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Two amps in to one cabinet?


Olli R�s�nen
Posted on Saturday, April 16, 2005 - 03:04 pm:   


I have a Music Man 65 Reverb and a hand made tube amp + a 2*12 speaker cabinet.

I was wondering if I could somehow connect them both into the same cab?

The cabinet's load is 8 ohms. It�s wired in series... so the speakers are both 4 ohm.
The Music Man has the switch for 4 ohm or 8 ohm output. The amp i have built has the same ohm selections.

Can i use an A/B box before the amps for switching between them? That means i would use one amp at time.

Hopefully someone can help.

Olli R�s�nen (from Finland)
Posted on Thursday, September 22, 2005 - 04:12 am:   


I know someone there can answer...
Posted on Sunday, December 18, 2005 - 05:54 am:   

Is anybody reading these posts?

I haven't yet found the answer, can someone help?
Steve Kennedy (admin)
Username: admin

Registered: 03-2002
Posted on Sunday, December 18, 2005 - 03:04 pm:   

I'm sorry I haven't jumped in here before now, I have been essentially absent most of this year due to job-related pressures.

Tube amps REQUIRE a load. You cannot switch the output side of the amps to your cabinet which will leave the unselected amp with no load! This can and will damage the output stage of the amp.

Instead, separate the speakers so they each have their own jack. Then set both amps for 4 ohms and connect each amp to its own 4-ohm speaker within in the same cabinet. Using a common A-B or A-B-Y switch, you can switch your input signal (guitar or guitar + effects) to drive either amp's input individually or even BOTH amps simultaneously!

You could have one clean & one distorted or one dry & one with effects, the choices are many!

This would be perfectly safe. In essence, you have two independent amplifier systems and you are just selecting which one to use at the low-level input. This is how many pros have done it (i.e. Eric Clapton).

mike kaus
Posted on Tuesday, December 20, 2005 - 04:55 am:   

AS Steve said(and I'm sorry I didn't see this one!), your amp needs to "see" a 4 or 8 ohm load, even while idling. You could use a dummy load to switch to but the amp would have to be cut back to an idle immediately or the load would get real hot quick. The power has to be disipated somewhere. Or you could use a load mass from weber for your switching load but that get expensive too. The easiest thing, like Steve sugested is to split the cab and power the two speakers separately. Or get a cab with four speakers and power two with each amp. Or, like I do, just use two small cabinets. Just depends on your situation and how much room you want to take up! Mike.