to the sound (why this happens?).


I would greatly appreciate if someone could give me explanation like in this style:

The master volume controls the level of WHAT? (electric current?) which reaches WHAT PARTS? and therefore making WHAT? sound like WHAT? which leads to WHAT?

The gain/pre-amp controls the level of WHAT? (electric current?) which reaches WHAT PARTS? and therefore making WHAT? sound like WHAT? which leads to WHAT?

I think you got the point.

And in which point of amplifier guts does these parts go and function?
Like does gain/pre-amp affect in between pre-amp and power-amp?
Where does the master volume function?

Also, what are the differences between MV and PPIMV?
How does these differend master volumes affect to tone?

What does VVR actually do?
How does it affect to tone?

I understand that there's a lot of questions and answers might not be simple but I hope someone can help and that the questions where not too complicated to understand.

 

[veryLOUDdsl100]

I get lost with a amp that has more than two channels because of my ADD, so this I try not to think about, it would surley provoke me to have an aneurysm, but I bet someone around here knows.

 

[bulldozer1984]

The 'Gain" knob as it is turned up allows more current to flow through the Pre-Amp circuit. Which is a network of tubes or diodes (depending on the design of the amp). This current allows them to clip which distorts the signal. (makes the sound waves square)

The 'Master Volume' as it is turned up allows more current to flow through the Power Amp circuit. Which is a network of tubes or transistors (depending on the design of the amp). The Power Amp circuit will usually stay clean throughout a large sweep of the knob but it can clip at high volumes level's which distorts the signal (makes square sound waves)

The way i have always though of it is that the 'Pre-Amp' SHAPES the sound and the 'Power Amp' DRIVES the sound.

Both Pre-Amp and Power Amp sections amplify the sound, but the Power Amp is responsible for getting the sound up to concert level's.

Does that make sense ??

There are guys on here that can put that into alot more detail for you. but i thought that my layman explanation might be of some use.

 

[Jonathan Wilder]

The preamp/gain pot controls how much of the first gain stage signal voltage gets to proceed through the rest of the preamp.

The master pot controls the how much of the preamp signal voltage gets to pass to the power amp.

The greater the 1st stage preamp signal voltage you allow through with the gain pot, the harder the 1st gain stage drives the preamp.

The greater the preamp signal voltage you allow through to the power amp with the master pot, the harder the preamp drives the power amp.

 

[Ampster]

Thank you! There's still few extra questions in my original post if someone wants to answer them.

 

[bulldozer1984]

Thank you! There's still few extra questions in my original post if someone wants to answer them.

We all know that turning master volume up increases the volume level coming from the speakers and turning it down decreases volume level.
And the more you turn the master volume up the more you will get power-tube distortion (why this happens?).

Because you are feeding the power amp section more signal voltage, and as the power tubes start getting a certain amount of signal voltage they start to clip (distort).


And I also know that turning gain/pre-amp up gives you more distortion (and volume) to the sound (why this happens?).

Because you are feeding the pre amp section more signal voltage, and as the pre-amp tubes and/or diodes start getting a certain amount of signal voltage they start to clip (distort).



Also, what are the differences between MV and PPIMV?
How does these differend master volumes affect to tone?

a master volume is usually positioned between the pre amp and the power amp. And it is usually positioned BEFORE the phase inverter tube/valve. So therefore when you turn down the master volume it does not allow to phase inverter to clip (add more distortion to your sound)

A PPIMV (Post Phase Inverter Master Volume) is positioned AFTER the phase inverter tube/valve which allows you to get more distortion in your sound because you can distort the phase inverter tube/valve whilst still maintaining your desired volume. So basically it allows you to get more distortion into your sound without having to CRANK the overall volume of your amp.

 

[clutch71]

I'm reading Dave Hunters the Guitar Amp Hand Book. It's pretty good for some of the questions above. I also picked up Geral Webers Tube Guitar Amplifier Essentials. Both are actually pretty interesting reads. I thought they might be a little dry, but i'm making good progress in them.

 

[Les Moore]

This article is very good. It explains the whole "chain of command". I´ve posted it before but it can be hard to find info sometimes. I´m on my 4:th read I think
http://www.ax84.com/static/p1x/p1-ex-theory.pdf

If you want an even more comprehensive understanding I suggest you read some basic electronics. I´ve posted this one too before. It´s the navy electronics course. Also very good. Choose the module 1 and 2 to begin with. Then you have modules for amplification and tubes. Again, very well written.
Navy Documents

Hope it helps and inspires you.

 

[chadjwil]

The gain and volume controls are setup electrically as voltage dividers. Yes they control the amount of "signal", whatever that means to you, that gets passed on to the next stage, but if you really want to know how they do it just let me know and I'll be happy to share. It's just a bit of very basic math. If you can add and divide you can handle it. Now, that being said...there is a LOT more to it than just that, but if all you want to do is understand the basics or tweak around an existing circuit then this basic info will be very helpful.

Distortion, or clipping as you've heard it called, goes like this. Any amplifier of any sort only has so much it can give you as an output, and when you give it an input that results in an output that is more than it's capable of outputting the signal will level off at the max possible output until the input falls to a range that it is capable of producing. As an example, let's take an amplifier that puts out twice as much as you put in...if you put in 1 volt it will give you 2 out. The max output of this amp is 10 volts (the why's and how's of this are not nearly as simple), so what happens when you give it an input of 6 volts? The amplifier will operate normally between +5v and -5v (the result of that input is +/-10 right?) but from 5-6volts the output doesn't change, it's just a flat 10volts...because that's all it's capable of doing. Make sense? Now clipping diodes are an entirely different thing. They cause the signal to do the same thing but in a totally different way.

Hope this helps, and I hope it gets you curious to learn more

 

[CaptainZero]

PFM? J/k

 

[chadjwil]

No idea what that means. Clue a brother in please.