I have heard the Blowtorch in several systems including mine. Bob Crump visited and was kind enough to bring his personal preamp. I am sure John has made it clear that this product is the combined effort of three talented people. John does the design and board assembly. Carl Thompson did the design of the boards. He is a retired designer of state of the art video production equipment. Layout is so critical with that type equipment. And, the late Bob Crump was responsible for the voicing and final assembly of the preamp. Bob was one of those unique people who carefully evaluated every component for sonic character. Every switch, wire, connector, resistor, cap, etc. is specifically selected for their application. I mention all this to point out that the circuit design is just a part of this amazing product.
This thing throws the most holographic image I have experienced. The noise floor is nil and every performer is so clearly defined in that space. Let me give you a example of it's ability. I was sitting in the sweet spot while Bob sat at least 45 degrees off axis close to the left channel speaker. He asked me to switch places with him and check out the image. I did and to my total amazement, the image was stayed steady and everything was still in the same place in the soundscape. Simply amazing IMO. Now if I could just afford one
This thing throws the most holographic image I have experienced. The noise floor is nil and every performer is so clearly defined in that space. Let me give you a example of it's ability. I was sitting in the sweet spot while Bob sat at least 45 degrees off axis close to the left channel speaker. He asked me to switch places with him and check out the image. I did and to my total amazement, the image was stayed steady and everything was still in the same place in the soundscape. Simply amazing IMO. Now if I could just afford one
Imaging
If the imaging works off axis as well as it does in the sweet spot, the speakers also are very special. My speakers are not so forgiving.
This artifact of playback indicates that the phase is fairly flat across the midband. Plus no frequency related delays.
This is an area where the lack of feedback is beneficial. Feeback usually screws with the phase response. This may be why some prefer no feedback for small accoutic music and feedback for large orchestra. The multi-miked recordings really are all over the place when it comes to preserving an event.
George
If the imaging works off axis as well as it does in the sweet spot, the speakers also are very special. My speakers are not so forgiving.
This artifact of playback indicates that the phase is fairly flat across the midband. Plus no frequency related delays.
This is an area where the lack of feedback is beneficial. Feeback usually screws with the phase response. This may be why some prefer no feedback for small accoutic music and feedback for large orchestra. The multi-miked recordings really are all over the place when it comes to preserving an event.
George
Re: Imaging
This is a total nonsense, demonstrating how the "marketing science" washes brains of the poor DIYers.
Phase reponse is unambiguously related to amplitude response. Wide amplitude response means minimal phase shift in the midband. For the system with bandwidth 2Hz - 300kHz (which is quite normal) there will be no interesting phase shift in audio band.
Panelhead said:
This is a total nonsense, demonstrating how the "marketing science" washes brains of the poor DIYers.
Phase reponse is unambiguously related to amplitude response. Wide amplitude response means minimal phase shift in the midband. For the system with bandwidth 2Hz - 300kHz (which is quite normal) there will be no interesting phase shift in audio band.
Badge...
I would suspect that what you experienced was a combination of the dispersion characteristics of the speaker combined with the exceedingly low noise floor of the preamp (and amp?). The low noise certainly contributes to the illusion of image specificity. For what it's worth, I have noticed the same phenomenon with the Blowtorch, Parasound JC1s, and Sound Lab A-1s.
I would suspect that what you experienced was a combination of the dispersion characteristics of the speaker combined with the exceedingly low noise floor of the preamp (and amp?). The low noise certainly contributes to the illusion of image specificity. For what it's worth, I have noticed the same phenomenon with the Blowtorch, Parasound JC1s, and Sound Lab A-1s.
I have been told before that the CTC preamp 'images' better than most preamps. Bob Crump was very sensitive about imaging. I suspect that is was the open-loop circuit, serious separation of components for low x-talk, and Bob's choice in passive components that makes this so.
I know what doesn't work however. Asymmetrical x-talk, and secondly, any significant amount of symmetrical x-talk. Many preamps have a combination of these problems.
I know what doesn't work however. Asymmetrical x-talk, and secondly, any significant amount of symmetrical x-talk. Many preamps have a combination of these problems.
Epopa,
I read your somewhat negative posts, and find myself wondering what you do know, Pavel. You disagree with everyone, yet have nothing constructive to add..... Could it be that you know it all, but are too worried about IP to tell us?
Your friend, PMA, has been a large contributor here, and helpful to others with questions. Perhaps you should follow his example?
Cheers,
Hugh
I read your somewhat negative posts, and find myself wondering what you do know, Pavel. You disagree with everyone, yet have nothing constructive to add..... Could it be that you know it all, but are too worried about IP to tell us?
Your friend, PMA, has been a large contributor here, and helpful to others with questions. Perhaps you should follow his example?
Cheers,
Hugh
Negative posts... truth is little bit different, Hugh.... I like it all very much... I doing it all my life... I was living in country, where was problem to get quite usual PNP transistor...JC was at this times my God... I was learn from him really very much... but now I see, that these giants ( JC, NP and others ) need little feedback from lustily thinking ones...healthful opposition, you know.... 
Epops,
I'm not sure I agree, but OK, let's take it on face value and assume you really do know what you are talking about.
Rather than 'lustily oppose' these old greats (and you must be fifty yourself, surely??), how about some equal ranking ideas?
For example, what are your thoughts on MC head amps? How do you increase PSRR on a simple SE JFET input stage? Do you use feedback? Cascoding? What about EQ on MM designs? What are your thoughts on Le Pacific, Monsieur Walther's design from Maison D'Audiophile? Active, or passive, tube or SS? And so on......
In closing, I appreciate that you post in a foreign language. It is good to have so many Europeans on this forum.
Cheers,
Hugh
I'm not sure I agree, but OK, let's take it on face value and assume you really do know what you are talking about.
Rather than 'lustily oppose' these old greats (and you must be fifty yourself, surely??), how about some equal ranking ideas?
For example, what are your thoughts on MC head amps? How do you increase PSRR on a simple SE JFET input stage? Do you use feedback? Cascoding? What about EQ on MM designs? What are your thoughts on Le Pacific, Monsieur Walther's design from Maison D'Audiophile? Active, or passive, tube or SS? And so on......
In closing, I appreciate that you post in a foreign language. It is good to have so many Europeans on this forum.
Cheers,
Hugh
Hugh,
People who think they know it all are impervious to reality. Their egos won't allow them to admit to things that don't fit with their preconceived notions.
And yet they dare accuse others of disregarding facts...
It's just arrogance masquerading as knowledge. They--and only they--are the bearers of Truth. That's not science, it's religion. They skipped class the day the teacher taught that science is supposed to check theories against the real world.
John,
Your comment several posts back about non-linear capacitance is interesting. Presumably, an open loop circuit with wide bandwidth either has little capacitance to begin with or the native capacitance has been scotched by various topologies, board construction, etc. The wide bandwidth and good imaging aren't necessarily causal to one another, they both just sort of naturally fall out of the circuit if you can tame the capacitance. The problem with testing this is that to change the capacitance (presumed non-linear, derived from the devices themselves), you have to change the devices or the topology or both. At that point, you're going to have a circuit that sounds different, regardless. Heisenberg could have been speaking of electronics instead of particle physics.
Unfortunately, I live in a very poor corner of the country. The chances of me ever hearing this circuit are slim to none. However, I have a kid entering Berkley this year for graduate work in chemistry and biochemistry. Any given county in California represents more money than my entire state. Perhaps I'll visit her and try to hunt down one of these things while I'm over there.
I don't have my schematic program with me, so I'll try describing something verbally, knowing full well that the odds are against me:
Assume something similar to the single-ended JC-2 line stage--a differential followed by an output stage that is both folded cascode (Source driven from one half of the differential) and common Source (Gate driven from the other half of the differential). Is it practical to use two resistors in series as the load for each side of the differential and make a balanced circuit that way (each output phase hooks to both sides of the differential, for a total of four connections to the front end differential loads) or does the Ciss of one output foul up the other output's Source?
If my description is too opaque, I'll draw it up when I get home.
Grey
P.S.: What do you call that topology? It's more than just a folded cascode, surely.
People who think they know it all are impervious to reality. Their egos won't allow them to admit to things that don't fit with their preconceived notions.
And yet they dare accuse others of disregarding facts...
It's just arrogance masquerading as knowledge. They--and only they--are the bearers of Truth. That's not science, it's religion. They skipped class the day the teacher taught that science is supposed to check theories against the real world.
John,
Your comment several posts back about non-linear capacitance is interesting. Presumably, an open loop circuit with wide bandwidth either has little capacitance to begin with or the native capacitance has been scotched by various topologies, board construction, etc. The wide bandwidth and good imaging aren't necessarily causal to one another, they both just sort of naturally fall out of the circuit if you can tame the capacitance. The problem with testing this is that to change the capacitance (presumed non-linear, derived from the devices themselves), you have to change the devices or the topology or both. At that point, you're going to have a circuit that sounds different, regardless. Heisenberg could have been speaking of electronics instead of particle physics.
Unfortunately, I live in a very poor corner of the country. The chances of me ever hearing this circuit are slim to none. However, I have a kid entering Berkley this year for graduate work in chemistry and biochemistry. Any given county in California represents more money than my entire state. Perhaps I'll visit her and try to hunt down one of these things while I'm over there.
I don't have my schematic program with me, so I'll try describing something verbally, knowing full well that the odds are against me:
Assume something similar to the single-ended JC-2 line stage--a differential followed by an output stage that is both folded cascode (Source driven from one half of the differential) and common Source (Gate driven from the other half of the differential). Is it practical to use two resistors in series as the load for each side of the differential and make a balanced circuit that way (each output phase hooks to both sides of the differential, for a total of four connections to the front end differential loads) or does the Ciss of one output foul up the other output's Source?
If my description is too opaque, I'll draw it up when I get home.
Grey
P.S.: What do you call that topology? It's more than just a folded cascode, surely.
AKSA said:
Hugh,
as you know, we both are over fifty with Upupa Epops. He is a great designer with plenty of experience and results during his professional career. His unlucky fortune was to be born behind iron curtain. Nobody can make a choice of his place of birth. Upupa is very straightforward and protects thoroughly his point of view. He has a right to do that based on his excellent results.
We may have different circuit design attitude compared to JC or CH.H. e.g., and it is based on different results with different topologies than they were using. We sometimes feel that the DIY community is pushed to some sort of "subjective truth", that we do not find universal, so we dare to oppose. I do not think this would be a problem and a lot of e-mails I receive from people with different tastes than non-feedback e.g. convince me that I am probably not wrong. Most of those people do not have courage enough to oppose the Big Guys here. And do not forget that the Big Guys have basic advantage in using of their native language.
All the best,
Pavel
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