Archive for the ‘Amplifier’ Category:

2019-07-06 Earliest Audio Amplifiers I built

from FB group Building Transistor Radios July 6 Bill Korbak The early germanium alloy transistors didn’t have enough bandwidth for RF, they were only good for audio. That’s where I built my first amplifier, a three transistor audio amp on a PC board I etched in ferric chloride. I also built the power amplifier. It

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2019-04-29 Center Tapped Voice Coil And OTL Circuit

from FB group Vintage Transistor Radios Apr 29 Robert Abend Yeah, thanks for bringing that up. Many of the GE radios have a center tapped coil in their armature speakers. I never really thought about the unusual CT voice coil. The most important reason why is that a voice coil moves and has to be

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2019-03-05 The Low Frequency Audio Uses A Lot Of Power

from FB group Vintage Transistor Radios 2019 Mar 5 The ear is not as sensitive to low ‘bass’ frequencies so they use a lot of power. If the speaker is large enough to reproduce them, they will use quite a bit of power. With pocket radios, the audio amplifiers are limited in low frequency response

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2019-01-09 Bootstrap Principle In Audio Amps

FB group Building transistor radios 2018-01-09 Willie Barnett That is one deficiency of your circuit: the output transistors do not have the ‘bootstrapped’ bias resistor. I’ll explain why it’s needed. In your circuit, the signal turns the driver transistor as close to off as possible. The current through the base bias resistor causes the top

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2018-08-24 2N3904 & 2N3906 for Output Transistors

From FB group Building Transistor Radios 2018-08-24 – The discussion was about the OTL complementary symmetry audio amplifier that Mr. Barnett has posted several times to the group, which uses a 2N3904 and 2N3906. Willie Barnett Let’s talk about current. Suppose your amp has a 9V supply. When the output transistor is turned fully on,

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