This thread is about quality audio reproduction. BT is designed for low rate data transmission: at its best, that is with aptX, it's still sub-CD standard, and nowhere near Hi-Rez. The difference between BT and simple CD or 16/44 FLAC is clearly audible from my vanilla car radio.
My job is to give people pleasure while listening to the music that they prefer. Higher order distortion can detract from that. So can TIM, etc. Of course, amps and preamps are only part of the chain, but still important. Of course, huge amounts of negative feedback can pretty well hide MEASURED DISTORTION, but we still seem to hear differences, and sometimes, an amp with somewhat higher distortion might sound better than an amp with virtually no measured distortion. Why this is so is still controversial. My approach is to make the OPEN LOOP performance as linear as practical, then applying just enough negative feedback to meet some spec in order to be competitive in the marketplace. More negative feedback usually means less optimum sound, in my experience.
In what way? I presume you get out from time to time......have you been here?
Question regarding phase differences of amps.
If it is claimed to be so because the listener prefers a little low-level low-order harmonic distortion, that doesn't seem to be all that controversial, at least not any more.
If that isn't the reason, then it might be less controversial to clarify that you are talking only about a lack of measured nonlinear distortion, and there my be some linear distortion that affects listener preference.
It really only seems to be if you go so far as to say you know it is because of some mysterious un-measurable nonlinear distortion that gets people going. However, these days it seems like most people appear pretty tolerant of things claimed as personal opinion, as opposed to things claimed as fact that seem to fly in the face of well established engineering principles. If you are careful to say what you actually do and don't know, and what is opinion, you probably will find people are likewise more reasonable in responding back at you, at least on average. There will always be some who hold their beliefs sacred (in the psychological sense, that is). Why Do People Hold to Their Beliefs So Stubbornly? | Psychology Today
You can differentiate between BT and CD over concentration, engine, wind and road noise, I don't think so?
I can remember back in the 70's every hifi setup required a cassette recorder/player and compared with an mp3 ripped CD, they sounded terrible.
There are now over 50 million streaming music subscribers in the US alone.
Markw4, for all your education, you can certainly rationalize. We KNOW that negative feedback, for example, is a major cause of PIM. Now, 50 years ago, I might have agreed with you, and when I achieved 0.005% IM at 1W which equaled 104dB on my K-horn in 1968, I thought that I had done enough, for a K-horn, at least. I used 0.5A quiescent current, complementary diff input stage and matched complementary transistors for the output. I was surely proud of my accomplishment, Until I directly compared it to an early 1950's triode amp design, with the same measured distortion at 1W, and the same maximum output, by Sid Smith, before he joined Marantz. After that, I was not so confident in negative feedback, because that was the major difference between my solid state, and the triode design, I used 10 times more feedback!
Keep saying it, it won't make it true. In Ron Quan's tests classic tube amps could be quite bad feedback or no feedback.
It sounds like you were saying you thought it was adversely affecting sound quality in a 50-year old amplifier design. Assuming that happened, didn't you listen carefully to the amplifier to find out if it sounded okay?
Hi John,
Of course, there is no way to use that much feedback with a tube design as the output transformer adds a ton of phase shift at the ends of it's response. Tubes only would have a far wider frequency response if it wasn't for the output transformer. Also, the transit time in tubes is a lot longer than it is for transistors too.
However, negative feedback improves performance as long as you get the design right before adding feedback - which is what you have been saying in a roundabout way. I'm finishing a tube amplifier project with custom transformers, and while it sounded pretty good without feedback, the addition of feedback improved everything. So feedback good, not bad!
-Chris
Of course, there is no way to use that much feedback with a tube design as the output transformer adds a ton of phase shift at the ends of it's response. Tubes only would have a far wider frequency response if it wasn't for the output transformer. Also, the transit time in tubes is a lot longer than it is for transistors too.
However, negative feedback improves performance as long as you get the design right before adding feedback - which is what you have been saying in a roundabout way. I'm finishing a tube amplifier project with custom transformers, and while it sounded pretty good without feedback, the addition of feedback improved everything. So feedback good, not bad!
-Chris
First, I had to get rid of the TIM in my amp. Yes, it had a low slew rate, because I had overcompensated it to achieve absolute stability with a capacitive load. 50 years ago, slew rate was not as known as it is today. PIM is what I try to control today. Mark, has your favorite amp been tested for PIM? I doubt it.
As far as the amp that I designed was concerned, it sounded better than stock Dyna tube power amps with the K-horn, etc. I suspect that only a Marantz model 9 in triode mode would beat my little power amp in those days, except for its successor, also designed by Sid Smith, of course. In fact, Mark Levenson was so impressed with the sound of my power amp that he heard in 1968, that he hired me on the spot, 5 years later, when we re-met for the first time. My solid state amp was very good for the time. Today it is in a drawer, because it did not develop enough power for anything but k-horns, and when I went back to direct radiators (LS3-5a's) back in 1979 I needed a bigger amp. so I switched to an Otala designed Electrocompaniet power amp that I used happily until the firestorm in 1991. By then I was using the WATT Puppies, but I still liked the Electrocompaniet better than any other amp in reach. Now, of course, I use my own amp designs.
As far as the amp that I designed was concerned, it sounded better than stock Dyna tube power amps with the K-horn, etc. I suspect that only a Marantz model 9 in triode mode would beat my little power amp in those days, except for its successor, also designed by Sid Smith, of course. In fact, Mark Levenson was so impressed with the sound of my power amp that he heard in 1968, that he hired me on the spot, 5 years later, when we re-met for the first time. My solid state amp was very good for the time. Today it is in a drawer, because it did not develop enough power for anything but k-horns, and when I went back to direct radiators (LS3-5a's) back in 1979 I needed a bigger amp. so I switched to an Otala designed Electrocompaniet power amp that I used happily until the firestorm in 1991. By then I was using the WATT Puppies, but I still liked the Electrocompaniet better than any other amp in reach. Now, of course, I use my own amp designs.
Aassuming for the moment that an amp should be tested for PIM (belt and suspenders?), how do you test for PIM, and how do you decide if it pass/fail?
Hi John,
There you go insulting other people again.
So considering the scrap you were using, just when did the urge to build something a lot better bite you? I mean, did you even know what good sound was, considering your reference system? My audio journey began with a Fisher 400 preamp and FM-100 tuner along with an amplifier I can't remember the make of. That system gave way to a Marantz 2245 and Ortofon speakers, then a 2265B. My first system for only me was a Marantz SC-9, 300DC, 2120 and 5030B. I still have that system, modified for higher performance. That system is well received by visitors. I'm using PSB Stratus Gold speakers. Not the best, but pretty darned good. My tube amplifier design drives those speakers pretty well, a single pair of 6CA7 per channel. The best amplifier I've heard now? A Marantz 500 after a total rebuild where I match all the new transistors. The Bryston rep is very enthusiastic about it, and he recently bought the 4B Cubed. That amplifier runs pretty close to the 500. The 500 was designed in 1968, sold from 1969 to 1974. That's an old design, around the same length of time you have been active in electronics design, right? Now there is a design you should study John.
-Chris
There you go insulting other people again.
The Dynaco amplifiers were cheap kits that sounded terrible, a very low bar. I've been repairing those for years, and doing the accepted mods as well. So how come an accomplished amplifier designer was using such a piece of scrap to begin with? The K-Horns were worth a lot of money (I did warranty work on those as well), so I know your system far better than you give me credit for. Try to stop insulting people - especially considering the junk you were driving those poor K-Horns with. You also brought up the excellent Marantz amplifiers. Been restoring those for years, and the Dynaco doesn't even deserve to be mentioned in the same post.
So considering the scrap you were using, just when did the urge to build something a lot better bite you? I mean, did you even know what good sound was, considering your reference system? My audio journey began with a Fisher 400 preamp and FM-100 tuner along with an amplifier I can't remember the make of. That system gave way to a Marantz 2245 and Ortofon speakers, then a 2265B. My first system for only me was a Marantz SC-9, 300DC, 2120 and 5030B. I still have that system, modified for higher performance. That system is well received by visitors. I'm using PSB Stratus Gold speakers. Not the best, but pretty darned good. My tube amplifier design drives those speakers pretty well, a single pair of 6CA7 per channel. The best amplifier I've heard now? A Marantz 500 after a total rebuild where I match all the new transistors. The Bryston rep is very enthusiastic about it, and he recently bought the 4B Cubed. That amplifier runs pretty close to the 500. The 500 was designed in 1968, sold from 1969 to 1974. That's an old design, around the same length of time you have been active in electronics design, right? Now there is a design you should study John.
-Chris
Bob has been found to be incorrect in his early work. PIM has been published in several articles in the AES. Why don't you look them up. Matti Otala did some original analysis, Ron Quan is the best author of this sort of distortion at this time.
I thought they were beloved by the owners? I wouldn't know, they came out before I was born.
Have you seen them now?
Anatech, what does a Dyna MK 3 with matched KT-88's cost today? The Dyna had some problems, but it actually measured better at 1W, than an equivalent McIntosh design. I used to sell them too, and I did not like their sound with a K-horn.
A Marantz 500 we used in Switzerland in 1974 as a woofer amp, up to about 500Hz. It was marginal full range, very low slew rate. We used the Marantz 250, which was better and faster for the midrange,. 400-4000Hz, then I had to design the JC-3 power amp (my first professional power amp) based on Otala's findings that achieved 100V/us driving a horn tweeter. The tweeter amp sounded great, and Levinson took over the design in 1975 to make one of the most famous amps in history, the ML2 You might look it up.
A Marantz 500 we used in Switzerland in 1974 as a woofer amp, up to about 500Hz. It was marginal full range, very low slew rate. We used the Marantz 250, which was better and faster for the midrange,. 400-4000Hz, then I had to design the JC-3 power amp (my first professional power amp) based on Otala's findings that achieved 100V/us driving a horn tweeter. The tweeter amp sounded great, and Levinson took over the design in 1975 to make one of the most famous amps in history, the ML2 You might look it up.
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