#1
I really am looking to buy a new amp soon, and Ive been doing a lotta research but I really dont get what stacks, pre amps, heads, and cabs are. Can someone break this down for me please?
#3
An amplifier needs to make a signal BIGGER and a speaker converts that signal into sound.

A head contains only an amplifier, and no speakers.
A cab contains only speakers, and no amplifier. They need to be connected together to produce any sound.

A head on top of a cab (or two) is a stack.

A pre-amp is a part of an amplifier. It is basically the first "stage" of the amplifier. Most of the tone shaping happens in the pre-amp. After this, the signal goes to the "power amp" which is wehre it is made large enough to drive the speakers and produce an audible sound.

I hope that makes sense. Also, read the stickied threads.
#4
Quote by sashki
An amplifier needs to make a signal BIGGER and a speaker converts that signal into sound.

A head contains only an amplifier, and no speakers.
A cab contains only speakers, and no amplifier. They need to be connected together to produce any sound.

A head on top of a cab (or two) is a stack.

A pre-amp is a part of an amplifier. It is basically the first "stage" of the amplifier. Most of the tone shaping happens in the pre-amp. After this, the signal goes to the "power amp" which is wehre it is made large enough to drive the speakers and produce an audible sound.

I hope that makes sense. Also, read the stickied threads.

Ditto.
Jackson DK-2 [2004 MIJ] (EMG 81/SA)
Jackson RR-3 [2007 MIJ] (EMG 81/60)
Ibanez RG370DX [2009] (EMG 81/60)
Epiphone Les Paul Custom [2004] (EMG 81/85)
Ltd/Esp M-17 7-String [2013] (EMG 81-7 set)
Bugera 333XL 120watt Tube Head, Crate BV412 Cab
#6
Quote by Random3
A head is the actual amplifier with all the dials and input jacks on.

A cab is the speaker.

A stack is a head on a cab.

A combo is a head and a cab in one (all one piece).

A preamp is a type of tube in tube amps.

No.
A preamp is the part of the amp that shapes the sound.
Current Gear:
LTD MH-400
PRS SE Custom 24 (Suhr SSH+/SSV)
Ibanez RG3120 Prestige (Dimarzio Titans)
Squier Vintage Modified 70s Jazz V
Audient iD22 interface
Peavey Revalver 4, UAD Friedman BE100/DS40
Adam S3A monitors
Quote by Anonden
You CAN play anything with anything....but some guitars sound right for some things, and not for others. Single coils sound retarded for metal, though those who are apeshit about harpsichord probably beg to differ.
#7
To put it simply, the pre-amp is the "knobs" section of the amplifier
#8
Here's how I think of pre-amps in terms of electrical engineering going into an analog to digital converter.

To perfectly reproduce a signal (which is just a sum of sinusoids, see Fourier series), you need to take at least 2 points on the signal's period. With these 2 points, you can perfectly reconstruct the signal frequency component. So if you have a 10kHz signal, you need to sample at least 20kHz or more. This is all theory, so generally you want to sample more than twice the largest frequency.

The other aspect of a signal is the amplitude. You can never perfectly reconstruct a signal's amplitude because you do so by the resolution (number of bits used on the ADC). If you have a 5 mV peak to peak signal going into an ADC with a reference voltage of 5V (the reference voltage is the max voltage the ADC can reproduce), and if you are using say... a 12 bit ADC, you can represent a signal with 2^12= 4096 different lines of code to represent an amplitude. If you are sampling such a small level signal such as 5 mV peak to peak with a 12 bit ADC, each piece of code will represent (5)/(2^12) = 1.22 mV. So to represent a 5 mV signal, you can only represent roughly 4 different pieces of code, so your signal will sound like crap.

To solve this problem, you amplify the incoming signal as close to 5V as close as possible (anything above will clip). Now that you have a 5V incoming signal, you can use all 2^12 pieces of code to represent the signal, so you can represent the signal with 4096 pieces of code. That's the purpose of a preamp when using an ADC.
#9
Quote by farmosh203
Here's how I think of pre-amps in terms of electrical engineering going into an analog to digital converter.

To perfectly reproduce a signal (which is just a sum of sinusoids, see Fourier series), you need to take at least 2 points on the signal's period. With these 2 points, you can perfectly reconstruct the signal frequency component. So if you have a 10kHz signal, you need to sample at least 20kHz or more. This is all theory, so generally you want to sample more than twice the largest frequency.

The other aspect of a signal is the amplitude. You can never perfectly reconstruct a signal's amplitude because you do so by the resolution (number of bits used on the ADC). If you have a 5 mV peak to peak signal going into an ADC with a reference voltage of 5V (the reference voltage is the max voltage the ADC can reproduce), and if you are using say... a 12 bit ADC, you can represent a signal with 2^12= 4096 different lines of code to represent an amplitude. If you are sampling such a small level signal such as 5 mV peak to peak with a 12 bit ADC, each piece of code will represent (5)/(2^12) = 1.22 mV. So to represent a 5 mV signal, you can only represent roughly 4 different pieces of code, so your signal will sound like crap.

To solve this problem, you amplify the incoming signal as close to 5V as close as possible (anything above will clip). Now that you have a 5V incoming signal, you can use all 2^12 pieces of code to represent the signal, so you can represent the signal with 4096 pieces of code. That's the purpose of a preamp when using an ADC.
So only ADC amps have preamps, since tube amps and the likes have a fully analogue signal, right?
#10
So only ADC amps have preamps, since tube amps and the likes have a fully analogue signal, right?


To be honest, I don't have much knowledge of guitar amplifiers but I think pretty much every guitar amplifier has a pre-amp even if it doesn't have an ADC.
#11
Quote by Eddy~
So only ADC amps have preamps, since tube amps and the likes have a fully analogue signal, right?

No, all amps have preamps. He was just giving an example of a what would happen in a digital amplifier or computer interface.
#12
Quote by Eddy~
So only ADC amps have preamps, since tube amps and the likes have a fully analogue signal, right?

All amps do. You can see the preamp as the part that shapes the sound, the power amp the one that enables the sound to be heard, and the speaker to play the sound. That is, in a nutshell, an amp system.
#13
hmmmm a analog to digital converter has absolutely nothing to do with what the hell a pre-amp does. Music is analog.Period. What a pre-amp does it takes the minuscule signal from a guitar and amplifies it to a usable level for a power amp. I am not giving a electronics lesson here.There is enough out there if you are motivated look it up. God I hate the internut and the bullshit that is spewed sometimes.
Bhaok

The following statement is true. The proceeding statement is false.
#14
Analog to digital conversion (& D/A afterwards) happens in modelling amps and many effects.
There's a lot more to it than sampling rates, no. of bits used and how they are scaled affects how accurately the signal is sampled as well.
Moving on.....
#15
Quote by schwinginbatman
All amps do. You can see the preamp as the part that shapes the sound, the power amp the one that enables the sound to be heard, and the speaker to play the sound. That is, in a nutshell, an amp system.

Ok, right.

I thought a preamp was more of some sorta booster but seems they call the actual signal processing/transformation that.
#16
Quote by Eddy~
Ok, right.

I thought a preamp was more of some sorta booster but seems they call the actual signal processing/transformation that.

It does boost the signal a bit. A guitar signal is tiny and difficult to process on its own. It has to be boosted slightly to reduce losses in the different components that the signal has to travel through.

For example, EQ in many amps just reduces the volume of certain frequencies. In order to make up for the loss, the preamp has to amplify the signal slightly.

It's also used as a buffer between different devices for better transmission of the signal.