E-bay Diy power amp's.

[tjolle62]

Hi everyone, for a couple of week's i ordered some pcb'n from e-bay for a small project that been grinding in my head for a while now,
I got my pcb'n in form of 1pc of to me seems to be a Gainclone copie or something who claim's to be a 300W mono amp based on 4 x LM3886
and then 2 pc Sanken based 100W amp with a power board.
My project supose to work out to be a small sound source for my summer house and 2x100W for stereo and a 300W amp for a modest subwoofer would
be great in a rainy sommer day/night with a stack of movies with'in reach ,
I have searched for some kind of info about these pcb'n but no luck and the
seller's didn't have a clue on them so i look somewhere else,
I have all components execpt for those LM3886 that i try to get me a matched set of them and for the Sanken's 100W i got the
finals as a matched set.
Is there any one know what kind of sound these can generate ?
the components i use is only high quality and high grade parts,
i also posting a few pictures on these boards ( it might help )





Regards from Sweden.

[vincent s]

hi tjolle62,
obviously these pcbs are from a Chinese seller yuanjing,lm3386 btl circuit.
a 7915 and a 7815 works as the supply for the opamp,what is the opamp?maybe ne5532 from ti.
basicly,lm3886 is a listening warm powerful ICAMP,but it need a high grade preamp,especially a big current driven preamp.
BTL,so the two 3886 works in a parallel,so the input impedence is lower than signal 3886,
so an opamp working as the preamp is poor.

regarding the sub amp,dont know too much about it,how will you install the two sanken transistors and the heatsinks?

Best regards from China!

[Atilla]

This appears to be a either a 2x2 Bridged-parallel setup, or 4 parallel, with an on-board buffer, but I'm not sure without a schematic. The theoretical power rating suggests it's a bridged-parallel design.

At any rate, I wouldn't try to get anywhere near 300W out of it, especially if the package is the insulated LM38886TF. Not unless you've got seriously good heatsinking.

They should work just fine for most purposes though, try them out.

[tjolle62]

Hi Vincent s and Atilla, like i wrote before i dont have any schematic or anything for the LM3886 based board, ( Vincent ) can you obtain anything
for this board ? and can you recommend a faily good pre amp board or kit
for this ?
I heard that the Sanken's SA1216 and SC2992 can deliver serious power but
need a lot of amp's and more than plenty of cooling,
haven't got to that point in this early stage yet execpt for a nice piece of
high grade copper flat bar in size 6x60mm that i thought to use as a heat - spreader and connect some kind of copper or alu heatsink to that.
The copper piece is almost 1 meter long so something should work out fine.
Samething with the Sanken's board if anyone have more info about these so
please post them here or e-mail me,
at least i got a small circuit diagram for Sanken board in size 75x75mm .

[tjolle62]

Hi again, just wanna post a few pic's on my first audio project,
on the sanken board have i a question regarding the BD transistors,
do i need heatsinks on these ? didn't get a clue of schematic,




Here is my first pic on my 4 x LM3886 amp waiting for cap's and finals




Guess that's all for now.

[nigelwright7557]

This seller has a couple of ready made PCB's.

http://cgi.ebay.co.uk/ws/eBayISAPI.d...STRK:MESELX:IT

[gbolly]

@tjolle62,

i currently have a standars lm3886 stereo setup which i bought from ebay in kit form, they sound great considering the price.

i drive really large mordaunt short floorstanders which have metal drivers , two midbass drivers and a woofer cone so you can imagine how well it copes with it and they hold up marvellously, lows,mids and highgs are excellent with music.

the sankens are usually incoroporated into the cambridge audio a5, a5i, a500, p500, azur 540a, 640a and may be some more and in creek audio amps manufactured in the 90s.

cambridge audios are uk amps and they are really powerful as long as they are partnered with good powersupply and adequate heat sinking as incorporated in the cambridge amps.

sankens pairs hold their own in current driving capacilities, really punchy and can really drive difficult speaker loads.

i was really pleased with the sanken based p500 (ran them in biamp mode)

[Atilla]

I'm looking at the LM3886 board and it looks like it's in BPA mode - they parallel two chips on each side and the output is in brigde mode. I guess the IC in the front is delivering the balanced output required for the bridging. What is the part number of the DIP8 IC in the front of the board?

That can theoretically give you the power output they claim, but do not try to use that with high-voltage rails or too low impedance loads, not without serious heatsinking.

[tjolle62]

hi, that's was some nice info about these amp's,
almost started to wonder if they only build 2 of them and i ended up with them ,
can't find so much about them on the net but here i got a lot of info ( thnx )
regarding cooling on the Sanken so have i just got my heatspreader done and
now is time to find a good heatsink to go with that,
i also gonna use the same kind of heatspreader for the LM3886 board who is
a solid flat bar of high grade copper in size 6 x 60 x 240 mm for Sanken's and
6 x 60 x 220 mm for 3886 amp.
Just got a transformer today from a friend and it was a toroid at 325 VA -
2*21V so it should deliver a good punch ,
at a later time i have to get a trafo for the 3886 amp too of course.
For filter board i was kind of impressed by CarlosFM's design and i was thinking
to use use those in my project's.

Regards
Kjell.

[vincent s]

Originally Posted by tjolle62

Hi Vincent s and Atilla, like i wrote before i dont have any schematic or anything for the LM3886 based board, ( Vincent ) can you obtain anything
for this board ? and can you recommend a faily good pre amp board or kit
for this ?
I heard that the Sanken's SA1216 and SC2992 can deliver serious power but
need a lot of amp's and more than plenty of cooling,
haven't got to that point in this early stage yet execpt for a nice piece of
high grade copper flat bar in size 6x60mm that i thought to use as a heat - spreader and connect some kind of copper or alu heatsink to that.
The copper piece is almost 1 meter long so something should work out fine.
Samething with the Sanken's board if anyone have more info about these so
please post them here or e-mail me,
at least i got a small circuit diagram for Sanken board in size 75x75mm .