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Old 21st December 2012, 01:50 AM   #1
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Default replacing Maudio BX5a amp need advice

hey guys...got a Maudio BX5a studio speaker....took it to the shop and its gonna be wayyy expensive to repair...he replaced a couple parts and found even more fried...(i still have the other one and its been repaired and working just fine). i got these used for $20 so i cant complain. but what im after is im wanting to replace the innards. i havent had much luck finding a decent mono (already built) amp board....im nowhere near good enough to build my own...but i thought maybe you guys could give me some tips or point me in the right direction of what i need to replace the amp and power supply. the crossover i can build/buy myself. specs on the original is its a bi-amped speaker....40 watts to the woofer and 30 watts to the tweeter. im trying to keep this as low budget as possible. need any other info just let me know.
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Old 23rd December 2012, 02:00 PM   #2
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Nobody has any ideas? Just need pointed towards a decent low distortion amp in the 50-75 watt range that is mono or bridgeable to 1 channel
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Old 23rd December 2012, 02:45 PM   #3
JMFahey is offline JMFahey  Argentina
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Build this or a similar one.
You will need to replace the amps in *both* speaker cabinets, running as passive with internal LC crossovers.
LM3886 Amplifier Kit | Chipamp.com
And, of course, somehow seal the huge hole in the back where the old amp used to be.
Which can be as easy as using a rectangle made out of MDF.
Sound will be *very* good.
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Old 26th December 2012, 10:40 PM   #4
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ahh ok thanks for the advice...i have another question...im not very experienced in putting together my own amp....ive found quite a few kits on ebay that are already put together....are these reliable? or are they cheap china/hong kong knock offs with inferior parts? here is one example that has everything i need except a volume control LM3886TF Amplifier Amp Power Supply Rectifier Filter Completed Audio Board Kit | eBay
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Old 26th December 2012, 11:37 PM   #5
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or this...... Amazon.com: SainSonic LM3886TF Amplifier AMP+Power Supply Rectifier Filter Completed AUDIO Board Kit: Electronics
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Old 27th December 2012, 01:39 PM   #6
JMFahey is offline JMFahey  Argentina
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No, they look very similar, plus there's no rocket science in these amps ... and since most are built in Asia now, the USA made (if any) would be the actual knockoffs !!
That said:
1) think how/where you will mount them.
You may use a regular chassis/cabinet and connect them to the (now passive) monitors, *or* , if you dare, maybe you can have somebody cut a couple 1/8" aluminum plate rectangles, proper size, and mount them inside the cabinets, similar to the original ones.
If not much experienced or lacking proper tools, go the classic external amp route.
2) remember you'll need a passive crossover inside the enclosure, or you'll fry the tweeter.
Read original specs to know proper X-Over frequency.
And just in case, wire a 5 to 8 W 12V car interior light bulb in series with the tweeter, you don't want to burn it by mistake.
3) it won't have the same max sound level as the original, biamplified one, but still is more than loud and clean enough for home monitoring and mixing, just don't try to power a Rave party with it.
4) the kits don't show it, but besides some kind of cabinet (which if you are cheap may even be an old computer case or something similar) , remember you'll need to properly heatsink the chipamps.
Look around the chip amp gallery to get ideas about mounting.
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Old 27th December 2012, 09:49 PM   #7
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Yeah been looking around the forums at enclosures and such. I'm thinking I'm gonna make an enclosure outside of the speakers. I'm very inexperienced at this stuff...only thing I'm unsure of is how to get a volume control built in and I need a power transformer right? Theres one inside of the amp but no idea how to tell what size it is....also a volume knob as well....could they be salvaged and used? If they work of course. I've found the original specs for what crossover is needed.... tweet is 6 ohms woofer is 4 ohms crossover point is 3khz. Original one was a 4th order. I can manage to build that...except original had a sibsonic filter built in as well. No idea how to manage that (or is it extremely simple and I'm overthinking it?)
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Old 27th December 2012, 10:44 PM   #8
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Volume control could be solved with a preamp right? Or will that be expnsive? Don't want to get a cheap preamp and ruin the sound quality....do they make preamp kits as well? And are there certain ones compatible with the lm3886 or will any preamp wok?
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Old 28th December 2012, 02:06 AM   #9
JMFahey is offline JMFahey  Argentina
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Your powered speaker was driven by a line level signal, so the new amp will too.
No need for a special preamp.
Just wire 2 input jacks (your pick) to a stereo volume control, each half will drive one power amp, each of which will drive one passive speaker.
Look at the chipamp gallery to get ideas.
*or* you can buy a used 10 or 20 y.o. home stereo amplifier, and use it to mix.
You can set it flat or , as some have a direct power amp input, you can go straight there.
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Old 28th December 2012, 02:15 AM   #10
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ahh yeah true. running off a computer more than likely so volume can be done from there (overthinking this a but much lol). ill post more once i get the amp ordered. ty for your help so far!
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