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  #1  
Old 2007-05-14, 22:58
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Tube amp and preamps questions

Hello, I have a question regarding tube amps. I am a complete amp noob and im working on getting a tube amp (maybe a carvin pretty cheap 100w) and i need to know what kind of maitenance it needs. do you need to let it warm up before playing? how long do i let it set once i turn it on? what does bias mean?is 100watts tube very loud? what are stero cabs? (i think i have a good idea) is ther anyhting particular i need to know?


also, alot of you have racks. what are on those and what do they do?
and also what is a preamp? srry for so many questions but im a totall amp and electronics noob.
thank you.
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  #2  
Old 2007-05-15, 15:57
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Hey! Don't be sorry to ask, always cool to help out.


The maintenance. Well, one in a while you will need to replace the tubes. The tubes look a little bit like a long clear light bulb, and they wear out somewhat in the same manner as a light bulb.

There are two "types" of tubes, preamp and poweramp. Preamp tubes are smaller and require no warming up. They can last many years, but they gradually start fading away. If you gig / rehearse very often try replacing these every two years. They'll easily work for 15 years but the tone gets worse and worse and you won't really notice it because it happens so gradually. Try replacing them every two years anyway.

Then there's the power tubes. These are bigger and require to be warmed up before you put them in operation. If you don't warm them up you lose a lot of life on them, so they wear out faster. If you look inside a tube you will notice that on the bottom there's a wire much like the one inside a light bulb glowing red. This is the one that heats the tube up.

To do everything correctly before you press the power switch make sure the "Standby" switch is in the off position. Then flip the power switch. Now, wait as long as you can be bothered before you flip the standby switch. 15 minutes is very safe, 10 minutes probably too, 5 minutes is okay. I usually don't have patience to wait more than 2-3 minutes and my power tubes are fine, but i would recommend you wait longer.

When you turn it off it's good practice to first turn off standby then turn the power off, so that next turnon the standby will be in "off" position. You don't need to turn standby off, but do it anyway.

Bias. The signal that goes out from your guitar varies in voltage. Voltage is in electrics the same thing that pressure is in water pipes, and is measured in Volts. There's also a thing called current, which is the same as flow in a water pipe, which is measured in Amperes. If you multiply current by voltage you get power, which is measured in watts.

Now, the thing is, tubes block all signal going through them unless it's higher than a given voltage (for simplifying things, let's say it's 1 volt). So, since your guitar signal varies in voltage (let's say from 0 to 5 volts), the tube won't pass any signal until the voltage goes above 1 volt, rendering you unable to hear the signal below 1 volt. This results in what is called "crossover" distortion, which some people find harsh to the ear.

The solution to the above issue is to provide a constant signal to the tubes, so that the tube is always open, letting signal flow through it. It doesn't matter if the voltage from your guitar is 0.1 volts, it will still pass since there's a constant voltage opening up the tube to a signal of any strength. This constant signal is called Bias, and might be measured in current, voltage or watts. It doesn't matter, you just need to find out what to set it to.

How to find out:

To set the bias (in current) on the power tubes right you need to know how many watts one tube can put out and the voltage they run on. Usual value for the power tube is either 25 watts or 30 watts (EL34 and 6L6GC respectively). Operating voltage is commonly 450 volts, but it might be more or less (my 5150 runs at roughly 470 volts). Usually the bias power is set to 60-70% of the maximum power.

So. Max power is 30 watts per tube. You want 60% of that as the bias power, which is 18 watts. Divide 18 watts by the operating voltage, which is 450 volts. Result will be 0.04 amperes, or 40 milliamperes (mA). Set the bias current to 40mA using your bias meter, and you're good. (By the way, 30 watt tubes usually run on a bit higher voltage so that the amperage will be less, but this was just an example).

Preamp tubes bias themselves, you just rip them out and put them back in without problems.

100 watts of tube power is very, very loud. Using more speakers and more efficient speakers also makes the sound louder. A 100 watt tube amp with a 4x12 cab is pretty much earth-shattering.

Stereo cabs are cabs that are wired so you can run one amp on one side of it and another amp on the other side, or use a stereo amplifier with it.


A rack is a cabinet you can put things in, like effects, a noise gate, an amplifier, a preamp, a poweramp, a wireless system etc. Things that are made for a rack is standardized in size so they'll fit.

A preamp is an amplifier that amplifies the voltage from your guitar so that it's high enough to run the power tubes (a guitar by itself would be too weak). A preamp also generates distortion, and provides sound sculpting tools like an equalizer and a gain and volume control.

On the other hand, the power amp amplifies current, to make your speakers push air. A power amp can also generate distortion and have sound sculpting controls like a master volume and Depth/Resonance and a Presence control.

For the record most distortion in metal comes from the preamp, with very little or no power amp distortion. Some metal styles also use power amp distortion to a large degree, and in rock'n'roll there's generally very little preamp distortion and a lot of power amp distortion.

To get preamp distortion, turn the gain up. To get power amp distortion, turn the volume up
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  #3  
Old 2007-05-15, 20:07
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So pretty mutch the preamp head would be alot less confusing and easier for a noob like me to operate?

how do the sounds of the different tubes vary?

Witch is more expensive?

Witch type is better for metal? and is a preamp a neccesity (spelling?) if you want a tube amp to play metal?

can you get a rack with thos boxes to run into instead of a head?

is a stereo cabinet(say 4X12) seperating 2 speakers for 2 different amplifiers?
were two people can play through it?

Is'nt a stereo head a head that can plug into 4 cabs?

lots of questions lol
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  #4  
Old 2007-05-16, 01:55
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There's no thing as a preamp head, it just called a head.
A head contains both the preamp and the power amp inside it as an integrated package.

And a preamp is indeed necessary if you play metal, but if you have a head it's already built into it so you don't need another external preamp.

If you had a rack setup you would need one separate preamp and one separate poweramp. IMO this is not the way to go for most metal guitarists - there's much more to choose from if you get a head, and a head is cheaper.

There's nothing wrong with more preamps using the same power amp though, so you could have more flexible tone by switching between them.

Yes, the sound of different tubes vary. For most amps you and me would like to play there's either EL34 tubes or 6L6GC tubes in the power amp.

EL34 tubes generally don't have as much bass and treble as the 6L6GC and have a very prominent grinding, cutting midrange. The "Marshall" rock sound are all EL34's played very loud (so that they distort).

6L6GC tubes generally have a deeper, bigger bass, a darker midrange and a stronger treble than EL34's. They sound very deep and is the preferred tube by most metal musicians They start sounding better at a lot lower volume than the EL34's too.

Yep a stereo 4x12 separates 2 speakers so you can run two amps into it, one on each side. A stereo head is a head with two power amplifiers and effect loops, so you can run stereo effects.
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  #5  
Old 2007-05-19, 11:52
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Man still kindy muddy about stuff but if i think of more quesiton ill ask
but itr definately cleared some stuff thanx alot bro

o ya so all amps have preamp amp and power amp tubes?
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  #6  
Old 2007-06-21, 23:12
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OK time has passed and i may have learned a bit more but its opened up enw questions.

on rackmound items

all rack units are the same size?

and preamp gives you your tone and you plug the preamp into the poweramp and it makes it louder? or gives it power (like to turn on and work and stuff)?

is a preamp and a pweramp all you really need? to make sound for shows? (without effects and eq and whatnot)

what is a power conditioner?

can i plug a preamp streight into a cab and it be loud enough?


what is MIDI?

is ti the power amps that are stereo and can play through 4 cabs or is that the preamps job? ( im thnking power amp)

is this http://cgi.ebay.com/ENGL-PREAMP-STE...1QQcmdZViewItem is this as good as a head? does the same?

is it the power amp that gives your set the wattage? so on that ebay item it says 2X 100 means its a 100 watt amp for 4 cabs?

is F.X. short for effects?

is a valvestate amp haveing half tuybe and half solid state?
witch part is tube and witch is solid state?


whats the send and return inputs for on my amp?
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Last edited by Arsis : 2007-06-21 at 23:53.
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  #7  
Old 2007-06-22, 03:28
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Yes all rackmounts are 19" in horizontal length, but some are taller than others and can take up 1 or 2 spaces in a rack unit or more. Most preamps are 1 rack space, some more pro ones are 2.

Think of the poweramp as the motor that puts a high voltage signal out to the speaker cab, it takes any audio signal and amplifies it to a really high wattage signal to push a speaker cab and make some noise. The preamp just takes your guitar signal and processes it, adds distortion/clean sounds/effects if it has any etc. but on it's own it CANNOT make any sounds going straight into a cab, so you need a poweramp to amplify it.

Think of it this way, you can't plug in your portable CD player straight into your hi fi stereo's speakers, you need to plug it into the stereo because it has a poweramp, and will amplify it for you.

There are TONS of metal guitarists that use rack type setups, and in many cases rack setups are far cheaper than any head.

For playing live you need a cab, preamp and poweramp if you're going to be producing all of the sound from the stage. Everything else is optional.

A power conditioner is a rack device that you plug in all of the other things in the rack into, it acts as a barrier between the electrical outlets and your rack gear, it "conditions" the electricity and prevents voltage spikes from damaging your gear, as well as also reduce some noise created by faulty electrical outlets.

MIDI is a protocol used for sending complex signals to a preamp or similar via a footswitch, this only matters if you have a high end preamp. With it you can make some very sophisticated patches with different settings and have them available at the press of a button on a MIDI controller pedal.

A stereo poweramp can power 2 cabinets, that's all.

The poweramp you just posted is TWO 100W poweramps in one, PLUS each of them are stereo, that's why t can power 4 cabs, but most poweramps only work in mono or stereo and only power 1 or 2 cabs.

Valvestate has a hybrid solid state/tube preamp, and an all solid state poweramp.

The send and return jacks are the effects loop, you place effect pedals like reverb or delay or EQ through here because they make a bigger effect than going into the guitar input on the amp.
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  #8  
Old 2007-06-22, 13:03
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Thanx very veyr mutch Jopop and soeru


can you mix a solid state preamp and a tube power amp and vice versa with no problems?
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  #9  
Old 2007-06-22, 13:35
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Yes! Try the Sansamp PSA if you want a ripping solidstate preamp. Peavey Classic 60 makes for a decent power amp too. Or a Carvin T100 if you like "marshall" tones.
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Last edited by Jopop : 2007-06-22 at 13:45.
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Old 2007-06-22, 13:51
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Yeah you can mix anything, in fact there are few amps out there with a solid state preamp and tube poweramp(opposite as valvestate), the Marshall 3203A in particular, which I've played and sounds amazing.
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  #11  
Old 2007-06-22, 21:29
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Quote:
Originally Posted by Jopop
Yes! Try the Sansamp PSA if you want a ripping solidstate preamp. Peavey Classic 60 makes for a decent power amp too. Or a Carvin T100 if you like "marshall" tones.


does poweramp ever have an effect on your tone?

and is this carvin nice for metal? i have a metla amster distortion pedal that i sometimes use if it would help.
i always see carvin poweramps that dont look long enough for the rakc but all the preamps do.


http://cgi.ebay.com/MARSHALL-JMP-1-...1QQcmdZViewItem is this any good by your knowledge i know someone on this fourm had "but its not for me" he says
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Old 2007-06-22, 22:03
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http://cgi.ebay.com/TECH-21-SansAmp...1QQcmdZViewItem under the sansamp theres a cry baby wah Rack how does that work?

do PA systems need to be plugged into poweramps?

y do ppl on this fourum hate krank so mutch haha? never heard one


http://cgi.ebay.com/MARSHALL-1960-A...1QQcmdZViewItem

For metal?
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Last edited by Arsis : 2007-06-22 at 22:52.
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Old 2007-06-23, 03:02
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Yes that Marshall is a good solid cab for metal. A PA is basically preamps and poweramps hooked into PA Speakers. Although the preamps and power amps used in a PA are typically designed for things like vocals, keyboards, drum triggers, stuff like that. Plugging your guitar straight in wouldnt get you what you want, PA's would be used in conjunction with a mic in front of your cab if you are playing large venues. People hate Krank because they are the "guitar center" of amplifiers.

The crybaby wah is basically a wah-wah pedal but in rackmount format.
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Old 2007-06-23, 03:33
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Quote:
Originally Posted by Arsis
does poweramp ever have an effect on your tone?

Yes especially if it's tube, in particular tubes like EL84's or 34's, as 6L6GC's are a bit more transparent(though have more bass) and take very high volume levels to be pushed into breakup.

Solid state poweramps for the most part are transparent.
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  #15  
Old 2007-06-23, 17:31
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Quote:
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The crybaby wah is basically a wah-wah pedal but in rackmount format.


i dont get it it shift tones by itself (basicly like moving the pedal up and down)
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Old 2007-06-23, 19:05
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No it's still manual, it has an expression pedal that you connect to it to control the wah effect like if it was a normal pedal, but all the guts of the pedal are in the rack unit, which means you can tweak the sound a lot more and have different settings and stuff I think.
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Old 2007-06-23, 23:33
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and if you had such an item along with eq and stuff would you plug it into the send and return?
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Old 2007-06-24, 01:58
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EQ yes, but wahs are generally not used in the fx loop.
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Old 2007-06-24, 12:14
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kay kool. I see alot of cheap preamps and stuyff on ebay maybe i should experiment with my new knowledge lol.

and this thing has ppoweramp tubes And preamp tubes but isnt it jsut a power amp? http://cgi.ebay.com/Marshall-EL34-1...VQQcmdZViewItem
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Last edited by Arsis : 2007-06-24 at 12:22.
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  #20  
Old 2007-06-24, 17:57
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Quote:
Originally Posted by Arsis
kay kool. I see alot of cheap preamps and stuyff on ebay maybe i should experiment with my new knowledge lol.

and this thing has ppoweramp tubes And preamp tubes but isnt it jsut a power amp? http://cgi.ebay.com/Marshall-EL34-1...VQQcmdZViewItem

The preamp tubes are used to split the signal to the powertubes (somewhat simplified explanation).

The Marshall EL34 poweramps are not that great IMO for their price, ESP. not in the US.
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