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Everything posted by Rinat

  1. A few thoughts about replacing transistors to a contemporary parts: 1. I thought that stn9360 is just an ersatz for 2sa1486, but it seems that it is even better than the original one. 9360 has mush higher hfe and a little lower capacitance. It means that it is more suitable for the active battery and CCSs 2. KSA1220A has lower Vbr (160v instead of 200v for 2sk216) but it is ok even in original scheme. Does it mean that 2sk214 is safe to use ? I also afraid to get lower sound quality because of poor linearity of this mosfet (. 2sk216 is much better in this term. So, I am trying to find better substitution 🙂 . I don't like to use obsolete parts. It makes me slightly nervous. Now I am going to use 216/79 but I want to build someday a "fully-contemporary parts" T2 🙂. 3. 2SC3675: FJPF2145 has lower hfe and Vbr (. I have enough 3675s but also want to substitute them in future. Maybe cascoded CCS using JFET + DMOS ? It has much better resistance(look at the photos from the book) than single-bjt CCS. Cascoded CCS measured resistance Single BJT CCS measured resistance 4) 2SK246 -> 2SK208 5) 2SC3381 -> HN4C5J . What about matching of halves ? There is no info about max difference in datasheet. Also I want to build the amp with replaceable active battery - soldered to the main board in 2 points. I don't trust mechanical connection. UPD: It looks like KSA1220A is obsolete now (official status - "last shipments")
  2. Nice! It will be interesting to hear what do you think about Maida 21st. I replacing(or reducing) now all unregulated CLC filters in favor of this power supply in my tube amp. Also I am thinking to build Maida 21st based on LT3045 and some other transistor.
  3. I've definitely helped someone, who had immediately bought all 2sk208-GR from digikey 😄. There is only an R-grade on mouser/digikey with very low Idss now (( Did someone try to buy something at arrow.com ? They have 2sk208-GR at japanese warehouse and FQP8N80C.
  4. I've been trying to understand what should I measure to be sure that a transistor is genuine, for example in case of 2SK246-GR. But what if I will replace it with 2SK208? It is still in production and it is just a SMT version of 2SK246, with lower max power dissipation (100 mW vs 300 mW). But in the original scheme of active battery power dissipation of the JFET is around 1-2 mW. So... It would be ok to use 2sk208. Am I right ? Thanks and I hope it would help someone else 🙂
  5. I can't find what current measures DY294 in the breakdown test ( In the datasheet for 2SK246 Vgds is 50V and in my measurements I have 69-73 Volts. Maybe DY294 just can't detect 0.1 mA ( Unfortunately I can't limit current to 100uA in my etracer, but I will think what can I do. I hope the measurements will not damage the FET, because it measures using pulses with duration up to 5-10 ms. But I know it is still not safe. Thanks.
  6. Is this 2sk246-GR a genuine one ? The plot is Ids (Vds) for different Vgs
  7. Hi all! I've just bought via a friend in Tokyo a few transistors in a strange japanese shop (it has not it's own site). I want to test them and if they are genuine, then I will buy more. But how should I test them ? I've measured a breakdown voltage: 230-240 volts for 2sk216/2sj79s from Japan 228-233 volts for 2sk214s from bdent.com Is it ok for genuine parts ? Is it ok that 2sk214 and 2sk216 have almost the same breakdown voltage ? I am measuring with DY294 and etracer (tube curve tracer). I am going to trace full curves for 2sk216/2sk246gr via etracer at this thursday. Do good curves mean that transistors are genuine ? If no, then what should I measure ? Thanks for help! Ps: example of breakdown measurement for 2sk214:
  8. About using 2sa1413 as a substitution of 2sa1486. Am I wrong that they looks pretty similar? I am waiting them from bdent, they are in TO-251 cases. I've found only one datasheet with this type of case for 1413: 1413 datasheet jp to-251 1413 datasheet en 2sa1486 en
  9. Thanks! I think I can use 2SA1413 everywhere with a proper heatsink. It could dissipate up to 10W with an "infinite heatsink" by datasheet. I can't find what 1486 dissipates more than 10W. But I am going to buy STN9360 and 2SA1156 as well just in case.
  10. I've found that 2SA1413 is the 2SA1486 in a D-PAK TO-252 case. Thanks!! Ok, my new plan: 1) Try to make an adapter for 2sa1413 as the most authentic option. 2) If the first case would not successful for some reasons, I will try STN9360, thank you, JoaMat. Reducing voltage is the last option for me. 🙂 I want to make initially the most authentic T2 and only after that I would make another T2 variations. For example I would like to completely change all CCSs in favour to higher internal options, modern components, etc... 🙂
  11. https://diyaudiocart.com/ON-Semiconductor-Bipolar-Transistors-BJT-16A-250V-200W-NPN Is it a reliable source?
  12. Hi all. I've found that I can't buy 2SA1486 transistors ( Could they be replaced with 2SA1413 ? I don't see any differences between them in datasheets except a lower constant power dissipation: 10W instead of 15W. Maybe I missed something important....
  13. I know about fakes and try to buy all silicon from trusted sources - forum members, bdent etc. Anyway, thanks for the advice! I also would test all the transistors before use them, and not only test for breakdown voltage, but build curves, measure capacitance, etc. I would not allow my NOS transistors to burn 🙂 Why don't I build modern version of T2? Because I already have many rare components and I believe that I could find necessary components or replace them with something similar.
  14. Hi. I am searching for 2SA1468 and 2SK246-GR There are only 5 pcs on the bdent ( Could I replace them in the original T2 scheme (I already have PCBs) without lowering sound quality ? 2SA1468 -> 2SA1968 | 2SA1413 ? Or maybe just someone knows where could I buy them ? Or what device should I destroy to get them ? No, really - I don't afraid used, but original transistors 🙂 I just a little desperate to find at least a little reliable source of these transistors 😞 Thanks!
  15. Does it mean that if I would raise loudness level so much so that amplitude of output current would be more than 3A(or 6A in balanced configuration - with 2 boards per channel), then It would work in AB? Ok, It means that I do'nt need to buy x*3 number of transistors. Thanks 🙂
  16. Thank you very much! About the bass filter - I think I'll add it to the feedback, just need to calculate conditions of stability properly. Just a two questions(sorry if they are stupid): 1. How much transistors I need to purchase ?) I mean if they should be matched with each other ? For example: I need to get 4*9 2SA1943 (for balanced configuration). But how should I match them for such a parallel connection? And how much should I buy them ? Asking just because they are not cheap 🙂 and as a fan of tubes I have no experience with matching transistors. 2. The uberamp2 works in class A or AB ?
  17. Hello! I am going to try to build the Uber amplifier for Raal Sr1a. But Kevin said that What should be changed in the scheme to drive 0.2 ohm load better? Is it the last version ? Thanks in advance. uberamp2.pdf
  18. Hi all. Maybe a stupid question, sorry, but what about using Maida 21ct voltage regulators for the power supply ? It look like it have a nice PSRR, noise (20uV at 400v) and impedance. It could be confugured for voltages up to 525v and it could be used for negative voltages too (with a separate wind). What are the disadvantages of this regulator in comparison with original from Kevin ? I am asking, because I already have 6 boards 🙂 Thanks in advance !
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