lets talk about tube amp parts, and what they do

[bluesboy]

iwhat are the general parts of any tube amplifier, and what exactly do they do?

 

for example, power supply, what's in a typical preamp section, output transformer, etc.

 

im just looking for general knowledge here.... so the signal comes from the guitar, and what exactly happens to it?

 

Im hoping this will become a helpful thread, with minimal arguing

[bluesboy]

for example, you look inside the amp, and you see tubes hanging down, and then a bunch of other stuff... like a black box by the power cord, some other metal box things, what is that stuff?

[bluesboy]

also, feel free to include pictures, images, schematics, etc. whatever would be helpful.

[blargh]

The power transformer takes your AC power and converts it to the voltages your tubes need to work.
The rectifier basically converts this AC to DC that your amp needs, and the filter capacitors and the choke (the smaller transformer looking thing on some amps) filter AC ripple from the DC current.

[HKSblade1]

after the amp is plugged in and powered up by power and standby switches, the guitar jack is inserted and it's signal is coupled to a cap>>

[bluesboy]

so it seems like the power transformer and the rectifier tube work together?

so there would be a power input section, (PT and rectifier), a preamp section, and an output section?

the PT and OT are different, correct?

[Weathered]

Wow. Big topic.

I'm typing.....please hold.

Here's a good explanation:

http://www.el34world.com/charts/currentflow.htm

You've basically got your guitar signal, which is AC, and the power, which is DC. Understanding what flows where will help you understand more on how amps work.

[Sixtonoize]

I've been studying this for about 3 years, and I've still got a LOT to learn...be prepared for either:

A) a very long, detailed discussion about the workings of amps, or

B) A2M/GAPE, STFU N:o:oB, etc...

I'm guessing it'll veer toward B).

[blargh]

Tubes in amps are amplifying devices. Your guitar's signal will first go through several gain stages in the preamp, and if its a high gain amp, some of these tubes will get overdriven, and start clipping, which gives you distortion.

You've got your tone stack, which is the EQ knobs on the front of the amp. The master volume is found at the end of the preamp.

After the preamp gain you might also have an FX loop, which can output the preamp signal and input signal to the power amp.

After the FX loop most amps will have a phase inverter, which feeds the power tubes. The power tubes amplify this signal to loud-ass levels, and the output transformer will convert what the tubes are putting out to what speakers like.

Something to keep in mind is that the presence and resonance controls on most amps are in the power section, not the preamp.

[bluesboy]

Wow. Big topic. I'm typing.....please hold. Here's a good explanation: http://www.el34world.com/charts/currentflow.htm You've basically got your guitar signal, which is AC, and the power, which is DC. Understanding what flows where will help you understand more on how amps work.

cool, thank you, thats along the lines im looking for

[bluesboy]

I've been studying this for about 3 years, and I've still got a LOT to learn...be prepared for either: A) a very long, detailed discussion about the workings of amps, or B) A2M/GAPE, STFU N:o:oB, etc... I'm guessing it'll veer toward B).

 

 

im hoping for A, and i think others would find this helpful too

[bluesboy]

Tubes in amps are amplifying devices. Your guitar's signal will first go through several gain stages in the preamp, and if its a high gain amp, some of these tubes will get overdriven, and start clipping, which gives you distortion. You've got your tone stack, which is the EQ knobs on the front of the amp. The master volume is found at the end of the preamp. After the preamp gain you might also have an FX loop, which can output the preamp signal and input signal to the power amp. After the FX loop most amps will have a phase inverter, which feeds the power tubes. The power tubes amplify this signal to loud-ass levels, and the output transformer will convert what the tubes are putting out to what speakers like. Something to keep in mind is that the presence and resonance controls on most amps are in the power section, not the preamp.

 

 

cool, thanks for chiming in

[Weathered]

Basically, all a guitar amp is is multiple voltage amplifiers tied together. You take a small signal coming into the amp, run it through gain stages that can multiply the signal to hundreds of times the voltage swing (AC voltage), and then it goes through an output transformer that turns the signal from high voltage, low current, to low voltage and high current to move speakers.

The DC (B+) voltage in the amp provides the type of electricity that the tubes operate on. You've 2 major different types of voltage in the amp - heaters and B+. Basically, the power transformer uses windings to turn your wall voltage into the correct current. The heaters are 6.3 volts for all of the preamp and power tubes in the amp, and it simply heats the cathodes to boil off electrons. The B+ comes from a center-tapped winding on the transformer (written as 300-0-300 or similar), and runs through a full-wave rectifier to turn it into DC voltage. The DC voltage still has remnants of the AC voltage, known as ripple. The filter caps serve to "filter" this ripple out of the DC voltage. Your B+ can be anywhere from 300-600 volts DC, depending on the circuit. This voltage comes into the tubes on the plates, hence the measurement of "plate voltage".

[tommythelurker]

I didn't see anyone cover the power amp section yet.

 

Most guitar amps (50W and up) are class AB amps which work like this:

After the preamp, loop and master volume, it goes to the Phase Inverter which is another preamp type tube but drives the power tubes so it's considered part of the power amp. The PI splits the signal into two versions, one the same as the original and the other one inverted. These two signals each go to two different power tubes (in a 50W amps, or pairs in a 100W). The power tubes that get one of the PI signals drive half of the signal (i.e. the top half) and the tubes getting the other PI signal drive the other half of the signal (i.e. the bottom half). The power tubes are what take the small signal from the preamp and make it strong enough to drive speakers (which takes a lot more power than a preamp tube can provide).

 

From the power tubes the signal goes into the output transformer. You still have two sets of signals from the power tubes, one for the top part of the original signal and one for the bottom part. These two signals are connected to the primary of the OT at opposite ends and are combined by the OT back into one complete signal. That's one of the OT's jobs.

 

The other job of the OT is to match the impedance of the power tubes to the speakers. The tubes impedance is typically on the order of thousands of ohms, while speakers are usually 4 to 16 ohms. So the output transformer transforms the load impedance from the speaker to match the tubes. Some OT's have multiple taps for different load impedances which are connected to an impedance selector or different outputs on the amp. That's what matching impedances is all about. As long as the output on the amp matches the load that's connected, the power tubes see the same load and will put out the same power even with different impedance settings.

[bluesboy]

thanks guys, awesome posts here

[JKD]

1. Plug guitar in
2. ....
3. BREWTALZ!

[Steveanders86]

but every tube amp has preamp tubes and power tubes. so what makes them sound different from amp to amp? what piece of the amp makes it have a certain voicing? what makes it have that power like the mesa mark series where you can feel it literally moving your pants. what gives it sustain what gives it all these things that we desire in our amps?

[Weathered]

but every tube amp has preamp tubes and power tubes. so what makes them sound different from amp to amp? what piece of the amp makes it have a certain voicing? what makes it have that power like the mesa mark series where you can feel it literally moving your pants. what gives it sustain what gives it all these things that we desire in our amps?

 

 

Circuit design. Where the designer places the tone stack (plate driven and early in the preamp, cathode follower and late in the tone stack), the # and design of gain stages, the B+, what type and design of PI, the power amp design, etc. Lots of variables.