What impedance do you design the output of the preamp to drive? 600 ohm balanced? Are Mosfets or bipolars better for the job?
john curl said:
What you call successful is nothing more than your opinion. Many other manufacturers have enjoyed equal if not more success than you but maybe they are different to you and they don't bathe in their past glories or let a few of their designs go to their head.
It appears that you are closed minded to other peoples opinions which are contrary to yours as though there is only one correct way to do something and that is the JC way !! Sorry to disappoint you Mr Curl, the mere fact that not everyone owns your brand of equipment and there is no unanimous agreement amongst people as to what constitutes the best, suggests this to not be the case.
I would like to make a few comments about Julian Vereker and Naim Audio amps. Back in the middle '70's, these were SOTA amps. Yes, they were quasi-complementary, but for a good reason. The specific output devices had very good safe area, but were faster than typical devices, yet had no complement. Julian revealed this to me, after I had known him for years. He seemed to make relatively crude circuits, but they competed well in the marketplace, AND they had many design decisions in them that parallel mine. This gave them a competitive advantage in the audio marketplace, that many here cannot yet comprehend why.
I would think that all science is but a collection of opinions that, with time, will change, or at least evolve. It is those who think that they know, without experience, that causes the problem here. Of course, not everyone should believe that ONE WAY is the only way. Try different approaches, but please try to make your listening comparisons fair, and not personally biased. It is in the listening that we are trying to achieve the best result.
MikeW, the Parasound JC-2 preamp uses complementary mosfets running at about 50ma, or as high as the internal heatsinks will allow. It is really designed for 5K or more loading, but it apparently will work with 600 ohm loads, if necessary. I don't recommend it, however, as it appears to bring out some extra higher order distortion. Bigger, or external heatsinks, and more standing current would fix that, but it was not designed for 600 ohm loads, and the output balance will have to be reset internally, if it were used deliberately in that manner.
john curl said:
Naim and every other amplifier designer was using the same topology at the time for the same reasons. Nothing ground breaking here. Just look at an old RCA application notes design book and you'll see a dozen or so of the same designs from low power to high power. Just take your pick, it's not rocket science 😉 The only difference is that Naim cleverly charged a premium for an otherwise stock standard amplifier design topology which was not much better than anybody else's offering at the time. Just some clever marketing and gullible people who bought them for a lot more than their real worth 🙁
As well there were all of these "better ??" power supplies you could buy, designed to extract even more money out of the unsuspecting punters 🙁
Whilst in the 80's the Jap's were building gear which was decades ahead of the likes of Naim and yet gullible audiofools were still tripping over themselves to pay a lot more to buy a stake in a mediocre design from the 60's 🙁 Somehow it never made much sense to me.
Like they say there is a sucker born every minute and a little knowledge is a dangerous thing 🙁
john curl said:
Hi John,
In a sense I understand your postion but there is an obvious dichotomy with your circumstances that you impose on yourself.
Aside from the dichotomy ( I am sure you are smart enough to figure that out for yourself) your knowledge or interlectal property is a collective or accumulation of experience over the long term.
It is unlikely that any of the diy people who come to this forum could mimic that on a practical level let alone the theory.
One way of side stepping all of this and keep everyone on side this is to put forward a scaled down or simplified version of an amp or preamp for the diyers to tackle.
The concepts could evolve in stages ie power supply etc where where the discussion as a whole results in incremental outcomes and in the end a complete project. That way bystanders can observe and those more adventurous and be actively involved with their own project.
This can only help popular opinion. Otherwise what is the point of even being present on anactive discusison level?
We already know how smart you are. You dont have to prove that to anyone.
I think the real value to the Naim products in this context was missed. Its not so much the circuitry but the sensitivity and quality of the execution of the details. Despite the simplicity of the circuits the Naim products are very highly regarded. There have been times I thought the external components like connectors, controls etc. would have much more influence than the core circuitry. The high value some find the the "Gainclone" with its compromised performance (the transistors are all fabbed with a power transistor process) ceretaionly suggests that the passives could be most important.
John has been pointing in this direction, to look at the details, from the beginning of this thread. There isn't one perfect path, there are many ways to get the desired results. And each of us value different aspects more so we will make different choices when balancing the constraints. I don't focus as much on ultra low distortion or higher harmonics and put more effort into some other aspects, ones that ultra low distortion might compromise. other designers make different decisions witin the constraints of what they have to work with.
If all anyone wants from this thread is the secret to copying a John Curl design there are easier ways to get there. And you will learn nothing from it. However to learn more about how to solve difficult problems, or understand that feedback can absolutely increase distortion in certain cases is very illuminating. I may not agree with John on some of his views but I'm very interested in learning from his experiences.
I collect old test equipment to learn how others solved difficult problems even though I don't build anything like them. and no one would make similar products that way today. If I could afford to buy a naim amp to study it I might. The FM Acoustics amps are not very sophisticated in their circuitry either but the execution and the tricks in the design and construction could also tell us a lot. And I would not want to copy either since I have my way of doing the same. but i might learn a better way to manage connectors or reduce power supply coupling.
John has been pointing in this direction, to look at the details, from the beginning of this thread. There isn't one perfect path, there are many ways to get the desired results. And each of us value different aspects more so we will make different choices when balancing the constraints. I don't focus as much on ultra low distortion or higher harmonics and put more effort into some other aspects, ones that ultra low distortion might compromise. other designers make different decisions witin the constraints of what they have to work with.
If all anyone wants from this thread is the secret to copying a John Curl design there are easier ways to get there. And you will learn nothing from it. However to learn more about how to solve difficult problems, or understand that feedback can absolutely increase distortion in certain cases is very illuminating. I may not agree with John on some of his views but I'm very interested in learning from his experiences.
I collect old test equipment to learn how others solved difficult problems even though I don't build anything like them. and no one would make similar products that way today. If I could afford to buy a naim amp to study it I might. The FM Acoustics amps are not very sophisticated in their circuitry either but the execution and the tricks in the design and construction could also tell us a lot. And I would not want to copy either since I have my way of doing the same. but i might learn a better way to manage connectors or reduce power supply coupling.
macka said:
Yeh John put your money where your mouth is !! After all this is a DIY forum and most DIY's don't necessarily have an engineering degree or even understand a small signal model or base width modulation in a bipolar transistor. They just want to see a schematic and possibly a proper board layout ready to go 😉 Are you up to the challenge 😉
So what?
There are literally thousands of threads here that supply these things.
There are maybe 2 dozen which have mostly professional engineers arguing things out. Given the number of views this thread has had, it's obviously fulfilling a need.
There's lots of room for everyone at this site.
I don't see why John should do what you want. If you don't like his attitude, read somewhere else.
I'm not an engineer and I don't intend to design any circuits in the near future but I've read this thread from the beginning and found it extremely helpful in extending my understanding: When the time comes to replace my electronics I'll have a pretty good idea what to look for in quality of design.
There are literally thousands of threads here that supply these things.
There are maybe 2 dozen which have mostly professional engineers arguing things out. Given the number of views this thread has had, it's obviously fulfilling a need.
There's lots of room for everyone at this site.
I don't see why John should do what you want. If you don't like his attitude, read somewhere else.
I'm not an engineer and I don't intend to design any circuits in the near future but I've read this thread from the beginning and found it extremely helpful in extending my understanding: When the time comes to replace my electronics I'll have a pretty good idea what to look for in quality of design.
FrankWW said:
No I think macka has a good point that I never thought about 😉
Anyone can come onto this forum to suggest the best way to make part of a circuit. That's OK but part of the circuit doesn't make the end product and John keeps boasting about how good all of his end products are and about his vast knowledge base and experience. With this wealth of knowledge he could easily offer another variation of a design which doesn't conflict with his existing designs albeit maybe in a simplified cut down version. Then let some of the keen diyers build it up and report back to us how good it really is 😉
That's not asking a lot from someone who has a vast wealth of experience and knowledge in electronics and audio designs 😉 Even if he just sketches it out on the back of a cornflakes packet some of the keen diyers could throw something together 😉
snoopy said:
Its one thing to create a neat schematic that might according to sims be the blameless amp. In practise its quite a challenge to realise the design.
I mean I found out the hardway in my down under project that things like using high quality ofc low capacitance wiring to the gates and short sinal paths made a light and day difference.
There are also other subtle adjustments that can only be appreciated with a working amp and some auditions.
People expect because they have a schematic its all down hill.
This is where most diy efforts fall over unless its a kit and on that score I think John is fairly safe.
At the other end we have supidity. I knew I guy in a local audio cub who decided to up the bias of a Parsound 3 channel amp. The outcome was he welded his screw driver and blew up the amp!
Personally, I think that it is rather impractical to make a comparable Parasound amp from basic parts. It is easier and cheaper just to buy a used unit and modify it. The Parasound schematics are so complex, because of the housekeeping circuitry, that it is almost impossible to make them on an individual basis.
The basic design is just a JC-3 on 'steroids', you know, cascodes, mosfet drivers, super safe area output parts. Still, it is essentially the same thing from a topology point of view.
IF you can't do anything with that simple explanation, please don't expect me to make something 'simple to understand and copy'. I just don't teach elementary circuit design, and others can certainly do it better than me. This reminds me of having to teach Mark Levinson fine points of circuit design. I finally told him to either please take a course in elementary electronics, or hire a resident engineer, who could take the time to explain it to him. He chose the later course of action.
The basic design is just a JC-3 on 'steroids', you know, cascodes, mosfet drivers, super safe area output parts. Still, it is essentially the same thing from a topology point of view.
IF you can't do anything with that simple explanation, please don't expect me to make something 'simple to understand and copy'. I just don't teach elementary circuit design, and others can certainly do it better than me. This reminds me of having to teach Mark Levinson fine points of circuit design. I finally told him to either please take a course in elementary electronics, or hire a resident engineer, who could take the time to explain it to him. He chose the later course of action.
john curl said:
🙂
On the other hand, at least ML did choose one of the two alternatives. I am afraid thar far too many wouldn't have done that either. I hope he didn't let the new engineer take over your job too.
john curl said:
John,
I think you missed the point.
Perhaps you should focus on making simpler circuits sound better.
From an elementary and factual perspective and really great amp need not be complex if only for the designer to claim only he could design it as such. Indeed many would argue a complex circuit is more difficult to make sound good.
On that score I wittnessed a comparison of another power amplifer of relative complexity to one of your Parasound amps.
The Parasound owner agreed the Phase Linear was a superior amplifier in a blind test.
john curl said:
Hang on !!
First you say they are too complex for a diyer to build but then on the other hand you recommend for someone to purchase a second hand unit in order to modify it, without access to a schematic diagram (that you won't provide) for an otherwise overly complex design 😱 This sounds like a paradox !!!
snoopy:
why should john provide schematics for parasound products to you? did you try contacting parasound directly?
mlloyd1
why should john provide schematics for parasound products to you? did you try contacting parasound directly?
mlloyd1
snoopy said:
OT posts removed.snoopy:
Bashing everyone in sight doesn't do any good to this forum.
Regarding the Parasound amp, if you look around, you can find a schematic; I did. Plus, John has posted elsewhere that the best thing to do to this amp is to increase the power supply capacitance, and that requires no schematic at all.
John:
You're suprisingly smooth these days. Getting soft? 🙂
Zung
Bashing everyone in sight doesn't do any good to this forum.
Regarding the Parasound amp, if you look around, you can find a schematic; I did. Plus, John has posted elsewhere that the best thing to do to this amp is to increase the power supply capacitance, and that requires no schematic at all.
John:
You're suprisingly smooth these days. Getting soft? 🙂
Zung
Zung said:
Jees I thought I was just trying to engage in some intelligent debate. And no, in case you hadn't noticed I am not bashing everyone on this forum 😉
When people make claims they should back it up with solid evidence otherwise it is just their own opinion and they should state it as such.
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