Which amp

coolhead · 26th July 2011, 07:07 AM

I have a 150va transformer with secondary of 24-0-24 un-use and since i have some free time I want to build a chip amp. From schematic it is quite easy to build and can do with simple point to point connection.

The problem now is which chip to choose with the transformer I have. Older chip LM3875, LM3886 and LM4780 or newer chip LME49810 and LME49811 or OPA548 and 549?

Guthorst · 26th July 2011, 07:44 AM

Dear coolhead,

after rectification, your transformer will give you a +/-34V supply voltage. Your chipamp should withstand that voltage, including a 10 percent overvoltage margin. This voltage is too high for OPA548 and OPA549, they have a limit of +/-30V.

The LME49810/49811 is not a power amplifier. It is only a driver, which needs an externally connected and designed output stage.

LM3875 and LM3886, and also the stereo amplifier LM3780 will work and are easy to implement, with few external components.

Regards,
Guthorst

26th July 2011, 07:07 AM	#1
coolhead diyAudio Member Join Date: Mar 2010	Which amp I have a 150va transformer with secondary of 24-0-24 un-use and since i have some free time I want to build a chip amp. From schematic it is quite easy to build and can do with simple point to point connection. The problem now is which chip to choose with the transformer I have. Older chip LM3875, LM3886 and LM4780 or newer chip LME49810 and LME49811 or OPA548 and 549?

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26th July 2011, 07:44 AM	#2
Guthorst diyAudio Member Join Date: Aug 2008	Dear coolhead, after rectification, your transformer will give you a +/-34V supply voltage. Your chipamp should withstand that voltage, including a 10 percent overvoltage margin. This voltage is too high for OPA548 and OPA549, they have a limit of +/-30V. The LME49810/49811 is not a power amplifier. It is only a driver, which needs an externally connected and designed output stage. LM3875 and LM3886, and also the stereo amplifier LM3780 will work and are easy to implement, with few external components. Regards, Guthorst

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