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In Reply to: RE: final update .... posted by Triode_Kingdom on June 10, 2017 at 08:46:03
Tk most of your responses to my last several posts up to now have been both antagonistic and condescending to say the least. I don't mind helpful suggestions or even pointing out errors in a friendly way, and you have done both in the past. What I do mind is the attitude that you have once in awhile that I am an idiot if I don't see things the way you do. If you don't agree with what I say, fine, you don't have to, but please temper your replies with a bit of restraint.
My comments were based on the links I posted, and there is some very valid information in them, including how much of recorded music is below 12k. Look at the chart and you will see what I mean. I am attempting to understand why I am hearing what I am, and I plan on taking it one step at a time. Any suggestions you can offer in a friendly manner that might help me figure it out will be welcome. I think there is more to it than just me being an old fart or using less than mega buck opts. I plan to report my findings here as I go along.
Vinnie, I don't think TK was being condescending, sometimes it's difficult to interpret the tone of an email or post. This new digital world can be challenging at times.... Engineers deal with facts, statistics and measurement data, sometimes answers may seem harsh but i never take it personal. I work with electrical engineers every day, I always back up my answers with factual data. We all know music is under 12k but I'm sure there's a reason why we choose transformers with extended bandwidth, sometimes 100khz and above.
My Hammond opt performed pretty darn well, especially in the base region but didn't have that live sound of other opts. Could it be the extended freq response of my other opts? Or the amorphous core? I just don't know the answer to that but do hear a difference.
My Khorns reveal everything and makes this process easier to interpret.
On my ribbons, not so much.
" We all know music is under 12k but I'm sure there's a reason why we choose transformers with extended bandwidth, sometimes 100khz and above."
If we look at a simple, single pole 6db per octave low pass filter we see that the amplitude is still down 1db one full octave below the -3db point.
A OPT that is rated for -3db at 15kHz will still be down 1db at 7.5kHz
Then there's the matter of phase shift. A filter causes not only a loss of amplitude but also a shifting of phase. The music's phase is shifted for a decade from the -3db point. So if the amplitude is -3db at 15kHz the phase will be shifted all the way down to 1.5Khz
If we want the response (phase and amplitude) of a system to be flat 20Hz-20kHz we need the filter's (high pass and low pass) -3db points to be 2Hz-200kHz.
If we want response of a system to be flat 50Hz-15kHz we need the filter's (high pass and low pass) -3db points to be 5Hz-150kHz.
These are "tall" orders, especially for an output transformer, but there are real world benefits in meeting them whenever possible.
BTW There are low pass and high pass filter everywhere in a circuit. Every cathode bypass cap forms a filter, every coupling cap forms a filter. The Miller capacitance of each stage forms a filter. Stray inductance, stray capacitance etc. It's not just OPT's.
Have Fun and Enjoy the Music
"Still Working the Problem"
I'm sorry deaf, but if it is that easy to misunderstand the tone of a given post, then the poster needs to be more careful. We are talking about being polite here, and being technically inclined does not excuse someone from politeness.
As far as the rest of your post, I am simply trying to show that there may be more involved with this than just opts and old age. I will keep looking to see what turns up.
what are your operating points for each stage of the amps?
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