Bob, a highpass filter does not create distortion, instead it reduces lower frequencies causing any distortion in the input signal to have a higher percentage.

 

Bob, a highpass filter does not create distortion, instead it reduces lower frequencies causing any distortion in the input signal to have a higher percentage.

Thanks bud.

 

A filter (either high- or low-pass) will change the shape of a non-sinusoidal waveform. I think that the TS is confusing this effect with distortion.

 

I've abandoned the attempt to get linear amp. from an inherently non-linear device.

it Is possible to get nonlinearity down to about 1 part in 200,000 using bipolar transistors and feedback.
[edit] with the benefit of being able to fabricate matched transistors on the same chip, even better linearity is possible, but compared to non-linearities of 3 to 5% in loudspeakers, why go to all the effort?

 

@Audioguru calculates the heating in the power transistors at 81W, and I don‘t doubt his figures. That would require a power transistor such as MJ15003. You are obsessed with eliminating capacitors. A power transistor that large has an internal capacitance of 1nF between collector and base (see middle of page 2 of the datasheet). That is larger than several of the capacitors one would normally use in a audio amplifier.
@Patrick Malarkey ,How do you propose to eliminate that capacitor?

 

Bob, a highpass filter does not create distortion, instead it reduces lower frequencies causing any distortion in the input signal to have a higher percentage.

Which will distort any waveform except a pure sine wave. Take any waveform with harmonics, and put it through a high pass filter. The waveform wiill change. That is a form iof distortion.

Edited to add: The Wikipedia article distortion supports this usage: Distotion

Bob

 

How do you propose to eliminate that capacitor?

Doesn’t a cascode remove the effect of that caoacitor?

Bob

 

Doesn’t a cascode remove the effect of that caoacitor?

Bob

A cascode configuration greatly reduces Miller capacitance - the capacitance between the output and the input of an amplifier. It is used to improve the bandwidth.

 

Audio distortion is harmonic distortion that is caused by a non-linearity. Harmonic distortion has harmonics added to sounds.
A transistor or amplifier that produces signal clipping converts a sinewave (maybe from a flute) to a squarewave (maybe from a buzzer) which has many added harmonics.
The capacitor in an RC filter is linear and changes only the frequency response. It does not add harmonic distortion.

Dolby noise reduction and FM radio use a pre-emphasis RC filter (high audio frequencies boost) when transmitting and use a matching de-emphasis RC filter ( high audio frequencies cut) when receiving. This cuts hiss noise. The capacitors in these filters filters do not cause harmonic distortion.

Vinyl records and audio tape circuits use RC filters to boost and cut frequencies. The capacitors in these filers also do not cause harmonic distortion.

A ceramic capacitor changes its capacitance when the signal voltage changes that causes harmonic distortion with low audio frequencies. A film capacitor does not cause harmonic distortion.

A bipolar or FET transistor is non-linear and causes harmonic distortion. An audio amplifier uses a few transistors to create a high open-loop gain then it uses lots of negative feedback to minimize the harmonic distortion. Most audio amplifiers produce extremely low harmonic distortion that cannot be heard.
A tone controls RC filter or an equalizing RC filter also does not cause harmonic distortion.

I am an old geezer (76 years old) with normal-for-my-age high audio frequencies hearing loss. My hearing aids boost the high frequencies with RC linear and digital filters but produce no audible distortion. What I hear with my hearing aids sounds completely normal even though the high audio frequencies pass through and are filtered by capacitors.

Go to www.sound-au.com to see many excellent audio amplifiers made with bipolar and FET transistors and ICs.