Is this a good LM3886 Kit?

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Hi everybody! :)
May I ask all of you a question? Why most people prefer LM3886, and very few people use TDA 7294/93? In fact, TDA 7294 is also a very good chip.

I used the TDA7294 in a design and it just blew up.
It oscillated badly.
Turned out I had reduced the gain and that makes it unstable.
I put a cap across +/- inputs and that tamed it.
If you are doing your own pcb make sure feedback resistor path is as short as possible.
 

AS posted below an XY board IMO. Complete utter junk Yes it works,
but the sounds?
Not even worth the postage costs TBH.
LM 3886 amps even in their Very Highest level iterations (definitely not Chi Fi) designs are ..not.. the best possible choice for Audio goodness.
But at that quality point their Main possible advantage: Cheap price..is eliminated.
Rendering the exercise pointless.
Been there done that.. simply trying to pass on what it took me Some time /effort to learn.
There ain't NO free lunch.
 
LJM is a good designer - I've used one of the L7 mosfet amps for years and been very pleased. The L20.5 looks good too - AP tested at 0.001% - so low it becomes irrelevant? and fully built for US$150. And I see they do an LM3886 Gainclone that is DC coupled - anyone tried that? 【DIY KIT】LJM GC LM3886TF Power amplifier kit with Speaker protection CL190 | eBay

I miss opc - he did some great gear at normal prices too. "The Wire" Official Boards for All Projects Available Here! BAL-BAL, SE-SE, LPUHP
 
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I see they do an LM3886 Gainclone that is DC coupled - anyone tried that? 【DIY KIT】LJM GC LM3886TF Power amplifier kit with Speaker protection CL190 | eBay

Well perhaps they should not, because although components are tight to the IC, I can't see the HF output filter anywhere. Tweeter killer? Probably not but you first ;-)

Has anyone tried the second one? It supposedly tests almost as well as Neurochrome's LM3886DR. Hmmm.
An externally hosted image should be here but it was not working when we last tested it.
 
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Well, I built one. No obvious defiencies. The chips are the old non-isolated t grade and the pcb holes are a little more widely spaced so the chips don't drop in - no big deal since I wanted to bend the legs to use an underslung heatsink. The kit included some isolation pads. All the parts are labelled which is unusual but no circuit diagram or instructions as you might expect. The PCB markings are sufficient anyway. The coils are supplied as two lengths of wax coated copper so I stripped the ends of wax and wound the coils on a chopstick and that gave the length that matches the PCB and seller's pics. I also made my own bridge rectifier with ultrafast diodes and snubbers instead of the kit part. The reservoir caps were bought separately - Nichicon LS 22,000uF 35V. I'm using a Talema 80va 18-0-18 and that gives +/-25v rails. Sounds good. Heatsink runs warm for the last 3 hours, but not hot. The kit doesn't include a heatsink or any terminals but for under US$10, well, lets just say RS, Mouser, etc are a tad overpriced. The relay switches off immediately and on after 3 seconds, as expected. The left offset is below the mV level of a Fluke - it reads 0 - and the right is 7.5mV. The PCB is of similar quality to AMB's stuff so it needs a fair bit of heat to get the solder to flow on the heavier traces/ground.
p_20180310_151614.jpg
 
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I received these boards this week and made the connections (datasheet needed to find out how) and assembled a heatsink of considerable size. The amplifiers play well, but I am a little bit concerned of the heat they produce. The heatsink has a temperature of 50 degrees Celcius. Is this normal and safe? I use a balanced power supply of 35V.
 
How good is good? Do you have any other amps that its compared with?

Good simply means no deficiencies with a pleasant signature. I don't like to wax lyrical about sound signatures and I haven't done any measurements in years so it's just an opinion. Given the very low cost, I'd say this was the best value for money amp - only rivalled in that regard by full digital amps like STA326. Worth pointing out if you're looking for a LM3886 kit that this one, as with most but not all servo designs, has no input coupling cap so the amp can perform at its best - allows greater transparency. The link you posted above has two big red input coupling caps in the signal path so that wouldn't be my first choice. Amps I have or had are TPA3251EVM, TDA8932, TA2020, TK2050, TPA3116, LME49810, LM4766, L7 mosfet, STA326 full digital amp. Also worth mentioning DACs + speakers in this regard - ESS9018, Dual NOS 384Khz AD1955, WM8741, etc. and speakers are Klipsch RF52 (biamped using 2x TPA3251EVM), Kef 4" coaxials (homemade), Fountek 3" with AMT tweeters and a Tang Band sub. Anyway, this is all to say that "good" is not a wholly misinformed opinion. If it were crap, I'd warn others for sure. :)
 
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Good simply means no deficiencies with a pleasant signature. I don't like to wax lyrical about sound signatures and I haven't done any measurements in years so it's just an opinion. Given the very low cost, I'd say this was the best value for money amp - only rivalled in that regard by full digital amps like STA326. Worth pointing out if you're looking for a LM3886 kit that this one, as with most but not all servo designs, has no input coupling cap so the amp can perform at its best - allows greater transparency. The link you posted above has two big red input coupling caps in the signal path so that wouldn't be my first choice. Amps I have or had are TPA3251EVM, TDA8932, TA2020, TK2050, TPA3116, LME49810, LM4766, L7 mosfet, STA326 full digital amp. Also worth mentioning DACs + speakers in this regard - ESS9018, Dual NOS 384Khz AD1955, WM8741, etc. and speakers are Klipsch RF52 (biamped using 2x TPA3251EVM), Kef 4" coaxials (homemade), Fountek 3" with AMT tweeters and a Tang Band sub. Anyway, this is all to say that "good" is not a wholly misinformed opinion. If it were crap, I'd warn others for sure. :)
Thank you for the informative post. We have had some similar experience with amps and dacs.
I have an 18-0-18v 160va toroid and never built a chip amp so just ordered two lm1785 boards that came recommend and would also like to try the lm3886. However, It seems more difficult obtaining a 3886 on a budget (University student) so might try this one.
Did you buy from the same Taoboa seller in your earlier link? I haven't seen this board on eBay or AliExpress so will need to use a forwarder.
 
I rather doubt that. I bet those skinny output inductors saturate rather quickly. That causes the THD to shoot up rather dramatically at higher output power.

Do you have a link to these purported measurements?

Tom

The output coils are air core so their inductance is not affected by current flow and they do not suffer non linearity due to saturation - you are perhaps confusing them with inductors that have ferromagnetic or ferrimagnetic cores. The UK's Surrey University, the guys who design satellites, have some pages about air core coils if you need to have proof. Google is your friend.

I guess you also missed the "supposedly". I'm not making any claims, just reporting on what was advertised. In China. Highly unreliable ... but then the PCB was excellent quality. So, who knows.
 
Thank you for the informative post. We have had some similar experience with amps and dacs.
I have an 18-0-18v 160va toroid and never built a chip amp so just ordered two lm1785 boards that came recommend and would also like to try the lm3886. However, It seems more difficult obtaining a 3886 on a budget (University student) so might try this one.
Did you buy from the same Taoboa seller in your earlier link? I haven't seen this board on eBay or AliExpress so will need to use a forwarder.

I think that PCB + kit is only available through the designer's shop on Taobao which I posted before. I wouldn't use the bridge rectifier in the kit though - ultrafast diodes like MUR860 sound much more dynamic. The seller also has a drop in replacement if you don't want to make one like I did - here's a link ????? ?? ????? 16A 600V 18?? ??????-???
An externally hosted image should be here but it was not working when we last tested it.
 
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