My Vox Mini 3 now is rechargeable

thermionic

I posted a while ago that the replacement power supply I bought for my Vox Mini 3 was leaking 170 V AC to the chassis ground. Vox couldn’t supply one of their own, so I ran it off batteries for a while.

They lasted surprisingly long, but I didn’t want to create landfill, so thought about rechargeables. Six is an awkward number when they come in packs of four, and many chargers take 4 or 8. Then it dawned on me that 6 AAs in series gave 9V… the idea of pedalboard powerbanks occurred to me. Turns out that Thomann sell a very reasonably priced one - about £35.

It came with a small selection of cables, so I cannibalised one so that it plugged into the pcb header instead of the AA battery holder.

I bought a piece of velcro from ebay, which Royal Mail took a week to deliver… and there we have it.

According to the specs of the amp and the powerbank, I should get around 60 hours of playing time on one charge! One slight drawback I didn’t foresee is that the powerbank has an on/off switch, so I either have to leave it on, or switch off the amp and  pull open the back to switch the powerbank off as well. However, I don’t think the current draw of the amp on standby added to the powerbank’s 4 pinprick charge status LEDs amounts to much.

ElectricXII

Good work! 

thermionic

The dc socket for the PSU is 12V, so I didn’t realise that the battery option runs at 9V until I tried it, then the penny dropped. Also I hesitated a while because I assumed pedalboard powerbanks were £100+ and it seemed an expensive mod for an amp that I paid £55 for. When I found I could get one for £35 it was a no-brainer. Not being tied to being near to a mains outlet is great for a couch amp!

midlifecrisis

great idea, Ive got a little laney mains /battery amp that takes 6 AA batts so will look at doing this.

Voxman

Cool! - I have a mini 3 too so might steal your idea.   My only slight confusion though is that whilst the batteries are 9v total, the DC socket is for a 12v supply??  

thermionic

Correct. I have connected the cable that went from the 9V battery pack to a plug that connects to the 9V socket on the powerbank. I don’t use the 12V socket.

The internal circuitry clearly works at 9V, so a bit puzzling why they specified 12V for the AC adapter.

Voxman

thermionic said:

Correct. I have connected the cable that went from the 9V battery pack to a plug that connects to the 9V socket on the powerbank. I don’t use the 12V socket.

The internal circuitry clearly works at 9V, so a bit puzzling why they specified 12V for the AC adapter.

More headroom perhaps? 

thermionic

In my digging around for schematics I found that the speaker is driven by a chip running on 5V (might be a class D amp, not sure). That’s probably the most power-hungry part of the circuit, I’d guess the DSP chips are running off 3.3V or less. I don’t think there’s anything in it that would benefit from a larger headroom.

DartmoorHedgehog

On a similar note, it's surprising how long my Cube Street runs on (rechargeable) AAs.  I hardly ever use the mains adapter even when I'm using it as a practice amp at home.  Main downside is the "low battery" light doesn't give you much warning before it conks out - just have to make sure I charge it up before I need it for anything outside.

EDIT: Just noticed it doesn't actually have a low battery light as such - I'm just relying on the power light going dim as a warning so no wonder there isn't much time between "oh it's getting a bit low" and dead.  Some sort of charge status indication would be a very useful mod.