I tried to reply to an old thread and it wouldn't let me. A member wanted to unplug a speaker in his 5150 to reduce the volume.

Here is my reply. Maybe this will stop someone from ruining his or her amp:

**Please(!) do not disable, unplug, etc. any speaker in your 5150. The amp must have a minimum "load", else you will blow the transformer, tubes, and who knows what else.

(Assuming the 5150 output is wired for 16 ohms): If the two speakers, wired in series, put a 16 Ohm load on the amp, unplugging one will reduce that load to 8 Ohms and blow your amp up - so to speak. However, if they're wired in parallel for 16 Ohms, they would be 32 Ohm speakers (individually) and would put a 32 Ohm load on your amp, which is safe but won't give you the results you're after.

Tube amps are very sensitive to the minimum load that should be placed on them (most are 16 Ohms). If you want to reduce output power while driving your output stage, this is what the Hot Plate or Power Brake is for. Or, do some research on removing two of the 6L6 power tubes.

Mark

I guess if it was a old thread the guy has figured it out by now.

__________________

Good point.. I'll look into what Roger Crimm has said.. I dont remember him heeding any possible dangers.

__________________

Yep, dont fuck with tube amps, not a good idea.

__________________

Or he screwed it up and blew the amp to hell....


.....who knows?

that could be the other option

__________________

Lots of tube amps are designed to work at both eight and sixteen ohms without any rewiring or anything and the 5150 is one of those amps. I'm sure that old thread was moderated by trained professionals and no guitarists were injured during the making of that thread.

OMG!!!! Someone dropped the soap in thread number 2875!!! Please, for the love of god, don't pick it up!!!!

Correct. And I'm not trying to argue with you, but I'd like to point out that since the original poster didn't consider the consequences, he's not likely to know correct usage of the impedance switch on the back of the amp. Further, we're talking about a 5150 combo, on which the 8/16 impedance switch is for the "external speaker" out, not the hardwired speakers within.

Upon looking at a 5150 today, I noticed it is actually 8 Ohms internally. But the rule still applies. If those two speakers are 4 Ohm and wired in series to make an 8 Ohm load, the amp can easily die with one disconnected. This poster was wanting to disable a speaker in his 5150 combo in order to play it cranked up to 10! Unfortunately, no one in the forum told him of the consequences. Some people assume this sort of knowledge is common, when it's often not. I include this very warning with the amps I design and build.

Killing a $1000 amp could be devastating for some folk. Especially younger ones who are working all summer to save up to buy one.

You make amps? Cool, have a website?

__________________

Last I checked the 5150 combo has one internal 16 ohm and allows any speaker network >=16 ohms to be plugged into the parallel jack in the back resulting in >=8 ohms combined.

What amps do you design and build?

Ah. We're talking about two different amps. Maybe that makes sense as to why we're not connecting on this, huh? The 5150 combo I'm talking about is this one:
http://www.andysmusiconline.com/Pro..._5150_212_COMBO
It has two 12" 16 Ohm Sheffields in parallel and the 16 ohm tap at the external jack. I was unaware that Peavey even made a 1x12" version of the 5150, but I don't know much about Peavey's history either.

I'm not an expert on the 5150. I just bought a non-working one to repair and keep for myself. I couldn't let it pass: it was less than the cost of an empty chassis and cabinet alone, and it has other features that are cost prohibitive for a small-time, boo-teeq builder. It's due to arrive tomorrow. I've just recently become a fan of Peavey amps. I also bought a new SS XXL 100w head in March. Without a doubt, it's the best-sounding SS amp I've personally played through.

I'm sorry. I shouldn't have mentioned my amp building. The logical question from others is "tell me more", but there isn't much more to tell yet. The amps I build are modified 18-watt knock-offs, a simple 10-watt (no pre), and a 1-watt design I've melted together from people much more knowledgeable than I. I don't have a website for my amps, nor have I registered a name. I'm still looking for both liability and reliability issues, and I can't use my personal builds for anything but a control group. I built several of them as Christmas and birthday gifts for co-workers and friends last year. They are my guinea pigs.

They dont.

__________________

BLS would know better than I. I haven't even seen a 5150 that I know of, I just reviewed the data sheet awhile back for someone. As I recall it said the internal was 16ohms, so it could be two 8ohms in series or whatever.

That's very cool that you built those amps for your buddies (or guinea pigs)....

id take one. how much it cost you to build one? whats they sound like

__________________