Yet another 3886 gain clone!

[ianpengelly]

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! 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.

[ianpengelly]

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.

[ianpengelly]

A shot of the insides

[ianpengelly]

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

[Dxvideo]

Hi Ian,

I am also working on a LM3886 project. But i designed my own PCB and still under development
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...

[ianpengelly]

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.

[mr.duck]

the case is interesting, it can dissipate the heat from the 3886 ok? Have you tried turning the volume right up to see how hot they get?

[ianpengelly]

The sides are heatsinks with the chips bolted directly to them. Unfortunately I haven't had a chance to give it a good thrash, but under normal use they don't even get warm!

[Vikash]

Congrats

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

[Vikash]

I had my wire thicknesses wrong, but here you go: http://www.diyaudio.com/forums/showt...748#post414748