3886 based power amp kit, how to find the best AND the less expensive PCB board? - Page 2 - diyAudio
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Old 17th February 2011, 10:21 PM   #11
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Brian Bell (ChipAmp.com) was one of the first to make/sell LM3886 kits. He has been around forever, thousands in the field, loads of support, and a solid design.

DIY Chip Amplifier Kits, PCB's, Components and Information.
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Old 18th February 2011, 08:57 AM   #12
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Ok, many thanks for all comments and advices.

There are some interesting materials to read before starting to purchase components. Good so, it will allow me to be less of a beginner, hopefully, and build with more understanding.
Sincere thanks again.

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Old 18th February 2011, 10:49 AM   #13
AndrewT is offline AndrewT  Scotland
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Originally Posted by bidibidi View Post
many thanks.................... it will allow me to be less of a beginner........... and build with more understanding.
There's a wonderful attitude to lifelong learning.
A new hobby and the expectation of investing some time in that new hobby.

Welcome on board and enjoy the results of your endeavors.
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Old 18th February 2011, 08:24 PM   #14
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The ebay link does not say you get two assembled amplifiers for the price.
I would not buy the kit. I do not know which components are genuine and which are fake.
The PCB is common between different resellers.
Buy a bunch of PCBs and source your own components.
Hi

Andrew T is correct on this one as I found out to my cost.
The boards are good and work - the components however are questionable.

Andrew
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Old 19th February 2011, 07:56 AM   #15
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Hi

Andrew T is correct on this one as I found out to my cost.
The boards are good and work - the components however are questionable.

Andrew
Ok, well understood.
Getting directly the fully populated board removes half the fun anyway.
I intended to purchase electronic parts from reputed suppliers such Digikey, Mouser or Conrad (in Switzerland). Soldering is fun too.

Now that you mentioned it, I was wondering if the part specifications are provided with the naked board, or should I guess on my own?
Also, even if the specs are given, what would be the knowledge required to confirm that these are good enough, or to replace them with objective/measurable better performance?

... again, I am asking newbie questions. Please apologize in advance.

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Old 19th February 2011, 09:30 AM   #16
syklab is offline syklab  Hong Kong
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Hi,
New to the Chipamp world too, always read people mention non-inverting LM3886 and some inverting one, what is the different? Which one to choose from?

Thanks
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Old 19th February 2011, 10:14 AM   #17
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So you get 2 amps for 30 US$. That is ~22 . A LM3886 costs ~5 here, so for 12 you get two assembled boards, with all parts. The work is more or less for free then. Sooner or later those Chinese will go broke.

Interesting, he claims 20 days for shipping to Germany and further down it says he does not ship to Germany. Why would that be?

Funny, he does not ship to China either although he is located there.
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Old 19th February 2011, 10:53 AM   #18
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Originally Posted by bidibidi View Post
Again, question of a newbie: using the same power amp chip, what makes one power amp design better than the other?
In real estate they have a saying that the three most important aspects of a property are 'location, location and location'. For chip amps, these three most important things are 'layout, layout and layout'. Most of the single chip designs copy National's datasheet so the schematics are the same. The expertise of the designer can be seen in how he/she handles grounding, decoupling, placement of critical components and routing of tracks. Secondary is the choice of components - caps and resistors. If those turn out to be the lowest possible quality, its a great tweak to upgrade them. Changing sub-optimal layout though isn't for the faint-hearted.

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Please correct me if I am wrong: I guess that the number of power supply regulator depends on the number of power transformers.
Regulators aren't needed in the supply for chip amps - just rectifiers and smoothing caps. Plus snubbers across the rectifiers for lower EMI.

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So, the same question for the power transformer: ideally, how many is best? One power transformer for 2 channels? Or for 3 channels? Or for 4 channels?
Go for the biggest transformer size you can comfortably fit into your case. Make sure it has at least two separate secondary windings and not a single centre-tapped one. Big transformers perform better in terms of regulation - the voltage sags less under load. Custom toroidals aren't particularly expensive to have made, you can specify multiple pairs of secondaries if you want to implement isolated supplies. There's also another advantage to having just the one trafo - less noise coming across from the mains owing to reduced overall capacitance between the primary and secondary sides.
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Old 19th February 2011, 11:00 AM   #19
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Originally Posted by syklab View Post
Hi,
New to the Chipamp world too, always read people mention non-inverting LM3886 and some inverting one, what is the different? Which one to choose from?
The choice between inverting and non-inverting largely depends on what's upstream from the chip amp. Inverting chip amps have lower input impedance so might come with an on-board opamp buffer. Bob Cordell's chosen this route for his design - running the chip amp inverting gives lower distortion. If you're of the school that fewer parts will sound better, choose non-inverting because then there's no need for that extra buffer. Ultimately though, choose based on excellence of overall design (i.e. layout) rather than detailed circuit configuration.

Quote:
Originally Posted by pacificblue
So you get 2 amps for 30 US$. That is ~22 €. A LM3886 costs ~5 € here, so for 12 € you get two assembled boards, with all parts. The work is more or less for free then. Sooner or later those Chinese will go broke.
The economics in China are rather different from those in Germany. For a start the LM3886 retails here on Taobao for 2-3€. Those builders will be paying less in quantity. Their overheads are way lower too. So, no - no danger of them going broke just yet.
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Last edited by abraxalito; 19th February 2011 at 11:12 AM.
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Old 19th February 2011, 12:46 PM   #20
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The economics in China are rather different from those in Germany. For a start the LM3886 retails here on Taobao for 2-3. Those builders will be paying less in quantity. Their overheads are way lower too. So, no - no danger of them going broke just yet.
Yes, I have been to China and have seen the prices to be usually a third of ours. I have seen products that cost less than the world market price of their raw materials. So, how can that be in a rather globalised economy without someone losing money?
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