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Old 17th October 2010, 08:48 AM   #1
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Default Ebay Experience?

So I've decided to take the first step easy, since this will be the first amp I've put together myself. I'm going to get a transformer, case, wires, etc. plus a couple boards for a 3886 amp.

I've found some kits I will have to solder together, and some already-assembled kits on ebay. I'm worried about the quality of these products... some look good, some just give me a bad "vibe." Since most of the kits for sale on ebay are coming from china, I'm worried about possible counterfeit parts and/or poor quality in other areas.

So I'm asking those of you who have purchased these, what was your experience? Do you recommend any seller specifically? Ever found counterfeit or shoddy parts?

Thanks in advance.
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Old 17th October 2010, 03:50 PM   #2
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I think in general the main concern is the legitimacy of the chips. Also in general, I've heard the PCBs are usually of great physical quality, the layout quality however, really varies.
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Old 17th October 2010, 05:26 PM   #3
Minion is offline Minion  Canada
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Ive boughten a few Ebay kits and didn"t have problems with counterfeits in these kits but I did notice that some of the Parts were under spec"d , meaning instead of useing 1000uF or 2200uF Bypass caps like is generally recomended they came with 100uF or 220uF caps ......

Eventually I just ended up buying the PCB"s on E-bay and getting my own parts , I have most of the parts here anyways so it isn"t a problem for me but for a First kit you should be okay with an e-bay kit .....

Cheers
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Old 18th October 2010, 06:28 AM   #4
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Quote:
Originally Posted by Minion View Post
Parts were under spec"d , meaning instead of useing 1000uF or 2200uF Bypass caps like is generally recomended they came with 100uF or 220uF caps ......

Cheers
There are two different camps on this. I like to use 100uF at the lm3886 chips and 10000uF at the power supply. Some people like to use 1000 to 2200uF at the chips.

Neither is wrong ,it is a preference.
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Old 31st October 2010, 07:21 PM   #5
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Default I can recommend LM3886 chpip amps amps like these...

I have bought several assembled chip amps from Ebay. I stick to the ones that do not have extra "stuff" apart from the amplifier circuit, e.g. no power supply, no protection circuitry, and one channel per board. These seem to pretty much follow the datasheet standard application circuit, so they should be pretty dependable. They are cheap (less than $30 for two), and there are not many critical components that can be scrimped on.

Here are a couple of examples:
ANY AMP BOARD LIKE THIS IS GOOD:
Click the image to open in full size.

The above boards can currently be purchased from sellers such as:
may139189
anna758595
giorgio11185
and others. Just do a search for "LM3886" in the category "Electronics > Home Audio > Amplifiers" and look for amps boards looking like the photo above.

I you also want a power supply board to go along with it, some sellers also package a PS board with two amps boards. These also seem to be a safe buy, at least the one I bought worked fine.

This is SO INEXPENSIVE, I don't see a reason to get much anything else unless you need much more power (e.g. over 100W in to 4 ohms). The LM3886 chip has been vetted well, and the design is simple. Unless you want to step up to one of Nelson Pass's F amps, the sound quality is good, better IMHO than Tripath amps. Not sure yet about TDA7293/TDA7294 amps, but I am evaluating those soon.

Don't forget, you must strap the chip down on a heat sink before using it!
Here is a place in the USA to get inexpensive heat sinks (shipping costs might vary):
Heatsinks - Medium, One Surface
or for good quality new heat sinks:
HeatsinkUSA
which are also sold on Ebay (seller ID: barrredboss).

Charlie
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Old 1st November 2010, 11:59 PM   #6
jog is offline jog  Iceland
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I bought one of those kits item nr 260425032471 and the results are very good. Nice sound.
I use 24v transformer and old JBL 4ohm speakers.
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Old 22nd July 2011, 12:32 AM   #7
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Does anyone have the correct schematic for this circuit board I bought 5 of these boards and they came without any shematic.
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Old 22nd July 2011, 02:04 AM   #8
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I usually do not buy "kits" per say, but rather just bare PCBs if I can find them. You are right. A lot of the times, the chips are fake, as well as some other pricey components. For example, if you see a board with 4x 2.2uF Wima MKP4, and it's selling for $10, you can predict that the Wimas are counterfeits because 4x Wima MKP4 alone would be over $12.

So if you can get bare boards, you are usually better off, as you can source the components from Mouser, Digikey, Farnell/Newark etc. The boards as others have said, are usually very good quality...usually better than most production boards that you'll find in commerical electronics.
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Old 22nd July 2011, 09:44 AM   #9
AndrewT is offline AndrewT  Scotland
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Art,
compare the PCB traces and pin layout to the datasheet schematic.
All the components should fall into place.
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Old 22nd July 2011, 11:39 AM   #10
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Question Lm3886 bare board

Hi Andrew thank you for the reply, I thought that that would be the cace as well but it is not ,I guess that the supplier reworked the design somehow to get by the origional design pattent
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