john curl said:
An externally hosted image should be here but it was not working when we last tested it.
Um, John, I already know that there are differences in your measurements. I've known this for some four years now. And I've never disputed that there are differences in your measurements nor has anyone else for that matter.
So why are you sending people on wild goose chases to download a file and to overlay images to show something that is already known and has never been disputed?
And why didn't you simply say that the images you were telling people to overlay were the images that I already have and I'd already asked you about?
se
john curl said:
I'll take look at it tomorrow. I probably just have to sign up or something similar. I'm curious. Thanks.
Now that this is settled, perhaps we can go forward at talk about circuit topologies. YBA, I am still waiting. 
john curl said:Now that this is settled, perhaps we can go forward at talk about circuit topologies. YBA, I am still waiting.
Here, here! I'm still looking for a 0-20dB open-loop line amp ideas, preferably with no servos.
Just one more slight OT if I may:
Scott,
I now know where you got your cap divider idea (just kidding) 😉
"HP 11039A Capacitive Voltage Divider "DSA900-76-M-5303" with vacuum capacitor 15 pF / 40 kV
(requires HP 11018A probe adapter )
Specifications:
Division ratio: 1,000:1.
Maximum voltage: 25,000 V AC at low frequencies,
decreasing to 7000 V at 20 MHz.
Frequency range: up to 20 MHz.
Accuracy : within 3 %
Input capacity: 15 ± 1 pF"
Jan Didden
Scott,
I now know where you got your cap divider idea (just kidding) 😉
"HP 11039A Capacitive Voltage Divider "DSA900-76-M-5303" with vacuum capacitor 15 pF / 40 kV
(requires HP 11018A probe adapter )
Specifications:
Division ratio: 1,000:1.
Maximum voltage: 25,000 V AC at low frequencies,
decreasing to 7000 V at 20 MHz.
Frequency range: up to 20 MHz.
Accuracy : within 3 %
Input capacity: 15 ± 1 pF"
Jan Didden
Attachments
janneman said:
Actually it was Walter Kistler (still around I think).
http://en.wikipedia.org/wiki/Walter_Kistler
No servos! NO, we don't want any stinking IC's in our circuitry, and IC's do servos so well.
The cap loading concept is still flawed, check with Dick Sequerra, if you can't believe me or Erling.
The cap loading concept is still flawed, check with Dick Sequerra, if you can't believe me or Erling.
My favorite thing to do with IC's but it is a bit of work, is to shave away as much of the casing on them as possible. Very carefully, of course. Then encapsulate them in something a bit more complimentary to signal propagation and more uniformly temperature stable. Of course, the are still compromises at that point, but with higher voltage loading, there is more of a field effect going on, and thus the internal fields can be a bit more, er, connected and stabilized, besides all of the other potential changes that need be considered with such thinking. A simple experiment, but it involves a bit of work. Trying them with their 'pants pulled down', ie, with less of a casing material -is quite interesting all on it's own. Due to the multitude of transistors in the given IC unit, one could say with a bit of correctness, that this can have the effect of potentially showing (through sheer multiplication of the given effect) how a Transistor casing material can and does affect the signal propagation with in the given transistor, and in the end, is a major factor that is little thought of.. outside of the audio world. This, with regards to say, how we consider capacitor materials, transformer materials and wire sheathing materials and effects.
Forgetting this point is slightly akin to trying to ignore air as a consideration when contemplating breathing. The same thinking on materials effects of the above mentioned devices and considerations...should also be thrown at the transistor casings.
We need to find our best material for casings..and see if we can convince some of the audio parts manufacturers to implement such consideration for series of parts that are more correctly designed for audio use. For example, in my experience, metal (casings) are seriously bad news.
Forgetting this point is slightly akin to trying to ignore air as a consideration when contemplating breathing. The same thinking on materials effects of the above mentioned devices and considerations...should also be thrown at the transistor casings.
We need to find our best material for casings..and see if we can convince some of the audio parts manufacturers to implement such consideration for series of parts that are more correctly designed for audio use. For example, in my experience, metal (casings) are seriously bad news.
john curl said:
I finished a pair this weekend, sounded great and my first recording fooled one of my dogs into thinking his brother was somewhere in the room. At low volume Dick's speakers are great. I was planning on e-mailing Erling, funny our in-house MEMS guys ignored me.
I'm just watching now waiting for some circuits. PMA's doing a good job in his own thread, but I'm having a hard time finding some decent substitutes for those unobtainable FET's.
KBK said:
Fuming nitric acid works well and leaves the circuit functional most of the time. You make a little hose assembly to blow a small stream onto the package (a laminar flow hood is recommended). The grinding is problematic in that you often grind off the loops of the bond wires before much package is removed.
The DA on the encapsulant is the ****s. Once had a sample and hold (remember those) that was limited by the DA on the 2pF parasitic between the bond wires trying to get to an external 100pF polyproplene.
PMA, I am sorry. When I said YBA, it was an accident. He is not on this website, but he is good engineer. Frenchman, makes cables, amps and preamps. Been to his house near Paris about 22 years ago, good dinner, wine, sound system. SY would have been impressed.
But it is you, PMA that I hope to start further contributions of elegant circuit topologies. You are the best candidate here, I suspect.
But it is you, PMA that I hope to start further contributions of elegant circuit topologies. You are the best candidate here, I suspect.
Scott ADMITS that his IC cases are made of SH--! Glory be, we don't have to argue that point anymore! What about ceramic packages? I hear that they sound better
john curl said:
There used to ceramic packages where every surface and all the leads were 2.25mil thick solid gold plated. Last time gold was $900 an ounce they took them all away as scrap and all my junkbox parts too.
scott wurcer said:
That is interesting. I knew the stuff was bad, but I didn't know it was *that* bad...
john curl said:
One problem with ceramic packages is that they all have magnetic lead-out wires. I assume that is a requirement to maintain the hermetic seal.
Furthermore, ceramic capacitors don't sound all that good. Do you really think ceramic packages would be much better?
The closest parallel I can think of was the changeover from the old TO-3 output devices to the more modern TO-247 and TO-264 styles. In the case of the TO-3, there was *no* solid around the die (except for the baseplate itself, of course). But the baseplate was made from steel, as were the two lead pins.
Most people I know that have compared preferred the plastic packages over the steel packages. Any other input from others on this forum?
I heard a rumor that Krell had Motorola build a custom version of a TO-3 package from copper for them. I don't know if this is true or not. And even if it is true, I would assume that the two lead pins were still steel.
The problem, as always, is that our market is far too small to get people to build high performance devices. Look at the recent demise of the 2SJ74. Now there are no high-performance P-channel JFET's in the world. Twenty years ago you could get complementary pairs from Toshiba, Hitachi, and NEC....
Thieves! My cousin got fired from Fairchild or National, I can't remember which, for taking home gold plated ceramic packages that had failed inspection. She wanted to make jewelry with them, however they were not impressed. Some 'beancounters' are awfully petty, and they probably bought themselves a free lunch with the proceeds.
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