On Fri, 13 Oct 2017 23:37:27 -0700 (PDT), Sean B
wrote:
Hello,
Do different types of (let's narrow it down to small-signal devices) BJTs sound significantly different in anyone's experience, in various types of audio circuits? They all have that exponential relationship between base-emitter voltage and collector current. I'm wondering what could account for differences in sound, assuming those differences exist.
I recently built a BJT emitter follower with a another BJT as a current source feeding it, and even though it measures very well (junk down about 105 dB from the fundamental test tone) it added a noticeable brightness to audio passing through it. It just confounds me that this could be audible.
Thanks,
Sean B
Much more likely (if there genuinely is a brightening, which I somehow
doubt), that the reduced output impedance is flattening the top end of
a subsequent capacitive load - maybe the result of some cable.
I'd suggest you make an objective frequency response measurement to
see if there actually is an effect.
Your figure of junk at -105dB surprises me somewhat. Emitter followers
are just not that linear - the internal emitter resistance is roughly
26/Ic(mA) so a signal is always modulating the output voltage,
resulting in even + odd order harmonics.
d
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