Mr Wood,
as I can't quite fit it into your résumé, that was a product you intended as a private endeavour ?
Rotterdam eh?
One of my anscestors was the Burgermeister of Rotterdam late in the 16th century...I didn't know him personally though.
Yes, the company was (and I suppose still is) DNA, Donald North Audio. By the way, his gushing description of me that made its way to his website was wholly unauthorized by moi and frankly embarrassing.
Donald is a bright guy with a day job, and a degree from Caltech, where he was influenced deeply by Jim Boyk. From this and later experiences he is suspicious of "sand state" and loves thermionic valves. But he's mostly a speaker designer.
One of his speakers is a quasi-open-baffle design with the need for a large amount of bass boost and consequently a lot of power. People have favorably compared its sound to electrostats. I worked on a mostly-tube equalizer for it, with features like the high perveance triodes loaded with current generators for voltage followers for the highpass, and a bunch of other tubes for the low frequency boost (the loudspeaker requires two power amps per channel). We finished a board for that, and it worked, except that the low frequency excess noise was fierce and there was hum pickup from the toroid leadouts by the rather large loop areas of the Audio Note big paper-oil-copper foil output coupling caps in the vicinity
A little distance would have helped a lot, as well as smaller loop areas.In the interim a solid-state design was designed and built in a couple of days, and this and the speaker made its way to Europe where I suppose it remains. The highpass was a fairly simple cascoded 2SK389 stage with matched current loading, and the power supplies were current source/shunt regulator discrete designs. It worked very well despite the presumption that it would sound bad due to the sand.
That's my story and I'm sticking to it
Oh --- but the phono preamp development came along after that, another whole story.
The silver fired onto the ceramic strip would seperate and lift from the ceramic if conventional (non-silver bearing solder) solder was used..... so they supplied the silver solder alloy to assure no one would use anything else. Or else you would be ordering ceramic strips from them. The crude expaination is-- it came off because the silver would be leached into the lead-tin solder.... adding silver to the lead-tin stopped the leaching off the ceramic strip as the supplied solder was already saturated with silver. -RNM
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Nowadays they'll fire moly/mag into the ceramic, flash that with 50 microinches of nickel, then plate over that. edit: oops, sorry, 50 microinches is not a flash...10 microinches is a flash. (OMG, he's got a knife...You call that a knife?? That's not a knife...this... is a knife...Mick Dundee)
The problem with the "fill the alloy with the metal you don't want to scavenge" is that the alloy will be happy at some percentage at a specific temperature. If you exceed that temperature, the solution will no longer be saturated and more will get sucked in. So that technique requires very good temperature controls.
A good example is the trinary tin/lead/silver. It's eutectic at 179C, but if you raise it to 200 C, it'll dissolve a lot of silver. If you could keep it at 179 C, any additional silver will solidify the melt, keeping the silver percentage at 2%.
jn
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yes, you couldnt go using a solder gun of high Wattage. The silvered ceramic would come off without solder if the temp was too high.
[ TEKtronix expected professionals to be doing the trouble-shooting,repair and calibration work and spec'ed the Wattge /temp of the soldering iron used for their ceramic strips.]
Speaking of ferrous metals and their non-linear Z affects - Nickel - it is also used to plate over copper before gold plating -- pcb traces, for example. If JC was building this opamp - he would use purest copper and gold directly on it - all on specific Teflon base material. Then use best soldering alloy, temp control and flux with no residue. A purist approach. -RNM
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Leaves me out...
Hey, that's him..
No residue flux?? Man, I hate that stuff. Easier to just clean the daylights outta it. Just watch out for poly caps and solvents...
jn
I'm not sure I understand your response. I'm not concerned about test formats. I'm commenting on taking a reference and switching in another with a difference and being able to hear the difference. A simple apples to apples approach. The point was to trust your ears and also that simple differences do exist.
My point about double blind was that in a personal situation, where it is not a "test" and there is no right or wrong, just listening for difference as you switch is the goal. Sorting out what it means comes with extended listening. I do this all on a personal level so the results are for furthering my own enjoyment. If I fool myself I find out when I put on something I'm familiar with and it sounds worse then the last time. Then I know I have to back up or figure out what went wrong.
Regards,
Mike
Hi John,
Wow, I find this an interesting response.
Half perfection acheived and half your a local mechanic thinking a few little tweeks will improve on the basic design. I never mentioned the Blowtorch, and I as a rule hold that everything about any design was done for a reason. My understanding of things goes a bit deeper than it appears on the surface.
Regards,
Mike
I took my daughter 5 or 6 yrs. ago to visit the campus (you think MIT was nerdy) and when I called Jim's number I got a very sad sounding message that his special post was eliminated, just economics?
I don't know all the details, but I would say "politics and economics"
Don still talks to him and has been trying to encourage him to do more recordings, but I gather he's pretty bitter and negative these days. He did make some good LPs (I have a few of them) although (as he agrees) the tape machines and other electronics had a lot of hiss.
In theory based on what I understand on this thread would not mesh socks around the passives allow for a better ground at high frequencies? Given that to be true since the Teflon PCB is not a DIY reality and normal PCB's are inferior then point to point would be the only option as a low parasitic assembly option. Since the components are sockable
when done point to point and this would be a time intensive endeavor any way..... This would not be an improvement given the constraints? or am I just a pain in the booty?- Status
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