Can a Sunn Sceptre be safely run at 2 ohms?

[oxenrig]

So yesterday, I picked up thisbeauty for 200 bucks. Now here's the problem: I only have 2 4 ohm cabs.   Is it safe to run it at 2 ohms, or will I have to use my other head as well if I wanna use both cabs (other head is Fender Bassman 135, soon to be a Sunn 2000s)?

[loudthud]

On the back of your Sceptre there is a label for the speaker jacks should say 8 ohms next to the "Speaker" jack and 4 ohms next to the "Extention" jack. If it says 16 ohms and 8 ohms, your amp will need a couple of wires moved internally. I say this because some Sunn amps were wired for the higher impedance cabs and I don't have enough documentation to say for sure how your amp is wired. Second, make sure your amp has the correct fuse. This will prevent a lot of damage if something else fails. Thirdly, if your output tubes are weak, you should change them. Preferably to KT88's and get them biased properly. Under those conditions, your amp will probably survive unless you're playing thrash metal with lots of overdrive.

One way to solve the problem would be to get a "series connected" Y cord made. Plug that into the 8 ohm jack and plug your cabs into the Y cord. Your Bassman 135 basically does that when you plug into the speaker and extention jacks. It connects them in series and switches to the 8 ohm tap on the output transformer. You'll have the same problem when you get a 2000S. Another option is to rewire your cabs for 16 ohms and have your Sunn amps setup for the 16 & 8 ohm outputs.

[Spectrum II]

So is the 4ohm "extension" actually 4ohms if you're only running one 4ohm cab out of it & not two 8 ohm cabs? If not, I've been doping it wrong for the past couple months! Steer me in the right direction.

[loudthud]

See My posts under "Sunn 2000S Guitar & Bass heads" and under "200S bias".

[oxenrig]

I'm just thinkin of selling my current cabs anyways, as they're kinda rubbish. And I use the sceptre as a treble amp, driving the mids and highs at 10 with the volume at ten, bass at 0, and I use the bassman for the lows.

[Isaac]

The Sceptre output jacks are labelled 8 and 4 ohms. If you have one 8 ohm cabinet, plug it into the 8 ohm jack. Likewise with a 4 ohm cabinet.

However, the jacks are switched. If you have two 8 ohm cabinets, plug one into each jack, and both will be 4 ohm jacks (which is what you want, because the total impedance is now 4 ohms).

Ox, the Sceptre does not have a 2 ohm tap on its output transformer, and cannot be run safely at 2 ohms. You could wire the two cabinets in series, though, and run them from the 8 ohm jack.

[Gus]

Why not rewire the cabs in series instead of parallel? You would get two 8 ohm cabs, (assuming they're both 2-speaker cabs).