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Old 29th January 2015, 02:14 PM   #1
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Default LM3886 and LME49810 amp build advice

I'm thinking about building myself a pair of power amps, probably based on the PA150 LM3886 here:

DIY BPA300 6x LM3886 300W audio Amplifier

Being new to DIY hi-fi stuff, is this a good circuit design? Or is there something better around now? I can't seem to find the PCB for sale anywhere for the PA150. Although I do have the files I could get them made but it seems expensive.

I'm open to suggestions on better circuit designs, I like the simple is best approach and also like plenty of power in reserve due to the sort of music I listen to

So anyone have any words of wisdom or advice?

Last edited by flak monkey; 30th January 2015 at 07:37 AM.
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Old 29th January 2015, 02:39 PM   #2
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Its not recommended as a first DIY amp build - more for those already experienced with single chip designs. If you really need 300W then look for something using the LME49810/1 with a discrete output stage.
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Old 29th January 2015, 02:40 PM   #3
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Any particular reason why it wouldn't be recommended as a first build? I have quite a bit of electronics experience, just not with hi-fi
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Old 29th January 2015, 03:22 PM   #4
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Getting paralleled amps to work generates quite a lot of traffic on here. They can oscillate or fight one another. There are some misleading suggestions in AN1192 (which is often taken as gospel by noob paralleled amp builders) too - like that its quite OK to use 1% resistors to set the gains of the amps.

My own experience in getting paralleled amps to work too means I'd not recommend it to others who are just starting out on DIY amps - I also have a fair bit of electronics experience, also not just in hi-fi. Paralleled amps certainly can work - if you want one which will likely generate far fewer complications, you could go for one using TDA7293s. These chips parallel without needing to match gains and with no sharing resistors. Trouble is nowadays its getting harder to find real TDA7293s (as opposed to remarked TDA7294s).

All in all, its a lower work-up route I believe to go the LME49810 way.
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Old 29th January 2015, 05:08 PM   #5
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Thank you for the detailed response

I've had a quick look at the LME49810 options. Most of what I can find are cheapo Chinese, pre built boards. And I really don't want to be using them (!). Any pointers to DIY build boards with quality design? Bare boards are fine, I can get components easily.

As for the power, I don't need 300wpc. My current amp is 150wpc in class AB and 50wpc in class A. Something around that would be adequate.
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Old 29th January 2015, 10:06 PM   #6
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Can I ask what kind of amp do you have?
50Wpc seems a lot for a class AB.
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Old 29th January 2015, 11:42 PM   #7
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Panson_hk looked in detail at a Taobao pre-built board, you might find his blog a useful resource - he also plays with paralleled LM3886s - diyAudio - panson_hk

He has his own website too where he was selling his own LME4981x boards but since it hasn't been updated in almost 5 years I'm not sure if he's still doing that : Panson Audio Laboratories
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Old 30th January 2015, 06:32 AM   #8
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Thank you for the links, I will read those today. I found the TaoBao bare boards being sold on ebay and other places for about 15 and they seem to have been widely used. I'd be interested in seeing other feedback on their performance and any circuit mods to improve them.

Quote:
Originally Posted by mrWagner View Post
Can I ask what kind of amp do you have?
50Wpc seems a lot for a class AB.
Sure, it's an XTZ A100 D3 - heavy beast at 22kg and it does get very hot when in class A mode.

Output power class AB
2x110W 8 ohm RMS
2x180W 4 ohm RMS
2x300W 2 ohm RMS

Output power class A
2x50W 8 ohm RMS

Technical data:
Distortion: <0.03% (20hz to 20khz, 10w)
Input sensitivity : 1.0Vrms
Damping factor: > = 100
Input impedance: 20 kohm
4 output transistors per channel
Ring-core transformer
Phono amplifier (MM~2-5mV/MC~0,5mV)
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Old 30th January 2015, 09:01 AM   #9
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Ahh, so it can be switched to A. That makes sense.
Normally class AB amps stay in A for about 5-10W max. And can't switch between A and B.
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Old 30th January 2015, 07:47 PM   #10
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Yes it can be switched between A and AB.

After a bit of consideration I've bought a couple of LME49810 bare boards from eBay for 25 delivered. I need to find all the components for them now, looks like RS components have most of them.

I expect I'll need some help setting the bias on them once I have them assembled as that's not something I've ever needed to play with before.

Also need to figure out a power supply. Thinking something like this would be suitable, one for each board?

0500P1-2-055 | 2 Output Toroidal Transformer, 500VA, 55 V ac | Nuvotem Talema

With some 35a bridge rectifiers and suitable caps (4x 15,000uf)
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