difference between guitar power amp and PA power amp?

M

MegaGoo

New member
hi all looking for some advice here. somewhat related my my last topic

right now im playing with my j-station through a little power amp. well its 270 watts per channel @ 4 ohms. i have a new 4x12 on the way but we'll use the one im currently playing through in this question. it is 280 watts total capicity. today at band practice, i had to crank it WAY up (our drummer is a loud mofo). how i did not blow the speakers perplexes me. correct me if im wrong but 4 speakers at 280 watts means that each channel has 140 watts. if im pushing 270 watts per channel, how can that not blow the speakers very easily? i had the power amp on about volume level 6 (for each channel) and had the j-station turned up to 7 1/2. it was loud as hell but it had to be.

am i playing with fire? i dont want to blow my friends cabinet, and i sure dont want to blow mine when it gets here this friday (btw mine will be 2 celestion v30s and 2 celestion classic lead 80s). so that'll be 240 watts total. less than what i have now.

also, im playing through a regular power amp. used for i guess PA systems or home audio possibly. http://www.abamps.com

what is the difference between this type of amp and a tube guitar specific power amp like a marshall or mesa 50/50 or 90/90

AND.. how is playing through a $1,300 90 watt per channel amp better than playing through a couple hundred dollar PA type power amp thats 270 watts per channel. i think that the 2:90 is geared towards being used in conjunction with a triaxis so maybe thats an expensive comparison, but still..

im also playing through a j-station. the tone is so-so. .. my biggest concerns are playing at high volumes w/o blowing the speakers, and good tone, secondary.

is there anything i can do with adding to or changing my current rig (j-station through a regular cheap power amp) that would A) ensure i wouldnt blow the speakers, and B) have a decent or good tone, for a reasonable amount of money (i dont consider buying a triple recto head reasonable)

thanks
eddie
 
Megagoo,
Give us the exact configuration of the cab. How the connection is made etc. Not enough info.

bd
 
the cabinet? its 4x12. 4 celestions (70 watts apeice). 4 ohm stereo coming out of 2 channels of the power amp
 
How are the spkrs wired? Series, or parallel? It makes a difference. How many ohms does the tag say?


bd
 
well i cant be sure on this mesa. it has a 8ohm mono jack and 2 4ohm stereo jacks.

on the cabinet i am getting this friday, it will have 2 4ohm stereo jacks, and i believe the speakers will be 8 ohms each, so if im not mistaken, it will have to be wired in parallel.

http://www.avatarspeakers.com/wiring diagrams.htm

Parallel

2 x 4 Ohm speaker = 2 Ohm load
2 x 8 Ohm speaker = 4 Ohm load
2 x 16 Ohm speaker = 8 Ohm load

<picture>

my new cabinet's speakers are also 60 watts (v30s) and 80 watts (classic lead 80s). also, i told the guy to wire the v30s on 1 channel and the CL80s on a seperate channel. but they'll all still be on 2 4ohm channels

eddie
 
OK ....well, yeah you got a sledgehammer there! I honestly don't know the difference between the power amps though. I always thought power amp was a power amp. It probably has something to do with the freq. response.

bd
 
MegaGoo said:

what is the difference between this type of amp and a tube guitar specific power amp like a marshall or mesa 50/50 or 90/90

AND.. how is playing through a $1,300 90 watt per channel amp better than playing through a couple hundred dollar PA type power amp thats 270 watts per channel. i think that the 2:90 is geared towards being used in conjunction with a triaxis so maybe thats an expensive comparison, but still..
Click to expand...

A lot of people use amp heads because their simplicity. Take a marshall stack for example... All you have to do is place the head on top of the cab and plug it in. The amp heads are equivalent to a nice tube preamp and a power amp, except it's all in one unit and you can't exactly separate them.

You can make a similar setup with rackmount equipment... either a nice preamp + processors + power amp or an amp modeler and a power amp. These setups can easily cost more than the average Marshall amp head, which is why they're not as common. Plus, they take a lot more thinking to configure properly, there are a lot more options, and most preamps don't have the huge ass tubes found in amp heads, just the small AX7s.

Right now you're using your J-station as a preamp into the power amp which is okay, but it will sound better if you had a real preamp of some sort. I have an avalon U5 DI and a large crown power amp for my PA system which i use for acoustic guitar. I plug my electric into the same preamp or an Art TPS preamp (which i usually use for mics) and it sounds nice.

You probably won't blow out your speakers with your setup. Just make sure that the signal going into power amp isn't too hot or you'll clip the speakers which may cause some destruction.
 
hm. a pre-amp? ok so it'd be j-station>pre-amp>power-amp>cabinet?

whats the point of pre-amping an already really powerful poweramp??

and what should i look for in a preamp, for my situation? brands, specs, prices, etc? thanks

eddie
 
The J-station is a Pre-amp, and you are using it for effects and distortion right? So if you ditch the j-station and get a deticated mic pre, you will lose the effects and distortion, unless the mic pre has an insert and you can add effects/distortion. but then I dont see the difference, might as well use the J-station. I don't see using a pa power amp is a problem, as far as whether you have you have too many watts or not enough I am not sure! Most guitar amp Heads are 100 or 200 watts, where as your pa power amp is a little more. I can't believe that you had to crank the pa power amp up to the max so your drummer could hear ya. Does your J-station have a volume on it, if so is that cranked? Plus your Pa Power amp is probably set up for running 2 speakers right? (2channels) so if you are only using 1 channel to drive you 412 than you wont be using the full watts from the PA (I think) you would only be using half.
 
well im running through both channels. left and right outputs into channel 1 and 2 respectivly. and i have both channels cranked up to 6 or 7. and yes the j-station is turned up to maybe 6 or so. but our drummer is LOUD. also, i moved my rig away from him so i wouldnt have to stand so close to him. that did help

i think esun was saying use the j-station AND a preamp. but i dont get it. not using the j-station means i will have to run through my metalzone, which sounds better with an eq pedal that i dont have, and also means i would have no effects so thats not the best possible solution

eddie
 
hmmmmmmmmmmmmmmm well I don't really know what to tell ya, I think that if you go J-station>preamp>poweramp>412 you will run into noise problems cause you would be sending a pretty hot signal to the power amp, but I could be wrong! Is your band using a mixer (for vocals, etc.....) when you practice, if you are I would just run the J-station right into the mixer (using the poweramp driving the main speakers) if you have enough channels and forget your power amp unless you wanted to use it as sort of a monitor out from the main mixer.

-if that is not an option then I would just use your power amp to drive the 412 and the J-station before the poweramp, and I don't think that the power amp will kill your new 412 cab. If you crank it to 10 and your speakers start puking then TURN it down. Other than buying a new power amp like the messa 50/50 that is made for this purpose than I dont think there is to much you could do, but I dont think that you NEED a preamp. Sorry I cant be more help than that!

-ps does your power amp head have an effects insert, if so you could run the J-station thru that and you adjust how much of the J-station goes thru the amp. Don't know what good it would do ya but it might be neat to see what it sounds like, might make it quieter also!

peace!
 
well the seperate pre-amp isnt that big a deal. esun brought that up anyway. but i think he meant in place of the j-station, which i dont think will solve anything

see, the power amps confuse me. you have a 50/50 or 90/90 for a lot of money, or just a plain old solid state power amp for not a lot of money. and im hearing that you can push 50 per channel, or you can push 270 per channel. that doesnt make sense to me but i'll accept it

also, i'll probably be hooking up my friends cab sometimes to the power amp. so that'll cut me down from 270 watts per channel 4 ohm stereo to 145 watts per channel 8 ohm mono. but apparantly watts dont mean jack so that should be ok. besides, untill recently i've been playing through my friends mesa at 8 ohms mono anyway and it sounds ok cranked. i've heard its bad to run a cab with not a lot of wattage, but if a 50/50 is typical, how much wattage is not a lot. 20 watts? 10? where do you draw the line at for minimum and maximum wattage here

eddie

also, running j-station through a pa is possible, but with the types of pa speakers we have, it sounds way too harsh and high end
 
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