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Old 6th September 2012, 04:22 PM   #27341
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Quote:
Originally Posted by bcarso View Post
For one high-end design (phono pre) with tubes (and some solid-state assistance)
Mr Wood,

as I can't quite fit it into your résumé, that was a product you intended as a private endeavour ?
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Old 6th September 2012, 04:29 PM   #27342
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Originally Posted by jacco vermeulen View Post
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.
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Old 6th September 2012, 05:21 PM   #27343
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All kidding aside, it is going to be a monumental effort to even make an acceptable working version of one of these designs. Save your strength for sourcing the active parts.
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Old 6th September 2012, 05:23 PM   #27344
bcarso is offline bcarso  United States
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Originally Posted by jacco vermeulen View Post
Mr Wood,

as I can't quite fit it into your résumé, that was a product you intended as a private endeavour ?
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.
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Old 6th September 2012, 06:03 PM   #27345
RNMarsh is offline RNMarsh  United States
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Just has to be silver solder right?
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

Last edited by RNMarsh; 6th September 2012 at 06:10 PM.
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Old 6th September 2012, 06:14 PM   #27346
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All kidding aside, it is going to be a monumental effort to even make an acceptable working version of one of these designs. Save your strength for sourcing the active parts.

What can I do to start getting parts together...any ideas?

Walmart is open 24/7...
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Old 6th September 2012, 06:30 PM   #27347
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Originally Posted by SY View Post

And that's why, if all you care about is what your ears hear, it's easy for anyone to design a preamp which will be indistinguishable from one of John's excellent designs, but at a minuscule fraction of the cost and none of the complexity. There's no mystery to making an electrical signal bigger, it's done all the time in far more critical apps than hifi.
Do you have an actual example of such preamp(s)?
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Old 6th September 2012, 06:39 PM   #27348
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Originally Posted by RNMarsh View Post
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
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

Last edited by jneutron; 6th September 2012 at 06:45 PM.
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Old 6th September 2012, 07:07 PM   #27349
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Originally Posted by SY View Post
There's no mystery to making an electrical signal bigger, it's done all the time in far more critical apps than hifi.
Contamination matters. Mystery is how to suppress all kinds of contamination, or how to get immune.

Just "bigger" is an academic, pedantic approach, indicating lack of experience in real circuit design and evaluation.
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Last edited by PMA; 6th September 2012 at 07:11 PM.
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Old 6th September 2012, 07:08 PM   #27350
RNMarsh is offline RNMarsh  United States
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Originally Posted by jneutron View Post
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
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

Last edited by RNMarsh; 6th September 2012 at 07:18 PM.
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