Diy class a 5W amplifier

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#41
So I found the problem, I had one of the wires connected to ground when it should have been connected to c5. Its all fixed now.
It sounds great, I am very Happy.

One final question is what size heatsinks do you reccomend using?

THanks so much for all your help Mooly!
 
#42
That's great, well done ! Yes, its a good amp when all properly constructed and it will hold its own quality wise against commercial amps costing £$1000's

Heatsinks should be big enough that you can hold a finger on the hot transistors. The temperature shouldn't be higher than a hot radiator as a comparison. If you can hold your hand for 5 to 10 seconds on the heatsink before its to uncomfortable then that's fine.
 
#46
Alright so I ordered the correct heatsink along with a bluetooth receiver. Now I was wondering if I could incorporate fm radio in this. What would be nice is just to have a 3.5mm plug out put into the Jack of my amp. Any suggestions, I'm having trouble finding a good one.
 
#49
There are lots of options really, depending on local broadcast quality (assuming that's what you want to receive) which will dictate whether something Hifi or MP3 quality or just portable radio quality is best suited. Hifi quality tuners aren't cheap but some are small and good too, like this stand alone tuner and add-in modules: Needle Doctor - Tuners - 1-800-229-0644 http://www.needledoctor.com/Online-Store/Tuners

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Are we on the same wavelength or are you looking for something else?
 
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#52
$20 eh? Well there are options available even down that low. The catch is that DIY options won't be as good as many retail products. They will be noisy, reception may not be good and stereo function may not be the best either, assuming you can assemble and set up the operation properly, given there probably won't be any instructions and you really need a tutortial to gain some insight on FM tuner design. Here's an interesting kit of parts that even has a 5W amplifier included. Digital LCD FM Radio Stereo Receiver Module Remote 5W Power Amplifier | eBay

The best value is one of those quality, brand name shirt-pocket types that could be connected via a headphone 3.5mm lead and these have been around for many years. If you'd like something cool for the bedside or desktop that is more in keeping with the quality of your class A amplifier, this appeals to me, at least.

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Amazon offer this version:http://www.amazon.com/Sony-SRF-M37-...pebp=1434222422336&perid=0A7597A3DC4841AB9F52

A word of caution though - Headphone output is actually very low voltage - too low to plug direct into a high impedance power amplifier line input and the sound will be poor, direct from many phones and portable players. A purpose -built low impedance preamp may be necessary in cases where the manufacturer didn't have an audio system connection in mind.
 
#55
Alright so I got 2 1.86°c/w heat sinks. Mounted my transistors and I can tell a significant drop in temerature than the other heat sinks. But these larger ones still get uncomfortably hot after a half an hour or use.
I want to strive towards perfection so I will do anything I can to make it better of course.
And I'm ditching fm radio because I don't really need it lol.

My main goal is to have the confidence to leave it alone while it's on, but right now I'm constantly watching over it in case something bad happens.
 
#57
It will get hot. To get some real idea measure the current drawn by the amp. If its 1 amp and you are running on 12 volts then that is approx 12 watts of heat to get rid of. The heatsink is rated at 1.86C/watt for 10 watts... so lets say 2.0C/watt for this which gives around 24 degrees over ambient temperature. So if ambient is high (lets say 30) then you could be seeing 54C or more. That is actually well within safe limits.

Measure the current though to be sure. If its higher than needed we can easily reduce it by changing a resistor and even a small reduction in current can make quite a difference to the heat produced.
 
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