Power issues

[Colb]

A technical question, I have a Marshall 100 W per speaker stack plugged into a 112 V 60 Hz wall outlet that is also supporting mulitple effects and another (about 80 W 2 speaker) Crate combo. I notice with both plugged in at the same time, I get the mud sound when you something is not right (power or speakers). Since the amps are on (the same) surge protection, I don't think the circuit is surging. Does anyone have this problem, is there anyt suggestions? I know another surge protector might help, but will that really up the power from the 4 plug outlet? I am assuming they are wired in 2 parallel series pairs.

[Gabriel E.]

You are overtaxing the curcuit and as a result, getting a voltage drop. It's not enough to blow the breaker or fuse but is enough to affect the way the amp sounds.

 

Your amps are also designed to run at 117-120 volts so 112 is a little low to begin with.

 

Two remedies:

 

1. Use a line regulator.

 

2. Plug some of the gear into an outlet that is running on a separate circuit.

 

Note: Eddie Van Halen used to use a variable AC transformer (Variac) to drop the voltage on his amp to get a more mushy sound. This can be pretty dangerous and is not reccomended.

[Caevan O’Shite]

Hey, Colb, welcome to the forum!

 

Gabriel E is, as usual, quite correct (good man, that Gabes).

 

I just want to be sure of something... are you also plugging the guitar into both amps, or using them simultaneously some other way?

 

If so, you may also be altering the impedence matching between your guitar and the amp unputs. This will also give you a muddy, lifeless response.

 

If this is the case, Myles Rose, our moderator and amp expert (and he is) can be querried and quizzed on the "Feel free to ask Myles" thread, here on this forum.

 

Craig Anderton over on the Sound, Stage, and Studio Forum, would also be an excellent person to work out guitar-to-amp impedence issues; he wrote on these things for Guitar Player magazine in the past.

 

Best of luck, and keep us posted!

[Colb]

Thanks guys. I never thought about the impedance issue. It also never occured to me the 112 V thing. Is there anything you would recommend as far as specific line regulator? It would be nice to have for a constant sound. Thanks.

[BillWelcome Home Studios]

Originally posted by Colb:

... I have a Marshall 100 W per speaker stack plugged into a 112 V 60 Hz wall outlet that is also supporting mulitple effects and another (about 80 W 2 speaker) Crate combo. I notice with both plugged in at the same time, I get the mud sound when you something is not right ... I am assuming they are wired in 2 parallel series pairs.

Your problem could be any number of things, from poor incoming service, through ear fatigue or compression due to volume level.

 

My guess would be the latter, if you are playing in a reflective room at significant volumes. The sound bouncing around is probably mudding things up for you.

 

Your wall socket, assuming a standard supply, is providing about 117 volts... give or take. Posible variables? Over or under voltage supply at the transformer source (on the pole)... line loss between the pole and the service entrance, line loss from the panel to your outlet, line loss due to the number of items using power on that line at any given time.

 

Just guessing, but your amp probably draws about 6 amps. That is about 1/4 of the total available to a typcal 20 amp circuit, or 1/3 of what is available on a 15 amp circuit. (Everyone is pretty much using 20 amp breakers or fuses, even though our plugs and sockets are rated at 15 amps.) So you aren't really stressing out the circuit.

 

A little bit of line sag is possible, but probably would not be noticable. Who knows what other devices are on the same circuit.... maybe a refrigerator, or something.

 

So you might consider a dedicated line from the panel, using a heavy gauge wire, just for your amps. That way you know that there is only so much draw on it.

 

Still, there isn't anything in the panel to prevent total building usage from causing a drop in the voltage available to your circuit. And there is not much that you can do about that.

 

a surge protector only protects against surges. will do nothing to help regulate power.

 

Power regulation for a 10 amp reactive load (giving you some headroom over your 6 amp requirement...) could be pretty expensive, and would definitely be heavy.

 

Most of the exotic things that you read about for amps on the road dissappeared from the road after the 1970s. I really don't see anything exotic anymore for guitar amps.... just good stage power distribution panels and runs. Gone are the Variacs (which is a big, wire-wound variable resistor used mostly to dim lights)and the transformers and other exotica. Occasionally, someone will bring in a balanced power rig, but not often enough for me to remember who or why.

 

It's the computer guys who carry all the voodoo these days. (g)

 

Bill