Yet another 3886 gain clone!

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I became interested in the DIY Audio Forum whilst looking for speaker projects, but during my time here I noticed that a lot of people were using Gainclones to power their speakers. This got me interested and after a lot of reading I decided that I would take the plunge and try one of these things out, so I bought a kit from Madaboutsound.com (our good friend Vikash), along with all the other bits (transformer and connections).

I had good fun soldering it all together and standing at the other end of the room when I turned the power on for the first time! :xeye: Thankfully it all went well and we had sucess from the word go.

My first setup was with it mounted on a sheet of plywood whilst I did some testing and listening. This proved very entertaining, although I did have some fun with ground loops and humming.
 

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After a bit of fiddling I managed to reduce these significantly and started to really enjoy what I was hearing, so it was time to procede to stage 2 and purchase a proper case to fit it all into. Originally I wanted to house the power supply and amp boards separately, but I wasn't able to find a suitable housing. After a bit of searching on this forum I came across a company in Italy producing some fine cases, so I bit the bullet and bought 2 (1 for this amp and 1 for a pre-amp). The layout was fairly straight forward and had sketched it up in Visio before I received the cases.
 

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And then was the fun of wiring it all up in the case.

There is still some hum when used with my Audiolab 8000S in pre-amp mode, but I am hoping that I'll resolve that when I build a matching pre-amp based around the OPA627 opamp.

I am really impressed with the sound, I just can't get over the clarity of this amp compared with my previous set up, especially given the money!

Now I just need to decide what next, the pre-amp or the speakers??

I hope you have enjoyed reading about my project as much as I enjoyed completing it.

Ian
 

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Hi Ian,

I am also working on a LM3886 project. But i designed my own PCB and still under development:confused:
I dont know the layout of Madaboutsound.com kits. Do they make a common ground on PCBs or seperated?
And for your installation; have you got a star ground point on your platform? Can you explan your installation a bit pls...
 
The boards are those from ChipAmp.com, I believe the BrianGT design?!

They have a common ground plane and have a connection for the chassis ground on each board. You should be able to see from the photo with the wiring shown that there are 3 green wires, one from each amp board and one from the safety earth on the inlet. These form a star gound point, albeit different from that of the one formed by the board.
 
Congrats :D

Those side panels look like they're a few mm thick at best. You're going to need some proper sinking on them really.

These amps can have ground loops when positioned as they are at opposite end of each side. One way to solve it (you can search for more authortive descriptions) is to put them close to each other and run a thin cable between the chasis ground tabs and then a thicker wire from the centre of this to the ground. Please do a search though, there's a lot been said on the matter and CarlosFM's posts will be of particular help here ;)
 
I did try with a thick wire between the two when I was testing and it helped massively. I may have to experiment with it in the future, but I think I may be able to reduce it when I build my pre-amp, currently if I put my Audiolab onto Mute it reduces the humming.

As for the heatsink, its about 1cm thick and ribbed on the outside and, as said before, I haven't had problems with it getting hot yet, if I do then I'll look at attaching some heatsink to the case.

Thanks for the suggestions!
 
The case as a heatsink may be better than it looks. After all its not just the sides that dissipate the heat, the heat can spread out to all the other panels of the case as well. Plus the 3886 is very efficient (80% ?? or a bit less?). So it may only be about 20-40 watt of heat the has to be removed.

I am thinking of getting one of those cases (you got yours from audiokit.it?), so please report back after you have had the chance to give the amp a good thrashing :)
 
I run my LM3886 with two sidepanels, each 6.5 x 16 x 1.0 Cm, and they only get slightly warm at listening levels far beyond my personal taste.
So unless you like it really loud, or have very inefficient speakers, i'm sure that'll be enough heatsink:)

Best regards
Ebbe
 
ianpengelly said:
The cases came from www.Autocostruire.com, I think they sell the same products as audiokit.it. I was really impressed with the quality considering the 2 cases were £62 including delivery from Italy! They come flat packed which makes assembly easy.

I'll report back on the heat issue once I have some time when the girlfriend is out! :D

I agree, nice case, and price looks like it doesn't rip the bottom out of the bank account.
Only problem is, i can't get the link you provided to work :confused:
 
es44 said:
Oups, sorry, didn't see that. :clown: Thanks a lot

Not a problem :p

ianpengelly said:
Nice catch markiemrboo, stupid comma! :rolleyes:

Damn that grammar! :)

I like the case, though a black front would suit my equipment rack a lot better, but it wasn't an option. I may send the front off to be anodised black.

How much does anodising actually cost? Is it quite expensive?

I did consider the Maplin's 2U cases until I found the ones I have, but I would have had to cut the ears off! :devilr:

To be honest, I think the construction quality of the one you have is probably far superior to that of the Maplin case :) The main gripe I have with this case, is that there is no support on the front. Like, the top and bottom "plates" / "sheets", if you push down on the front center they bend slightly. Probably easily solved by just drilling a couple of screw holes and putting a stick of wood as supports in there, but still!
 
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