John Curl's Blowtorch preamplifier part II

Status
Not open for further replies.
View attachment 481457
Esperado thinks that a PCB designer is a lower form of life, gifted with unearned skills, but easily managed with a bit of ersatz brown-nosing, due to his inferior intelligence.
If it's humor, it is a form of humor that has to laugh hyenas.
Otherwise, it looks like a personal attack against both AlexMM, who chose these credits himself, and against me.
Very graceful as this project is a gift to the community, an innovative idea and a long time consuming work from both of us..
This is false, unjustified, stupidly aggressive. And it is the second time i had to suffer the same kind of personal attack from you.
I Understand, now, what means "counter culture". Buy-you a brain and an education. In that order.
 
Last edited:
Counter Culture,
Where did you just come up with that drivel about what Christophe thinks about a circuit designer, if anything I think he was complementing the skills of the guy who helped him do the board layout?

Christophe,
You ask why so many speaker enclosures do not have impedance compensation to go with the speakers that are used in those enclosures. The real bottom line is that the majority of the speakers we see in the audiophile world are designed by people who;s basic skill is in making a fancy box and stuffing them with commodity speakers they buy from another company and just stuff in their pretty boxes. I highly doubt that more than a very small % have ever assembled a speaker or understand the basic functions of the individual parts of those speakers. They are truly just box stuffers and this is why the market is so full of mediocre speakers that have so many similar sound problems, Another problem is the simplistic thinking that goes into many xo designs, they are just classic by the numbers networks that just aren't very well thought out. Now I will say that this is not always the case and there are some really smart guys that do understand what they are doing but this does not seem to be the case with many audiophile speaker companies.


Marce,
One question about that article you put up about the PIM. When in the first few lines they are talking about the length and width of the trace, can I assume that the width is actually the width looking down on the trace or are they talking about the thickness of the trace, that is not made clear there? How does the trace thickness come into this or is it only the actual width that is the critical factor here and the spacing of those traces? I'm sure you could teach us a lot about board layout from your advanced knowledge of the subject.
 
As to PC card distortion this is the result of the same circuit with two different layouts. Note the nomenclature of "Fixed." I can't find the original but the unfixed counted on a through plated hole on the ground point and the performance was much worse. The repair was to fill the hole with solder.

I did show these before in this thread.

I also seem to have lost my test results on the distortion caused by different types of solder. I made up PC cards with 200 or so joints interconnected by the lead clippings from Holco resistors. I used both 63/37 60/40 and a sampling of lead free solders. Using my most sensitive distortion testing apparatus I was quite surprised to find with the all of the solder joints none were bad!

The lead free solders took a bit more heat and did not flow as well, nor were they as shiny. However even going through hundreds of joints there was no significant difference in distortion.

My PC tests clearly showed that if you resolder all of the connections on a PC card you most likely will see improvement as soon as you fill in the through plated holes.

ES
 

Attachments

  • Fixed PC THD jpeg.JPG
    Fixed PC THD jpeg.JPG
    317.2 KB · Views: 139
Disabled Account
Joined 2012
Richard did not tell it this way, Stuart.

That is correct. SY is a spin-master full of assumptions and distortions. Like being paid and on My web site. I do not have a web site and I never have been paid for anything related to Walts writings. And, I just said what I think about passive parts as far as hearing them is concerned. I may know about the gory details and made measurements but I havent been the one saying I hear all this. Others have. End of story.


THx-Richard Marsh
 
Last edited:
I was surprised when I looked up the formulations. They could be made much, much better than they are.

I always supposed it was some kind of silicon oil with a vanishingly low vapor pressure, but really don't know. I'd like to learn more if you can volunteer some information.

Esperado, indeed, better stay away from ferro-fluid filled tweeters for quality speakers. It is not just that the stuff turns into muck over time. In good tweeters, that is, those with a shortening ring over the pole piece, the magnetic flux in the air gap is pretty constant. Ferro-fluid sloshes around in the air gap, and as such introduces non-linearities in the magnetic field. Furthermore, it considerably decreases Qms, symptomatic of the friction ferro-fluid creates. Bad for efficiency and linearity.

Shitty tweeters get better from ferro-fluid though.
 
vacuphile,
It seems the only redeeming quality of ferro-fluids has been in the increased heat transfer it allows in Pro-audio applications where the speakers are running on the edge of melt-down of a voicecoil under less than ideal conditions. I have been pushed to use it by others many times and the more I looked into it the more I decided it was a bad idea, at least with the current chemistry and the problems that were at first denied by the Ferro Fluidics company. They do now if you look carefully admit that the viscosity of the oil they use is changing over time. Voice-coil wire coatings have improved over time and so have the former materials so unless it is a critical application where a speaker is running close to melt down on the voicecoil assembly, which is bad design to begin with, I don't hear much of the hype about using this stuff anymore.

ps. Many companies used ferro fluids as it made the assembly tolerances looser so the fluid made up for sloppy assembly. Voice-coil rub and buzz were much less a problem on these poorly assembled speakers.
 
Last edited:
Disabled Account
Joined 2012
Kavi Alexander just had a birthday and that reminded me of a story I had which involved him and his listening ability or sensitivity:

He sent me some recorder modules to evaluate and try to fix one that had an unwanted low level sound in it. I I measured the wide band noise level on the module output and it was really low. I told him it was OK. No, he said listen with headphones. So, I listened with headphones on. I could not hear any noise. I called him and told him there was no problem i could hear. he described the character of this mystery unwanted sound.... I still could not hear anything. he said listen deeper. And deeper still. keep listening deeper. I tried and tried. In searching the deepest sound I could muster.... there it was.... a steady low freq buzz... 120Hz. It was really low level. No one would ever hear it in normal use with music playing. But he heard it and I didnt until he steered me and directed by words right to it. Kavi isnt technical or could have told me the freq to listen to etc. Once I detected it far far Far down in level i heard it easy then and could hear it each time i listened.

This is what high-End audio is like IMO. Many things people say are so obvious to them really isnt obvious to most people.


THx-RNMarsh
 
Last edited:
diyAudio Member RIP
Joined 2005
vacuphile,
It seems the only redeeming quality of ferro-fluids has been in the increased heat transfer it allows in Pro-audio applications where the speakers are running on the edge of melt-down of a voicecoil under less than ideal conditions. I have been pushed to use it by others many times and the more I looked into it the more I decided it was a bad idea, at least with the current chemistry and the problems that were at first denied by the Ferro Fluidics company. They do now if you look carefully admit that the viscosity of the oil they use is changing over time. Voicecoil wire coatings have improved over time and so have the former materials so unless it is a critical application where a speaker is running close to melt down on the voicecoil assembly, which is bad design to begin with, I don't hear much of the hype about using this stuff anymore.
When Harman used it in teeny transducers it was all about cooling. Otherwise it was a nuisance.
 
Disabled Account
Joined 2012
the story about Kavi is telling about hearing in that the oft quoted aging of our ears is not as important to our understanding of audio as the knowledge we bring to our hearing.

High frequency loss, which we undergo, is not the be all factor of "hearing quality". The ability to hear changes and differences is what we have learned over the years. It is not innate, but learned. The discerning ear is an educated one. Young or old.

Alan
 
Member
Joined 2014
Paid Member
Christophe,
You ask why so many speaker enclosures do not have impedance compensation to go with the speakers that are used in those enclosures. <snip>

I will pin my flag to the post that says a speaker designer should try and flatten out impedance, but I remember last year when there was a thread on this a number of amplifier designers were adamant that their creations could drive anything down to rusty nails and so no such cosseting was required.

Vive la difference.
 
diyAudio Member RIP
Joined 2005
I will pin my flag to the post that says a speaker designer should try and flatten out impedance, but I remember last year when there was a thread on this a number of amplifier designers were adamant that their creations could drive anything down to rusty nails and so no such cosseting was required.

Vive la difference.
Do I recall that it was a Wilson speaker that hit a minimum of 300mohms?

I also seem to remember that Apogee ribbons drove the development of power amplifiers that could manage to drive them.
 
Status
Not open for further replies.