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Help me not destroy my GK amp

#21
DrDAV14 said:
Just buy the 112MBX and know your doing the right thing. I have one I'll sell you if you need.
Click to expand...

That's what started this whole thing. I was thinking about buying a 112MBX but then I said to myself, "Self, I have a MB150S, which is essentially a 112MBX with an amp. Why not save $300 and use the 150?" Since the opinion is a universal "DON'T DO IT!" I'm going to do something rare and take your advice!

Here is what I did instead. The 150 has a switch that disconnects the internal speaker from the amp. Unfortunately it also disconnects the speaker from the external speaker jack too, or I would have just used the switch. Anyway, I tapped into the speaker wires that come up through a hole in the cabinet and added a new jack. Now I plug the output of the 200 into the new jack and push the button to disconnect the 150s amp. It seems to work fine. This seems safe...doesn't it?

I don't go parallel into both amp inputs because the 200MB sounds a LOT better with my upright than does the 150. I would rather have the 200 powering both speakers than have one good sounding amp and one ok sounding one. I'll be playing a big hall Sunday and want to get a full sound. This should do it!
 
#24
garytw said:
That's what started this whole thing. I was thinking about buying a 112MBX but then I said to myself, "Self, I have a MB150S, which is essentially a 112MBX with an amp. Why not save $300 and use the 150?" Since the opinion is a universal "DON'T DO IT!" I'm going to do something rare and take your advice!

Here is what I did instead. The 150 has a switch that disconnects the internal speaker from the amp. Unfortunately it also disconnects the speaker from the external speaker jack too, or I would have just used the switch. Anyway, I tapped into the speaker wires that come up through a hole in the cabinet and added a new jack. Now I plug the output of the 200 into the new jack and push the button to disconnect the 150s amp. It seems to work fine. This seems safe...doesn't it?

I don't go parallel into both amp inputs because the 200MB sounds a LOT better with my upright than does the 150. I would rather have the 200 powering both speakers than have one good sounding amp and one ok sounding one. I'll be playing a big hall Sunday and want to get a full sound. This should do it!
Click to expand...

Try it out before Sunday, if you don't have the polarity correct on the speaker it will be quieter and much less lows when combined. That will give you a chance to correct the polarity if need be before your gig.
 
#28
garytw said:
Thanks everybody. I think the consensus is... DON'T DO IT! I forgot to mention though that the internal speaker on the 150 is wired to the circuit board at the same point that the external speaker jack is. My plan was to backfeed through the external jack to the internal speaker. I know it works after doing some (safe) testing with a meter. And remember, the 150 will be a brick, totally off and unplugged from power. So I doubt there would be fireworks, but would the voltage from the 200 output harmlessly pass to the 150 speaker or might it have some affect on the output circuitry of the 150, which is totally without power?
Click to expand...

The 200 will still be "driving" the 150 power amp circuitry, even if the 150 is turned off.

Does the 200 have a preamp output? You could run a cable from the preamp output of the 200 to the "aux" input of the 150, thus feeding the signal through the power amp of the 150 into the 150's speaker. The power amp of the 150 is sonically neutral.
 

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