Powering a Mackie mixer (18vac 1A) on 32x AA batteries?

Thread Starter

Plo

Joined Oct 26, 2021
6
Hi Everyone,

I don't have a ton of electronics know-how, but i do like to build my own synths and power them with batteries.
I've had recent success powering an echo unit that asks 12vac, with 2x 9v batteries.
What I'm wondering at now, is if it would be possible to run my small Mackie Mixer5 on AA batteries.
The Mackie asks 18vac @ 1000ma.
I'm thinking four banks of 8 AA: 16+ & 16-
The batteries in mind are EBL brand rechargeable Ni-MH (same as my 9vs for synths) @ 2800mah.
Assuming maximum efficiency, shouldn't this setup work for about 2.5hrs?

Just want to make sure i'm not missing anything before spending $$ on all the batteries, haha.

Thanks
 

MrChips

Joined Oct 2, 2009
30,821
Given that the battery capacity is rated at 2800mAh, you can use that as a starting point.
I would derate the capacity by 50%, i.e. 1400mAh.
 

bassbindevil

Joined Jan 23, 2014
828
NiMH cells are expensive and a pain to charge properly. Lithium 18650 cells are free if you're lucky at recycling; just add a "BMS" (really a protection board). Or maybe use two 18V tool packs, if you have them; you can get connectors for popular types on Aliexpress etc, if you can't salvage sockets from dead tools.
 

BobTPH

Joined Jun 5, 2013
8,998
Not if you need 18VAC.

Some devices that take AC input put it immediately through a bridge rectifier to get DC. If that is the case, you can power them by a DC voltage if about 1.4 x the AC voltage -1.5V. Thus us why you could power your 12V AC device from 18VDC.
 

Thread Starter

Plo

Joined Oct 26, 2021
6
I was thinking i could just plug the AC power adapter that comes with the mixer into the power bank's AC outlet?
 

WBahn

Joined Mar 31, 2012
30,075
Many inverters produce very dirty AC power. Unless your mixer has very good power supply rejection, there's a good chance that noise will make it into your audio output.
 

bassbindevil

Joined Jan 23, 2014
828
That should work. The AC from an inverter is usually a "modified" sine wave, like a step pyramid rather than a nice sine curve. That may not be a problem, though.

Mackie most likely used AC so they could get + and - rails from a simple power supply, rather than using a noisy switching converter to get a - rail. But, that's another option to consider: DC-DC converter to make -18V or so, then some RC filtering or an additional linear regulator to make it quiet.
 

Thread Starter

Plo

Joined Oct 26, 2021
6
Oh! I am just now checking out the 18650s. They have 9900mah! Looking at the BMS boards, they seem to only support 2-3 cells in series. If they are 3.7v each, wouldn't that simply be 5 in series for each polarity? Would it be possible to hook up a couple of these BMS boards in series and if so, how? Thanks!
 

Thread Starter

Plo

Joined Oct 26, 2021
6
" DC-DC converter to make -18V or so, then some RC filtering or an additional linear regulator to make it quiet "
^ this sounds promising, but i have no idea what any of it means, lol
 

MisterBill2

Joined Jan 23, 2018
18,584
IF the TS has the technical ability to open that mixer and see what is inside, and understand it, there could be another option. That would be an 18 volt battery pack consisting of three rechargeable six volt batteries in series. BUT that would require that the input feeds a rectifier not a transformer.
SO I suggest contacting the Mackie company and asking them. They might possibly be able to supply a circuit of the power supply section.
 
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