John Curl's Blowtorch preamplifier part II

[scott wurcer]

Originally Posted by simon7000

microdiodes that create bandwidth changes or other distortions.

Forgot about those. Just finished my 130dB gain instrumentation preamp. The 1nV noise almost rails my A/D and no spurs above the noise over 700Hz on heavily averaged 65K FFT's. Haven't tried batteries yet but the line noise residue is pretty low on a cheap supply (5nV spur at 180Hz) I'm ready to begin my search. I bet you can't wait.

I used the THAT 1512 based pre-amp from one of our sponsors. At $79 complete I couldn't see spinning a board and sourcing all the parts. Very few mods were needed (It had a 20MHz whistle on the LM317 when not in their manifold due to probably some external bypassing or not using their external PS.)

[simon7000]

Originally Posted by scott wurcer

Forgot about those. Just finished my 130dB gain instrumentation preamp. The 1nV noise almost rails my A/D and no spurs above the noise over 700Hz on heavily averaged 65K FFT's. Haven't tried batteries yet but the line noise residue is pretty low on a cheap supply (5nV spur at 180Hz) I'm ready to begin my search. I bet you can't wait.

Scott,

Just since you don't remember I have done the microdiode copper wire experiment. I measured the distortion in a copper strip then heated it until lots of oxides formed, let it cool and the distortion stayed the same.

In mechanical contacts it turns out the issue is not gaps but sulfur contamination. The silver or copper sulfide causes the molecules to grow a bit and hold off the mechanical contact. Application of voltage if the growth is not too thick causes ion migration and restores the contact. This shows up as no conduction until enough current and voltage to restore the contact and then if left unused the sulfur ions grow back.

ES

[Pano]

Originally Posted by simon7000

1,2,3
2,3,4
3,4,5
4,5,6
5,6,1
6,1,2
1,3,4
5,6,2
1,4,5
2,4,5
6,1,3
1,2,4
3,5,6

I see 18 possible groupings. Or 3x6.

[simon7000]

Originally Posted by Pano

I see 18 possible groupings. Or 3x6.

Which did I miss? 3 x 6 -5 duplicates!

[Pano]

I think these are the groups. Any dups?
123
124
125
126
134
135
136
145
146
156
234
235
236
245
246
345
356
456

[scott wurcer]

Originally Posted by simon7000

Scott,

Just since you don't remember I have done the microdiode copper wire experiment. I measured the distortion in a copper strip then heated it until lots of oxides formed, let it cool and the distortion stayed the same.

In mechanical contacts it turns out the issue is not gaps but sulfur contamination. The silver or copper sulfide causes the molecules to grow a bit and hold off the mechanical contact. Application of voltage if the growth is not too thick causes ion migration and restores the contact. This shows up as no conduction until enough current and voltage to restore the contact and then if left unused the sulfur ions grow back.

ES

Yes, I will repeat some of these experiments. The above explanation does not work for the sine wave plots with a dead zone at each crossing, and you should at least have a disclaimer on the speculative nature of this.

I would oxidize two bare wires and twist them together to see any effect and I STILL don't picture what you mean by the "distortion in a copper strip". Where is signal forced and where is voltage measured. I find it hard to believe a four wire measurement on a bar of copper shows any distortion.

[SY]

Originally Posted by Pano

I think these are the groups. Any dups?
123
124
125
126
134
135
136
145
146
156
234
235
236
245
246
345
356
456

Yes. Remember, if you pick 123 you've eliminated 456. As long as you don't care which group is which, those choices are degenerate.

[simon7000]

Originally Posted by scott wurcer

Yes, I will repeat some of these experiments. The above explanation does not work for the sine wave plots with a dead zone at each crossing, and you should at least have a disclaimer on the speculative nature of this.

Let me know and I will send you the actual part I used in that test. (Assuming I can still find it!)

I also have samples of the old 1N4004 diodes that made so much switching noise that people started to notice it!

[Pano]

Originally Posted by SY

Yes. Remember, if you pick 123 you've eliminated 456. As long as you don't care which group is which, those choices are degenerate.

Right, got it.

[jan.didden]

Originally Posted by Steve Eddy

Fair 'nuff as long as the groups don't have to be identified.

se

That'll be Part II

jan didden