Mod for Vox AC15 (to enable attenuator to be used)

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Hi all,

I’m trying to work out the best way to modify my vox ac15hw1x so I can use an attenuator.

The internal cable that connects the speaker to the amp is not terminated with a jack plug (I believe), it is hardwired instead. So I need to do a mod so that the attenuator can be connected to the internal speaker. 

I am not an expert with these things but here is my plan:

1. Purchse two new 1/4 inch mono jack inputs (similar to the type you get on a guitar) and fix them to the back wood cover of the amp.

2. Disconnect the cable (from the spade connectors on the speaker) and attach it to the spades of the first of the new jack inputs.

3. Create a new cable with 2 female spade connectors on both ends and attach one end to the speaker spades and the other end to the spades of the second of the new jack inputs.

Then for normal use of the amp without the attenuator i’d need to run a short patch cable between the new input jacks.

And when using the attenuator - i’d need to run a guitar cable from the speaker out socket on the attenuator to the second of the new jack inputs. 

Is my plan the best way to achieve what I’m trying to achieve? I can’t be the first to try to solve this problem.  Is there an easier way?

If the plan is sound can anyone tell me if there is a kit for it so I don’t need to buy all the individual bits and pieces?
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Comments

  • LastMantraLastMantra Frets: 3822
    edited May 2019
    You want to use speaker cable not guitar cable. 2 core mains is good.
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  • ICBMICBM Frets: 71963
    It would be far better to modify the extension speaker jacks. If you make one the ‘amp output’ and the other the ‘speaker input’, and use the jack switches to connect the two together when no cables are in them, it will do what you want without unnecessary extra holes in the amp or needing to connect them with a cable when you’re not using the attenuator.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • PhilKingPhilKing Frets: 1473
    If you get the plastic switching jacks, you don't need 2, just conned the amp side to the switch wipers (the pieces that go across the top of the body of the jack) and the speaker to the other side.  When no jack is plugged in it will use the internal speaker and when a jack is plugged in, it will disconnect the internal speaker.  One of these is what you need 

    Neutrik NMJ4HC-S 1/4" Mono Phone Jack Switched

    090-972_ALT_0jpg
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  • ICBMICBM Frets: 71963
    edited May 2019
    You still need two jacks if you're going to insert the attenuator in the combo speaker circuit.

    For the switching, you can either do it so the first jack switch breaks the path, and the second jack is simply connected to the speaker, or if you want better reliability (and safety, for the amp) you can cross-wire the jacks so *both* switches need to be open before the path is broken. This is easy to do if the jacks are fitted with the terminals facing each other.

    Looking at this pic, it looks like the jacks are about the right distance apart to mount like that with short jumper wires between the terminals. They may even both be switched jacks as stock - at least one of them must be if it turns off the internal speaker. If so, you only need to rewire them.




    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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  • PhilKingPhilKing Frets: 1473
    You're right, it's still early morning here in the States!  I was thinking of an external cab.
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  • stavrosestavrose Frets: 1
    Thanks for the advice so far guys, much appreciated!
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  • hendrix2430hendrix2430 Frets: 40
    thinking of doing something similar to my AC15C2... ideally I'd like to keep the extension cab out (which disconnects the internal speaker) and make the internal out the input for the speakers... 

    can this be done? 
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  • ICBMICBM Frets: 71963
    thinking of doing something similar to my AC15C2... ideally I'd like to keep the extension cab out (which disconnects the internal speaker) and make the internal out the input for the speakers... 

    can this be done? 
    Yes, it can be done - but it's likely to involve ditching the PCB that the two jacks are mounted on and rewiring them with free wiring. You need to make the external cab jack the one that's first connected to the amp, and its switch contact then goes to the extension speaker jack which is also connected directly to the speaker. (All sleeve contacts remain connected all the time.)

    So you connect the external cab jack - which disconnects the speaker - to the input of the attenuator, and the output of the attenuator to the extension cab jack, ie back to the speaker.

    "Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski

    "Just because I don't care, doesn't mean I don't understand." - Homer Simpson

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