Amp switching box

[Voltron]

Not an amp build but “amp adjacent”, I have put together a box to switch between my amps.

I’ve got a silver jubilee, and ac30 and a wee orange terror stamp lined up in my garage. It struck me as a hassle to switch between them casually, particularly as I’m generally running effects in front of the amp as well as in the effects loop, plus the orange doesn’t have speakers of its own, I just plug it into either the v30s in the silver jubilee or the greenbacks from the ac30.

So I hatched a little idea in my head to be able to switch amps and also speakers in a little box. It grew to include the effects loop and here we have it:



So the signal path goes
Guitar
Front of amp effects
Into amp box through the first rotary switch (“pre amp”)
3 outputs, one going to the input of each amp
The 3 amp send go back to the switch box, through another pair of poles on the pre amp switch. This allows the single switch to select the amp input and send from each amp (1, 2 and 3)
Single output from rotary switch to modulation effects
Effects return to the second rotary switch (power amp)
3 outputs from power amp switch to the amps return jacks
Amp main outputs back to the power amp rotary switch
Output from the rotary to attenuator output (not necessary but good to play in the garage, can loop this out if needed)
Attenuator returns to the speaker switch - just a 2 way toggle
Speaker switch out to either the greenbacks or v30s

I don’t know if that makes sense but essentially I can choose any of the 3 preamps, power amps and 2 speaker cabs in whichever combination I like.

Seemed like a fun idea at the time.

[Jay]

Cool idea. I have used those rotary switches for selecting speaker ohm value (4, 8, 16). A single pole cannot handle the current of a grunty amp, so I used 3 poles in parallel for each setting to spread the current out. Not sure if this is what you have done too.

[Voltron]

Yeah I did notice the same thing but I figured that for proof of concept (wasn’t sure if it would actually work or just descend into a mess of interference noise) I would just take the risk on low current switches. Didn’t have enough poles to parallel them, these ones are 4 pole 3 way to switch both positive and negative in and out.
If one burns out it’s not the biggest drama. Might have to see if I can track down gruntier switches.

[robthemac]

This is awesome!

[Voltron]

Oh, it may also be of interest: I needed shit loads of cables as you may imagine (about 20) which was looking pretty expensive. Upon looking for some suitable cable to make my own I found these:

https://www.jaycar.co.nz/high-quality-s ... e/p/WB1552

https://www.jaycar.co.nz/high-quality-s ... e/p/WB1552

Basically 3 single core plus screen cables joined together. Easy enough to split. Insulation is a bit harder than normal guitar cable but otherwise essentially the same. Obviously they want rid of it as the discount is outrageous. I went into the local branch and got every bit they had. Just over 160m for about $26

[Optical]

Good work - but as noted those little rotary switches cant handle the current on one pin, and a second issue is those pins don't always make stable electrical connections. Any vibration or maybe even temperature change might cause a momentary bad connection. The issue isnt so much burning out the switch - it's burning out the amp when the power amp goes unloaded for a moment and blows your tubes or output transformer $$$.

You could source a tube amp impedance selector - that's fit for purpose.