first easy cheap ect...

[theChris]

ok. I am not rich. follow me very very carefully here, not rich. i am a student in electrical engineering, but am only in second semester circut analysis which is coverng RC and RL circuts now. no semiconductors yet.

In any case, i've been wanting to build a VERY SIMPLE amplifier for some speakers i have or could easily get.

I am looking to spend as little as possible for everything. seriously here. you must make note of this. I can't buy a gold plated heatsink or diamond powder coated inductors ect...

I noticed an IC amplifier: http://sales.goldmine-elec.com/prodinfo.asp?prodid=4392

and was wondering if it would be any good at all. not looking for audiophile quality, but also don't want it to hiss at me ect...

i also haven't chosen the speakers yet, so I'm open to suggestions. cheap suggestions.

I've also been toying with the idea of bi-amping or i guess in this case tri-amping a setup. I don't really watch DVDs, mainly just stereo. I do like bass, but i live in a dorm and don't want to get myself in trouble, so i guess i really shouldn't have a huge amount of output.

Also, i don't have a huge amount of room in my room, also, should you use one set of tweeters for the front and none in the rear, or what? for a small room needing little output, and also a small box, what should i look for?

[Peter Daniel]

For what you are looking for, the best choice is this amp: http://home.student.utwente.nl/f.s.b.../thor-amp.html
More info in the following thread: This is not just another gainclone

[theChris]

hmm.. thats interesting. i'm looking to find prices on the IC (or ICs)...

i am thinking of 6 of the lm1875, 1 per channel, and 2 lm3875 for the subwoofer channel. the datasheets say they don't like a capacitive load. don't speakers exibit a capacitive load near resonance?

[seangoesbonk]

You can get free samples from National Semiconductor. Check out their sample program on their website. Because you are a student, they will give you some free samples.

A chip amp is a great way to go, if you don't want (or can't) spend much money. If you get the amp chips as samples, you can make the amp modules for basically nothing. The power supply, enclosure, and heatsinks are the things that will cost money.

I just finished a 4 channel amp using the LM3886 chip. You can read about it here:
LM3886 stereo to quad conversion
I am happy to report that my concerns about the heatsink size are aleviated. The only time the sinks get to 20 above ambient, is when I have a 4 ohm sub with the volume maxed out. During normal use, they barely even get warm. I think I would feel quite safe about putting 3 chips on each sink.

There is lots of info on this site about these chip amps(sometimes called Gainclone). Search around and read as much as you can. Also, I don't think I have to tell you because you're in EE school, but one of the best things you can read is the datasheet for the particular chip you use.

[theChris]

i will read and try to understand the datasheets.

BTW, for a small room and say 90dB 1w-1m efficient speakers, how much power will each speaker use for a normal to load listening level?

[seangoesbonk]

Well, my amp is about 38w per channel assuming an 8 ohm load. I have used it with my Shiva sub, which is 87.2db @ 1W/1m. Using the 38w on each voice coil, you can easily get enough output to get evicted. Also, I have used my TangBand w4-657s (88db @ 1W/1m) full-range ported speakers. The music gets plenty loud with the volume about half-way up.

So, I don't think you need much power for music with 90db speakers. You may want a little more power if you plan on using your amps for watching DVDs. DVD has more dynamic range than CD, so the average line level is a lot lower when playing DVDs.

P.S. If you have any trouble with the datasheets, you can post your questions, and they'll probably be answered. Alternatively, (and I suggest this) you could ask for some help from one of your instructors at school. They can definately help you. And it probably won't hurt your grades to let them know that you're doing extra projects on your own time.