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>I have a Peavey 4x12 and I just sold my amp
>head for some cash to get a rack mounted power amp. Now, seeing as I
>bought the cabinet used, most of the info on the back is scratched off,
>and I'm not sure of the wattage. It was wired wrong when I got it so I
>had to redo it, and I think it's 100W (50Wx4), but I'm not sure. Putting
>that aside, and assuming it's 100W, what would be a good power rating of a
>power amp for me to use, for guitar? I've been looking at Peavey M-2600's
>(260 watts) and at Rocktron Velocity 150's (75 wats). Would I screw
>myself by using 260 watts on the cabinet? or would I be under powering
>myself with the 75 watts? Any advice would be GREATLY appreciated,
>because I need a power amp SOON! E-Mail me 'cause I'll get that sooner,
>thanks A WHOLE LOT!! (address is also below)

You should pull out a speaker and write down the information.

You should use more powerful speakers than amp. If your speakers are rated at a total of 100 watts, use a 50 watt amp. If your speakers add up to 150-200 watts, use a 100 watt amp. It's easy to blow speakers when you blast them at full capacity for a while.


>I have a very old all tube PA amp (so old it has a fixed male threaded mike input on the front in addition to 1/4 inch phone plugs) that I got great distortion from without too much volume. After perusing your site, I'm inspired to light her up again. I'm thinking of getting a Celestion G-12 M-25 watt Greenback reissue to go with it. What do you think of that choice for lower watt breakup?

I had good results driving this 25-watt speaker with a 15-watt tube amp. (I used the Fender Pro Jr., an amp which I, together with at least one other person, have found to be unacceptably noisy/hissy, and which in my unit, had a disasterously discontinuous jump in the volume pot -- my Guitar Center salesman was so ignorant, he claimed, with the voice of condescending authority, that this volume jump was "the power tubes kicking in"! In fact, when power tubes "kick in", turning up the volume pot produces *less* increase of the resulting sound level, not *more*.)

>Also, I was looking through the Mesa Boogie catalog and noticed they have a 20/20 watt rackmount power amp with a slave out they claim acts as a larger power amp "tone generator" to take advantage of the 20/20's "musical tone clip." I assume this slave out is line level, so with a Marshall Power Brake of THD nullifying the 20/20's power out, how do you think a cranked 20/20 might perform in the effects loop of a guitar processor such as a Roland GP-100?

That setup would preserve *some* power-tube saturation tone; however, it would lack two crucial factors required for the authoritative, reference Tone: overdriven speakers, and the feedback from the guitar speakers, through the output transformer, to the power tubes.

Re: 4 Watt Amps--12" speakers
Author: Tom Shaw
a0005868 at airmail.net
alt.guitar, alt.guitar.amps

> > Bret Spencer wrote:>
> > > Running 4 watts through a 12" speaker! What? Are you nuts?
> > >Thats kind of like ordering a Corvette ZR-1 and asking them to
> > >put a lawn mower engine in it.
> Jim at Analog Bros. wrote:
> >
> > Bret,
> > Not quite. A 4 watt amp can drive a 12" speaker very well.
> I play a 7 watt HI-MU through a 4x10 or 2x12 all the time! Sometimes
> I even use a HOTPLATE to take the volume DOWN for late-night practice.
> I've also heard the Jarrod Lee 4 watt "Lawbreaker" through a single-
> twelve and it sounds great. Jarrod recommends using a 4x12 with
> it for a bigger sound!! Many reviewers have heard the 4-watt into
> the 4x12 have been blown away by the great tone it produces!
> I think a lot depends on the design of the amp--and the current
> delivering capapability of the output transformer???

Tom Shaw wrote:

>What it depends on most is the speaker design. High efficiency speakers will be over driven by 4 real watts, meaning 4 watts out of the output transformer. One fourth watt is listening-loud in a high efficiency speaker. Low efficiency speakers, which have been on the market for several years, because they give better fidelity for audio enthusiasts need lots more wattage. These speakers were never popular before the advent of transistor amps because the cost of high watt tube amps was prohibitive.

quark at sprintmail.com

>Speaker efficiency is a crucial factor. For example, a switch from a 100db to 97db efficiency speaker is equivalent to cutting power in HALF--i.e. 18watt GHIA becomes as loud as a 9watt GHIA.

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