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Old 19th July 2012, 04:24 PM   #12471
Rush is offline Rush  United States
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Quote:
Originally Posted by jackinnj View Post
Shoulda said -- the TDH+N% is well below 0.01%

2SK170 in GR and BL are generally available which is better than the 2n5457 (suddenly in short supply) -- and it may make sense to use 3x matched 2n5460.
Are you suggesting using 2SK170 GR or BL with a pair or 3 matched 2N5460? I assume you want to equal the idss of the 2SK170 with what ever number of 2N5460 it takes?

Rush
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Old 19th July 2012, 04:33 PM   #12472
doolav is offline doolav  United Kingdom
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Hi, it likely has been discussed here, but searching through about a half of this thread I still cannot find it, so can anybody advise/point to: what has to be changed on cviller's boards (v.2 - not the current one rev.2) in order to build F5 Rev.1?
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Old 19th July 2012, 04:47 PM   #12473
Zen Mod is offline Zen Mod  Serbia
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Old 19th July 2012, 05:00 PM   #12474
Marra is offline Marra  United Kingdom
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Here's the link

http://www.diyaudio.com/forums/blogs...version-2.html
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Old 19th July 2012, 05:22 PM   #12475
doolav is offline doolav  United Kingdom
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thanks, will try.
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Old 19th July 2012, 09:22 PM   #12476
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Quote:
Originally Posted by Rush View Post
Are you suggesting using 2SK170 GR or BL with a pair or 3 matched 2N5460? I assume you want to equal the idss of the 2SK170 with what ever number of 2N5460 it takes?

Rush
I substituted one 2SK170GR with Idss of 6.1mA, and the THD was equal to the paired 2N5457. Interesting, however, the 2nd harmonic was a bit higher, but the 3rd was lower and the 4th way down in the weeds.
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Old 19th July 2012, 10:05 PM   #12477
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Quote:
Originally Posted by jackinnj View Post
I substituted one 2SK170GR with Idss of 6.1mA, and the THD was equal to the paired 2N5457. Interesting, however, the 2nd harmonic was a bit higher, but the 3rd was lower and the 4th way down in the weeds.
shouldnt hurt, should it? I like a little second harmonic...

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Old 19th July 2012, 10:09 PM   #12478
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Some more numbers -- using a matched J74GR/K170GR the THD% was 0.0018% 1W, 1kHz. With the 2N5460/2N5457 the best that I could do was 0.0029% -- either number is very respectable. The noise of the J74/K170 seemed to be -135dBV just as in the article while the 5460/5457 was -128dBV.
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Old 20th July 2012, 10:43 PM   #12479
alazira is offline alazira  United States
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Quote:
Originally Posted by noSmoking View Post
My fets are on the way,,,,
I have a bunch of 170's in the gr region and all about 10 sj 74 are BL,Ive been stacking the 170 to a close match,I read that the P really needs to be about a ma or two more than the n do you know ?
I believe you are referring to EUVL's source degeneration matching trick.
http://www.diyaudio.com/forums/attac...t-variants.pdf
Although I think it would mostly be useful with complementary output mosfets like the Toshiba 2SJ201/2SK1530.
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Old 20th July 2012, 11:11 PM   #12480
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Originally Posted by alazira View Post
I believe you are referring to EUVL's source degeneration matching trick.
This is what P3 in the F5-R1 does.

I set up the amplifier bias @1.3A, and output of 2.83V in to 8R and then let the FFT run while adjusting P3. Even with a 25 turn trimpot you find that only a small fraction of a turn will knock the 2nd harmonic down by several dB. As I said previously, be patient, let the beast warm up for a while before making the adjustment --
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