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Tektronix SG505 low-distortion audio oscillator

The Tektronix SG505 instrument is an ultra-low distortion and low-nose oscillator intended for testing of audio grade electronic products. This one came to my possession as a non-working unit and I set-out to fix it.

Front view. Tektronix SG505
Front view

LME49811 + THERMALTRAK AMPLIFIER AND SERVO CONTROL – PART 1

Here is my circuit adopting the famous LME49811 amplifier front-end and ThermalTrakTM

transistors. This one is a rather conventional topology but implementing some tricks to improve the performance.

Grounding System In Power Amplifiers

Here is a very good schematic showing a tipical power amplifier grounding system. I have tried it ina many of my projects and it works every time. No hum, no ground loops no noise. Dead silent. Of course a proper power supply routing on the main PCB is critical. If done properly some very very high performance could be achieved.

Update 18.10.2014

The schematic was proposed by D. Self in his book “Audio Power Amplifier Design”. For any further info, please check out his work.

Power Amplifier Design by P. Baxandall Part 2. Negative-feedback Concepts.

In the January issue the concept, and possible consequences, of slew-rate limitation were discussed, with particular reference to one cause, in which the first stage of an amplifier is unable to supply the current demanded by the collector-to-base feedback-stabilization capacitor in the second stage. With suitably modified circuit designs such effects may be made insignificant. Before specific circuits are discussed in later articles, the present article will deal with some basic ideas about negative feedback and transfer functions.

Baxandall power amp design part2 – >>>LINK<<<

Power Amplifier Design Considerations by P. Baxandall

Articles describing particular amplifier designs, or advocating specific solutions to design problems, abound in the literature, and it is evident that some quite conflicting views exist on certain topics for example, concerning the amount of negative feedback that should be used. The present approach is of a fairly broad nature, and aims to elucidate and compare various familiar and unfamiliar circuit techniques in such a way that their advantages and disadvantages may be clearly and logically appreciated.

In exploiting the very great virtues of negative feedback, the problems and difficulties that arise are largely those associated with obtaining adequate stability margins under all conditions of, operation. In a.c. coupled amplifiers, there are stability problems at both low and high frequencies, but the elimination of output transformers, together with the adoption of d.c. coupled circuitry in most modern designs, has virtually removed the low-frequency problems.


Audio Power Amplifier Design by P. Baxandall – >>> LINK <<<

 

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