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Old 16th November 2009, 02:30 PM   #181
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Hello! I did not found 2sk170 too, as well as J110. I made a simulation according to Wrenchone's advise, using BF244A with 15 ohm source resistors and 100uF bypass caps (voltage is 30V). THD is about 2.2 with huge 2nd and 8nd harmonics! I had an idea to build something simple with "pleasant distortion"..just for grins)) but i'm in doubt now. Riaa curve is not changed, good at least.

Just noticed that with inverse RIAA connected to the ground 8th harmonic disappeared and THD is ~0.6 now. How to measure it properly? I'm novice in Microcap.
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Old 16th November 2009, 02:42 PM   #182
Salas is offline Salas  Greece
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R4 3.3k, V2 24V. No C5,C6, you need some degeneration to lower THD. Do you have 2SK170BL model? So to compare what you may check for BF244 to match THD with original.
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Old 17th November 2009, 11:28 AM   #183
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Thank you very much! Now THD is about 0.3 at 44 dB gain, almost entirely 2nd harmonic (I think I can deal with it). BF244 mutual conductance is not so linear as 2sk170 at low gate-source voltage. i think I'll build it, maybe change jfets to 2sk170 when will find them.
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Old 17th November 2009, 12:48 PM   #184
Salas is offline Salas  Greece
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Up the Rs resistors to 27R, aim for 7-8V Vd, no less than 40dB gain, by adjusting the drain load resistors, if you are going to use 5mV MM. THD will go lower. For 2SK170 available look in http://www.hifituning24.de/0000009b2...a415/index.php
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Old 18th November 2009, 03:08 AM   #185
sakdi is offline sakdi  Thailand
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Hello

I can't find 2sk170. Is it possible to replace this jfet with j310?
Could you please help and suggest?

Regards
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Old 18th November 2009, 11:15 PM   #186
Salas is offline Salas  Greece
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J310 has enough more noise in comparison. Better with BF244A, adequate enough for MM cartridges.
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Old 18th November 2009, 11:28 PM   #187
ra7 is offline ra7  United States
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Can I run these simulations on LTSpice? What simulator would you guys recommend?
I want to learn one.

Salas,
I'm planning to make a pcb for the one you suggested, hence taking more time!

Thanks guys!
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Old 20th November 2009, 06:05 AM   #188
sakdi is offline sakdi  Thailand
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Thank you.
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Old 26th November 2009, 05:50 AM   #189
ra7 is offline ra7  United States
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Salas,
read all your posts for my problem in this thread.
One question I left unanswered was the cartridge...
ADC QLM 34 III... 7.8 mV.

taught myself some spice. Simulated the circuit and
am getting the same results as you. I can't get the
THD numbers to make any sense. Dug up some old
threads here and found that it is pretty unreliable
for measuring THD and harmonics. Also, I'm not sure
if I'm using the software correctly.

Anyway, I'm etching PCBs right now (for the first time)
for the circuit you posted. Its tough going... but
hopefully I'll get there.
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Old 26th November 2009, 05:58 AM   #190
Salas is offline Salas  Greece
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Good luck with your PCB. THD is going to be good enough, better than in the Pacific. When you got results, let us know.
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