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Old 9th April 2020, 03:28 PM   #1761
vdi_nenna is offline vdi_nenna  United States
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What is the highest value that can be used for C4 (5pF)?
I have a WIMA 68pF available.
Can a cap be made by twisting covered wire?
How reliable would a DIY cap such as this be?
I don't think my cap meter will measure it.

Thanks.
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Old 9th April 2020, 03:54 PM   #1762
6L6 is offline 6L6  United States
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Old 9th April 2020, 04:15 PM   #1763
vdi_nenna is offline vdi_nenna  United States
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Ugh, another order.
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Old 9th April 2020, 04:19 PM   #1764
6L6 is offline 6L6  United States
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Yeah, I know how that goes.
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Old 9th April 2020, 04:20 PM   #1765
JeffYoung is offline JeffYoung  Ireland
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68pF would be way too high.

Twisted wires would work, and are reliable. I don't know how they're measured, though.
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Old 9th April 2020, 04:39 PM   #1766
TungstenAudio is offline TungstenAudio  United States
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Twisted wires are measured by looking at the amp's output on a scope.
Papa describes the procedure in some of his Zen articles.
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Old 9th April 2020, 04:53 PM   #1767
Dennis Hui is offline Dennis Hui  Canada
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Yes, ZV4, page 3:

http://www.firstwatt.com/pdf/art_zv4.pdf

"Digikey doesn’t have 5 pF caps anymore, but I have listed 10 pF
parts in the parts list. You can buy 2 and put them in series to form
a 5 pF capacitor. Alternatively, you can twist two fine insulated
wires (like those used in wire-wrap construction) together at a
length of about 1.5 inches and get about 5 pF. This technique
has the advantage that you can start out too long and trim it with a
pair of scissors while watching the square wave of the amplifier."
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Old 9th April 2020, 06:05 PM   #1768
vdi_nenna is offline vdi_nenna  United States
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Thanks everyone. I remember the post/article, but couldn't remember where I saw it.
It's what gave me the idea. I have wire-wrap wire, so I'll try it.
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Old 14th April 2020, 12:59 AM   #1769
vdi_nenna is offline vdi_nenna  United States
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Finished it less than a hour ago.
Still processing it.

It's the one with the blue button on the front.
I'll take more pictures when I put it back on the bench.

The matched quad p-ch jfets were 11.4 idss and the ccs jfet is 10.4 idss.
Is that a big problem?

When setting the offset, I had to make micro adjustments as the offset would jump in large increments. The trimmer is 10k. Used four semi-south R100.

Listening to it now and beginning to see what all the fuss is about.
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Old 14th April 2020, 01:07 AM   #1770
Zen Mod is offline Zen Mod  Serbia
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wherein schm. is that trimpot situated?
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