ibuski

As you know, There are a bit higher chances to find obsolete Japanese semiconductors in Japanese auction than eBay. However it's true that still some (or many) of them are fakes, probably not as bad as eBay though. I obtained reliable name list as below. Their price isn't cheap, but you get guaranteed genuine parts. masayanmori kusto30145 wyxnb12593 Actually they belong to the company Tohri Electronics trade inc. and they use those Yahoo! auction accounts for private customers since Tohri's business is mainly B2B. Tohri is known to have good stock of 2SJ79 and many other rare parts. They can make combined shipping when you buy from those accounts in the same time, the sales contact person of Tohri said. BTW I failed to get quote for large volume of J79 as they want to keep serving their limited stock to the customers who needs for long time. I like that answer.

Surprisingly, punkydawgs gave me full refund immediately when I reported my measurement result to him. He wrote he guarantees 0.1 mA range and apologized for the error. I expected argument, but he just trusted me. What an honest seller he is! His pricing isn't low, but I learned importance to buy from reliable seller. Thanks Craig for the information about DIYAudio. I'm a member of it, but wasn't aware of their store contents. Now I can consider that also as one source with refunded budget. Pars, yes, they aren't bad at all. That's still less than 1 mA of range. Maybe I'm unnecessarily picky. I don't know how it affects amplifier's performance. Probably my ears can't recognize that influence.

I ended up relying on matched quad sell on eBay, famous punkydawgs. Of course he sells genuine Toshiba JFET. I bought 2 sets. It took ca. 100 EUR incl. shipping to Germany. The first set was perfect! J74: 247mV@1mA, IDSS 7.8mA, 229mV@1mA, IDSS 7.8mA, K170: 268mV@1mA, IDSS 7.8 mA, 270mV@1mA, IDSS 7.8mA. The second one contained one J74 with 0.9mA higher IDSS although all other three stayed at 8.2mA. He advertises that all his FETs were tested at 72 degree, probably it's 72 degF so this means 22 degC, slightly higher than my room, but I wonder if that can cause such error although all others were so accurate. OK, now I got perfect one quad set. Probably it's time to give up and find best compromise from the rest of parts for the other channel.

Hello everyone! I thought I should build Dynahi from the parts I purchased more than 15 years ago. Yes, original Dynahi. I was kept busy in decade for job or for family. Now my daughters are independent and I work less. I should use my free time in something productive. Before starting amplifier building, I made up a Tr/JFET measurement device and started measuring those devices. Since I had so many transistors, Tr matching wasn't difficult. An issue is JFET, K389 and J109, since I have only 4 pairs. Luckily all JFETs have good match within a package, so I'm talking about matching between N ch and P ch. I read old HeadFi thread about device matching, and found that people often measure only Idss for FET. I understood that the FET's characteristic is defined by both Idss and Vgs. They are usually correlated, but not well, right? So I measured both Idss @ 10 V and Vgs @ 1mA because I read that 1mA is working condition of them in Dynahi. Unfortunately I can't find even one pair with close enough for both parameters. Some have very close Vgs such as 290 vs 300 mV, but Idss showed more than 2 mA difference. One pair has good match in Idss, but Vgs are 390 vs 290 mV, totally different. My question is which parameter should I prioritize for Dynahi input stage usage? I tried to calculate the slope in V/A, but all K389 have ca 45 V/A of slope while J109 have ca. 35 V/A and don't fit. I'm tempted to match Vgs and allow Idss gap of 2 mA... Any advise?