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L'Amp: A simple SIT Amp
L'Amp: A simple SIT Amp
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Old 27th June 2018, 01:58 PM   #2931
Soundhappy is offline Soundhappy  France
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Quote:
Originally Posted by jolintsai View Post
I could not find detailed high voltage curves, unlike tubes
where the IV curves are usually published, and is within 10-20% tolerances.

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Bunch of informations and softwares for SIT's
: simulation and curve tracer can be useful to test this real transistors on Your work bench

Load Line Tutorial L'Amp 2SK180

Frankentracer part 1

Frankentracer part 2

Apps & Files | AudioMaker
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Old 27th June 2018, 07:25 PM   #2932
Soundhappy is offline Soundhappy  France
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Use curve tracer first , simulations after to avoid SIT in fire
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Old 28th June 2018, 02:50 AM   #2933
jolintsai is offline jolintsai  Malaysia
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Thanks Max!

That definitely helps. I've been thinking on what to do with the power up sequence, and the slow start from PowerReg definitely is interesting. I'm just a bit concerned on regulator on power amps - will it limit the dynamics? Based on my listening experience, I prefer unregulated PSU for power amps. It sounds more relaxed - just my 2 cents.

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Originally Posted by maxlorenz View Post
The PowerReg (maybe all power regulators) make the voltage climb slowly, so it is sort of a soft start. You will need good quality, high voltage, low leakage capacitors (and high voltage transistors) if you decide to use it. Of course, the negative V bias circuit will be there first if you use a conventional voltage regulator.

The regulated power has the added advantage of reducing the capacitance required for a linear PS.

I attach an App. Note that deals with high voltage regulation.

Good luck and have fun.
M.
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Old 28th June 2018, 12:21 PM   #2934
maxlorenz is offline maxlorenz  Chile
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Yes, I had this concern too: sometimes I feel the regulator might taint the sound but a well executed VFET amp will erase your concerns in two seconds, probably, plus the bass is great.

The PowerReg, with film caps, ends up being BIG.

My own preference is for a resistor loaded VFET amp (the R protects the VFET, as MR explained before) with a "low thermal memory" input section, like the one I posted before. This really opens up the sound and increases dynamics and transparency.
(I use slightly different local feedback resistor values now)

Good luck.
M.

PS: apparently the 2SK30 JFET has low thermal memory effect, as shown by Hephaïstos, so I will check this with a simple differential pair soon!
Attached Images
File Type: jpg diffamp CFP comp cascodo TOKIN SK180.jpg (99.2 KB, 543 views)

Last edited by maxlorenz; 28th June 2018 at 12:26 PM.
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Old 30th June 2018, 06:44 AM   #2935
jolintsai is offline jolintsai  Malaysia
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Ya, high voltage high current PSU are huge.

At the end, I'm probably gonna use a tube driver stage, but for initial phase, anything simple to hook-up will do. Thanks for the schematic and links! I've read Mike's stuff over and over again, hoping not to smoke my limited THF-51s.

Enjoy the 2SK130!

Quote:
Originally Posted by maxlorenz View Post
Yes, I had this concern too: sometimes I feel the regulator might taint the sound but a well executed VFET amp will erase your concerns in two seconds, probably, plus the bass is great.

The PowerReg, with film caps, ends up being BIG.

My own preference is for a resistor loaded VFET amp (the R protects the VFET, as MR explained before) with a "low thermal memory" input section, like the one I posted before. This really opens up the sound and increases dynamics and transparency.
(I use slightly different local feedback resistor values now)

Good luck.
M.

PS: apparently the 2SK30 JFET has low thermal memory effect, as shown by Hephaïstos, so I will check this with a simple differential pair soon!
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Old 1st July 2018, 05:21 PM   #2936
coolnose is offline coolnose  Europe
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2SK130 or 2SK30 ?
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Old 2nd July 2018, 05:07 AM   #2937
jolintsai is offline jolintsai  Malaysia
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Oops. 2SK30.
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Old 2nd July 2018, 03:54 PM   #2938
maxlorenz is offline maxlorenz  Chile
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I am already listening to the 2SK30A GR input. Sounds nice. Probably "rounder" than the 2SK170, though transconductance is much lower than the later.
Anyway, the cascoded-CFP input ("Low TMD") sounds better than both, IMHO, more dynamically contrasted, more transparent and with a certain "magic" to it.

Cheers,
M.
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Old 9th July 2018, 08:38 AM   #2939
jolintsai is offline jolintsai  Malaysia
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I just wonder, if 2SK180 and such SITs can be used in source follower configuration, like MOFO? Anyone tried that?
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Old 9th July 2018, 04:59 PM   #2940
Michael Rothacher is offline Michael Rothacher  United States
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L'Amp: A simple SIT Amp
I wouldn't recommend the MoFo circuit for a SIT. Some other follower, perhaps. But If I had some 2SK180's lying around, I use them in a CS amp.
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