Ok, here you are. This is an original K170 - curve tracer proved.
All of my K170 show the same kind of somehow whitish but not white imprint.
All of them show the same characteristics on top - from the moulding process. The breaking point of the injector is always in the middle of the joint.
I have had a lot of them and all looked like that.
J74 share these characteristics.
Hope this brings you somewhere.
All of my K170 show the same kind of somehow whitish but not white imprint.
All of them show the same characteristics on top - from the moulding process. The breaking point of the injector is always in the middle of the joint.
I have had a lot of them and all looked like that.
J74 share these characteristics.
Hope this brings you somewhere.
2N7000 is an enhancement mode MOSFET.
It only starts to conduct with Vgs > 2V.
It is also much noisier.
https://maker.pro/forums/threads/noise-performance-of-small-package-mosfets.74536/
"I measured two small TO-92 MOSFETs with my hp4470A: a 2n7000 and its older brother, a VN01. Both MOSFETs were very noisy. The VN01 was 50 to 100x more noisy than a quiet JFET like a 2sk170, and the 2n7000 was 2 to 5x worse yet, over 1uV/rt-Hz. This was at 100kHz - the noise was much higher at lower frequencies and offscale below 3kHz. Also, this was at 10mA - the noise was much higher at lower currents, like 1mA or 300uA."
Patrick
It only starts to conduct with Vgs > 2V.
It is also much noisier.
https://maker.pro/forums/threads/noise-performance-of-small-package-mosfets.74536/
"I measured two small TO-92 MOSFETs with my hp4470A: a 2n7000 and its older brother, a VN01. Both MOSFETs were very noisy. The VN01 was 50 to 100x more noisy than a quiet JFET like a 2sk170, and the 2n7000 was 2 to 5x worse yet, over 1uV/rt-Hz. This was at 100kHz - the noise was much higher at lower frequencies and offscale below 3kHz. Also, this was at 10mA - the noise was much higher at lower currents, like 1mA or 300uA."
Patrick
Hello All,
I feel like a miser or a Jfet pincher here.
I have a supply Toshiba Jfets but I want to conserve them.
I just purchased a pair of Pass Pearl 2 Riaa pre amp PCB's and a set of matched Jfets.
Plus I got a pair of Pearl 3 PCB's at burning amp a couple of weeks ago.
Both the Pearl 2 and Pearl 3 use a pair of low noise NPN transistors as a cascode to compensate for the Jfet Miller capacitance. (extended bandwidth). NPN transistors in place of Jfet's is okay by me.
The Pearl 3 PCB's Have both SMT pads for 4 parallel 2SK209's and plated through holes for 4 parallel 2SK170's.
I am thinking that 4 parallel 2SK170's will run a fair amount quieter than 4 parallel 2SK209's.
Thoughts?
Agree? Disagree?
Thanks DT
I feel like a miser or a Jfet pincher here.
I have a supply Toshiba Jfets but I want to conserve them.
I just purchased a pair of Pass Pearl 2 Riaa pre amp PCB's and a set of matched Jfets.
Plus I got a pair of Pearl 3 PCB's at burning amp a couple of weeks ago.
Both the Pearl 2 and Pearl 3 use a pair of low noise NPN transistors as a cascode to compensate for the Jfet Miller capacitance. (extended bandwidth). NPN transistors in place of Jfet's is okay by me.
The Pearl 3 PCB's Have both SMT pads for 4 parallel 2SK209's and plated through holes for 4 parallel 2SK170's.
I am thinking that 4 parallel 2SK170's will run a fair amount quieter than 4 parallel 2SK209's.
Thoughts?
Agree? Disagree?
Thanks DT
As already mentioned elsewhere, 2x 2SK209GR // is a close equivalent to 1x 2SK170BL.
https://www.diyaudio.com/community/threads/njfets-for-source-follower-applications.329131/
Patrick
https://www.diyaudio.com/community/threads/njfets-for-source-follower-applications.329131/
Patrick
Hello,
I have a pair of Pearl 3 PCB's here with pads for 4 2SK209's and thru holes for 4 2SK170's.
I have both K209 and K170 Jfets in stock. I suspect that the set of 4 matched K170's will perform better both in terms of noise and distortion.
@EVUL,
Your link that you posted says that the testing of Jtets was done with Bulk Foil resistors.
My testing of resistors shows that Bulk Foil resistors produce a 1/f series of 3rd HD, much more than metal film RN60 resistors.
Thanks DT
https://www.diyaudio.com/community/threads/what-causes-resistor-distortion.347259/page-12
Start with post #229
The 2SK170 are indeed a bit quieter with more gain. The measurements aren’t much different in a completed unit between the two device types. If you want maximum gain and lowest noise use the 170’s.
Whatever you do don’t stick your cell phone on top of the input stage while calling someone, you will think your Pearl 3 is broken.
I learned that last night.
Whatever you do don’t stick your cell phone on top of the input stage while calling someone, you will think your Pearl 3 is broken.
I learned that last night.
@wayne,
Thanks for the insights.
Yea, do not put the cell phone up against your head either.
Big picture there are other active devices included that may also contribute to noise and distortion; the cascode transistors and output stage transistors.
I plan on trying some PF5102's (Low Idss) to see how things work with a not so good JFET.
I play with and test this stuff for fun.
Thanks DT
Thanks for the insights.
Yea, do not put the cell phone up against your head either.
Big picture there are other active devices included that may also contribute to noise and distortion; the cascode transistors and output stage transistors.
I plan on trying some PF5102's (Low Idss) to see how things work with a not so good JFET.
I play with and test this stuff for fun.
Thanks DT
They work differently. FETs are "voltage controlled" devices and NPN/PNP which are bipolar transistors are "current controlled" devices.
It needs to be another FET and in this case a JFET to work as a substitute.
In some cases the 2SK209 can be used instead of the 2SK170 (done in Pearl3 phono pre-amp).
It needs to be another FET and in this case a JFET to work as a substitute.
In some cases the 2SK209 can be used instead of the 2SK170 (done in Pearl3 phono pre-amp).