Low volume from a 120 watt amp (help)

I bought a Peavey 5150 used about 5 years ago. I then took a break from guitar for a few years and I just recently got it back out.

I plugged it in and noticed I wasn't getting the volume I should out of it. Since it still had original tubes I replaced all of them, but I am still getting very little umph out of this amp.

I know when I put it away nothing was wrong with it. The tone seems decent but the volume is very low.

I don't remember a whole lot about this amp, and I don't know much about tube heads and cabinets in general as this is the only one I have ever owned.

The way I have it set up is guitar straight to the head. The head is plugged into an extension chord that is running from a surge protector with some other things plugged into it (only one outlet where I practice). The amp is connected to the cabinet through a short guitar cable. On the back of the cabinet is a a big connector with prongs in it (sort of like the male end of a cannon plug). I have no idea what that is for.

Any help would be appreciated. I wanted to make sure it is set up correctly before I go and drop a bunch of cash to get it fixed.

There's at least one, maybe two things wrong with your setup:

• "The amp is connected to the cabinet through a short guitar cable."
  

You can't possibly get the high-current drive that speakers need through a guitar cable. A piece of #14 lamp cord (also called twinlead) is much better suited to the task. A guitar cable is meant to carry a few millivolts at a few microamps of current. At 120 Watts, an 8 Ohm cab needs something close to 30 Volts at about 4 Amps. A guitar cable can't do it for you.
• I'm not familiar with those Peavey cabs, but some old Ampegs used a special cable and connectors to provide an interlock protection for the amp. If the output was not connected to a suitable cab via the proper cable and connector, the amp would not produce enough power to hurt itself. You may find that you need a Peavey speaker cable to connect your amp to your cab. The connector you describe sounds like something called a Speakon connector. A generic Speakon cable may do the trick, but it wouldn't hurt to get a Peavey part.

Either way, toss that guitar cord!

Thanks a ton for your advice. I'll try and find a different cable asap.

So, did you get yourself a better speaker cable for Christmas?

How is it working for you?

On my way to the music store as we speak. I'll let ya know in a few hours!

Got a new speaker cable and I'm still getting low volume. It has great tone but volume is seriously lacking. I'm starting to wonder if I shouldn't just sell this thing and quit dumping money into a 15 year old amp.

I did some research and the other connector on the cabinet is an XLR input. I don't know what it would be used for though.

XLR??? IIRC, Ampeg used that on some of their old V-series cabs for the safety interlock. Is this a Peavey 5150 cab?

Replacing the power tubes usually means that you need to re-bias the output stage to match the new tubes. You could try stuffing the old power tubes back in, just to see.

I think you need some advice from someone who has one of these amps. Shoot a PM to PRSplaya and see what he thinks.

Yeah it's a peavey 5150 cab. Sadly all of the tubes are fixed bias (unable to adjust without a serious mod to the head.)

Yeah I'll shoot him a PM right now.