Ohm-age

[Stilettoprefer]

Okay, acoustic b200 combo amp has it's built in 1X15 8-ohm cab and a jack for another cab. If I use another 8-ohm cab that makes 4-ohm impedance. So if I wire in a bypass for the built in cab so that full power runs through the external jack, I can run a 4-ohm cab?

Do I have this right?

Also, what would happen if I just plugged a 4-ohm cab into the output without any mods to the amp (still have sound running through the built in 1X15 8-ohm cab)?

I'm a newbie to amps bigger than practice amps and am playing in pep band at the rose garden next week and am wondering how to get more out of my current rig...

[Munjibunga]

You do have the right to wire in a bypass, and you'd be fine. You'd be much less fine if you just plugged a 4-ohm cab into the extension jack without modifying the output as proposed. What would happen? You might let the smoke out. Letting the smoke out = bad.

[Arjank]

Yes, the bypass would work.
When you don't use the bypass the impedance would drop to a dangerously low 2,7ohms. Some amps can handle that, but most can't.

[Stilettoprefer]

Okay, thanks guys!! I'm gonna be researching on wiring in a bypass on this thing! any suggestions on a switch?

[lbwdog]

If you don't know how to do it, you don't know enough to do it.

Take it to a professional.

[RickenBoogie]

Wait a second,....isn't the Acoustic combo amp wired in series, (yes, I believe it is). 8 ohms to the internal spkr, and adding another 8 ohm cab brings you to 16 ohms, and less power. Adding a 4 ohm cab would be 12 ohms, etc. Check the manual, but I do believe this to be true.

[Stilettoprefer]

Originally Posted by RickenBoogie

Wait a second,....isn't the Acoustic combo amp wired in series, (yes, I believe it is). 8 ohms to the internal spkr, and adding another 8 ohm cab brings you to 16 ohms, and less power. Adding a 4 ohm cab would be 12 ohms, etc. Check the manual, but I do believe this to be true.

And further up the page it says "200 watts at 2-ohms. And as said in the pic, wired parallel.

[Arjank]

So if it can handle a 2ohm load, adding the 4ohm cab will be no problem at all.

[Stilettoprefer]

Upon further inspection of the wiring diagram for the amp, the speaker installed is a 4-ohm load. So an additional 4-ohm cab would make a 2-ohm total load. So full power of the amp is being used? Is this right? For some reason I'm scared of plugging in a 4-ohm cab.....

[GrowlerBox]

On the page you've reproduced here, it does refer to a 4 Ohm minimum load -- you may be right about the 2 Ohm thing, but worth a double check. Perhaps contact someone at Acoustic through their web forum??

[RickenBoogie]

If the spkr jack is parallel, it must be a newer feature. I remember reading (here on TB) about these combo's, and the problems their series spkr jack was causing. Good deal if they actually made this improvement.

[Stilettoprefer]

Originally Posted by RickenBoogie

If the spkr jack is parallel, it must be a newer feature. I remember reading (here on TB) about these combo's, and the problems their series spkr jack was causing. Good deal if they actually made this improvement.

Well it says so in the manual. I'll have to try to contact someone at acoustic and get some answers about this and the ohm rating business.

[coreyfyfe]

Originally Posted by GrowlerBox

On the page you've reproduced here, it does refer to a 4 Ohm minimum load -- you may be right about the 2 Ohm thing, but worth a double check. Perhaps contact someone at Acoustic through their web forum??

That first line in the manual section provided could be interpreted as 4 ohm minimum plugged into the speaker outs - at least that was the impression I got at first. Given that it has a 2 ohm rating further up in the manual that might make sense.

[Stilettoprefer]

Originally Posted by coreyfyfe

That first line in the manual section provided could be interpreted as 4 ohm minimum plugged into the speaker outs - at least that was the impression I got at first. Given that it has a 2 ohm rating further up in the manual that might make sense.

I'll take a pic of the top part of that page and let you guys look at it. I'll also post a pic of the wiring diagram they have in the back for the amp. It'll be when I get home though.

[Stilettoprefer]

Top of page specs

[Stilettoprefer]

Wiring diagram.

[GrowlerBox]

It looks like you were correct: an internal 4 Ohm speaker and capacity to handle an external 4 Ohm cabinet for 200 W at 2 Ohms. No need to bypass the internal speaker.

I can't quite read what it says on the signal flow diagram under the "External Speaker" symbol in the bottom left-hand corner of the page (looked at right way up) -- some further clarity may be gleaned from that.

[Stilettoprefer]

Originally Posted by GrowlerBox

It looks like you were correct: an internal 4 Ohm speaker and capacity to handle an external 4 Ohm cabinet for 200 W at 2 Ohms. No need to bypass the internal speaker.

I can't quite read what it says on the signal flow diagram under the "External Speaker" symbol in the bottom left-hand corner of the page (looked at right way up) -- some further clarity may be gleaned from that.

That's the slightly less blurry pic of what you couldn't read. Sorry if it's sideways.... Sometimes photobucket makes things difficult:P. And thanks everyone for helping me out! I learned a lot and am using this knowledge to better my rig

EDIT: that says series.... Where in the other part of the manual it says parallel.... ***?!?!? I'm confused

[GrowlerBox]

That's weird -- there's no way of getting to 2 Ohms if it is in series. If you have the opportunity to add a second cab, it may be worth just trying it. Assuming it really can handle 2 Ohms, you won't damage the head however the speaker output is wired. Assuming you leave the gain and master volume the same, it'll be way louder with a second cab if it's in parallel, and only a little louder if it's in series. Hard to be more precise, because that will depend on the cabinet.

[Stilettoprefer]

Hmmm well I'll try it with another cab sometime. I have that guitar center "pro coverage" deal on it so I should be covered if something goes haywire....

How difficult would it be to rewire it parallel?