Ultrasimple mm/mc RIAA preamp 2

[RCruz]

Originally posted by jazzzman
I see that amplabs.com has 2sk170bl at 20 pieces for $20. Are 20 pieces enough to ensure that I can get 4 pieces that match? I have no idea how variable the Idss is on these things.

Hi jazzman

Could you please point me a simple way to match fets.... maybe measuring Idss ?

I am building one phono stage with the help from Salas but I am quite new to these matters.

Hope I do not bore anyone with my question

Regards

Ricardo

[mlloyd1]

ricardo:
try the site's search function.
doing so yields this link as one example:
http://www.diyaudio.com/forums/showt...63#post1626063

good luck!

mlloyd1

Originally posted by RCruz
Hi jazzman

Could you please point me a simple way to match fets.... maybe measuring Idss ?
...
Ricardo

[jazzzman]

Ricardo: Here is a link to an article that explains in pretty basic language how the JFET works and how to measure Idss.
http://w7zoi.net/jfet101.pdf

[nicoch58]

+9v on drain ,tester on mA beetwen
gate and source on gnd

for good match what is important is the time, more are better, 15-30minute

becouse the idss after five start to go up and down .........

[RCruz]

Originally posted by mlloyd1
ricardo:
try the site's search function.
doing so yields this link as one example:
http://www.diyaudio.com/forums/showt...63#post1626063

Originally posted by jazzzman
Ricardo: Here is a link to an article that explains in pretty basic language how the JFET works and how to measure Idss.
http://w7zoi.net/jfet101.pdf

Originally posted by nicoch46
+9v on drain ,tester on mA beetwen
gate and source on gnd

for good match what is important is the time, more are better, 15-30minute

becouse the idss after five start to go up and down .........

Thank you very much...... As I am quite new to these subjects and considering the high tech conversations I read in this thread, I really was afraid to ask...

Now I will study the matter and report to you latter.

Regards

Ricardo

[jazzzman]

I have a couple of pretty dumb questions. Please don't kick me off the forum but:
(1) What kind of capacitors are best to use (it looks like something pretty exotic is used in Mad-K's picture (see post #2 above)); and
(2) Is there a common ground between the left and right channels?
Thanks,
Jazzzman

[nicoch58]

for resitor use Dale ,Prp are good too than if you want play with more exotic

caps I use vishay mkp 1837 on riaa but you can try polystyrene -mica

for serial caps 100nf and out clarity caps SA but the same you can play whit more exotic.....

[jazzzman]

Thanks, Nicoch46. How about the ground? Do you have to keep left and right channels separate, or can they share a common ground?
Jazzzman

[nicoch58]

same gnd as madk share ,but separate are better

gnd in-out rca/ in-pcb , connect out-pcb gnd only on pcb to avoid loop

psu are important too , good reg ,tray two minireg from ska-audio ....and optivol if you need a pot ...with this one you can remure the last 100k and caps are only 1uf ......

[RCruz]

Originally posted by nicoch46
+9v on drain ,tester on mA beetwen
gate and source on gnd

for good match what is important is the time, more are better, 15-30minute

becouse the idss after five start to go up and down .........

Hi

Why wait for 30 minutes... do we need the fet to heat up ?

Do fet´s become stable with temperature ?

Hegards

Ricardo