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In Reply to: RE: final update .... posted by Triode_Kingdom on June 08, 2017 at 09:59:53
Oh for pete's sake TK, give it a rest already! Why don't you go build something so you won't be harping at everyone else all the time. You are beginning to sound like a broken record. When was the last time you posted an ongoing amp or preamp project with pictures? Don't you think it's about time?
Vinnie, I admire your spirit and optimism!
I started playing with tubes and electronics as a teen in the 1960s, so I'm firmly into the age range TK mentioned, where the higher frequencies, at least, are fading. And he is quite right, I have to say. But although I've already built N amplifiers it doesn't stop me from wanting to build the (N+1)th, even if I can't hear any difference.
In the end, the things I enjoy are the music itself, and at the other end of the spectrum, I can enjoy tinkering with the circuit to boost the technical measured performance, even if I can't actually hear the difference.
Actually, I'm not sure I would ever have been able to make trustworthy judgements of the difference in sound between systems. I learned recently I have aphantasia (no mental visual imagery), and I am suspecting I have the audio analogue too. It has always been a mystery to me how someone can compare two sounds that they hear sequentially.
I do enjoy the hobby, that is for sure. As to the hearing part, I am not so sure he is all that much correct. Take a look at the attached link and you will see there is an awful lot of music below the 12k mark, with the ear being most sensitive to the range of 300 hz to 5000 hz. Even us old farts can still hear a lot of recorded music and therefore hear differences if they are there.
Soooooooo, the next obvious question is, is there really that much difference between amps, and if there is what else besides frequency range might be at work there? I am about to start a web search on that topic and will report back on what if find.
Are you testing the amplifiers at all listening levels? I find that many amps do sound similar or the same at low levels but when pushed the shortcomings are apparent. I start my testing with something dynamic.
These shortcomings can almost always be measured so you need to challenge yourself by using a scope more often and do some frequency sweeps. More advanced hobbyists may use equipment to check distortion.
Can I hear a difference between a Hammond OPT and a Slagle or Monolith OPT? The answer is hell yes and they all measure different as well.
I read that most amps start distorting a little below clipping, but I rarely push mine that hard.
My philosophy for mine own listening is that if I can't hear a difference, then for all practical purposes there is no difference. I am not much of a fan of dialing in the last little bit with instruments if I am not going to be able to hear a difference.
I have heard differences between some opts also, but even the late Don Garber said the 125ese "sounds better than some people would like to admit" and offered it as an option on some of his builds.
Right now I plan to focus on building a small diy 6bq5 PP amp so I can do the A/B test between it and the SE 6bq5. I am guessing I will hear a difference between them. If I don't, then I will have to start digging deeper for an explanation. I am determined to find one.
"My philosophy for mine own listening is that if I can't hear a difference, then for all practical purposes there is no difference. I am not much of a fan of dialing in the last little bit with instruments if I am not going to be able to hear a difference."
That's fine, but it's not what we're discussing. Here's what you said earlier that started all this: "I kind of think it is the fact that they are both SE amps that is the main reason." That statement means you believe the lack of audible difference lies with the equipment, rather than your own lack of auditory acuity. This is what I was responding to.
Seriously, I don't understand why you're arguing about this. It's not rational to believe we can hear all the subtle differences when we get older. I was only making a comment that I thought would be helpful.
Buy Chinese. Bury freedom.
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?
It would seem there is more at work than just frequency response
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