With Arnie's blessing for the 200C's sound quality being in the "same" universe as his huge and exotic vacuum tube amplifiers (though not in the same league), we were thrilled.
To put this in perspective, at that time, no solid state amplifier had ever come close to Arnie's high standards, so this was a major triumph for us.
As you may recall from yesterday's post, the one big change we had to take care of was to eliminate the output inductor. With the inductor pianos and strings lost their luster and sounded dull and uninvolving. Removed, the life of the music returned. Allow me to explain why.
An inductor is basically a coil of wire. When music is passed through this coil, lower frequencies pass without any interference (hence the term lowpass as the lows will pass through). However, as the frequency rises so too does the impedance of the coil. Any frequencies above the coil's cutoff begin to reduce in volume level and continue to do so until there's no output at all at very high frequencies.
Inductors are routinely used as low pass filters for woofers inside speaker crossovers. Rarely are they used at the output of a power amplifier. That said, Dr. Bob had found this to be a safe solution for connecting and disconnecting speakers without upsetting the amplifier. Turns out the circuit was extremely fast and on the edge of instability whenever a speaker was connected or disconnected when the power amp was live. (Good practice is to always turn off your equipment when connecting and disconnecting from it)
Oy.
So now it's time for me to own up to something. In our lives we all make mistakes. Just part of life and hopefully we learn from those mistakes. At this juncture I had three choices: put back the inductor, design a new protection circuit that would shut down the amp at the hint of instability, or plaster a huge warning sign on the back of the amplifier not to plug anything in or out while the amp was on.
I chose the third alternative. Why? First off, I am unwilling to sacrifice sound quality for any reason. Nada. Just not in my universe. Second, the right approach would have been to delay the launch of the amp and spend the 3 to 4 months designing and installing the new protection circuit. Well...I have never been applauded for my patience.
And so…
