preamp vs. poweramp (basic question)

[rhubyrhod]

basic question indeed

is the preamp section of an amp for adding effects and the poweramp section used purely for making it louder? and thats it?

preamps add gain, dont they? is that just to make the original signal "loud" enough for the preamp circuit to "see" it since the voltage from a guiar is so small?

obviously im confused


so is a pod a preamp only?

[kwright]

There are sooo many people on here that are more qualified to answer this question, but in my simple brain view:

Pre-amp section - Adds gain and brings the source signal up to an appropriate level to hand over to the power section.

Power section - Amplifies the signal (read as makes it good and loud) to output section.

Tone stacks are typically in the pre-amp sections in various configurations, and there can multiple pre-amp sections.

Phase inverters are between the pre and power sections as are (generally) fx loops and reverb/trem sections.

Not sure on the presence and cut, but for the most part these appear to be tone coloring or negative feedback controls in or behind the Phase inverter section.

Anyway, I'm sure that there are some folks here that can correct me where I'm wrong...

As for the pod.. ? I've not really thought about it, I just considered them as a multi-effects processor.

[Kiwi]

You're basically on the right track. Pre-amp sections take the very low-power signal from the guitar up to about 1 watt or so, then hand it over to the power section. The power tubes boost it up to whatever your amp puts out.

The pre-amp section is nearly always where the boost in gain occurs for channel-switching amps. For high-gain amp channels, it's generally a series of pre-amp gain stages (cascading the gain).

Another really helpful generality: Pre-amp tubes can usually be swapped and changed without any adjustment. Power tubes - with a few exceptions - need to be "re-biased" when you change tubes. That's a job for an amp tech or an experienced electronics worker.

The main exception to the "re-bias your power tube" rule is in a lot of amps that use EL84s (not to be confused with EL34s!) in the power section.

The Line6 POD is best used (in my opinion) as a direct-recording device; I've used one since introduction in Jan-99 and it's tremendous at that. Major rock acts are reportedly using it in the studio. Its second-best use is straight into a PA system, which is getting increasingly common for live performers. The third-best application for POD is as a "super effects box" pre-amp, and thus running it into the power amp section of your amp. That's where a lot of people have said it may not sound that great. It can be done, but that's not what it was designed specifically to do. Your opinion may differ, and your opinion is all that counts.

Kiwi