John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
Second, Bob Crump found that transformer leakage could be important sonically. Why, I cannot easily explain, but Bob found that the 'housekeeping' transformer to be leaking AC voltage on the chassis and that reversing its windings, helped.

I am finishing a book review and this is one point I cover in detail. The explanation is simple. You want the AC line neutral wire connected to the windings closest to the transformer core. Otherwise you will actually induce a small AC current into your chassis! Happens on all transformers! How much leakage current depends on the transformer design and quality.

Interconnect two pieces of gear and you will have a small current flow between them.
 
In Germany it is virtually imposible to sell expensive High End equipment when the AC line is not marked for phase. A lot of equipment has now an indicator bulb or a display message for this. A fried in Vienna ( Mace Audio ) was able to measure an increase in distortion in his poweramp when the AC line was connected the " other way around ".
In a country like Norway this seems to be less of a problem beause the AC line is symmetrical. Still my audiophile friends there listen what way around it sounds best. As i already reported some time ago, audiophiles in Japan are absolutely fanatic about "direction" and i really had to guaranty my importer back in the 90th that the coils in my speakers are wound " from the inside to the outside, the right way around". I can not remember if the "good" winding direction was left or right and i do not claim that i can measure or hear that but i second Johns experience 100% that to be successfull in "the real world" ouside the lab measures like that have to be taken to satisfy demanding customers. If they are a victim of their own imagination i can not tell and that is not my duty.
 
At least Clarity Caps in England invested to make a cap that is mechanically strong based on what they found. It is the MR range and everybody can try them if they make any difference or not. I do not use them because i work traditionally with German suppliers for my German Products and Allen Perkins in Berkeley who produces speakers that i designed for the American and international marked uses American suppliers if that makes sense to you. Still i was surprised that the american supplier uses " foils from Germany, they are the best", so people that actually make "audiophile" parts ( at least this particular supplier ) care about the ingredience and physical behavior of the raw materials they buy.
 
Administrator
Joined 2004
Paid Member
From the cap test.
"...driving with a sine wave, like an audio signal, will produce a mechanical force at twice the driving frequency; an example of this ‘frequency doubling’ effect is shown below. This raises the issue of the capacitor being a possible source of intermodulation distortion products at double the frequency of any audio signals present."

Funny, I thought that was called 2nd harmonic distortion. Also seen in single rail power supplies. Is this something else?
.
 
Joachim, IF some caps resonate more than others, that is what is. This was also tested by 'Hi Fi News' back in 1985. They found some caps very resonant. Others, less so. I have never personally measured caps for mechanical resonance, but I know the difference between caps. Some caps actually 'tinkle' when struck. Could this be good? I don't think so. The caps that I use are more dead sounding, when you bang them together.
 
I do it as you i think. For example Brain Daley in the States listenes to passive components and decides which ones go into the product. He is much more sensitive to component changes then i am and i trust him that he has the sensibility to decide what is demanded.
In a certain way he is much more of an audiophile then me. That way i can wash my hands in clear water and can focus innocently on the engineering i hope. Still customers ask me what components i like as if a was a kind of guru. It´s weired out in the real world there.
 
Joachim, I realize that it is difficult to be an 'engineer' and believe in component differences. However, there are differences in components, some even more subtle than Clarity has put forth.
Most engineers here must make some pretty mundane products. At least, products that are immune to most component differences. There is nothing wrong with this, but it is usually not successful for quality audio design. You should know this by now. Look at the phono cartridges that you represent. Are THEY phony? Would a Shure really give the same quality reproduction? If not, why not? Prove it, especially with a double blind test. Can you see the problem when you are connected with the products you represent? Many engineers here do NOT design audio products on a continuous basis, like you and I do. Most engineers do not know other audio designers and their challenges, like you and I do. Is Allen Perkins a fraud? I don't think so, but his cartridges are awfully expensive, to the point where I can't get the one I want. Am I imagining things to think that my $1000 phono cartridge purchased from Allen, could be really be replaced with a better sounding, but 2 or 3 times more expensive unit? What about the $5,000 phono cartridges? Are they really better, or just prettier? Think it through Joachim. Please remember I am on your side, not against you. '-)
 
Last edited:
Thanks, i apreciate that very much. With my current salary i could not afford a Titan i too but i have the privilege that Mishima builds it for me. What many people may not know is that such a cartridge does not reflect the cost of the actual components that go into it. Actually the cost comes partly from the assembly that very few can do with the precission that Mishima does. He really builds the more expensive models totally alone from the ground up. He has trained over the last years a young and very talented lady. She even models and is an actress be he does not even trust her, only on subassemblies of the smalest model, the Delos and even that he tunes by hand and ear using a choir record and a special Stax headphone with extremely thin diafragms. I can really not explain what is going on there in detail but it is like a miracle to me. It is a piece of art and from that point of few the price is relative. He can make only just so much that way and Allen is in constant shortage of supply. The other problem is the cost of marketing. Stig travels the globe tyredless with risk of personal health and show atendence and aftersales service eats up a lot of quality time. I saw Sterling talking for 3 hours to a guy, explaining him how to setup and get the best out of the product. I do not want to give the impression that we do not make money with what we do but we work hard. It´s about the quality of the experinece and not the hard quantity of numbers, i know.
 
Of course, Joachim, and I could not afford a CTC Blowtorch, if I didn't design the electronics.
We had to put time and trouble into each Blowtorch. Everything had to be selected, matched and individually cleaned before assembly. It took hours, and hours. Assembly in Taiwan, even with the JC-1, or JC-2 is much less complicated, and that is part of the compromise that I have to make to make 'cost effective products.
However, if you want to make 'miracles' it takes what it takes. Our initial costs were much more, maybe $5,000-$6,000, just for the raw parts, for the CTC Blowtorch.
 
Last edited:
No direct measurements show the difference.

Aah, they do. But these measurements and their graphical output would be very unacceptable from the marketing purposes point of view.

Several hints:
- you can measure ANY change you make to a power supply, rectifiers and filters. Just do note use voltage divider behind power amplifier output terminals, but measure FFT directly with high sensitivity, like 0dB = 1Vrms. You will get measurements that are not nice at all, but revealing. They will show plenty of mains frequency-related spectral linest, at multiples of 60Hz, spread above several kHz. Any change in transformer construction, rectifying diodes, filter caps will be visible. But these measurements are not shown by J.A. in Stereophile, for the reason that no manufacturer would be happy to see them.

- try some 'high end' signal cables (of obscure construction usually) and measure EMI induced interference HF voltage and reflections. Again, results would not be nice, and most of cables valued for 'detail' and 'rich sound' would reveal as nonsense construction result and peculiar taste of individual listener.

---

My question - were the PCBs of HCA-3500 and JC-1 the same, absolutely same? If not, I would start right here to explain differences in sound.
 
Last edited:
AX tech editor
Joined 2002
Paid Member
As far as i know the University of Salford did an AES paper about their findings but it did off cause not make it into the Journal.

I attended the presentation of that paper. As I remember it, the conclusion was that the mechanical movements of the capacitor, at the outside, were less than a molecule diameter, worst case. The audience was VERY critical that that would be audible.
The presenters promised to do controlled listening tests but I haven't heard about it.

jan didden
 
If you care about capacitor resonances, then the most important parameter is winding tension. Get that thing like a brick and it won't rattle. What this implies is that you DON'T want limited production "audiophile" caps, you DON'T want Teflon. You want biaxially oriented polypropylene film and high speed machinery. With cost no object, you'd use COC for the film- better tensile, better flexural, dielectric properties comparable to Teflon, relatively low cost material and easy to process (much easier to extrude than Teflon, comparable to PP).

Anyone can check cap resonances for themselves with a battery, a resistor, an oscilloscope, and a pencil. The least resonant caps I've seen were cheap Wima FKP.

The Clarity "white paper" is an exercise in puffery and trying to look technical while offering no substantive content. I pity the poor student who got dragged into that!
 
I attended the presentation of that paper. As I remember it, the conclusion was that the mechanical movements of the capacitor, at the outside, were less than a molecule diameter, worst case. The audience was VERY critical that that would be audible.
The presenters promised to do controlled listening tests but I haven't heard about it.

jan didden

Don't hold your breath. There is no mystery here and it's easy to put numbers on this. Easy demo, take an unpolarized microphone capsule and put a 20 or 30V sine wave on it and out comes the second harmonic. Electrostatics 101. I suspect 10's or 100's of volts would be needed to measure anything
 
Status
Not open for further replies.