Lol, same here
The matching was directed by Patrick and done by heinz1. The credit goes to them.
I just did the data analysis
Since then I have sold my soul to lucky_z and efficiency
A friend of mine asked me to check whether a few 2SJ74 which he bought at ridiculously low price from Hong Kong are genuine. Well, here are some curve and photo comparisons. By checking the curve, we know right away his jfets are all fake. Gm is vey low comparing with the real ones. The fake's shape also looks slightly different than the real ones, if we look at it close enough. The legs are thinner and easy to bend, surface with marking appears to be rough. The top view also looks different than genuine.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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Hi, Liubin!
Those fakes are very common.
The most probable they are sourced from remarked cheap 2SK246/2SJ103.
For being sure you can measure parasitic capacitance of the JFET intrinsic gate diode.
Hi Pav,
Good point! The curve from the fake J74 indeed looks like J103
Good point! The curve from the fake J74 indeed looks like J103
An externally hosted image should be here but it was not working when we last tested it.
2SJ74/2SK170 matched octa (4N/4P) to be sent to a forumer. A 5 Ohm source resistor is used for 2SJ74 to reduce its Gm, as Patrick suggested in his publication.
An externally hosted image should be here but it was not working when we last tested it.
As the demand for single j74 is far more than J75 (two J74 in one metal can) and I am running low for J74, I decided to try to get the two J74 out from a J75. Here is some photos of the "experiment".
before the destruction PS：I started with J75GR
After cutting the Al can and getting the two lovely J74GR out. The two J74 are intact, and show normal curves when measured.
Zoom in view of J74 from the can, there is no marking on it
before the destruction
PS：I started with J75GR
After cutting the Al can and getting the two lovely J74GR out. The two J74 are intact, and show normal curves when measured.
Zoom in view of J74 from the can, there is no marking on it
Thanks giving sale is extended to Monday mid night.
Pls take note that shipping would be slightly delayed due to the large amount of orders I need to fullfill. I will try my best to ship your order within 3 working days upon payment though. Thanks for your kind understanding~! Hace a great weekend, everyone.
Pls take note that shipping would be slightly delayed due to the large amount of orders I need to fullfill. I will try my best to ship your order within 3 working days upon payment though. Thanks for your kind understanding~! Hace a great weekend, everyone.
Hi Bob,
Thx for the suggestion. I was thinking of donating towards the year end. Looks like now it is a good time
$50 is just donated to the forum. Will donate more in the near future.
Thx for the suggestion. I was thinking of donating towards the year end. Looks like now it is a good time
$50 is just donated to the forum. Will donate more in the near future.
Attachments
Hi Bob,
Thx for the suggestion. I was thinking of donating towards the year end. Looks like now it is a good time
$50 is just donated to the forum. Will donate more in the near future.
Any time is a good time!
Thanks for supporting the forum and also for your awesome parts and service to keep all kinds of great audio projects going.
BK
Any time is a good time!
Thanks for supporting the forum and also for your awesome parts and service to keep all kinds of great audio projects going.
BK
Always my pleasure [emoji3]
Updated with a table showing all available parts, not sure whether it is clearer...
An externally hosted image should be here but it was not working when we last tested it.
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