PIM? No, that is TIM. That also took a long time to straighten out. Slew rate limiting? OF COURSE, we knew about slew rate limiting, it was what these new-fangled IC's had that made them so compromised in performance. I remember talking to a fellow engineer at Ampex Instrumentation in 1967, as he was assigned to evaluate the LM-301, uA709, etc, for analog instrumentation use as I had done at Friden Inc one year earlier, for lower frequency stuff. His main gripe was the slew rate, as we were designing 2 MHz preamps for NASA. STILL, try to get a thorough analysis of slew rate limiting in 1967. Dr. Cherry didn't even mention it in his almost 1000 page textbook on amplifier design, you know Cherry and Hooper. Find slew rate distortion in THAT textbook! Of course, you could get some theory at the senior-graduate level in college. You could also have read Solomon's essay that came out in the early '70's that really nailed it: 'The Monolithic Operational Amplifier: A Tutorial Study' Invited paper IEEE JSSC Vol. SC-9 No. 6, Appendix A, NSC Linear Applications Handbook
Hi John,
I only respond to you when you become patronizing to those around you. There are times when you do bring up some technically useful stuff, but it tends to be buried in a lot of attitude.
You also have what can only be called a special knack for berating real engineers who are rather more accomplished than you are. Not unless you've done something cool - lately. 20+ yrs. ago really isn't news.
No kidding! However, you have gone on about how you go about designing things enough. I suspect that you have a chart that gives you the 7th harmonic for all test fundamentals.
You really have to be mad at someone else there John, you've got me confused with someone it seems.
But look at it this way, now we know a little more about each other!
Go in peace, brother?
-Chris
I only respond to you when you become patronizing to those around you. There are times when you do bring up some technically useful stuff, but it tends to be buried in a lot of attitude.
You also have what can only be called a special knack for berating real engineers who are rather more accomplished than you are. Not unless you've done something cool - lately. 20+ yrs. ago really isn't news.
No kidding! However, you have gone on about how you go about designing things enough. I suspect that you have a chart that gives you the 7th harmonic for all test fundamentals.
That may very well be, but not from me. I haven't ever done that to you. Level your cannon at a true enemy buddy.
I can understand that. I've found a similar thing to be true myself. However, to grow you need to learn. I try to buy newer, more capable equipment as I can, and also employ what I have in other ways. Just learning. But still, you're going on about something I do not do to you. You're barking up the wrong tree.
I wouldn't think so, but then I don't use a simulator at all. I just write it down on paper and build it. Normally things work the first time out, or just need some component changes. I don't use proto-boards either.
You really have to be mad at someone else there John, you've got me confused with someone it seems.
But look at it this way, now we know a little more about each other!
Go in peace, brother?
-Chris
Anatech, it is rare that I actually address you about anything, unless I am directly berated by you for some reason. Is this a message address issue? Last I remember, I was addressing SY (to a small degree) and Scott (to a larger degree, as we have known each other for more than 25 years, and he was, by the way, VERY HELPFUL in 1984, when I was trying to figure out sophisticated RF bypassing for a 30MHz power amp that I was building for the laser project. Ask him yourself about this, if you want to know about good COMMERCIAL RF bypassing.
Anatech, for the record, I am releasing the JC-3 phono preamp at this time, and finishing up on a $40,000 phono preamp for Constellation Audio that is just studded with rare to impossible to get complementary j-fets. Last year, I designed parts of an advanced power amp that uses switching amps as tracking dual supplies. We are very happy with its sonic performance. However, I just don't publish or even talk much about what I do at this time, on this website. I get paid for my efforts, and I can't afford to just give them away to amateurs. Sorry, but that is how it is.
However, I will still stand strongly behind the Blowtorch Preamp that started this thread, a few years ago, and the design principles that made it successful.
However, I will still stand strongly behind the Blowtorch Preamp that started this thread, a few years ago, and the design principles that made it successful.
Last edited:
Hi John,
Yes, I know about that preamp release. You have mentioned it in passing before.
Does the customer know they may not be able to repair this preamp?
Bob Carver used a very similar idea in the old Lightstar amplifier. The supplies are .. darn, I can't tell you! It's a commercial product.
What I can say is that the performance was better than most previous designs, very satisfying. I even owned one for a while. They did pay me to modify and repair all the Canadian models. So I can see where you're coming from John. I was exposed to an advanced design that I really ought not to talk to any amateurs for any money. So yes, I do see how it is John. You're quite right and I'm glad you mentioned it. I caught myself before I spilled the beans. I can say that the "down converters" used a higher frequency, but I am not able to mention the frequency used.
In case you haven't realized this, I have not once attacked the Blowtorch. I'm not about to start either. Nor have I ever attacked your measurements, or lack of same. I haven't attacked the equipment you use, the car you drive or the parts you use. I can't for the life of me understand why you keep bringing these things up with me. Well, I also tend to question claims you may advance without actual proof. But then, you'd do the same if anyone else pulled that one in front of you.
The only thing I have mentioned to you is your treatment of people around you - so there is no mystery involved. You abuse people, I call you on it. Simple.
-Chris
That's true most often. But you did feel a need to comment over a post directed to another person recently. You seemed to feel the comments were directed to you. They were not.
Why do I need to know this? Too much information.
I might ... if I knew the man well enough. I also know some high school friends that make a paid living doing RF IC design - very popular. They have I think 80% market share or so in high speed modem chips. He's a pretty smart guy, and a real engineer to boot! I have some very low noise clock distribution projects on the go where jitter would be disastrous. The oscillator needs to be 1 x 10^-11 or so, worst case at 10 MHz. Complete isolation between channels in order to avoid ground loops. Simple project, cool stuff.
Yes, I know about that preamp release. You have mentioned it in passing before.
For production or a one off? If for production, why on earth would you do a new design using parts not available for future service? I imagine there should be workable devices in surface mount.
Does the customer know they may not be able to repair this preamp?
Yes, you also mentioned that in passing.
Bob Carver used a very similar idea in the old Lightstar amplifier. The supplies are .. darn, I can't tell you! It's a commercial product.
What I can say is that the performance was better than most previous designs, very satisfying. I even owned one for a while. They did pay me to modify and repair all the Canadian models. So I can see where you're coming from John. I was exposed to an advanced design that I really ought not to talk to any amateurs for any money. So yes, I do see how it is John. You're quite right and I'm glad you mentioned it. I caught myself before I spilled the beans. I can say that the "down converters" used a higher frequency, but I am not able to mention the frequency used.
By Jove! So will I! After all, I started this thread for you.
In case you haven't realized this, I have not once attacked the Blowtorch. I'm not about to start either. Nor have I ever attacked your measurements, or lack of same. I haven't attacked the equipment you use, the car you drive or the parts you use. I can't for the life of me understand why you keep bringing these things up with me. Well, I also tend to question claims you may advance without actual proof. But then, you'd do the same if anyone else pulled that one in front of you.
The only thing I have mentioned to you is your treatment of people around you - so there is no mystery involved. You abuse people, I call you on it. Simple.
-Chris
Anatech, all autos are not the same, and all amplifiers are not the same. I was JUST describing the type of amplifier that I was working with. The switching power supplies are NOT what makes the amp special, it is other patented areas of the design, which make the amp perform better than just about anything I have ever designed, and better than most amps in the world today. Tall order, huh?
In fact, the very first tracking power supply power amp that I ever saw was made by Soundcraftsman about 30 years ago. It failed in the marketplace, because it didn't have anything else going for it, EXCEPT the tracking switching power supplies. It takes more that that to make a successful design, at least I think so. You might just stick with Bob Carver. I have known him since the early '70's and we have mutual friends. We do depart in design philosophy, that is why we don't know each other better.
For the record, I have 4 other power amplifiers available in the marketplace, all by Parasound, and they carry my design credit. I have a preamp as well, and it got picked as first rate, in both 'The Absolute Sound' and 'Stereophile' this very month, as well as for several previous months earlier, AND we don't even advertise in these magazines! Are they nuts? ;-) Still, the Parasound JC-2 is NOT as good as the CTC Blowtorch that is the essence of this thread.
Still, everybody, go out and design your own pre and power amps. See if you can get the same appreciation for your effort as I tend to get.
In fact, the very first tracking power supply power amp that I ever saw was made by Soundcraftsman about 30 years ago. It failed in the marketplace, because it didn't have anything else going for it, EXCEPT the tracking switching power supplies. It takes more that that to make a successful design, at least I think so. You might just stick with Bob Carver. I have known him since the early '70's and we have mutual friends. We do depart in design philosophy, that is why we don't know each other better.
For the record, I have 4 other power amplifiers available in the marketplace, all by Parasound, and they carry my design credit. I have a preamp as well, and it got picked as first rate, in both 'The Absolute Sound' and 'Stereophile' this very month, as well as for several previous months earlier, AND we don't even advertise in these magazines! Are they nuts? ;-) Still, the Parasound JC-2 is NOT as good as the CTC Blowtorch that is the essence of this thread.
Still, everybody, go out and design your own pre and power amps. See if you can get the same appreciation for your effort as I tend to get.
John et al;
A couple of points:
Distortions are not static. What you get at low levels is different than at higher ones. There are types of distortions that may be perceived when your interconnect levels are on the low end of consumer unbalanced and high impedance gear. At pro levels the extra 20 db or so of level may drop them to where they are not as much of a problem.
Folks who use low efficiency loudspeakers can with good reason prefer different power amplifiers than the idiots like me who have high efficiency ones.
Obviously when an audio power amplifier clips all bets are off as to sonic differences. When CD's are used as the source you have a pretty well defined maximum level and dynamic range. Not so with records or tape and forget live!
Looking at any one type of distortion is really like the parable of the blind guys encountering an elephant.
That said if you can hear it, then someone should be able to measure it. If you can't measure it doesn't mean it is not there, you might be measuring the wrong things.
In short If John uses a method consistently, that is fine, it gives him insight based on his experience, but any single figure of merit is silly.
Some days I like chocolate ice cream, others mint chocolate chip, Picasso paintings are valuable, my photographs are not. There are those who like low feedback amplifiers, and I have met folks who like amplifiers I would consider broken.
A recording of a performance looses information, if adding coloration to it evokes the same emotional response from it as from a live performance, is it a good crayon?
Next,
I don't know where the idea comes from that the folks who produce recordings run everything through a dozen opamps. There are some quite popular microphones that use warm bottles of glass to produce their output signals. Some current microphone designers even use FETs! Then there are quite an amazing number of microphone preamps in portable packages to choose from. Some get hot in use, others don't, recordists can take their choice. Discrete A/Ds also show up. I even know one guy who actually uses all those gizmos with high sampling rates. Believe it or not there are some recordings that sound much better than others!
Even when recordings are made on opamp based consoles there are many inputs placed in parallel either at the time of recording or at the final mix. Paralleling as you probably know is a valid method of reducing noise and distortion.
Scott,
As to why magic parts don't show up in many critical applications, sometimes they do. Have you ever seen the funny resistors used in X-ray machines? Not exactly suited for audio or even any consumer product but quite on target for their use. But that is slightly askew from your objection. I am sure you are aware that in sample and hold circuits capacitor choice can make or break meeting design goals. In strain gauge amplifiers resistor choice gets really dicey if you want lots of range.
I think the actual issue is what dynamic range is needed for audio reproduction. Since the operating levels vary so much I think that adds at least 20 to 40 db more than would be required from a well designed standardized system. When you design other sensitive gear you do not have as much miss-operation. So in audio the user expects the designer to have anticipated a much wider range of operating parameters.
I haven't really ever worked your company's application guys, but I have with others and sometimes how much they know is scary and other times the rote answers they give without understanding the issues is just as scary.
Sy,
In the 70's I worked with parts that still are not available anywhere I know of.
I remember one project where we need a device to meet certain performance requirements. The other guys in the lab pulled out a black box, hooked it up and it worked perfectly. I was very surprised at how simple it was, as it was based on a component I had never heard of before! For some reason it was not in any supplier's catalog. Today a not very good version of that device is available commercially.
All,
I am finishing up a review of a book on how to improve sound systems. I have trouble with some of the explanations in the book of how things work, but the final answers seem to be right. The author comes from the I hear it, so it must be true school. So the question is "If you think North is West and South is Up, but you always find a good restaurant, should I let you direct me where to eat?"
A fellow gets a flat tire, pulls over to the curb, loosens the lug nuts, jacks up the car takes off the tire. Gets out the spare and trips over the lug nuts sending them down a drain he hadn't noticed. Looking around he realizes he is just outside the fence from a mental institution. A group of patients have been watching all of this. One of them looks at him and says "Look just take one nut off of each of the other three tires and you can then drive to an auto parts store for replacements." The guy is amazed and says his thanks. The patient then says "Forget it, after all we are crazy, not stupid!"
Thank you for your patience my fellow patients.
ES
A couple of points:
Distortions are not static. What you get at low levels is different than at higher ones. There are types of distortions that may be perceived when your interconnect levels are on the low end of consumer unbalanced and high impedance gear. At pro levels the extra 20 db or so of level may drop them to where they are not as much of a problem.
Folks who use low efficiency loudspeakers can with good reason prefer different power amplifiers than the idiots like me who have high efficiency ones.
Obviously when an audio power amplifier clips all bets are off as to sonic differences. When CD's are used as the source you have a pretty well defined maximum level and dynamic range. Not so with records or tape and forget live!
Looking at any one type of distortion is really like the parable of the blind guys encountering an elephant.
That said if you can hear it, then someone should be able to measure it. If you can't measure it doesn't mean it is not there, you might be measuring the wrong things.
In short If John uses a method consistently, that is fine, it gives him insight based on his experience, but any single figure of merit is silly.
Some days I like chocolate ice cream, others mint chocolate chip, Picasso paintings are valuable, my photographs are not. There are those who like low feedback amplifiers, and I have met folks who like amplifiers I would consider broken.
A recording of a performance looses information, if adding coloration to it evokes the same emotional response from it as from a live performance, is it a good crayon?
Next,
I don't know where the idea comes from that the folks who produce recordings run everything through a dozen opamps. There are some quite popular microphones that use warm bottles of glass to produce their output signals. Some current microphone designers even use FETs! Then there are quite an amazing number of microphone preamps in portable packages to choose from. Some get hot in use, others don't, recordists can take their choice. Discrete A/Ds also show up. I even know one guy who actually uses all those gizmos with high sampling rates. Believe it or not there are some recordings that sound much better than others!
Even when recordings are made on opamp based consoles there are many inputs placed in parallel either at the time of recording or at the final mix. Paralleling as you probably know is a valid method of reducing noise and distortion.
Scott,
As to why magic parts don't show up in many critical applications, sometimes they do. Have you ever seen the funny resistors used in X-ray machines? Not exactly suited for audio or even any consumer product but quite on target for their use. But that is slightly askew from your objection. I am sure you are aware that in sample and hold circuits capacitor choice can make or break meeting design goals. In strain gauge amplifiers resistor choice gets really dicey if you want lots of range.
I think the actual issue is what dynamic range is needed for audio reproduction. Since the operating levels vary so much I think that adds at least 20 to 40 db more than would be required from a well designed standardized system. When you design other sensitive gear you do not have as much miss-operation. So in audio the user expects the designer to have anticipated a much wider range of operating parameters.
I haven't really ever worked your company's application guys, but I have with others and sometimes how much they know is scary and other times the rote answers they give without understanding the issues is just as scary.
Sy,
In the 70's I worked with parts that still are not available anywhere I know of.
I remember one project where we need a device to meet certain performance requirements. The other guys in the lab pulled out a black box, hooked it up and it worked perfectly. I was very surprised at how simple it was, as it was based on a component I had never heard of before! For some reason it was not in any supplier's catalog. Today a not very good version of that device is available commercially.
All,
I am finishing up a review of a book on how to improve sound systems. I have trouble with some of the explanations in the book of how things work, but the final answers seem to be right. The author comes from the I hear it, so it must be true school. So the question is "If you think North is West and South is Up, but you always find a good restaurant, should I let you direct me where to eat?"
A fellow gets a flat tire, pulls over to the curb, loosens the lug nuts, jacks up the car takes off the tire. Gets out the spare and trips over the lug nuts sending them down a drain he hadn't noticed. Looking around he realizes he is just outside the fence from a mental institution. A group of patients have been watching all of this. One of them looks at him and says "Look just take one nut off of each of the other three tires and you can then drive to an auto parts store for replacements." The guy is amazed and says his thanks. The patient then says "Forget it, after all we are crazy, not stupid!"
Thank you for your patience my fellow patients.
ES
Some of the best recordings I ever heard were from those square diaphragm
tube powered Pearl mics.
I've seen plenty of parts designed to do difficult jobs, all were done using solid engineering principles. No magic involved unless sophisticated knowledge appears like magic to some.
Scott
I think Lincoln got it right "You can fool some of the people all of the time...."
So magic be it! Hmm, maybe we could do a popular book series...
I think where you and I may disagree is that your feel for this is there are basic standards and folks should follow them, where I expect if there is a silly way someone will use it and complain when they get silly results.
And the other issue is that if folks tell me they can hear something I am willing to accept that is their perception unless it involves voices telling them to do something.
I every so often get 24 bit over sampled wave files that were well recorded. I think they sound better than most of the other sources I have, but there a number of folks who insist anything past 16 bits is wasted. I know that the 24 bits is not 24 bit linear and that it could just be better recording techniques, but I still prefer them. Do I need to convince anyone else of that... not really.
In the past I have done sound systems where due primarily to what is called the Haas effect I could not detect any coloration from the sound system even though the person talking into the microphone became louder and the STI readings improved. These system were quite unsuccessful.
It turns out the operator would always turn up the sound system until it fed back or clipped, then they knew it was on. Even those system where no operator was required someone would "fix" it because they could not hear it working.
I got high praise from a few who understood what was going on, but I even got a pan for this from the NY Times! (The critic though the loudspeakers were too small. Workers a mile away however would stop working and listen!)
The solution has been to color the sound so that everyone can tell the sound system is turned on. These systems are much more successful in terms of lack of service calls, longevity of the system and folks who just out of the blue tell me it is a great system.
So Scott you work with folks who know what they are doing, I work with folks who think they do. Maybe that is why we have different perceptions.
ES
PIM is covered by diff gain/diff phase. Well known since the 60's in TV's. Open-loop, closed-loop it does not matter, no one has produced any evidence that trivial amounts of it at audio frequencies separated from everything else that is going on is actually audible.
That graph from Matti's paper you like to show is a 741 driven into gross large signal overload, hardly a vehicle to study PIM.
Hi Scott,
Couldn't agree with you more. Thank you.
Hi John,
Gosh, you just don't get it!
Okay, I was pulling your leg. I ceased to take most of what you post very seriously until you get into actual design talk. The rest is noise, sorry. Your personal life has no meaning for me. Who you know (or don't) has little effect as well. What matters is what you actually post that deals with real circuits and design considerations (as long as we aren't talking about magic parts).
Having said that ...
John, the way you wrote this can be taken in ways you didn't intend. You got a big smile out of me, so thank you for that.
I lied. No kidding John, I have been working with some of their parts. But as you can see, there is a question on the P channel parts. Gosh, I knew all about that too.
I dearly wish I could attend again, but my medical status prevents that still, and I'm pretty darn short of money as well. There are a number of people I'd love to reconnect with.
If any members can attend the Burning Amp show, do it. It's is well worth the effort.
-Chris
Couldn't agree with you more. Thank you.
Hi John,
Gosh, you just don't get it!
Okay, I was pulling your leg. I ceased to take most of what you post very seriously until you get into actual design talk. The rest is noise, sorry. Your personal life has no meaning for me. Who you know (or don't) has little effect as well. What matters is what you actually post that deals with real circuits and design considerations (as long as we aren't talking about magic parts).
Having said that ...
Read my posts. We agree on that.
The power supply design is central to what Bob Carver achieved. I have had a good relationship with Bob's engineering department at Carver. The sound of that amplifier also depended on the rest of the design, of course! But, that amp and it's power supply are one unit. The matching preamp was pretty neat as well. I can still service both.
That is your opinion, and you are entitled to it. I haven't heard your new equipment, so I can't comment. I'm sure it sounds good though.
John, the way you wrote this can be taken in ways you didn't intend. You got a big smile out of me, so thank you for that.
No ....
I lied. No kidding John, I have been working with some of their parts. But as you can see, there is a question on the P channel parts. Gosh, I knew all about that too.
I was at the first Burning amp and enjoyed that immensely. This even though I worked through it down there and was in rough shape by the show date.
I dearly wish I could attend again, but my medical status prevents that still, and I'm pretty darn short of money as well. There are a number of people I'd love to reconnect with.
If any members can attend the Burning Amp show, do it. It's is well worth the effort.
-Chris
To complete the 'equation' dielectric absorption was fully documented in the 1950's for ANALOG COMPUTERS. Nobody in their right mind, then or now, could possibly concieve that 1-10% DA per coupling cap could possibly make any difference in audio reproduction.
Now, can we go on?
Now, can we go on?
Last edited:
I was more under the impression this came as a surprise in the early 60's when color television started. The phase modulation used to convey color information showed flaws in what was previously thought to be adequate.
My experience is that the types of coaxial cables in use prior to color TV needed to change to ones with more uniform properties. New cable tests and types started appearing back then.
The final fix was actually to re-tweak the phase information reference at the final receiver. This was known as the "tint" control.
Of course once the problem was acknowledged and it was recognized there were multiple contributors to the problem, then the solutions could be implemented.
- Status
- Not open for further replies.