So if you have an amp with 8 ohm and 4 ohm out can you use both?

[Mike9]

I have two amps each with 8 ohm and 4 ohm out. Can I an 8 ohm cab and a 4 o0hm cab at the same time?

[drgonzoguitar]

I have two amps each with 8 ohm and 4 ohm out. Can I an 8 ohm cab and a 4 o0hm cab at the same time?

No.

[Blue Strat]

No.

+1. Don't use both outputs.

What you can do is daisy chain the two cabs using the 4 ohm output. You'll get unequal distribution of power but it still might work for you.

[jdh]

Your impedance will now be 2.6 ohms, so a single 2 ohm transformer tap will be best. At a single 4 ohm tap you're dissipating more power across the amplifier's output than at the speaker. Some amps may complain about this mismatch. 8 ohms is even a greater mismatch. Using 2 taps at the same time will unbalance the transformer as part of it will be carrying more current than another part - not such a great idea. And you still have the impedance mismatch.

[m.z.]

Hi...... I'm an idiot. I should get what you're all saying by now but......... If I have a twin reverb, for example, and I am using the internal speaker..... can I also run a 4 ohm cab off the other speaker out?
:D

[hasserl]

Hi...... I'm an idiot. I should get what you're all saying by now but......... If I have a twin reverb, for example, and I am using the internal speaker..... can I also run a 4 ohm cab off the other speaker out?
:D

Yes! The amp was designed and intended to be operated this way.

[drgonzoguitar]

Yes! The amp was designed and intended to be operated this way.

L6 Spider Valve was designed that way as well.

[Mike9]

Great thanks for that info - :AOK

[FeloniousBishop]

+1. Don't use both outputs.

What you can do is daisy chain the two cabs using the 4 ohm output. You'll get unequal distribution of power but it still might work for you.

If you daisy chain (i.e. put them in series) them you'll have 12 ohms of load. So you wouldn't want to use the 4 ohm output.

Daisy chain them -> 12 ohms: use the 8 ohm output
Parallel them -> 2.7 ohms: use the 4 ohm output

[mooreamps]

I have two amps each with 8 ohm and 4 ohm out. Can I an 8 ohm cab and a 4 o0hm cab at the same time?

You have "two" amps. Both with 8 ohm tap and 4 ohm tap. You want to use "both" amps ; to drive "both" cabs?
So, that would be "both" amps driving both cabs ? I'm not so sure thats a good idea.

-g

[TopBooster]

If you daisy chain (i.e. put them in series) them you'll have 12 ohms of load. So you wouldn't want to use the 4 ohm output.

Daisy chain them -> 12 ohms: use the 8 ohm output
Parallel them -> 2.7 ohms: use the 4 ohm output

"Daisy chaining" means multiple parallel connections. How would you connect two cabs in series using the existing jacks??? Parallel is the only way, unless you custom-wire them together, or use a special junction box to get a series connection.

[FeloniousBishop]

"Daisy chaining" means multiple parallel connections. How would you connect two cabs in series using the existing jacks??? Parallel is the only way, unless you custom-wire them together, or use a special junction box to get a series connection.

Yes, you're right. I was thinking he meant in series by daisy chaining.

[Blue Strat]

If you daisy chain (i.e. put them in series) them you'll have 12 ohms of load. So you wouldn't want to use the 4 ohm output.

Daisy chain them -> 12 ohms: use the 8 ohm output
Parallel them -> 2.7 ohms: use the 4 ohm output

No one connects speakers in series with speaker cables;)

What I meant was plug one cab into the normal speaker jack and plug the second cab into the first cab. Daisy chain. :)

[Smitty]

OK. I've seen this community wrestle with this before. Here's how it works.

An output transformer is merely an impedence matching device, just like a hi/lo mic matching transformer. Let's say you have an amp with two 6L6 tubes in a push-pull arrangment that would like to have 5000 ohms plate to plate impedence and you also have an 8 ohm speaker. The output transformer solves this electronic problem by providing the correct impedence ratio. In this case it would be 5000 / 8 = 625. For a 4 ohm load the impedence ratio would be 1250. On a multitap output transformer the different taps (8 and 4 ohm) have different impedence ratios.

So, plugging an 8 ohm load into the 8 ohm tap and a 4 ohm load into the 4 ohm tap is electronically the same as plugging two 8 ohm loads into an 8 ohm output or two 4 ohm loads into a 4 ohm output. You simply end up cutting your reflected plate load by half. In the example above it would be 2500 ohms.

A lot of guys like the sound of more speakers and half load. The important question is can your output transformer handle the extra current from the reduced load and in most cases the answer is yes, but you should check your owner's manual or directly with the manufacturer.

There is nothing wrong with running the 8 ohm load and the 4 ohm laod in parallel for 2.6 ohms and connecting it to the 4 ohm output. That would give you a plate impedence of 3250 just like the 3x10 Bandmaster. If you were to plug the same setup into the 8 ohm tap you'd have 1625 at the plates which may be asking for trouble depending on the current rating of the output transformer.

[hasserl]

A lot of guys like the sound of more speakers and half load. The important question is can your output transformer handle the extra current from the reduced load and in most cases the answer is yes, but you should check your owner's manual or directly with the manufacturer......
....
If you were to plug the same setup into the 8 ohm tap you'd have 1625 at the plates which may be asking for trouble depending on the current rating of the output transformer.

This really shouldn't be a problem, tubes are self limiting devices. With a reduced load tubes will conduct to a point where they cannot conduct any more. The output transformer should not be strained under these conditions; if it is it is undersized for the job. Buy/build an amp with a proper transformer and this shouldn't be a concern.

[FeloniousBishop]

No one connects speakers in series with speaker cables;)

What I meant was plug one cab into the normal speaker jack and plug the second cab into the first cab. Daisy chain. :)

I had a brain fart about the "daisy chain" thing