Help building a Power Amp + Cabinet combo

[horaciocs]

Hi all, my name is Horacio and I'm from Brazil, my first post here!


I would like to build a system that consists of a power amp and a 2x12 cabinet. No pre-amp will be used, this will be combined with a POD effects processor. There is no need for extreme power, it will be used at home and for small presentations. I was going for something around 50-100W to keep a safe margin.

I was recommended this Guitargadgets' project for the power amp part: Power Amp. What do you think of the schematics? Do you know a better one based on the LM3886? It still needs a power supply, though. There's a schematic for that at GGG too (Here).

As for the speakers, which do you recommend? I play all kinds of music, from jazz to rock, an all-round speaker would be ideal. As I said earlier, I don't need much power. Instead, I go for quality, since this amp will be with me for a long time

I've heard that the LM3886 heats up quite badly and that it is a concern. Is that true? (By how far, if so?) Will it need any special cooling?


Thanks in advance for the help, guys!!

[loudthud]

Greetings Horacio. Your English is quite good. It seems from your questions that you do not have very much experience in electronics. As a relative beginner I would suggest that you start with some form of kit for the power amplifier. It is a whole lot easier than trying to gather all the parts together to build something the first time. Are you in Brazil now? I do not know what the availability of parts is down there. Some parts could be quite difficult to obtain.

The LM3886 requires a heat sink. It would only operate for a minute or two before it would shut off or fail completely without one. Another problem is the the metal heatsink tab on the IC must be electrically isolated from the heatsink otherwise one of the power supplys will be shorted to ground. You will also have difficulty assembling an amplifier without a printed circuit board. A proper kit for a beginner should include a circuit board, a heatsink and the hardware necessary to electrically isolate the IC from the heatsink.

A 100W power amp is more than you will ever need. I would start with something like 25W.

[turbolx5oh]

You could also try looking at the LM3875. I've build an amp based on that chip and it worked great. But as stated, it requires a good sized heat sink.

Do a google search on "gainclone" as there are all kinds of documentation on building amps out of these chips.

Also check out www.chipamp.com for kits to build an amp based on several of the National Semiconductor chips.

Also check out the Chipamp Forum over at www.diyaudio.com. Lots of good info there as well.

There is also another small site called www.ssguitar.com that has a couple of knowledgable people on it that have built several guitar amps based on chip amps.

Hope this helps.