The curves differ - and hence the loadline has to be 'drawn' different. Look at post #92 of how a nice fit can be made. (The problem with curves is the 'sensitivity' of the two axes. )
I have reached out to Pras, and he made me an offer which I did not react to because I had found a set I had in the closet somewhere for over 5 years.,.
And the current status:
- So here is his link, and he offers the pair of 2SK180 ; and the pair of current-matched THF51. It is on ALIExpress, so the EU import is all handled with VAT porepaid, including the dreaded customs handling (that lost me some device). It is the same price as his ex-VAT on the swap page.
And the current status:
Aliexpress? China parts? Really!?
Also, what's up with "old" and "new" versions?
This does not seem right to me.
Wait a second: Aliexpress is a market place that offers good services to handle the imports in the EU, is my statement. Yes, many offers are just 'shyt', components that are different. I am not the one to certify Pras, others could do that. If you do not like AE then contact him directly but then customs declarations is tedious from individual post dispatches, if you are in the EU. [And yes, I worked at The Tax Authority and think it is good not to double cross the economy, even though I'm Dutch and we have the nickname to do so... 😡 But that is just my private belief.]
I have these already waiting waiting and so decided against another SIT. Thats all. And I did not want Pras1170 to be let out. That is just private demeanour.
As to old/new I cannot comment . contact the seller.
I have these already waiting waiting and so decided against another SIT. Thats all. And I did not want Pras1170 to be let out. That is just private demeanour.
As to old/new I cannot comment . contact the seller.
Attachments
Last edited:
Yes, it's an incredible marketplace for many reasons that triode_al notes. It's no better or worse than Amazon in the USA, IMO. I can list them on Amazon for you, if it makes you more comfortable though. You may not appreciate the cost premium though. What's your preferred web marketplace that vets all suppliers for selling parts like this?
WOW! The vast majority of manufactured goods in the USA arrive from China. No wonder things in Switzerland are so expensive if nothing contains parts manufactured or distributed through China! BTW, technically, these are Japanese parts. 🙂 😉
I think "old" were pulls and "new" are NOS in box. Best to ask the seller for verification.
^ Then I'd advise that you not purchase them. Go with your gut.
With that said, every single part I've purchased from them (FWIW - I believe that they prefer "she") has arrived as described and is an authentic part to the best of my ability to validate.
Separate, but related - I believe, but am not 100% certain, that the Vgs noted on the parts (in the photo above) was measured per instructions from Aleks while vetting parts for the SissySIT prior to the modifications allowing a wider range of Vgs in that specific project.
Just poking you a bit for fun with some of my comments. I admit that I bristle a bit when I see what I perceive to be an unsubstantiated bias against the Chinese. IMO, it's wise to be leery of many sellers on ANY web site. This is particularly true if you don't communicate in the same native language as the seller to validate / confirm expectations prior to shipping. The good news is that AliExpress has excellent buyer protection, and I always use a credit card for my purchases, which also offers excellent protections in the event that goods purchased are not as advertised (or even as expected). I am fairly risk averse.
tl;dr - My
is that @pras1170 is a reliable seller.
Sure, @pras1170 is reliable.
Your Ali link looks like one of these Chinese thrift stores, not where you'd go while looking for hard-to-find and expensive NOS parts.
Amazon is actually worse in some ways. Most goods cannot be bought from Amazon here in Switzerland because they don't comply with our labour laws, I believe.
But why not just directly buy parts from the guys who have a good reputation here on diyAudio? No need to go through AliAmaz or whatever.
And then again I am not actually looking to buy THF51. I have too many already.
https://mbrennwa.github.io/curvetracedata/THF51/index.html
Your Ali link looks like one of these Chinese thrift stores, not where you'd go while looking for hard-to-find and expensive NOS parts.
Amazon is actually worse in some ways. Most goods cannot be bought from Amazon here in Switzerland because they don't comply with our labour laws, I believe.
But why not just directly buy parts from the guys who have a good reputation here on diyAudio? No need to go through AliAmaz or whatever.
And then again I am not actually looking to buy THF51. I have too many already.
https://mbrennwa.github.io/curvetracedata/THF51/index.html
^ Obviously, I'm just playing a bit of the devil's advocate, but...
I look for obsolete or hard to find things all the time at thrift stores and other locations like swap meets (live) or what we call flea markets or hamfests. I don't care one iota re: the outward appearance. That's how I find some great things. I know what I'm looking for and how to validate it if needed. When I lived in Hong Kong, some of the "most reputable" suppliers all over Asia had physical storefronts that you'd likely not step into. All the better for me, you'd leave me all the good stuff. 🙂
With that said, your point is well taken and appreciated. I'd advise anyone that is skeptical or doesn't feel comfortable validating their own parts etc. etc. to purchase anything from a supplier with known good reputation and/or from a web merchant that has a reliable refund policy, just in case. I value my time and that of others'. It's excellent advice.
My main point is that there are TONS of reputable suppliers on Ali. That's why I use that site frequently. I know how to find good suppliers and the goods that they sell. So, I generally save enough money to make it worth my time. A great deal of what I buy would be sold exactly as-is from a US-based vendor and simply marked up accordingly.
Wait... I already have a pile of them too.
Seriously, I hope lots of people get these before they truly are "gone". Mainly... I really, really, really want to see you do your 40th anniversary VFET 'clone'.
Have a great weekend!
Edited to add an easy example - I'd generally advise most people to not look for obsolete parts on Ebay. With that said, I'd tell anyone looking for bulk Toshiba J74s / K170s to look for punkydawgs on Ebay. It's not the site that I care about, it's the actual merchant. I hope that makes sense.
That's Pras's store. 😉 Not my Ali link. That was from Triode_Al.
I look for obsolete or hard to find things all the time at thrift stores and other locations like swap meets (live) or what we call flea markets or hamfests. I don't care one iota re: the outward appearance. That's how I find some great things. I know what I'm looking for and how to validate it if needed. When I lived in Hong Kong, some of the "most reputable" suppliers all over Asia had physical storefronts that you'd likely not step into. All the better for me, you'd leave me all the good stuff. 🙂
With that said, your point is well taken and appreciated. I'd advise anyone that is skeptical or doesn't feel comfortable validating their own parts etc. etc. to purchase anything from a supplier with known good reputation and/or from a web merchant that has a reliable refund policy, just in case. I value my time and that of others'. It's excellent advice.
My main point is that there are TONS of reputable suppliers on Ali. That's why I use that site frequently. I know how to find good suppliers and the goods that they sell. So, I generally save enough money to make it worth my time. A great deal of what I buy would be sold exactly as-is from a US-based vendor and simply marked up accordingly.
Because generally they charge a premium. Why do I care who I buy it from? I'm not prejudiced against a web site. I can have a dialog with a seller either in person, over the phone, or in writing. Then, I can gain enough confidence to make a purchase, or move along. I also have a "black list" of suppliers whose web sites have a lot more professional looking photos that (to me) are clearly running scams.
Share... share.... 🙂 🙂
Wait... I already have a pile of them too.
Seriously, I hope lots of people get these before they truly are "gone". Mainly... I really, really, really want to see you do your 40th anniversary VFET 'clone'.
Have a great weekend!
Edited to add an easy example - I'd generally advise most people to not look for obsolete parts on Ebay. With that said, I'd tell anyone looking for bulk Toshiba J74s / K170s to look for punkydawgs on Ebay. It's not the site that I care about, it's the actual merchant. I hope that makes sense.
Last edited:
I have been saving 20 pieces of NOS RCA JAN2A3 for over 30 years, now I have time to build but as mentioned, xfmrs are stupid expensive. Maybe an OTL with 10 tubes per channel? 😆 Also have 6336, 6AS7G, 6080 etc,., all triodes....but I still want to find a bevy of THF51s in an old elevator control box or ??
Cheers
Maybe it's actually better to sell some of the 2A3s that aren't close to a four or a pair.
And buy some SIT.
And buy some SIT.
before this UA-RUS problem i was buying cheaply VFETs from my supplier from Moscow and cities around.. i have tens of kilos at home waiting, probably will be Single ended transformer loaded amp, or PSE OT loaded.. when all finish ill try to restart importing and paste possible links
It is very hard to believe that someone abroad has at least one hundred "UA-RUS" VFETs in quantity. Not to mention kilograms, or tens of kilograms. I don't believe it, and that's all.
Because I know that a very limited number of them were produced.
"Russian" VFETs (SIT) - KP801, KP802, KP926 ( in the original language, КП801, КП802, КП926),
And that's it.
I measured the characteristics of UJ3N065080K3S
up to a voltage of 30V. For use in SE circuits.''
Possible operating point position in SE: 20 V, 4 A, offset. -8.5 V, S=4,25 A/V.
As you can see, the characteristic in the operating area is intermediate between the "triode" and "pentode".
So you don't even need to look for SIT.
Because I know that a very limited number of them were produced.
"Russian" VFETs (SIT) - KP801, KP802, KP926 ( in the original language, КП801, КП802, КП926),
And that's it.
I measured the characteristics of UJ3N065080K3S
up to a voltage of 30V. For use in SE circuits.''
Possible operating point position in SE: 20 V, 4 A, offset. -8.5 V, S=4,25 A/V.
As you can see, the characteristic in the operating area is intermediate between the "triode" and "pentode".
So you don't even need to look for SIT.
Last edited:
I can confirm that the UJ3N065080K3S works well in single ended circuits. I prototyped a choke loaded SE common source amp with an operating point of 30V, 2A, and it measured very well for such a topology. 1 watt at 0.2% THD into 8 ohms and 15 watts, 1.4% THD. Parts count is low, too.
This power JFET also works well in other topologies as I discovered: https://www.diyaudio.com/community/threads/sic-adventures-exploring-the-uj3n065080k3s.409636/
This power JFET also works well in other topologies as I discovered: https://www.diyaudio.com/community/threads/sic-adventures-exploring-the-uj3n065080k3s.409636/
Attachments
Wow, you do have a big stash 👍 Please let me know if you have a pair for sale.
These Russian SIT don’t seem to be available anymore on eBay so looks like your timing was good. The only one left are the Japanese one from Tokin.
Have you had a chance to compare for example the KP802A with another SIT ?
Thanks
Eric
the test amp was made several years ago, with source feedback winding , with double C core custom transformer (25 to 8 ohms, 70kHz top freq, wound by myself) first with Yamaha and and then after with KP802.. after was needed to add the driver circuit but never come back to it.. i think this year i need to complete it. and opet proper thread for it, some graphs from testing phase:
Attachments
Unfortunately nothing to sell, i was buying from the local stores .. hopefully one day will be possible to do again..
i have a lot of different VFets at home, also mamut 2SK77, but never had time to do all the measurements and comparations properly.. Built some experimental PP guitar amp in 2011. powered from 110V and it was working!!
I've never found enough time to dedicate myself to measurements and development in the last 10 years.. I think it's time this year to change this a bit..