What can you guys tell me about the China/ebay AB amps? - diyAudio
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Old 29th July 2014, 05:15 AM   #1
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Default What can you guys tell me about the China/ebay AB amps?

There's so many to choose from.

This one worth a $hit? http://cgi.ebay.com/ws/eBayISAPI.dll...:X:RTQ:US:1123
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Old 29th July 2014, 08:06 AM   #2
esgigt is offline esgigt  Netherlands
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Originally Posted by lazzer408 View Post
There exists a thread on this forum about the L12 amp. Use the search function.
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Old 29th July 2014, 08:16 AM   #3
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Quote:
Originally Posted by lazzer408 View Post
There's so many to choose from.
[/URL]
So you want us to choose one for you?

Quote:
Originally Posted by lazzer408 View Post
This one worth a sh**?
How do you define worth? Resale value? Maybe buy raw Copper instead then from a metal dealer, or find some in a junkyard, much better economic return.
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Old 29th July 2014, 02:37 PM   #4
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Amongst several Ebay amplifiers that seem more focused on maximum output power per $ than overall quality, L12-2 is a good amp. with some great quality components. I've heard a few out-of-the-box and kitform builds of this one and they make surprisingly good sounding, efficient and tidy amps when you add the other 90% of a finished amplifier with a decent transformer, power supply and protection circuits.

Best value IMO, is the already built up version on its own little heatsink.
Like Esgigt suggests, search the L12-2 thread and see what the designer and other builders had to say.
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Old 29th July 2014, 06:55 PM   #5
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Originally Posted by Ian Finch View Post
Amongst several Ebay amplifiers that seem more focused on maximum output power per $ than overall quality, L12-2 is a good amp. with some great quality components. I've heard a few out-of-the-box and kitform builds of this one and they make surprisingly good sounding, efficient and tidy amps when you add the other 90% of a finished amplifier with a decent transformer, power supply and protection circuits.

Best value IMO, is the already built up version on its own little heatsink.
Like Esgigt suggests, search the L12-2 thread and see what the designer and other builders had to say.
Thanks Ian. I hadn't specifically searched "L12-2" so I'll try that. It's always easier to just ask then spend days searching (which I had) and still not find anything. We're mortal after all.
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Old 29th July 2014, 07:14 PM   #6
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Yes, searches can be difficult without the right keywords but I just used Google instead. I only typed L12-2 and in less than 10 secs had 5 lines and one of those was for DIY audio:
Here: L12-2 CFP OUTPUT AMP 120W*2 8R
good reading
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Old 29th July 2014, 09:04 PM   #7
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I was flipping through that this morning. What worries me is people finding errors in the schematics or components being incorrect. Who's selling the right one?
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Old 30th July 2014, 12:09 PM   #8
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All the offers I've seen are for the same and only boards available AFAIK. The problem talked about "between the lines" on that thread is that neither the designer (OP) nor the seller want's us or their competition to copy them too easily and bypass their kits, so the schematic doesn't have errors, so much as it has been deliberately sabotaged - get it?

The schematic I posted was for an earlier (L12) version which is much the same apart from output stage emitter resistor values. Otherwise, it fills in most of the details that have been obscured in the L12-2 schematic. Just forget you ever saw the 12-2 schematic, right? That probably really irked LJM-LJM too.

If you are unconvinced, look at finished and working examples on their small but useable heatsinks (this is a CFP design, so they don't run hot). Friends and I have bought from 3 other suppliers as just parts, finished boards and also with heatsinks fitted and all were the same goods being supplied. I'm looking at complete modules from Along1986090 and Doukmall as I type - can't see any difference. Note though, not all sellers offer all options all the time. Sometimes you have to buy them separate. The sinks though, are predrilled and tapped, which is great so long as you have the washers too.

2pcs Mono L12 2 Power Amplifier Board Amp Assembled 2 CH 120W 55V w Heatsink | eBay
L12 2 Assembled Stereo Audio Power Amplifier Board 2pcs DIY Kit 2 0 Channel AB | eBay
At the end of the day, others are just going about using these kits without problems so unless you hear otherwise, I wouldn't worry too much schematic "errors". I don't even think building it from parts is worth the hassle anyway. All seem to work fine set with about 25-40 mA current as they come. There are no adjustments to make, so prebuilt is fine.
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Old 30th July 2014, 08:23 PM   #9
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I need 4x100w into 4 ohms. 4 of the modules would be mounted to a large heatsink that's about 16 x 10" with 1.5" fin. An SMPS is also needed since this is for 12v operation. The narrow 12-2 boards would lay out nicely on one end with 2 SMPS's on the other end. It may improve stereo separation by having one SMPS powering the right 2 channels and another SMPS powering the left 2 channels.

If it works well, I'll take another heatsink and build a monoblock AB for the subwoofer and bolt them together for an all-in-one 5ch amp.
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Old 30th July 2014, 08:30 PM   #10
srinath is offline srinath  United States
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I have one of these -
Tung Yung TA 802 PCB for 80WX2 Power Amplifier with Schematics | eBay


And I am impressed. But of course ... I didn't build it or even pay for it really, it turned up a few days ago when someone I traded stuff with had to get some space emptied in the car ... so out this one went, right into my garage.

Mine was put together with a toroidal transformer and a damn decent chassis too ... missing a top, but decent otherwise.

Cool.
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