Hopefully not a dumb impedance question

[LiquidMidnight]

Hey all, I checked the impedance thread and I really couldn't find an answer to my question.

I'm going to be using two cabs with a tube head on a gig tomorrow that is switchable down to 4 ohms. It has two parallel outputs. If I hook up an 8 ohm cab to each output, will I then have a 4 ohm load? Also, what would be the impedance implication of daisy chaining the cabs and using one output?

Sorry if those are elementary questions. I'm used to using stereo amps in which hooking a cab to one output doesn't change any implications for the impedance of the other output.

[KJung]

Yes, you would want to daisy chain the cabs and use the 4ohm setting. Daisy chaining two 8ohm cabs in parallel results in the amp 'seeing' the same impedance as one 4ohm cab.

Also, if you head has an impedance switch and parallel outputs, then daisy chaining each cab is identical to running each cab from the two parallel outputs (both would require the 4ohm setting).

[JimmyM]

what head is it? if it's an older head like from the 70's, you will more than likely want to daisy chain. newer amps from like the 90's and on it's not as critical, but it is on the old ones like 70's svt's.

[LiquidMidnight]

Thank you, sirs. KJ, thanks for the extra bit about seperate outputs with assigned impedance. My Mesa 400+ is like that, and I always wondered the proper way to hook up multiple cabs to it (I've usually only been in situations where one cab is sufficient).

Jimmy, this is a modern head.

[JimmyM]

modern heads are fine for either daisy chaining or using the speaker out. just set them to the correct impedance.

[KJung]

Originally Posted by LiquidMidnight

Thank you, sirs. KJ, thanks for the extra bit about seperate outputs with assigned impedance. My Mesa 400+ is like that, and I always wondered the proper way to hook up multiple cabs to it (I've usually only been in situations where one cab is sufficient).

Jimmy, this is a modern head.

Just to make triple sure, since tube amps are quite picky about correct impedance matching, you might want to PM Tom Bowlus just to again make sure what I'm telling you is absolutely correct (Edit: I eliminated the incorrect part of my post). He has a basement full of tube amps and cabs!

[JimmyM]

no, you're right, ken. only with older amps like old svt's from the 50's, 60's and 70's do you have to worry about it, and maybe some early 80's amps. the newer ones are all made where it isn't critical to daisy chain for the output tap to see the right impedance.

[JimmyM]

oops, should have said "only with amps from the 50's 60's and 70's like old svt's." so don't everyone start correcting me about svt's not being around in the 50's

[RickenBoogie]

Wait a sec, on the Mesa head, with multiple taps, you want to plug your cabs from the proper tap that matches the whole load. ie: if you're running 2 8 ohm cabs, they'd run from one or both 4 ohm outputs, and if you were running a single 8 ohm cab, it would run from one of the 8 ohm outs, etc. It has 2 ohm taps as well, if you were to use 2 4 ohm cabs. It's the same on other all-tube Mesa heads, like the Buster. The speaker outputs are labelled for the total load you're using.

[Bridge Cables]

Originally Posted by KJung

If you have multiple output 'taps'... i.e., two 4ohm outputs, two 8ohm outputs, then you have to either run the daisy chained cabs from the 4ohm output, or each 8ohm from the two 8ohm outputs.

Nope, not from my Mesa, D-180.

Read RickenBoogie, he’s got it. The (2) 8 ohm cabs (total load 4 ohms) are plugged into the (2) 4 ohm taps or if daisy chained into one of the 4 ohm taps.

BC

[LiquidMidnight]

Originally Posted by RickenBoogie

Wait a sec, on the Mesa head, with multiple taps, you want to plug your cabs from the proper tap that matches the whole load. ie: if you're running 2 8 ohm cabs, they'd run from one or both 4 ohm outputs, and if you were running a single 8 ohm cab, it would run from one of the 8 ohm outs, etc. It has 2 ohm taps as well, if you were to use 2 4 ohm cabs. It's the same on other all-tube Mesa heads, like the Buster. The speaker outputs are labelled for the total load you're using.

Ahh, thanks for the clarification. That's what made sense to me.

[KJung]

Originally Posted by RickenBoogie

Wait a sec, on the Mesa head, with multiple taps, you want to plug your cabs from the proper tap that matches the whole load. ie: if you're running 2 8 ohm cabs, they'd run from one or both 4 ohm outputs, and if you were running a single 8 ohm cab, it would run from one of the 8 ohm outs, etc. It has 2 ohm taps as well, if you were to use 2 4 ohm cabs. It's the same on other all-tube Mesa heads, like the Buster. The speaker outputs are labelled for the total load you're using.

That's why I wanted a double check on my logic. I felt I had something 'not quite right' with the multiple taps. Thanks for the fix.

[RickenBoogie]

No problem, but I was a little shaky doing anything but giving a +1 to most anything you post, so I was a bit skeerd to even mention it- You are a respected giant on these boards, KJung.

[tombowlus]

Originally Posted by RickenBoogie

Wait a sec, on the Mesa head, with multiple taps, you want to plug your cabs from the proper tap that matches the whole load. ie: if you're running 2 8 ohm cabs, they'd run from one or both 4 ohm outputs, and if you were running a single 8 ohm cab, it would run from one of the 8 ohm outs, etc. It has 2 ohm taps as well, if you were to use 2 4 ohm cabs. It's the same on other all-tube Mesa heads, like the Buster. The speaker outputs are labelled for the total load you're using.

+1 What he said.

[KJung]

Originally Posted by RickenBoogie

No problem, but I was a little shaky doing anything but giving a +1 to most anything you post, so I was a bit skeerd to even mention it- You are a respected giant on these boards, KJung.

I screw up with the best of 'em I edited the wrong stuff from my post.

[coreyfyfe]

KJung - you would have been right for other heads like the Orange AD200-B.

Kind of confusing, you'd think manufacturers would want to make amps, especially tube amps, as user friendly as possible.