4 channel parallell LM3886 amp

Hello!

I would like to show you some pictures of my latest projekt that I've just finnished. My four channel parallell LM3886 amplifier.

My name is Adam Eng and I'm 20 years old. I live in Karlstad, Sweden. I study electronic produktion and this was one of my side projekts (too much spare time ;) ). I've been reading this forum for about 3-4 months and got realy interested in these "gainclones". Almost all the information needed to build this amp has been found in this forum and i must say thank you to all who share information and designs!

The amplifier is based on the PA100 schematics and the pcb layout is based on alexw88's design with some changes to suit my needs.
The power supply consist of two 500VA trafos, eight 35A rectifiers (modded with 22nF caps across the legs) and 25000uF/rail (50000uF/channel) subberized.
The case is handmade by me an is mostly made out of aluminium. The feet of the amp is made from 2,5cm thick plexiglass wich I've put a ultrabright blue led in each on of to act like powerindicator.

My english is far from perfect but i hope you understand :)

Now it's time for some pictures!

[IMGHTTPDEAD]http://www.home.no/drdead/forstarkare/Forstarkare1.JPG[/IMGHTTPDEAD]
[IMGHTTPDEAD]http://www.home.no/drdead/forstarkare/Forstarkare2.JPG[/IMGHTTPDEAD]
[IMGHTTPDEAD]http://www.home.no/drdead/forstarkare/Forstarkare3.JPG[/IMGHTTPDEAD]
[IMGHTTPDEAD]http://www.home.no/drdead/forstarkare/Forstarkare4.JPG[/IMGHTTPDEAD]
[IMGHTTPDEAD]http://www.home.no/drdead/forstarkare/Forstarkare5.JPG[/IMGHTTPDEAD]
 
I'm glad you like it! :D

Forgot to say that it works like a charm without any 50Hz hum or hiss, just total silence when no sorce is connected.
It's also playing music better than anything i've ever listened to. Very detailed mids and highs with total control of the bass wich is tight and well balanced. Over all i just love it :cool:
 
G4ME said:
where did you score those nice heat sinks?

Got any pics of under her skirt?

Just as neutron7 figgured these heatsinks are made by myself. The "L" extrusions are also made my out of an aluminium sheet wich I've cut and bent. The base for the heatsinks are 8mm aluminium and the fins are 3mm.

Here's a better picture of it (hig res):
http://www.home.no/drdead/forstarkare/Forstarkare6.jpg

And here's one of the inside (the amplifier part anyway):
http://www.home.no/drdead/forstarkare/Forstarkare7.jpg



carlosfm said:
Cute.
Do the feets glow from blue to orange while the amp gets warm, a la Musical Fidelity? :D

Hehe no, unfortunate not but they glow (quite weak though) even if the amp is "off" as long as the power cord is pluged in and showing that the amp got power.

Feel free to ask any questions. I'll do my best to answer them. :)
 
Hi Adam,
i'm very impressed about your selfmade Heatsink - never thought about building one by myself -- really cool :)

Because of the high costs of low K/W heatsinks this is a great idea, especially for individual dimensions...

just for fun:
The lights in the feets could be electrical coupled with the temperature of the heatsinks (amppower) - for every temprange give another led colour (and/or brightness). Should be possible with e few parts based on the uaa 170 or uaa 180 (one is bargraph, the other singlepoint)...
:radar:
Michael
 
Hi All,
as you can see this is my first post but I'm looking around at this forum for a while. I'm building a 6 ch gainclone based on BGT LM3886 kit and soon I'll post my results.

Very interesting metalwork (I like also you output wires!!) but I got a doubt about you heatsinks: building them by separate elements leads you to a k/W rating very low.
I mean that heat conduction between adjacent fins (as between fin and support plate) should be blocked by the little "air gap".

did you use thermal grease between fin and plate?
Did you monitor in some way the temperature of the chips?
I believe that you could be in a very dangerous situation havinig you heatsink fins relatively cold but your chips really hot!!
:hot:


In that sense a circuit "showing" (by those geat glowing feet) you the real temperature of chips (using a diode or a NTC mounted close to every single chip) would be a good idea...

BTW great amp!!

Giancarlo
 
Off course i used thermalpaste between the baseplate and the fins to avoid air gaps. When i check the temerature i do it at the baseplate next to the chips and they stay quite cool even at high output.
When i tested the ampilifer boards before i put them in the case i used a small heatsink (lika a cpu cooler) and even then the heatsink didn't get warm. So i'm not worried about any bad contact or the heatsinks being too small. Btw, they are 30 * 17 cm.

About the idea with led changing color/brightnes it may be a later projekt.

Right now i'm planing to build a "signal inverter box" using the DRV134 chip to be able to turn the 4 channel amp into a 2 channel bridged one. It should work, shouldn't it? Using 2 channels each for left and right (one non inverted and one inverted). Could use some input from you experts here ;)

Have a nice weekend! /Adam