How many times have I been led down the path of the obvious only to discover all the detours I should have been paying attention to?
No doubt more times than I care to remember.
In our continuing story of the development of the MCA, PS Audio's first standalone Moving Coil phono preamplifier, I had designed a great sounding circuit based on the transistors we had formally adopted as our low noise, high-speed go to device—the MPS 8099 family from Motorola.
Only problem was it had too much noise. Way too much noise.
In my past experience with designing a low noise phono preamplifier I had figured out the chief source of noise was the amplifying device itself. That was easy. Pick a low noise transistor and life's good. If you need even lower noise, you can parallel the transistors and with each doubling you get half the noise.
That wasn't rocket science.
But somehow, with this new phono cartridge, that discipline wasn't working.
Back then there was no internet. There were encyclopedias which, for what I was doing, were about as useful as you know what on a bull. There were textbooks galore on low noise design of amplification circuits, but almost none applied directly to audio (since audio and especially exotic audio like what we were doing was a minuscule spec on the technology horizon).
Nearly no one I knew in the industry would be much help. The few pioneers at the time were convinced that the MC step-up transformers were the way to go. These tiny audio transformers (still in use today) had a turns ration of 1:30 so any signal coming in would be amplified by a factor of 30X. Just what the doctor ordered and without noise.
Obviously, that was the way to go. Only, I wasn't happy with the way they sounded. Even the most expensive transformers sounded wimpy and rolled off on the bottom end; their top end wasn't a whole lot better.
The obvious path forward would have to be a full range amplification stage. Unfortunately, getting lower and lower noise transistors wasn't getting me where I needed to go. I had the full range great sound, but it was ruined by the loud hiss.
I hadn't yet realized it but I had to move away from obvious solutions.
Obviously.
