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Old 15th July 2013, 11:42 PM   #1031
Eric is offline Eric  United States
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Hi Guys,

I ordered some 2sk2013 and 2sj313 transistors from Arie on eBay and had the opportunity to measure them (20v and about 45mA) last night. My result as are below:

2sk2013: 2.18, 2.20, 2.20, 2.27, and 2.28
2sj313: 2.04, 2.07, 2.12, 2.15, and 2.16

Are these "close enough" matches that I can use the trim pots for adjustment, or do I need closer matches?
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Old 15th July 2013, 11:49 PM   #1032
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Last two of each are great.
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Old 16th July 2013, 12:12 AM   #1033
Eric is offline Eric  United States
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Yes, but don't I need to match across the two types for a BA-3 front end? Thus, my best match is 2.16 and 2.18. From there it gets worse: 2.15 and 2.20 followed by 2.12 and 2.20. Are these useful or do I need tighter matches?
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Old 16th July 2013, 12:25 AM   #1034
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IMO, you are fine. Matching N to N, P to P is all I would worry about.
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Old 16th July 2013, 12:30 AM   #1035
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Sorry Buzz, I feel like I'm being dense here-perhaps I'm missing something. Doesn't each channel of the BA-3 front end have one N and one P channel MOSFET at the output? How does matching N to N and P to P enter into this?
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Old 16th July 2013, 12:42 AM   #1036
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It's not real important, but doing so would make two channels similar to each other. P3 is the great equalizer in the equation within a channel. Euvl has shown J313 and 2013 aren't perfect complimentary pairs and getting them close will take more selection. Run with what you got, if you like the amp, you can push further into performance improvements. This assumes you think they are needed.
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Old 16th July 2013, 01:37 AM   #1037
Eric is offline Eric  United States
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Guess I'll start populating the boards soon and see where it goes from there... 6L6 provided a nice reference for adjusting distortion while looking at harmonics.
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Old 16th July 2013, 04:55 PM   #1038
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single point matched does not do much for amplifying performance.
It's how well they match when the current sweeps to either side of the set bias current. This is effectively a form of curve matching. An easy way to do that is by 3point matching.

Single point is great for multiple pairs when trying to set bias currents.
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Old 17th July 2013, 12:44 AM   #1039
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Andrew, By 3-point matching, do you mean matching each set of transistors at three different currrent levels? In the case of the BA-3, the circuit indicates 45mA, so would I match at say 20mA, 30mA, and 45mA?

Hmmm... I don't even really have a match at 45mA here. I suppose I'll build the circuit and see what I get with the tools that 6L6 pointed out. This will take me a little while - too many other things going on right now. All of my projects seem to be on extended timelines.
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Old 17th July 2013, 01:23 AM   #1040
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Andrew,
Do you have any data showing difference in performance between singl point and 3 point matching?
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