Re: [ARSCLIST] FW: [ARSCLIST] Internet audio: What do you expect of it ?

[Mike Richter <mrichter@xxxxxxx>]

Scott Phillips wrote:
> A lot of the early transistor designs were attempts to use basic tube
> circuit principles with transistors. Regular bipolar transistors aren't
> all that linear all by themselves, they required new ways of thinking.

I'm not at all sure what is meant here by "bipolar" (the transistor is a 
three-terminal, continuous current amplifier of course), but let me 
support the general argument.

Fresh out of school in June, 1960, I went to work for a small company 
designing instrument servomechanisms. They had a solid-state amplifier 
of their own design, the best then on the market, constructed to 
apologize for the transistor's terrible performance as a vacuum tube. 
With no engineering background and only the GE transistor manual to 
start with, I designed and had built a "High Fidelity Servo Amplifier" 
(the title of the paper I wrote on the design). THD under 0.1%, flat 
from the cutoff frequency defined by the output coupling capacitor to 
too darned high a frequency. We added a capacitor to roll it off before 
100 KHz to prevent parasitic oscillation with external parts. This was 
before integrated circuits (the TI Darlington cans were just coming 
out), so with discrete transistors it occupied one cubic inch compared 
with well over ten cubic inches (and more than ten times the cost) for 
its predecessor.

It delivered two watts of clean power and sounded wonderful connected 
directly to Sennheiser headphones with their 600-ohm impedance - and not 
bad driving a reasonably efficient speaker until they hit clipping. The 
design could never have been implemented in tubes - but we were no 
longer designing for vacuum tubes. They were very poor transistors.

Mike
--
mrichter@xxxxxxx
http://www.mrichter.com/