Fender 18/30 BassBreaker question

erky32

I wonder if there are any knowledgable people who could answer my query on a Fender 18/30 BassBreaker ?
For gigging purposes I always try to have full redundancy in my gear. As a back up "get-me-home" amp I have a EHX Magnum44. IF I had a failure of the amp in the BassBkr, I wonder if I could plug the output of the MAGNUM44 into the ext speaker socket of the BassBkr (i.e. I presume a parallel output to int. spkr) to drive the internal speakers from the MAGNUM, since I could turn the power off the dead BAssBkr. I guess the Magnum would be looking at the internal speaker, and also to the output windings of the output txfrmr, so I couldn't imagine it would do any harm, maybe @ICBM  or the Fender rep. on here might have any thoughts on this?

photek

Edit: ignore me.

erky32

photek said:

Edit: ignore me.

OK,   

ICBM

As a general rule you should never connect the outputs of two amps together, even if one is turned off - and definitely not if both are on. The reason why not is because the output transformer will then operate in reverse and create high voltages inside the amp, even when the amp is turned off - if these voltages are higher than the amp is designed for it can cause arcing. If you keep the power input to below 30W it shouldn't produce any higher voltage than the amp will develop in normal use though, so that should be safe.

However, connecting the Magnum 44 like that would be a bad idea anyway - not only is it more than 30W (and will need to be cranked up to match the volume of the Bassbreaker, so it's likely to exceed 30W), in general it isn't a good idea to connect solid-state amps to a transformer without knowing they are designed to be safe like that - the impedance at low frequencies can be well below the amp's minimum rating, and the inductance can cause issues as well. (Don't connect two solid-state amps together either, even though neither has an OT.)

My guess would be that the Magnum - which doesn't have a great reputation for reliability anyway - would be the more likely to die than damage the Fender, but that isn't going to help if you're trying to do it to get around a problem with the Fender...

erky32

@ICBM ;
Many thanks for an excellent answer, I respect a response like that - totally educational, the business of generating damaging "primary" voltages, inductive impedance inbalance, ---mmm, dont think I'll be connecting as planned! You're a genius my friend, thanks for the help, much more enlightening than Fender support!

photek

You could get the amp modded so that you can simply unplug the speakers and plug them into the Magnum, basically turning your Bassbreaker into an extension cab.

erky32

I'll probably do just that, if I break the speaker connections with an cabinet mounted jack socket, I can wire it so that if the magnum is plugged in, it will cut off connection to the BB-amp and basically isolate the speakers as an independant 2 x 12. I'll either do that, or simply take the back off, unclip the spades and insert a spade-jack patch direct between the Magnum & the speakers. Cheers @photek anyway for your thoughts!!