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Low power speaker amp

post #1 of 17
1/12/10 at 12:14am
Thread Starter 
I have two 4 ohm, 7.4 watt speakers for which I'd like to build an amp for use with a portable player and my laptop. Hi-fi isn't a concern here, I just want an inexpensive amp to power them to volume without distortion. However, the DIY projects I'm finding tend to be rated far above what these speakers can handle, and I don't yet know enough about audio electronics to go modifying circuits. Can anyone recommend a design for me to build? I'd like to keep the budget as low as possible.

Edit. I'm not looking for a kit, and would like to do this p2p. Thanks!
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post #2 of 17
1/12/10 at 12:22am
Sonic Impact T-Amp - Class T integrated amplifier

hell cheap and moddable ^^
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post #3 of 17
1/12/10 at 12:40am
Comfortable with tubes? Millett mighty midget looks cool
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post #4 of 17
1/12/10 at 3:27am
LM1875. Very simple, very cheap.
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post #5 of 17
1/12/10 at 4:14am
..


--- never mind, a low voltage gainclone is not an portable option.
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post #6 of 17
1/12/10 at 5:25am
Though they're kits, you might want to look at the offerings from Bottlehead and Transcendent. They have some wonderful, affordably priced kits.

You can also buy books by Bruce Rozenblit (of Transcendent) that have plans for low power amps.

You might want to look at some of the low power DHT amps out there, too. There are a number of 2A3 amp plans out there and you might also want to look at some of the affordable Darling amps that use the 1626.
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post #7 of 17
1/20/10 at 10:29pm
Thread Starter 
Thanks for the suggestions, everyone. Though perhaps I should've been clearer about my budget - want to keep this well under $100.
The other thing is, I'd like to avoid AC voltages if possible. I haven't worked with that yet, and while I do intend to learn, this isn't the project I was planning to do that with. Are there any alternatives, perhaps with a wallwart like the SSMH, or a rechargeable battery?
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post #8 of 17
1/21/10 at 10:50am
Chipamp.com has a 20% off sale till the end of the month. You could get a 1875 for $40 shipped. Then get 2 20-25v notebook supplies for $30 off ebay and you would be done. It would be like a solid state starving student.
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post #9 of 17
1/21/10 at 11:39am
ClassT T-AMP TA2024 Audio Amplifier Board SMT 2X15 Watt - eBay (item 330396864601 end time Jan-21-10 21:00:09 PST)
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post #10 of 17
1/21/10 at 12:08pm
that t-amp on ebay is JUNK. I have one. hissy as all hell ;( even with a good psu its noisy as hell. not sure why but it is ;(

I'd pick another version; not this particular one.
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post #11 of 17
1/21/10 at 2:23pm
Just p2p the schematic from here: http://www.national.com/ds/LM/LM1875.pdf
It can't get much simpler...
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post #12 of 17
1/21/10 at 7:10pm
Quote:
Originally Posted by linuxworks View Post
that t-amp on ebay is JUNK. I have one. hissy as all hell ;( even with a good psu its noisy as hell. not sure why but it is ;(

I'd pick another version; not this particular one.
Strange, i have same board, work perfect (with modification). On DIYaudio are long tread about this board and modification.
Earlier this board sell different seller/manufacturer - Sureelectronic.
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post #13 of 17
1/21/10 at 7:49pm
what would I check on this board, for noise?

I tried switching supplies (not so great); I tried a wall wart and even a sigma-11 set to 12v. everything was much noisier than I had expected. almost like the old ipod shuffle v1 units; those were clean sounding but had a base noise level that never went away even at min volume.

maybe I have some bad parts or bad solder joints? its noisy equally in both channels, though, so I doubt I have a bad board or bad parts - but ???
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post #14 of 17
1/21/10 at 9:00pm
You may have better luck getting help on the class-D forum on diyaudio. Lots of helpful folks there.

Personally I'd recommend a TA2020-based board over TA2024.
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post #15 of 17
1/22/10 at 2:24am
after factoring in the $10 shipping, that ebay 2024 amp is $20..... By going that route you get a clean 5wx2 for $20, not bad, now if you add a little you can get the amp3 kit form 41hz.com for about $35 shipped to the US. The amp3 gives a clean 8~10w per channel and should be a bit better sounding (better chip, better coil).

I have done both the amp3 and amp32, the amp3 took longer to complete (had to wind the coil myself) but sounds a little better than the 32.

Linux, have you checked the output caps soldering ? cold soldering in that location can cause high frequency noise.
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