#1
A few questions:

1. I'm not entirely clear on what they are, I've read the big thread that's stickied in this forum but I'm not 100% sure.
This is what I've gotten from reading the sticky:
Pre-amp: Boosts the signal from the pickups, adds gain and changes tone (mids, treble, bass).
Power amp: Amplifies the signal enough for the speakers to produce sound.

From this it sounds to me like the power amp is pretty lame, why can't the pre-amp boost the signal enough for the speakers? Why is a second amplifier necessary?

2. Is there any advantages to buying a pre-amp and power amp as seperate units, as opposed to buying a regular amp head (like a Marshall JCM whatever)?

3. If you do buy a pre-amp and power amp as seperate units do you need to match anything on them or can any pre-amp go with any power amp? If any can go with any then do you match the Ohms of the speaker to the ohms on the power amp? Or the pre-amp?

4. If I were to buy a 100 watt amp (not actually doing this, it's purely hypothetical) and wanted to use it for bedroom use I could use an attenuator (I think that's what the thread said). Would this essentially be a volume control between the amp and the speakers? So in effect I could crank the volume on the amp and use the attenuator to lower the volume?

Thanks for any answers, I'm woefully ignorant when it comes to amps (as perhaps you've noticed) and am hoping to rectify this.
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Last edited by Aleksi at Sep 27, 2009,
#2
You pretty much got it right. I can't awnser everything on here but a few.

2. Yeah there are some, like having a marshall preamp with a mesa boogie power amp will give you there ebst of both worlds.

3. I think you can put any preamp through any poweramp, but you must match the speaker impedance with the power amp though.

4. Yes, thats exactly what they do, however some people complain they suck tone, or muffle your sound.
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#3
The power amp is not lame, it does most of the job. You can get the best preamp, but if you plug it in a crappy power amp, it will sound ****ty.
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#4
^That.

1. A good poweramp with a nice saturation is the key to many classic tones, it is not lame. That is just how amps work.

2. It just depends on what you want to do. If you want a JCM800 tone, get a JCM800. If you want a CAE 3+SE into VHT 2150 sound, get that.

3. Yes, you can mix and match any preamp and poweramp. You will need to match power amp output to cab input in ohms.

4. In simple terms, yes. But that much attenuation typically doesn't sound all that great.
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#5
Quote by Aleksi

1. I'm not entirely clear on what they are, I've read the big thread that's stickied in this forum but I'm not 100% sure.
This is what I've gotten from reading the sticky:
Pre-amp: Boosts the signal from the pickups, adds gain and changes tone (mids, treble, bass).
Power amp: Amplifies the signal enough for the speakers to produce sound.

From this it sounds to me like the power amp is pretty lame, why can't the pre-amp boost the signal enough for the speakers? Why is a second amplifier necessary?


lets go theory here, cuz yer confused as to why this is the way it is. lets say you are given a task to build an amplifier circuit using a given technology. when you implement the design you would try and make the machine work as intuitively as possible with linear predictable control and usable parameter ranges. in other word you want circuit to work seemlessly. also, a perfect amplifier circuit would also reproduce the signal with
100% accuracy. also they way you have to amplify a signal is through 'gain stages', meaning you raise the signal a bit at a time. this is necessary because of the range in which a circuit can amplify, each gain stage is expecting a signal of certain amplitude and outputs a waveform of no bigger than a particular amplitude. so you need different stages and tubes to get a tiny passive signal into a skyscraping speaker output signal.

well what happened was tube guitar amps were sounding more 'pleasing to the ear' when run past certain operating parameters or a 'normal' amp. people would drive them as loud as they would go to cause the tubes to run a top capacity, pushing the speaker beyond it's normal limits and creating a different sound. soon people started purposefully 'damaging' gear to accentuate these sounds more, they did things like poking holes in speaker cones, damaging key resistors and capacitors, and running the speaker out from one amp into the input of another! eventually artists started influencing amp designs(think marshall versions of the fender 5F6-A circuit). manufacturers started making amps purposefully imperfect cuz they sounded better.

this is when speaker rounding, power tube saturation, and preamp clipping became the 'rock guitar' sound, and that is how preamps became imperfect.
Quote by Aleksi

2. Is there any advantages to buying a pre-amp and power amp as seperate units, as opposed to buying a regular amp head (like a Marshall JCM whatever)?

yes. benefit is you can mix and match circuits easier. lets say you have 4 different preamps(some tube, some SS). and you also have a highly versatile power amp(lets say one of the 2 sided vht's). you would be able to run different tube sets in the vht at different circuit configurations(class a and a/b) with different ouput wattages. cool. then further more you can put any type of preamp pedal up to them. cool. this allows for tons of flexibility.

Quote by Aleksi

3. If you do buy a pre-amp and power amp as seperate units do you need to match anything on them or can any pre-amp go with any power amp? If any can go with any then do you match the Ohms of the speaker to the ohms on the power amp? Or the pre-amp?

a preamp gives out a line level signal(like the one that comes out of an ipod), the power amp takes the line level signal from the preamp and amplifies it to a very loud signal. it needs a 1/4" mono patch chord, like the ones you use on guitar pedals.
Quote by Aleksi

4. If I were to buy a 100 watt amp (not actually doing this, it's purely hypothetical) and wanted to use it for bedroom use I could use an attenuator (I think that's what the thread said). Would this essentially be a volume control between the amp and the speakers? So in effect I could crank the volume on the amp and use the attenuator to lower the volume?

yes, or you could just turn down the volume on the power amp. but if you want power tube saturation then you can use a hot plate. they do sound alright, but i think they suck tone(mainly harmonics and feedback). i mean, anything weening my signal to a dummy load is gonna suck tone. you like power amp distortion then get a 100 watt power amp, pull the tubes and put in 2 yellowjackets. they'll be loaded with el84's and turns your amp into a 'class a' cathode biased style amp, running at 4/5 watts, that give power amp distortion, nice and gritty.
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#6
^

+1
Quote by Junnage
GuitarUser knows what's up*

Quote by SimplyBen
I agree with GuitarUser

Quote by travs2448
digital amps are like Fapping, its good but nothings like the real thing.