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Old 24th November 2012, 02:05 PM   #8611
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Salas,
have you considered bf862 in the folded cascode version. Should perform simalarly to the 389, as it has higher yfs, as a rule. I think it may have lower ciss, as well.
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Old 24th November 2012, 02:10 PM   #8612
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Old 24th November 2012, 02:12 PM   #8613
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@buzz

That is 2SK369 high Yfs lower noise than 2SK170 and BF862. 2SK389 was just a single die K170 dual having best Tc and IDSS natural match for use mainly in differential inputs.

BF862 SMD only JFET you can use in the example that RC followed for double K170s. They are bit better but they will possibly need SMD coils in their gates if they will show any sign of oscillation. Also their D pin should be on some expanded copper area to dissipate.

@nicoch LOL, spaghetti master's approval seal, now we are blessed.
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Old 24th November 2012, 02:15 PM   #8614
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Quote:
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As can be seen here I upgraded output caps to some new low voltage MRs... (shortage of t$me).... The big MRs I used for the "normal" simplistic are much much better.
the bigger the better Hight V sound better ,unlucky....


btw Ricardo so much ?

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Old 24th November 2012, 02:54 PM   #8615
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@buzz

That is 2SK369 high Yfs lower noise than 2SK170 and BF862. 2SK389 was just a single die K170 dual having best Tc and IDSS natural match for use mainly in differential inputs.

BF862 SMD only JFET you can use in the example that RC followed for double K170s. They are bit better but they will possibly need SMD coils in their gates if they will show any sign of oscillation. Also their D pin should be on some expanded copper area to dissipate.

@nicoch LOL, spaghetti master's approval seal, now we are blessed.
Ahh. THats right. Scott Wurcer did the test, didnt he.
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Old 24th November 2012, 09:19 PM   #8616
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Nice shots. Having less noise than in a 48dB build normal, with a near 60dB one, no mean feat. Paralleling is just 3dB better SNR at same gain, the rest is design & execution. Copper shielding and reference to ground for 1st stage folded should have helped towards that goal. Also your total build execution is expert in those photos. Using K369s than K170s and same class caps as in the other maybe could reveal a bit more performance, but as it is its more than enough to prove that the concept works indeed. There will be proponents of the normal or folded regarding system synergy nonetheless. The normal is more configuration flexible OTOH. Like changing sensitivity easily or for combining pre pre stage. More focus and detail across the audio band can make the folded more finicky for parts, values, synergy I guess. I would consider the folded as the ''expert'' fixed build path. Is that a valid approach in your opinion RC?
Yes... definitely more finicky for parts, specially the riaa filter, it took me a while to get it working properly (but as always, hard work pays).

I also forgot to mention, it takes a while to reach propper working voltages after turn on, due to the special folded cascode biasing.

Maybe I should try the 2SK369... where can I get those ?

Can I use this actual build without major modifications ?
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Last edited by RCruz; 24th November 2012 at 09:28 PM.
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Old 24th November 2012, 09:21 PM   #8617
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the bigger the better Hight V sound better ,unlucky....

btw Ricardo so much ?
Yes... that much.

The big ones convey a much larger sounstage... overall presentation has much more poise.
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Old 24th November 2012, 09:47 PM   #8618
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RCruz, Could you point me to the schematic that you are working with.
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Old 24th November 2012, 10:25 PM   #8619
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Yes... definitely more finicky for parts, specially the riaa filter, it took me a while to get it working properly (but as always, hard work pays).

I also forgot to mention, it takes a while to reach propper working voltages after turn on, due to the special folded cascode biasing.

Maybe I should try the 2SK369... where can I get those ?

Can I use this actual build without major modifications ?
Its in conjunction with how fast the PSU settles and how fast the bias in the input JFET(s) settles. Could speed up if it was a BIB powering.

It would need enough modifications for 369s. I already posted a 57dB using just one. Which is same noise as with 2xK170 with an advantage in the mids to lows 1/F area though. Two would make it too strong for your carts. VGeorge hit on fakes on first try sourcing on ebay he told me.
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Old 25th November 2012, 05:06 AM   #8620
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Second try on ebay for the 369 was fine. Try to find some that are on tape. Less likely to be fakes. Out of 10 pieces I managed to find two pairs.
Very nice work though Riccardo!
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