Back to the Tube-Amp world :) Help needed please...

[Kac]

Got rid of my XXL head.
Picked up a brand new Peavey Valve King 50 watt tube combo.

The external speaker jack is rated at 8 ohms and my cabinet is 4 ohms... I want to use my cabinet for this amp, but I don't know if there is any possible way to do it.
If anyone can offer some insight that would be much appreciated!

(mesa/boogie 2X12 speaker cabinet)

Also ~ pics to come sooner or later..

 

[DeadSkinSlayer3]

Re: Back to the Tube-Amp world Help needed please...

Aw no 5150? Damn!

If your cabinet is 4 ohms, and a 2x12, then the speakers should both be 8 ohm. I forget which it is, but if it's in series now, wire it back up in parallel for a 16 ohm load.

It's alright to push impedances uphill, but not downhill (8 into 16 = yes, 8 into 4 = no).

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

Alright, I just need someone to tell me how to re-wire my Cabinet then... I have never looked inside it, but I know it has 2 8 ohm speakers.
~Kac

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

Someone please help!!! I know someone can tell me how to change this wiring.
~Kac

 

[Scott_F]

Re: Back to the Tube-Amp world Help needed please...

There is no way that I know of to rewire an 4 ohm cab as 8 ohms. Unless you drop two new speakers into it with the right impedance.

Two 8 ohm speakers can either be wired as 4 ohms or 16 ohms. Those are your choices. Two 16 ohm speakers can be 8 ohms easily though.

Depending on which amp and which transformers, it might be okay to run them slightly mismatched, like an 8 with a 4, but you wouldnt want to run a 4 ohm cab into a 16 ohm output. That's too big a stretch.

Check with Peavey and see what they say. I had a Mesa that I bought from Al C I think, that had in the Mark I manual the go-ahead to run it mismatched. they gave it their blessing.

if you think about all those old fenders that had two speaker jacks. A lot of times people were running two 8 ohm loads reducing the overall load to 4 ohms and those amps always held up pretty well.

Check with Peavey and see what they say. Don't take my words here as a go ahead to do it wthout checking first.

Unless the amp is made like a complete piece of crap, it really should stress it out too badly. Just my opinion.

 

[ksmith63]

Re: Back to the Tube-Amp world Help needed please...

You can't wire the cab to 8 ohm. What you can do is add another speaker cab in series with that one, or just run one of the speakers. As far as 'resistance' goes, it is basically how much power your speakers are drawing from the amplifier. This is why it is usually better to run a speaker with a higher resistance to the amplifier then a speaker with a lower. The speaker with the lower resistance will draw more power then the amplifier wants to churn out, and can cause the amp to overheat (not a 'death' experience for the amp but at the least it will make you go through power tubes faster)

Best results
1.buy another 4 ohm cab and wire it in series with the first. 4+4=8
2.modify your cab so it is only running one of the speakers
3.modify the cab so the speakers are in series (16 ohm)
4.use the cab with the 4 ohm impedance it has now
Worse results

 

[B2D]

Re: Back to the Tube-Amp world Help needed please...

I ran an 8 ohm MESA head into a 16 ohm Marshall cab for a looong time and while the tone was a wee bit depleted I had no problems. For the best tonal results I'd just get some 16 ohm speakers and swap out. Then in the wiring they're at now (parallel) they'd make for an 8 ohm cab and no cab rewiring would be needed.

On a related topic... how do you like the amp and how much did you pay for it?

 

[ErikH]

Re: Back to the Tube-Amp world Help needed please...

DSS, two 8 ohms in series is 16 ohms, two 8 ohms in parallel is 4 ohms. You have it backwards.

I'm pretty sure those cabs are wired in parallel so a quick rewire to put them in series will fix it up.

 

[DeadSkinSlayer3]

Re: Back to the Tube-Amp world Help needed please...

DSS, two 8 ohms in series is 16 ohms, two 8 ohms in parallel is 4 ohms. You have it backwards.

I'm pretty sure those cabs are wired in parallel so a quick rewire to put them in series will fix it up.

Ah ok. I wasn't exactly sure. Thanks!

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

On a related topic... how do you like the amp and how much did you pay for it?

Got another thread on that, and I like it a lot! traded my XXL head for it, but did a bit of other trading at the same time...
~Kac

 

[Gearjoneser]

Re: Back to the Tube-Amp world Help needed please...

To rewire.

Right now each speaker positive is going to the jack positive. Each speaker negative is going to the jack negative.

To wire it in series, turning it into 16 ohms, The jack positive goes to 1 speaker pos. That speaker neg goes to the other speaker pos. The 2nd speaker negative returns to the jack negative.

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

Thank you very much GJ, I'm gonna read the manual and see if it says it's ok to plug it into a 16 ohm cabinet.

Rock On ~ Kac

 

[Davey]

Re: Back to the Tube-Amp world Help needed please...

this is what you got right now
2 X 4 Ohm Speaker = 2 Ohm Load
2 X 8 Ohm Speaker = 4 Ohm Load
2 X 16 Ohm Speaker = 8 Ohm Load

this is what you need to wire it as a 16 ohm cab
2 X 4 Ohm Speaker = 8 Ohm Load
2 X 8 Ohm Speaker = 16 Ohm Load
2 X 16 Ohm Speaker = 32 Ohm Load

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

Thanks Davey ~ You Rock :headbang:

~ Kac ~

 

[Kac]

Re: Back to the Tube-Amp world Help needed please...

:notworthy GJ, DSS3, Davey, You Guys Rock!!! :headbang:

I printed out Davey's wiring scematic, warmed up the soldering iron and went to work.

All this after reading the manual that said the speaker extension was good to go for a 16 ohm cab.

Got it all done and it works great! ~ thank you guys very much!

Rock On - Kac

 

[B2D]

Re: Back to the Tube-Amp world Help needed please...

YESSSSS success!

 

[Davey]

Re: Back to the Tube-Amp world Help needed please...

patient alive and well!