Engineers too listen to music

[jlsem]

Now, will this conclude a DC blocking capacitor disturbes the signal path or more appropiately, the overall system behavior in an unmeasurable way?

Obviously the presence of a capacitor is measureable and so would any dc-blocking device inserted at the input. What is hard to correlate is how the measurements would indicate "good" sound or not. An input transformer may not seem to measure the "best", but many think it sounds better than an input capacitor. I had a friend here in Dallas, he has since passed away, who was a marvelous engineer (worked many years at TI/Raytheon on guided missile systems after an exemplary career in the Air Force) and had a great deal of interest in audio. He designed and tried many audio circuit schematics such as SRPP, mu-follower, long-tailed pair, cathode-follower, etc. He finally told me not long before he had to go into hospice care that, after all was said and done, a triode that was plate-loaded with a choke, transformer primary, or constant-current source sounded best. His name was John Camille and was well-respected as a designer and engineer. One of the things that interested him most was hearing something subtle in a system and then working out a method of measuring what was there.

John

 

[ingrast]

Obviously the presence of a capacitor is measureable and so would any dc-blocking device inserted at the input. What is hard to correlate is how the measurements would indicate "good" sound or not. .....

John

Correct, by I assume the DC blocking capacitor is used just for that, i.e. not only frequency response down to 20 Hz or lower if you want, but phase deviation, are kept close enough to a capacitor less scheme performance.

I may suggest several possible mechanisms why the NS phenomenom occurs - I put my faith in that it really exists - but it should be irresponsible without further knowledge of actual device inner topology and actual operating conditions like when the situation was noticed.

I hope National will find means to make the challenge profitable and demonstrate what is really happening. Otherwise, someone else will do.

For my part I can safely bet my life there is a perfectly measurable performance difference and a perfectly understandable mechanism explaining what happens and why. It may be subtle and complex in the worst case, but it is there.

It will be enlinghtening too. Hope it comes through.

Rodolfo