Finally got around building the briangt lm1875 amp and wanted to share its construction. What attracted me was the small size, but I am very pleased with the sound. I did a A/B comparison with a couple of amps and it may have come on top (class D, tube and LM38xx).
Parts can be ordered here (I deviated in the power supply somewhat):
http://www.chipamp.com/lm1875.shtml
Here you see the finished amp and power supply with a CD for a sense of scale.
Parts can be ordered here (I deviated in the power supply somewhat):
http://www.chipamp.com/lm1875.shtml
Here you see the finished amp and power supply with a CD for a sense of scale.
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The cramped inside of the power supply. The final power is +/- 26V to the amp. The transformer is a high quality one I pulled from a 60s dual amp (a $10 garage sale), same with the on/off switch. I was quite surprised at the components used in the dual, a couple of nice sterero pots, lots of quality resistors and caps too.
Notice the way the dual folks attached the tranny to the chassis with rubber to dampen vibrations.
Notice the way the dual folks attached the tranny to the chassis with rubber to dampen vibrations.
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Even with my noisy PC, this amp is dead quiet. With the computer volume turned all the way down, you can't tell if the amp is on or off with your ears next to the speakers. I opted for all the extra stuff such as the zobble and extra caps. Only the power supply's box is grounded to power. The amp's ground is the signal ground coming from the computer. Also the use of mini jacks helps with ground loops since only one ground signal is carried through.
I've had many difficulties cutting down the noise of my computer (it is a HTPC and connected to the Shaw cable). I can say with certainty that it is finally done.
I've had many difficulties cutting down the noise of my computer (it is a HTPC and connected to the Shaw cable). I can say with certainty that it is finally done.
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