Is this a good LM3886 Kit?

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AudioLapDance

Member
Joined 2003
Not good engineering

Is this a good LM3886 Kit?

They are cheap and that's good but the engineering is inferior.

dual3886.jpg

The blue ps high freq caps are too far away from the left 3886, swamped by the the trace inductance.

The right chip has no local low freq, mid freq or high freq ps caps. :eek:

The input is close to the right chip but far from the left.
...

These kits have the ps onboard, are cheap, fun and stereo but cannot have top performance.



For top performance you need at least:


close lf and hf ps caps (coming from the left) for each 3886 (low trace L and low loop area)

tight input circuitry

full data sheet circuit (emi input filt; dc input and fb; output ind etc; ... )

input referenced to output gnd

...



As DIYers we now have ample evidence backed by measurements of what makes a top performing 3886.

The cheap kits are fun and all but you should really save up and get (or make) a well designed PCB to unleash the Ultimate Potential of the LM3886! ;)

Cheers,
Jeff
 
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Hugh Jazz

Hugh Jazz

Banned
Joined 2013
AudioLapDance said:
Is this a good LM3886 Kit?
Click to expand...

Yes, it definitely needs better decoupling (to be added perhaps in due course) and the return path/loop isn't the tightest but the traces are very wide with a decent ground plane so I don't agree with your "swamped" appraisal. The PCB is far above the usual dross from China, which, along with fake components, is a major factor in why many of these kits underperform, regardless of how tight the layout is. So I ran this one hard for three hours trying to blow it up - if the components are fake, they don't seem to know it :)

I'm sure you know it's impossible to hear the difference between small reductions in already low THD, so the discussion about "how good is good" comes back to the worn out "measure it vs hear it" debate, when it's kinda moot anyway cos the weakest link in most people's hifi is speakers-room related.

If people don't mind spending big bucks for a "top end" kit with all the reassurances of such Gaincard priced stuff then they have that option. But people also want the 3% cost option in line with the Gainclone. You could buy one, test it and bin it for the price a meal. Why not? The one you posted looks like it has the typical nasty quality PCB and for the sake of return paths, it needs to have everything (except perhaps the rectifier) on the PCB, not added off board. If you can find one with a tight layout AND a high quality PCB AND have built it so you know it isn't fake stuff, please share ! Thanks :) We'll all be genuinely very grateful, except perhaps for the people selling expensive stuff.

And just for a giggle, here's a couple of pics to argue with - Photoshopped? Where do those cables really connect eh? It "cannot" be true? And even if it is true, that rectifier is lousy so it will sound a bit duller than it could. Perhaps the Kenwood VA is fake? I think they cost like US$7k so it probably is... etc etc
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J

JonesySA

Member
Joined 2014
Nanoloop said:
If you can find one with a tight layout AND a high quality PCB AND have built it so you know it isn't fake stuff, please share ! Thanks :) We'll all be genuinely very grateful, except perhaps for the people selling expensive stuff.
Click to expand...

It's actually a shame there isn't more interest in cheap-chip amps. The D-class forum is alive with comparisons. I often sort by 'most popular' on sales sites to see what people are buying. Its interesting that sometimes a kit is very popular with only one country so I think there must be a forum (non-English) where its discussed but find little info. For example the following sold quite a few recently:
Aiyima LM3886 Audio Amplifier Board Mono Amplifier Board Amp Support Parallel DIY KITS 60W-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
 
Hugh Jazz

Hugh Jazz

Banned
Joined 2013
Yes, that seems likely. Part of the the issue with chip amps is that it is "old" tech so no-one can patent what they do to ensure market success, and cos we live in a globalised world, it can be very hard for people in rich countries to compete against rivals with far lower cost structures. This pushes designers towards the niche "top end" design or the ultra cheap mass production design. Not so much in the middle which is where the best value stuff might be.

For new tech, my next big project is going to be a miniDSP feeding some full digital amps, but I've got a lot to get done before I can embark on that.

There are lots of the single chip boards about too - too many really. It's exhausting to keep hunting through them all - here's one from that same seller for example - note the absence of any claims about performance in the ad. 2014?????????LM3886??????-???
An externally hosted image should be here but it was not working when we last tested it.
 
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