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24V amp with MaxxBass + MiniDSP build

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bitSmasher View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Topic: 24V amp with MaxxBass + MiniDSP build
    Posted: 01 December 2016 at 12:21pm
It's been a while since I've had a new project, but here's something that's been on the "to do" list for way too long...
A stand-alone amp + battery box, that can take a few different inputs and spit out a decent amount of power on 4 speakons. MiniDSP as the brains, so I can use this for many purposes

So far all my portable systems have had the amp and batteries built in, which means it's very much fixed to that usage
As I'm closer to building a "proper" speaker stack, I'll need an amp setup that can run all sorts of combinations of top / sub / monitor / etc

So far I have:

Batteries and amp


Sure AA-AB3318, which is a 4ch TK2050 based board, 30v max input, "100w" per channel output. Have used it briefly previously, and was very impressed with output for its size
SLAs, have 2x 12ah (3.5kg ea) as well as 2x 7ah (2.5kg ea), plus a few bigger 30ah & 80ah (f'n heavy) if I ever wanted to have runtime measured in months

MiniDSP and cheapo playback unit


MiniDSP 2 in 4 out, the brains of the operation
Have a cheapo Bluetooth / FM / MP3 thing, I expect it to sound awful but see it handy to have the option of a 32gb SD card full of music to fall back on if phones die, and also FM receiver (for radio linkup)

Power bits


Stepdown from 24v to 12v + 5v, having 12v on tap will be very great for adding to the system, and 5v will run the playback unit
Have a 24v to 12v isolated stepdown, might stick that on the MiniDSP alone as I've read that it's a good idea to keep it isolated
Also have a volt/amp meter, something I'm keen to add to battery packs for new builds

So... what do I want out of this? Not quite sure yet, always wary of "scope creep" but will set a few goals:
  • Versatile! one day it could run big tops and subs for a free party, another day it could be used with a single box for speech and background music at a work/social event. MiniDSP will allow me to change crossover & EQ to suit
  • Multiple input options. Already covered a small amount of that with the playback module. Since a phone with analogue connection will be the primary source, need a preamp...
  • Not too heavy. Plan to build the batteries in to separate box, that will bolt to the amp box. So I could swap between big/small SLA batteries or even a 240v adapter or lithium if I'm feeling rich
  • Routing options. From MiniDSP to amp and external connections - might want to run only 2/3 channels of amp and then take the 4th channel of DSP for something else, whatever
  • Idiot-proof. It may get used by others, or just to protect it from my drunk self at the wonky end of a party
Since working to a deadline seems to be a good motivator, I'm hoping to throw a rough working system together within 2 weeks - just for running small speakers at work christmas party. From there, I can decide on final refinements

Right now it's the input section that needs attention - want a preamp and level meter in front of the MiniDSP as I'll be using anything between a measly phone headphone jack and a very hot mixer, primarily the latter

Seeking input on the input Embarrassed any suggestions?
Will have to spend some time trawling ebay and DIY projects to see what I can afford/build

Also, what would you consider necessary or nicety given I essentially want an all-in-one solution for power, processing and amplification

Let's see how I fare with productivity, being the silly season and all that
***edited topic title to add MaxxBass***


Edited by bitSmasher - 05 December 2016 at 9:45am
"Battery Acid Sound System" blog hopefully happening in 2017
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Ganon View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ganon Quote  Post ReplyReply Direct Link To This Post Posted: 01 December 2016 at 2:25pm
if you can get your hands on a broken playstation 3 you can get a nice power supply.
It uses a 24v 23A powersupply inside, that could be a way to power it from mains :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 9:47am
Uh oh, scope creep already!

Not sure how I forgot about the MaxxBass 103, which I have 3 of... bought them all discounted heavily, the first a few years ago which proved its worth on my trike system. Just picked up two on ebay since I know they're hard to find.


This will run off the 12v step down, between preamp and MiniDSP
Will result in a larger enclosure, so I'll have to get creative fitting it all in

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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 11:04am
If you need a pre-amp (by which I assume you mean a few db of signal gain) - I can more or less vouch for one of these :-

http://www.ebay.co.uk/itm/Car-Audio-Pre-Amp-RCA-Input-Output-Line-Driver-Signal-Amplifier-Module-/260745569341?hash=item3cb5a5a43d:g:a1MAAOxy66pRwDJV

Very light weight, very low 12V power consumption and sounds OK.
The 2 gain tweaks are bit clunky - but work - the spindles pull-out to leave a hexgonal socket.
One down side is that it emits quite a nasty squawk at switch-on - so need to solve that - I just make its switched on a few seconds before everything else.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 11:25am
Yep, not going to dub-style man the controls!
Just need a few db of gain for phone headphone output, and also to attenuate hotter signals where necessary
Might get a little kit like this http://www.jaycar.com.au/champion-stereo-dual-channel-preamplifier-kit/p/KC5531 and perhaps even have facility for remote volume control (ie, external pot plugged in to a switching jack). uh oh, creeping again...

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sapro2 Quote  Post ReplyReply Direct Link To This Post Posted: 05 December 2016 at 3:51pm
Originally posted by slaz slaz wrote:

If you need a pre-amp (by which I assume you mean a few db of signal gain) - I can more or less vouch for one of these :-

http://www.ebay.co.uk/itm/Car-Audio-Pre-Amp-RCA-Input-Output-Line-Driver-Signal-Amplifier-Module-/260745569341?hash=item3cb5a5a43d:g:a1MAAOxy66pRwDJV

Very light weight, very low 12V power consumption and sounds OK.
The 2 gain tweaks are bit clunky - but work - the spindles pull-out to leave a hexgonal socket.
One down side is that it emits quite a nasty squawk at switch-on - so need to solve that - I just make its switched on a few seconds before everything else.



I too can vouch for that. I use one in Baby Sham. Mine doesn't squeek when i turn it on though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jerronimo Quote  Post ReplyReply Direct Link To This Post Posted: 17 January 2017 at 1:13pm
Maybe it's a good idea to use a step-up converter for the Sure amp, as ideal input voltage for full power is 30V.
Your batteries will have a nominal voltage of 23,76 volts when ''empty'' and 25,8 volts when fully charged, so the Sure amp will never ''see'' the full 30V on it's input rail.
Another option would be to run the batteries in parallel on 12 volts, so no need for a step-down converter and only use the step-up converter for the Sure amp.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 18 January 2017 at 8:45am
Thanks for reviving the thread! This project has stalled, work and life went a bit silly over Christmas Confused 

After a bit of pondering, I am considering a DC-DC boost... all my other gear will be 12V (including lights and ancillary stuff) and I have a few different battery options big/small/parallel etc

The more I think about it, this make more sense, and I've already checked out the Sure option:
500W BOOST Converter for CAR Audio - TL494

Losing a bit of efficiency is OK, when it keeps things flexible
Will buy one and see how long it takes for me to get this together

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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 18 January 2017 at 7:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2017 at 11:36am
I'm pretty sure that style of "Bass Boost" is just a big parametric bump in the bottom end
The MaxxBass actually high passes, and creates fundamentals - different approach, more more speaker and power friendly
When I eventually get time to start playing around and posting a blog, measuring the MaxxBass will be one of the first things I do. Will be interesting to see the result
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 19 January 2017 at 12:04pm
Originally posted by bitSmasher bitSmasher wrote:


The more I think about it, this make more sense, and I've already checked out the Sure option:
500W BOOST Converter for CAR Audio - TL494

Losing a bit of efficiency is OK, when it keeps things flexible
Will buy one and see how long it takes for me to get this together


DC-DC converters like this can maybe work well, but can also cause complications. Unless there's some kind of soft-start going on, it can draw really high inrush current ar startup. One I had would go into protect/shutdown straightaway if the load (amplifier) was connected (as the amplifier itself itself also draws inrush current).

I  favour keeping things simple as possible .... I'd vote for using the 2 x 12V in series and maybe using another battery to power your "outboard" gear. I've used the naff "CCTV LiPo batteries" to power a small 12V DC DJ mixer (200mA or so) and sometimes a car 7-band equalizer (another CCTV battery) - also about 200mA - lasts the whole day with zero problems.

a) It takes a bit of load off main batteries
b) It neatly sidesteps any earth-loop type problems and any other hard-to-diagnose issues.
c) Really minimal size/weight

OK - it means remembering to charge em etc. .... but I reckon its worth it.
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