The LME49811 is a high fidelity audio power amplifier input stage designed for demanding consumer and pro-audio applications. Changing the power supply voltage and the number of output devices may scale the amplifier’s power output. The LME49811 is capable of driving an output stage to deliver in excess of 500 watts single-ended into an 8Ω load. Project 8’s prototype produces 36.02Vrms into an 8Ω dummy load or a power output of 162 watts.
The concept of Project 39 is Texas Instruments’ LME49810 spec sheet SNAS391C, April 2013 revision. This audio amplifier input and driver stage chip have similar impressive specs like the LME49811. However, a unique feature of the LME49810 is the internal Baker Clamp and Clip Flag circuit. According to TI, the featured circuit insures that the amplifier power output devices do not saturate when over driven. The resultant “soft clipping” of high-level audio signals suppresses undesirable audio artifacts generated when the power output transistors are driven hard into clipping.
During test, the clamp circuit on the prototype model was activated with an 18 to 20Vpp 1KHz sine wave input signal. This corresponds to a power output of more than 90 watts at 8Ω or 27Vrms across an 8Ω dummy load with ±49VDC power supply rails. However, a prototype of a high-powered version is also available as Project 40.
Project 41 showcases Texas Instruments’ LME49830 fully complementary, bipolar, ultra-high fidelity power amplifier input stage driver chip optimized for driving just about any available power MOSFETs. The LME49830 is a high performance driver that features low-noise, very low distortion, thermal shutdown and user adjustable compensation to minimize high-frequency distortion and an optimized slew rate. According to TI, the LME49830 IC can provide possible power output levels in excess of 1kW, if combined with a properly designed high current output stage topology and an adequate thermal management scheme.
The pilot prototype model has paralleled MOSFET devices per side in the output stage. There is no power output protection included with this project. However, with the recommended power supply rails and voltage ratings of the power output transistors and the LME49830, there is enough margin of safety. The input sensitivity of the project is about 1.68Vpp resulting in a power output of more than 150 watts with an 8Ω load and ±60VDC to ±72VDC power supply rails with only convection cooling. There’s also a high-powered version of this project featured as Project 42.
My listening skills.
Previously, Phillips launched the professional “Golden Ears Challenge” training program. This is a test of how good your ears are able to detect slight differences in sound quality based on timbre, details, spatial impression, bass and loudness attributes. I took the challenge, completed and was awarded an elite Expert Listener by Philips on 10 Nov 2015.