Amp techs: Is this doable?

[boobtube21]

I'd like to arrange a different kind of "speaker jack" for my '80 SF vibrolux. I use an attenuator for live gigs, and I have to say the hooking up of a speaker cable with female spades on one end is kind of a PITA. I already have a lot to set up with an Echoplex and assembling a pedal steel; every saved minute of set up time is golden.

I'm thinking of permanently wiring the speakers to a jack on the amp, turning the extension jack into a sort of "speaker input jack" so I can slam in some 1' cables like this:

cable 1: amp>attenuator

cable 2: attenuator>speaker input jack

Seems really basic and I would just go for it, the only problem I see is the main speaker jack:



Looking inside the actual chassis of the amp, it appears to have some sort of extra contact in it? Guess I could just replace it with a standard jack but I'd like to just use what's in there. Can I just rewire this jack to be a standalone speaker output jack or is it dependent on being in series or something with the ext. jack?

This is the proposed wiring scheme as I see it in my head (please excuse my crude re-drawing):



Just don't want to make any assumptions and fry my amp. Thanks for your help, gurus...

[Kap'n]

I'm not sure I understand your intended project. The extra contact on the main speaker jack is a switch. It's wired to short the output when nothing is plugged into it. Not good for the amp, but a lot better than having an open circuit.

[boobtube21]

Thanks Kap'n, let me try to clarify...

As it is right now with the amp in stock form, to use the attenuator I have to unplug the original wire set that goes from the amp's 1/4" speaker jack to the speakers, and set it aside.

Next I use a speaker cable to connect the amp from the amp's 1/4" output jack to the 1/4" input on the attenuator. Then, I use a cable (which I modified with female spade terminals on one end) to go from the attenuator's 1/4" output, to the male spade terminals on the speaker. Again, kind of a PITA...

I'd like to disconnect the ext. speaker jack on the amp from the amp's internals, and hard-wire the speakers to it instead. Then I can just use all 1/4" cables, like you would for an attenuator between a marshall head and 4x12 cab. Except in this case, the speaker's input jack is physically on the back of the amp chassis, making for a fast and easy hook-up.

Make sense?

[boobtube21]

Actually, if that's all that switch is, then in my eyes this is doable. I guess that should have been my question, "What is the function of the extra contact on the speaker output jack?"

[Kap'n]

Why can't you just get a 1/4" F to 1/4" F adapter?

[boobtube21]

Kap'n the issue is going from a 1/4" plug or jack, to the spade terminals on the speaker. I have a cable rigged up right now with the female spades on one end but just hate hooking it up in back of the amp every time I set up.

It's kinda hard to explain in words...I'll go ahead and rig it up, and take a photo for a reference...

[boobtube21]

Ok, I haven't done it yet but here's the idea.

Here's how I currently have it set up. 1/4" mono speaker cable from amp to attenuator, then another cable from attenuator to speaker terminals. I made the cables pretty long so I could put the attenautor in a remote location, closer to where I'm playing onstage:



Here's how I would like to have it, 2 short cables, wham bam thank you ma'am, all 1/4" hook ups. The speakers would be wired inside the chassis to the former "ext. speaker" jack:



Suppose I was traveling without the attenuator, I could just do this, like hooking up a head and cab, only both jacks are right next to each other:



If I decide down the line I'm not going to use the attenuator, I can easily wire it back to stock.

[Kap'n]

No, what I'm talking about doesn't involve the spade connectors.

Just take the standard 1/4" plug that connects the speakers


Unplug it, and use a double female 1/4" jack and a short speaker cord and connect it to your attenuator



Then use another short (well I didn't have a short one handy) speaker cord to connect the attenuator to the amp.



I guess the way you wired it could work too, but I'm always concerned about the possibility of failure if somebody else used it.

[boobtube21]

Ahhhh I see what you mean Kap. You're right, I could have just done that, but I already went ahead and rewired it the way I was describing... It works great though! very happy.

The only thing I worry about now is potential heat build-up...I ran the wires from the speaker in through the same strain relief as the wires from the output tranny. Not sure if those ever get hot anyway...I've been cranking it up and checking them and they seem to be fine. And no one else is allowed to use my amp, unless under my strict supervision (I sound fun don't I)

Thanks for lending an ear buddy.

[Kap'n]

No problem.

There's a whole lot of Weber in these photos.

[boobtube21]

Ha! Yes there is...

Just FYI for anybody who references this thread, I played a 2x 45 min. set gig last night with no problems, and setup was a breeze. Couldn't be happier I did this.

[Kap'n]

There's nothing worse than wrestling with a complex rig before a gig. It usually sets you up for a bad mood.

[boobtube21]

You said it Kap, especially on a tiny stage...though I am thankful I don't drag around 4x12's to every gig to make it even worse.

I dream of having an easily transported box that houses the guitar, pedal steel, amp, echoplex, pedal steel seat, and cables etc, with wheels on it...and everything unpacks with the cables/footswitches already hooked up.

[Kap'n]

That's a pretty complex rig.

All your missing is a tube reverb.

And I'm finding myself perplexed by the concept of a M9 and a couple of dirt boxes. And an expression pedal. And......

[boobtube21]

Yep, I enjoy setting it up almost as much as loading it in and out of my car... Not to mention the 2 flights of stairs to get it in and out of my house.