[R-390] OT: Transistor Amplifier Question

[Barry]

Okay, Roger.  Given that Marantz had/has a reputation for sounding great (and I tend to agree with that), if there was a way to enhance the sound, especially with such a small part like that, I'm sure they didn't hesitate to include it and I will restore it the same way it was.

Thanks!
Barry - N4BUQ

----- Original Message -----
> From: "Roger Ruszkowski" <flowertime01 at wmconnect.com>
> To: r-390 at mailman.qth.net
> Sent: Sunday, May 17, 2020 7:38:34 PM
> Subject: Re: [R-390] OT: Transistor Amplifier Question
> 
> Barry,
> The problem is complex and common.It is a bias stabilization method that
> works.In an audio pre amp any thing better is OK.
> We were looking at some 7805 or 7905 or 7812 voltage regulators.The comment
> was why the pf cps on the input and outputs of theregulators. What is + / -
> 50 pf going to do for the DC voltage andcircuit bias.
> It is not the exact value.At different device sizes, different pop corn
> noises get trapped insidethe specific device not the specific capacitor
> value.The science of what is going on in the circuit is complexand why RF is
> real squirrely compared to DC and Audio.Different cap types, silver mica,
> foil, ceramic, different dielectrics, and packaging all have different
> characteristics relevant to audio amplifiers.
> However the discussion of why the extra caps are includedwith three terminal
> voltage regulators explains it all the circuit science in nerd.
> The 50 pf caps do change the linearity of the amplifier stageeven if the
> improved nuisance misses your ears.The idea is that neutralizing the
> hysteresis on the transmission linebetween active amplification junctions is
> to retain signal fidelity.
> The caps self resonate and this effect extends or boosts the high frequency
> response in the amplifier stage giving better detail to lower audio
> frequencies. (Richer harmonic content)Those little caps just let the circuit
> sound better when the signal is more than just a simple sine wave.
> Roger AI4NI
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