Amp Hack Question

Yes, there is a potential problem.

As you have it, the amp you connect to the speaker cab will also be feeding power into the backside of Black Beauty, and can potentially blow both amps.

Better to completely disconnect the BB from the speaker.

 

"Switchcraft EHTSLB Toggle Switch DPDT Black Flange with 4-40 screws" from www.parts-express.com!

Something like that I think would be good. DPDT, so you literally have to throw the switch one way or the other. Speaker on the two center poles, one amp on one outer pole set, the other on the other.

No way to cross the signals, no way to accidentally forget to flip the switch to protect one amp or the other. Either one amp is hooked up, or the other, that's it.

 

You need to completely disconnect the amp to the speaker, even if one amp is off you will still send power through the wires.

Yours does not have a phone plug that plugs into the amp from the cab?
If it does, most do, then just unplug that from the head.
Secure that phone plug though as it is now live with the Aguilar going. Do not want it touching anything.

The cable just to the right of the power cable is for the combo's speaker.

 

Yes, bad. Can potentially damage BOTH amps.

 

I recommended a DPDT switch earlier to connect the speaker to whichever amp decided, but since you're here now with guru-level advice, is that a safe method?

And when doing that with something like the switchcraft jack linked a few posts above, is there a concern with power going through the switch? I understand volts and amperage and wattage regarding electricity,but I've never connected the dots to how does it translate to switching an audio signal.

 

However it's done, there must be no connection of either pole to ground, and the switch must be break before make.

I prefer a cable where it's just impossible to screw it up.

 

Even then it's not completely diot proof.

 

^^^To be fair, nothing is idiot proof. Some things are idiot resistant.

 

Idiot resistant would be disable the spare amp outputs and the original speaker wiring and cable the combo cab from the new single speakon jack as if it wasn't attached to the amp. But then you could never run an extension cab on the combo amp.

 

Parts of the service industry positively thrive on the imagination of "idiots".

 

This is how I approached a similar situation: Cabinet Jack Panel

Here's a pic:



In a nutshell, you run the leads from the speaker to the jack panel. Then you wire the output from the SWR into a 1/4" jack. If you want to use the front end of the SWR, you plug the 1/4" jack into the lower (mono) input jack - which is hooked to the SWR speaker. If you want to plug the Aguilar in, you unplug the SWR amp head and plug in the Aguilar. The amp heads are completely isolated from one another. (If you're using the Aguilar, you can unplug the SWR since you are just using it as a speaker cab.)

 

If those jacks don't have insulating bushings (or insulating shoulder washers), this set-up may destroy any class D or bridged amp connected to it.

ALL poles (including the jack sleeve) MUST be 100% isolated from each other. Without the insulators, all of the sleeves are connected together.

 

My combo (Fender BXR300C) has a jack on the back of the amp and a pair of wires running into the speaker box. I don't like the idea of a switch in a speaker path. I installed a 1/4" phone jack in the speaker box and made up a short speaker cord. Now I can unplug the short cable and run another head into the combos speaker.

 

LOL Ahh .. what was always known was finally said.

 

I did something similar, but hooked the combo amp to a 1/4 inch jack (like yours), and the internal speaker to a speakon jack. That way, nobody inadvertently connects an amp to an amp. I made a 10 inch cable with appropriate connectors to use it as a combo. I replaced the combo driver with a much more capable one, and this scheme allow that driver to be used with a more powerful, external amp.