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Old 28th April 2011, 03:14 PM   #1
bgee is offline bgee  United States
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Default 12V LM1875 circuit?

I'd appreciate pointers toward a circuit diagram for LM1875 amp powered from single ended 12V supply. I'm only looking for perhaps 5 watts output (mono).

thanks,
Barry
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Old 28th April 2011, 03:40 PM   #2
AndrewT is offline AndrewT  Scotland
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What does the datasheet have to say about low voltage operation?
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Old 28th April 2011, 03:43 PM   #3
lineup is offline lineup  Sweden
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Quote:
LM1875 datasheet:
Wide supply range 16V-60V
So, 16 Volt (or +/-8V) is the lowest.
But sure there are other chips out there. Especially for lower voltages.
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Old 28th April 2011, 04:15 PM   #4
bgee is offline bgee  United States
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Oops - now that I look at the data sheet, 12v single ended is not possible. I was mislead by seeing references to 12V LM1875 circuits.

Perhaps I can back up and describe my need: I'm hoping for a significant audio upgrade to the existing LM-380 in the af output stage of a radio. I built a circuit with discreet components that sounded good through headphones but couldn't drive a small speaker adequately. I figure 2-5 watts into 4/8 ohms would be enough. I'm more interested in quality than quantity.

If anyone has suggestions for a great sounding chip amp or discreet amp circuit for single ended 12V supply that would deliver 2-5 watts, I'd appreciate it.
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Old 28th April 2011, 05:00 PM   #5
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why not try a small class A discrete amp then.
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Old 28th April 2011, 05:19 PM   #6
lineup is offline lineup  Sweden
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In 12V with 8 Ohm speaker, you can max get 2 Watt
With 4 Ohm speaker max 4 Watt

A small transistor amplifer is one option.
It could be simple.
But there are not many around. Somebody have to design.

Have a look at National other audio amplifiers:
Audio Home - Audio Amplifiers, Far Field Noise Suppression/Reduction, Boomer, Overture, Class D, Audio Speaker Drivers, Headphone Amps, Microphone Amps, Stereo, 3D Sound, Audio Subsystems, Audio Codecs
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Old 28th April 2011, 06:03 PM   #7
bgee is offline bgee  United States
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Quote:
Originally Posted by digits View Post
why not try a small class A discrete amp then.
Thanks - that's a good idea. This is the circuit I built and sounded good but underpowered: Picasa Web Albums - BarryG

I'll search for a small class A circuit that looks good unless someone here can recommend one.
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Old 29th April 2011, 06:24 PM   #8
johnr66 is offline johnr66  United States
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Use the TDA2040. The the bias comes on at 5 volts (+/- 2.5) so they will work fine at 12 volts. With the samples I have, the chip came on at 3 volts, as did the 2050. The LM1875 came on at 9 volts, so that's cutting it close if on battery power.

Listening tests and differentiating the output signal with the input shows no distortion when operating at low voltage (as long as you don't clip).

To get 5 clean watts with a 12 volt supply on a single ended amp, you need to go below 4 ohm loads.

Use the TDA2003. It has an optimized output swing for lower voltages.

Last edited by johnr66; 29th April 2011 at 06:30 PM.
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Old 29th April 2011, 06:28 PM   #9
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Get LM4863 or SJ 2038 same ic or If you need mono then TDA 7052..
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Old 29th April 2011, 09:04 PM   #10
bgee is offline bgee  United States
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Quote:
Originally Posted by johnr66 View Post
Use the TDA2040. . . Use the TDA2003.
Thanks - those Pentawatt chips look promising.
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