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Old 22nd December 2011, 10:06 PM   #51
anatech is offline anatech  Canada
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Hi Gaetan,
The extreme resistances I have seen were encased in glass. They were pretty long too. I once had some 70 K Meg (yes, that was the value) for Geiger counters. As I recall, the resistors inside the glass were painted red. This had to be for voltage breakdown, but also getting the leakage path to be long enough. Normal humidity might very well decrease the value of those resistors, and a finger print would be your undoing.

Teflon standoffs are used to eliminate the "K effect" from PCB material as well as extend the leakage path as previously mentioned. The PCB material would become a capacitor, presenting a loss and doing funny things with charges at those impedance levels. Noise would be expected as a result - never mind distortion with a weird quality. With the Teflon standoffs, conductors now form a lower value capacitor using air as the dielectric. That means a good capacitor. Since the "K" of air is only slightly higher than that of a vacuum, the resulting capacitance is lower than you would get with a material between conductors. They do offer PCBs with a Teflon substrate, but you don't want to know how much. Actually, I don't even know how much that stuff is. It would be perfect for Mic, RIAA or general signal preamps. The main use is supposed to be for RF circuits I think.

If we don't post together before then, Merry Christmas to you as well. Do you think there will be snow in Quebec for Christmas??

Hi Scott,
Thinking along this line, would this be the reason for the small sound differences between the DIP-8 and metal 8-pin packaged op amps? To the best of my knowledge, the die is identical, the bond wires might be the same material, so that leaves the lead frame and material it is encapsulated with. The DIP-8 lead frame would also travel a much greater distance inside the material.

Personally I have never compare the two. I have no expectations at all beyond hearing other reports on this. You be da man to ask if there is anyone around here that could answer.

-Chris
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Old 22nd December 2011, 11:46 PM   #52
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Hello Chris

It could be fun to try to made some diy 1 G ohm resistors and put arround it some silicone glue.

I remember many comments from various diyers and audiophiles about a better sound from metal 8-pin packaged op amps. Yes maby the shorter wires inside the metal can, but maby also because the metal can do a total isolation from external rf noise.

I live in mountain in the Laurentides, here we have 2 inches of snow with ices everywhere on the snow and on the road.

Thank and Merry Christmas to you to.

Bye

Gaetan

Last edited by gaetan8888; 22nd December 2011 at 11:54 PM.
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Old 23rd December 2011, 03:36 AM   #53
anatech is offline anatech  Canada
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Hi Gaetan,
I figured you would have snow. Believe it or not, we don't have any. It's fairly warm outdoors still. Let's see what colour Christmas we get.

-Chris
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Old 24th December 2011, 09:17 PM   #54
1audio is online now 1audio  United States
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Default Photos of mike preamps

Here are pictures of the inside construction of the HP 1/2" mike and a B&K 1" tube mike. I could not figure out how to open the B&K preamps I have and the open ones I have are not here. The B&K has the ntube under the PCB. You can almost see it in the side view. Enjoy.
Attached Images
File Type: jpg HP preamp.jpg (766.6 KB, 72 views)
File Type: jpg B&K tube 2.jpg (818.0 KB, 71 views)
File Type: jpg B&K tube 1.jpg (678.4 KB, 69 views)
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