Need Primer on Amp Basics

eddie27 · August 4th, 2008, 01:13 PM

I'm currently playing thru a Mesa F-30 combo, which I like but I see it (maybe wrongly) as being a modern amp. It runs EL-84's. Playing live with a full band, I don't adjust the master volume past 12 o'clock. I'd like to get a second amp to get a purer sound - better cleans and a more natrual distortion. Something around 12 watts. I've always read certain amp terms, but don't really know what they mean - so I thought I'd ask here.

What is the difference between Class A and Class A/B?

What are harmonics - in relation to amp sounds? What do you listen for?

How does a master volume amp differ from a non-MV amp?

Thanks.

Wally · August 4th, 2008, 08:12 PM

Go to the Aiken Amp site and read through his tech info.
IF you are looking for cleans from that amp, turn the Master to max and set the preamp gain for volume. After doing that and if you don't care for it, try some combinations of reduced MV and increased preamp gain in increments to see if the amp will yield something that works for you. By restricting the MV to that one setting, you are missing out on the power tubes full production while pushing the preamp into higher gain, I would think.

Ben Harmless · August 4th, 2008, 11:08 PM

I absolutely second the Aiken site for good, understandable tube amp info, and a better description of operating classes than I'd be able to provide.

As far as the master volume issue goes, you've got a master volume amp. In a non-mv amp, that gain knob would be your "volume" and the amp would get much louder as you got your distortion. You'll notice a lot of amps don't have a "gain" knob, and you just have to crank the suckers. The mv just allows you to turn the distorted preamp signal down before it hits the power tubes so you get lots of crunch without all the volume - but then you miss out on the sound of power tubes distorting, which many people believe to be the holy grail of tone.

Harmonics are tones that exist within your guitar tone. When you pluck your A string at concert tuning, it vibrates 440 times per second. The vibrating string however, produces much more than just that one frequency. You'll also have a tone at 880 vibrations per second (hertz) and one at twice that, etc. Each of these tones is a harmonic, and as they get farther away from the root note, they get fainter.

Tube amp distortion is a form of clipping - if you picture a sound wave, at a certain input level, the amp can't produce the very top and bottom of the input signal, and it gets "clipped." If the signal is increased and the root tone clips, the first harmonic (that 880, if we're talking your A string) becomes louder in relation to the clipping root, and the guitar's tone becomes "fatter" because the different levels of the harmonics are being evened out. Eventually the 880 clips, and you hear the next harmonic more evenly and so on.

All this is something that you can't really do a whole lot of mental math about when you're trying out an amp at a guitar store, but what it really adds up to is that different amps can accentuate and distort various parts of the harmonic spectrum differently, which is what makes all amps sound different in the long run.

If that made no sense - and I suspect it didn't - feel free to ask for clarification on anything.

EDIT: BTW, I think it's really cool that you're asking these questions to better equip yourself, rather than just asking people what amp to get. This way, you'll be much happier with whatever you choose in the long run.

Daniil · August 5th, 2008, 06:02 AM

Here's a FAQ that gave me a lot of good info:

http://studentweb.eku.edu/justin_hol...s.html#tubefaq

JayFreddy · August 5th, 2008, 06:23 AM

Quote:

Originally Posted by Daniil

Here's a FAQ that gave me a lot of good info:

http://studentweb.eku.edu/justin_hol...s.html#tubefaq

Nice link, thanks!

Here's another one that's taught me a lot:

http://www.tone-lizard.com/Table_Of_Contents.htm

jefrs · August 5th, 2008, 07:52 AM

Not a primer but 'Valve Amplifiers' by Morgan Jones ISBN 978-0-7506-5694-8, though it has little to offer on tone and volume vontrols on guitar amps, it's the definative everything you never wanted to know about valve amplification.

sjhusting · August 5th, 2008, 08:11 AM

Here's one that's not specific to guitar amps, but a good one for tubes in general -

http://www.pmillett.com/tecnical_books_online.htm

about the 4th one down, "Basic Theory and Applications of Electron Tubes, Departments of the Army and Air Force, 1952, 215 pages"

I learned a lot from this one. It's an introductory text that has enough weight to it to be useful, but not so much so your eyes cross and you go off babbling about "The Miller Effect" to your small children.

steven

winny pooh · August 5th, 2008, 09:19 AM

Quote:

Originally Posted by Ben Harmless

Tube amp distortion is a form of clipping - if you picture a sound wave, at a certain input level, the amp can't produce the very top and bottom of the input signal, and it gets "clipped." If the signal is increased and the root tone clips, the first harmonic (that 880, if we're talking your A string) becomes louder in relation to the clipping root, and the guitar's tone becomes "fatter" because the different levels of the harmonics are being evened out. Eventually the 880 clips, and you hear the next harmonic more evenly and so on.

That is a fantastic explanation, kudos to you sir.

eddie27 · August 5th, 2008, 11:39 AM

Thanks for all the great info!

August 4th, 2008, 01:13 PM	#1 (permalink)
eddie27 TDPRI Member Join Date: Dec 2005 Posts: 18	Need Primer on Amp Basics I'm currently playing thru a Mesa F-30 combo, which I like but I see it (maybe wrongly) as being a modern amp. It runs EL-84's. Playing live with a full band, I don't adjust the master volume past 12 o'clock. I'd like to get a second amp to get a purer sound - better cleans and a more natrual distortion. Something around 12 watts. I've always read certain amp terms, but don't really know what they mean - so I thought I'd ask here. What is the difference between Class A and Class A/B? What are harmonics - in relation to amp sounds? What do you listen for? How does a master volume amp differ from a non-MV amp? Thanks.

August 4th, 2008, 11:08 PM	#3 (permalink)
Ben Harmless Friend of Leo's Join Date: Mar 2003 Location: Albany, NY US of A Posts: 3,244 6 Photos	I absolutely second the Aiken site for good, understandable tube amp info, and a better description of operating classes than I'd be able to provide. As far as the master volume issue goes, you've got a master volume amp. In a non-mv amp, that gain knob would be your "volume" and the amp would get much louder as you got your distortion. You'll notice a lot of amps don't have a "gain" knob, and you just have to crank the suckers. The mv just allows you to turn the distorted preamp signal down before it hits the power tubes so you get lots of crunch without all the volume - but then you miss out on the sound of power tubes distorting, which many people believe to be the holy grail of tone. Harmonics are tones that exist within your guitar tone. When you pluck your A string at concert tuning, it vibrates 440 times per second. The vibrating string however, produces much more than just that one frequency. You'll also have a tone at 880 vibrations per second (hertz) and one at twice that, etc. Each of these tones is a harmonic, and as they get farther away from the root note, they get fainter. Tube amp distortion is a form of clipping - if you picture a sound wave, at a certain input level, the amp can't produce the very top and bottom of the input signal, and it gets "clipped." If the signal is increased and the root tone clips, the first harmonic (that 880, if we're talking your A string) becomes louder in relation to the clipping root, and the guitar's tone becomes "fatter" because the different levels of the harmonics are being evened out. Eventually the 880 clips, and you hear the next harmonic more evenly and so on. All this is something that you can't really do a whole lot of mental math about when you're trying out an amp at a guitar store, but what it really adds up to is that different amps can accentuate and distort various parts of the harmonic spectrum differently, which is what makes all amps sound different in the long run. If that made no sense - and I suspect it didn't - feel free to ask for clarification on anything. EDIT: BTW, I think it's really cool that you're asking these questions to better equip yourself, rather than just asking people what amp to get. This way, you'll be much happier with whatever you choose in the long run. __________________ "I think I'll go for the life of sin, followed by the last-minute, presto-change-o, deathbed repentance." - B. Simpson

August 5th, 2008, 08:11 AM	#7 (permalink)
sjhusting Tele-Holic Join Date: Jul 2003 Location: Germany Posts: 649 15 Photos	Here's one that's not specific to guitar amps, but a good one for tubes in general - http://www.pmillett.com/tecnical_books_online.htm about the 4th one down, "Basic Theory and Applications of Electron Tubes, Departments of the Army and Air Force, 1952, 215 pages" I learned a lot from this one. It's an introductory text that has enough weight to it to be useful, but not so much so your eyes cross and you go off babbling about "The Miller Effect" to your small children. steven __________________ "When you have to kill a man it costs nothing to be polite" - WSC

August 4th, 2008, 08:12 PM	#2 (permalink)
Wally Friend of Leo's Join Date: Mar 2003 Location: Lubbock, TX Posts: 3,988	Go to the Aiken Amp site and read through his tech info. IF you are looking for cleans from that amp, turn the Master to max and set the preamp gain for volume. After doing that and if you don't care for it, try some combinations of reduced MV and increased preamp gain in increments to see if the amp will yield something that works for you. By restricting the MV to that one setting, you are missing out on the power tubes full production while pushing the preamp into higher gain, I would think.

August 5th, 2008, 06:02 AM	#4 (permalink)
Daniil Tele-Meister Join Date: Sep 2005 Location: Espoo, Finland Age: 29 Posts: 123 5 Photos	Here's a FAQ that gave me a lot of good info: http://studentweb.eku.edu/justin_hol...s.html#tubefaq

August 5th, 2008, 07:52 AM	#6 (permalink)
jefrs Tele-Holic Join Date: Nov 2007 Location: Newbury, England Age: 53 Posts: 602	Not a primer but 'Valve Amplifiers' by Morgan Jones ISBN 978-0-7506-5694-8, though it has little to offer on tone and volume vontrols on guitar amps, it's the definative everything you never wanted to know about valve amplification.

August 5th, 2008, 11:39 AM	#9 (permalink)
eddie27 TDPRI Member Join Date: Dec 2005 Posts: 18	Thanks for all the great info!