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Old 17th August 2012, 03:31 PM   #1
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Default LM1875 with computer smps

is it possible to drive LM1875 with psu from the computer smps. Ive checked that the HDD pow cable has yellow cable which gives +12 volts and 13 amps of current for any yellow cable. So there is not less than 100watts of power that we can expect from the smps if other parts are driven properly from a 450watts smps.

But for +12 volts single power supply how much output does LM1875 can give out? its not there in the datahseet is it equivalent to +/- 12 volts or +12 volts is equivalent to +/-6volts?
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Old 17th August 2012, 05:13 PM   #2
johnr66 is offline johnr66  United States
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The LM1875 will work at single supply 12 volts, You can expect less than 2 watts at 8 ohms or ~3 @ 4 ohms (pre clipping). The TDA2050 is a better pick as its output will swing closer to the supply rails. These chips are better suited for much higher supply voltages.

The TDA1517 is a good single ended stereo amplifier IC. If you need more power, the BTL chips made for car stereos would be best. These ICs are designed with an output swing that can get close to the supply rails and that means more power into the load. At 12 volts, you will get around 12 watts into a 4 ohm load (pre clipping) The data sheets will say 20 or 22 watts, but that is at a ridiculous 10% distortion (well into clipping) with a 14.4 volts supply.
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Old 17th August 2012, 05:40 PM   #3
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I always had a doubt that National chips or ST chips which gives better quality. I like the concept of just 5 to 6 components for quad channel chips from ST which still has decent figures but I somehow feel that national chips give better quality.

The application is towards PC speakers I see many companies like Cambridge soundworks, Logitech, creative use TDA chips in their pc 2.1 and 4.1 speakers but i never saw any pc speakers using National chips. I think they are expensive and also take more parts per channel altogether.

Which is good when it comes to quality of sound.

I saw TDA7560 surprisingly it uses just few components and still I think it delivers decent sound but I really suspect the quality of these chips...
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Old 17th August 2012, 05:41 PM   #4
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in the case of TDA7560 can I use the power from the pc smps? which can give +12 volts from the yellow cable (usually found in HDD power D connector ). If thats the case then we can have easy power supply.
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Old 17th August 2012, 05:42 PM   #5
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Old 17th August 2012, 06:19 PM   #6
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I had made a couple of TDA2006 audio amps powered from +-12 into the CPU unit itself, from yellow/black/blue cables and they work properly until I made a own-designed class damp from the same power supply.
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Old 17th August 2012, 07:36 PM   #7
AndrewT is offline AndrewT  Scotland
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There is no significant power available from the -ve of a computer PSU.
It really is s single polarity supply PSU with a little -ve tacked on the side.
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Old 17th August 2012, 07:42 PM   #8
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You can always bridge 2 chipamps for each speaker to double the voltage swing from a single 12V supply.
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Old 17th August 2012, 07:48 PM   #9
AndrewT is offline AndrewT  Scotland
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"always"?
This only applies when the amplifier channels can each deliver lots of current into the load.
If the amplifiers cannot deliver lots of current, then bridging fails to give the required doubled voltage.
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Old 17th August 2012, 07:51 PM   #10
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Ok not always, BTL probably wouldn't work on 4 ohm speakers.
But worth a try if the speakers are 8 ohms.

I stand corrected.
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