Questions about ohms, outputs, cabs (Marshall content)

[Hassouni]

Well call me oblivious, but after 2 years I just found an AMAZING bass tone, by plugging into the Bright channel-low input of my Marshall plexi reissue for the first time in 3 years of owning it. It sounds great through my 1960a 4x12 guitar cab, and great through my GK BLX-410. Decent headroom, no farting out, just wonderful, if not as loud as I'd want.

I'm thinking of upgrading the bass cab (to a 115, 212, not sure what yet), and I was wondering if it's possible to drive two speakers with one amp output -one of the two speaker outs on my amp has a master volume mod. The 4x12 has two inputs on it, one for 4 ohm, 1 for 16 ohm, and a switch whether it's to be run in mono or stereo.

Is it possible to, say, set the amp to 4ohm output, plug into the 4 ohm input of the guitar cab, then run a speaker cable from the other output into the input of a bass cab? Or is this fundamentally wrong and could seriously fry something?

I don't know much about this kind of thing, so any enlightenment would be appreciated!

[T-Bird]

Hi.

Originally Posted by Hassouni

-one of the two speaker outs on my amp has a master volume mod.

That sounds interesting, how it is done?

Originally Posted by Hassouni

Is it possible to, say, set the amp to 4ohm output, plug into the 4 ohm input of the guitar cab, then run a speaker cable from the other output into the input of a bass cab? Or is this fundamentally wrong and could seriously fry something?

I don't know much about this kind of thing, so any enlightenment would be appreciated!

99% of the time the link-connector in a speaker is connected parallell, so in the scenario You're thinking the impedance would be lower than it should, possibly creating problems. Connecting two inherently different cabs will create more problems projectionwise.

Tube amps are usually designed to work as planned with an exact impedance match, swaying in either direction may change the behaviour and operation of the amp. Any change in the output side impedance will reflect into the tube, and change its behaviour, that's for sure.

Back in the day I used 215 and 412 JCM800 bass cabs with my 1959 JMP, and the sound was great.

Regards
Sam

[Hassouni]

Originally Posted by T-Bird

That sounds interesting, how it is done?

It's the Lar/Mar post-phase inverter master volume (or a slight variation, can't remember), which itself is a version of something Ken Fisher came up with, if I'm not mistaken. It's just installed in one of the speaker out jacks so as not to drill another hole. Sounds great for screaming guitar at low volumes or bedroom-level Lemmy.

[T-Bird]

Hi.

Oh, I misread Your post, thanks for the clarification.

Regards
Sam