A 7805 with no load shouldn't oscillate and shouldn't get hot unless there was something else wrong. Excessive input voltage, maybe?
I worked in audio all my career. Sound "opens up" for people and animals who say they can hear the 20kHz sounds better when the 40kHz and 60kHz harmonics (that are not heard) are reduced.
Fundamental sounds must be very loud for 1% distortion (-40dB) to be heard but then the fundamental sound covers up the distortion harmonics.
Instead of saying "the sound opens up" I say "the sound is smooth". Instead of saying "the sound is closed" I say "the sound is rough".
Many expensive speakers are "pretty". The high cost is in the looks, not in the sound.
Some amplifiers have vacuum tubes on top but they are not parts in the circuit, they are there for looks.
I have been retired for many years and was shocked recently when a free hearing test revealed that I have normal-for-my-age (72) high frequency hearing loss. Like double the highs cut when a tone control turned all the way down and I could not hear most distortion anymore. My new hearing aids returned high frequencies to my hearing and produce no distortion and no noise. But some audio systems obviously produce distortion with my hearing aids turned on. The hearing aids have selectable modes that normal hearing cannot do like extra sensitivity, muting, noise reduction and directionality. Of course they compress sounds that are too loud and the compression is barely noticeable without any distortion.
I'm well into my 60's now but just before retiring people in the factory used to think I was mad (I probably was/am but by different criteria) because I cringed when I head a very loud high pitched whistle that they were oblivious to. Rather than doubt my sanity, I went to track it down and my hearing led me to an ultrasonic welder running at 20KHz. As the welder fixed windows into an enclosure, to me the noise was ear shattering. Everybody else, including much younger people heard nothing. Sadly, and I hope not because of the welder, I now suffer mild tinitus and always hear a crescendo of high pitched whistles so telling what is real and what's outside is a bit more difficult although I would still assess my hearing as pretty good.
I once argued with an audiophile that they weren't actually listening to the original sound waves anyway but the rate of change of sound pressure waves. They said I was nuts but couldn't find a way to explain how the voltage recovered from a tape head or magnetic record pick-up is proportional to the rate of change of magnetic flux or speed of stylus displacement rather than absolute amount. I won the argument. Please don't go into the rights or wrongs of my case as it leads to all kinds of problems with frequency and phase response and inevitably resolves to a discussion of how a capacitor or transformer manages to couple a signal anyway.
I admire your patience and skills a designing and building that amplifier. I've designed equipment for recording studios and TV stations but you show a devotion beyond normal call of duty.
Brian.
I cringed when I head a very loud high pitched whistle that they were oblivious to. Rather than doubt my sanity, I went to track it down and my hearing led me to an ultrasonic welder running at 20KHz.
I think I made a mistake of buying 6.3V secondary for 7805 and 15V secondary for 7812.
Hi,
You may use zener diodes to reduce voltage drop.
Additionally you should do some measurements on the real circuit, I assume you will see higher voltage than expected.
(No guarantee).
For my taste 7V of headroom for the 12V supply is a waste of power --> it just generates heat.
I'd choose a lower voltage transformer.
(Personal opinion)
Klaus
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