Running solid-state at lower impedances

[enim]

I have a Peavey Century 200 bass series, rated for 100 watts at 4 ohms.

What would happen if i connected 2 4ohm cabs to it?

Will the wattage increase at all?

Will i blow the power section?

 

[seamonkey]

I would hope that Peavey had the insight to provide amp protection. If so, the amp should shutdown when pushed and not come to harm. But I don't know that they did.

 

[enim]

the amp was made in 1979

 

[Marley's Ghost]

Just don't do it.

At very low volumes, prolly nothing. At high volumes, bad things.

 

[joegeezer]

They are not made for 2 ohms, but will run it for a while. The wattage rating will go down, though. Not up. And heat will make it shut down on you.

 

[Hookus]

The wattage rating will go down, though. Not up.

Come again? I think you are backwards here my friend. All else being equal, cutting resistance in half either doubles your current, or halves your voltage. Since voltage is regulated, if current doubles, your power (in watts) doubles, this is until whatever current limiting device (probably a fuse, or temperature limiting device trips. Ohm's Law. V = I*R, and P = I*E

 

[Jerrold Tiers]

Come again? I think you are backwards here my friend. All else being equal, cutting resistance in half either doubles your current, or halves your voltage. Since voltage is regulated, if current doubles, your power (in watts) doubles, this is until whatever current limiting device (probably a fuse, or temperature limiting device trips. Ohm's Law. V = I*R, and P = I*E

Actually, in this case I think he may be right..... your error is in assuming voltage is regulated.... it ain't.

Increasing the load on the power supply will cause a drop in voltage. Many manufacturers who make lower cost stuff will make the power supply and transformer just good enough to put out at the lowest impedance, and no lower.... Then the power supply volts fall due to resistances etc at lower impedance loads.

Peavey has done it, Crate has done it..... even Fender, and Ampeg, in lower cost units.

It isn't uncommon to see a power rating the same, or close to it, at 2 ohms as it is at 4 ohms. And that is when the unit is designed to operate at 2 ohms.

There isn't any problem with that. After all it is rated for 4 ohms, why should it have a power supply that can drive 2ohms?

 

[62bass]

Actually, in this case I think he may be right..... your error is in assuming voltage is regulated.... it ain't.

Increasing the load on the power supply will cause a drop in voltage. Many manufacturers who make lower cost stuff will make the power supply and transformer just good enough to put out at the lowest impedance, and no lower.... Then the power supply volts fall due to resistances etc at lower impedance loads.

Peavey has done it, Crate has done it..... even Fender, and Ampeg, in lower cost units.

It isn't uncommon to see a power rating the same, or close to it, at 2 ohms as it is at 4 ohms. And that is when the unit is designed to operate at 2 ohms.

There isn't any problem with that. After all it is rated for 4 ohms, why should it have a power supply that can drive 2ohms?

I believe you are right. The Mesa Walkabout I have will run a 2 ohm load fairly safely (although Mesa doesn't recommend it) at high volumes without shutting down. It's rated as 300 watts into 4 ohms. However, according to Mesa, the power is still a maximum of 300 watts at 2 ohms.

Some Yorkville bass amps are the same.

 

[seamonkey]

Some of the gutsy manufacturers like Crown will actually publish lower wattage ratings for 2 ohms on some of their amps.

 

[fdeck]

In addition, some amps have active current limiting in the power amp circuit itself.

 

[htharp]

From an old Peavey Century manual I just acquired -
"Speaker systems with less than a total of four ohms may be used with the risk of overloading the power amplifier. Slightly less power will be delivered to lower impedances because of the unique limiting action of our integral protection system."

 

[mastervolume]

It's a peavey. If you hook it up out of its operating specs it will break on you. I suggest you find another amp if you need more ooomph.

 

[Vic20]

A few years back when I was less knowledgeable about these things I hooked up an extension to an Ashdown combo which took the load down to two ohms.

It was amazing how quickly the amp stopped making sounds and started making fire!

That was a fine but very expensive motivation to learn about the technicalities of the gear I use. I can recommend anyone else obtain this knowledge before boldly going beyond the operational range!

 

[Crockettnj]

It's a peavey. If you hook it up out of its operating specs it will break on you.

I have found that Peavey's are typically up the the task of taking a pretty good beating while still working. Tone and weight are usually the gripes with Peavey (warranted or not). You rarely hear complaints about PV reliablilty.

 

[mastervolume]

Peaveys are great amps that will work for what seems like an eternity if you keep within their intended purpose. If you push them out of their comfort zone they will die a horrible death. I'm not putting down the brand. I've had my fair share of peavey experience in my 30+ yrs of playing but they are what they are. Nothing more. Nothing less. If the peavey sound is what you like then choose the correct model for your purpose. While this is true of any amp it is especially true with peaveys in my opinion.

 

[Corporem]

I seem to have something back asswards here... Doesn't two cabs' add up to the total speaker impedance? Wouldn't the total speaker impedance be 8 ohm, in this case, rather than 2?

 

[alfredpunkjazz]

I must say...

peavey is great for one thing... in the middle of a gig, if your amps starts doing weird things... a good kick will help...

LOL

They are battle-workers...

 

[62bass]

I seem to have something back asswards here... Doesn't two cabs' add up to the total speaker impedance? Wouldn't the total speaker impedance be 8 ohm, in this case, rather than 2?

No. 2 cabinets connected in parallel, which would be the case in most instances, halves the impedance. If the cabinetes were connected in series then the impedance would double. Some people believe that adding a speaker cabinet to the chain puts it in series. This is not what happens unless the speaker jacks are wired to make adding an extension cabinet a series connection. Only a few amps are built this way.

Some very low cost amps are designed to put out their full rated power at 8 ohms and will go no lower safely. One of my small practice amps, a Peavey Minx, is like this. 30 watts to its 8 ohm internal speaker and no lower. Within its rated power it sounds fine. Its just not designed for playing a bigger room at high volumes. Sounds good at home in a small room though and has been working fine for almost 20 years.

If you need more speaker area and more power, buy a bigger amp. Peavey's are tough, but not indestructable.

 

[Selta]

Peaveys are great amps that will work for what seems like an eternity if you keep within their intended purpose. If you push them out of their comfort zone they will die a horrible death. I'm not putting down the brand. I've had my fair share of peavey experience in my 30+ yrs of playing but they are what they are. Nothing more. Nothing less. If the peavey sound is what you like then choose the correct model for your purpose. While this is true of any amp it is especially true with peaveys in my opinion.