Suggestions for High Gain low noise transistor replacements

Discussion in 'Solid State' started by Tom B, Apr 22, 2016.

  1. Tom B

    Tom B AK Subscriber Subscriber

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    I have done a lot of restorations over the past years, Any of us who have done these restorations have come across our share of noisy preamp transistors, and the problem differential pair transistors used in many of the older Japanese 1970 to 1982 units. Transistors such as the 2SA750, 2SA725, 2SA726, 2SC1312, 2SC1313, 2SC1775 stc.

    I have over the last number of years been using 2SA970, and 2SC2240 as pretty generic replacements. I have typically bought them on the big auction site, and usually get the GR versions for replacing 200 to 250 HFE originals, and get the BL versions for the higher gain of 450 HFE plus.

    I also used to buy all of my caps on the auction site, but now I go buy high end audio caps from Mouser because they are a lot closer to the optimum value and they usually have similar low ESR readings.

    But I have found that these transistors (and caps) which are probably counterfit, have to be checked before use. You have to check them because the HFE of the transistors could vary a whole lot, and similar with Caps, having varying values and varying ESR. While the caps are usually in tolerance, I don't like installing on that is 19 % below on one side, and 19% above on the other side. Same with transistors and their HFE gain ratings way up and way down. I spend too much time matching parts.

    So now I am thinking about going to Mouser for supplying my high gain, low noise transistor needs. But I am really familiar with the 2SA, 2SB, 2SC, and 2SD devices, I am really not too familiar with the modern ones available with KSC and others.

    Can anyone recommend manufacturer, types and Part numbers for good preamp PNP and NPN pairs, (usually around 60V 100mw 450-750 HFE), as well as good replacements for differential PNP, and NPN pairs (Usually around 100V to 120v, 100 to 300mw, 450-750HFE

    Thanks for any recommendations in advance
    Tom
     
  2. eizner23

    eizner23 Active Member

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    Madison, WI
    I've been using ksc1845fta + ksa992fbu for diff pairs from mouser, they are around 500 hfe 100v
     
    wlhd1610 likes this.
  3. FootFungus

    FootFungus Super Member

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    The KSC1845FTA and KSA992F are the only game in town left without resorting to surface mount. The KSA992 have binned versions FA and FB. The NPNs tend to be lower on gain though. So depending on whether or not you get a good batch of the NPN or a bad batch of the PNPs, it sometimes can be hard to match a quad.
     
  4. ZOOM

    ZOOM Well-Known Member

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    780
    If you buy new KSC1845 and KSA992 you don't need to do matching since they all have the same HFE these days. It's around 450 for all parts.
     
  5. Tom B

    Tom B AK Subscriber Subscriber

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    Thanks guys.

    Actually in addition to the HFE matching issues, I have at times found some of the clone pirated 2SA970's and 2SC2240 so poor manufacturing wise, that the legs break when you try to spread the leads just enough to measure.
     
  6. gslikker

    gslikker Super Member

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    Yes buying pirated anything is of no use, if the package even cannot be done properly, what about the innards.......
    In that case, better rely on pulled components from scrap units (if removed properly) if "the real thing" is wanted.

    Matching of new is close indeed. My latest test on some 100 KSA1845 from Mouser shows in between 370 and 400 roughly, but also a few 320 and 330 HFE within this 100 pieces batch.

    So a manual check is still required.

    Although buying separate transistors is nice because of no glue, the ones on the paper tape allow you to write vbe/hfe on it making it easier to pick a pair!
     
  7. EchoWars

    EchoWars Hiding in Honduras

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    The highest gain low-noise PNP transistor with a center-collector arrangement available now is probably the 2SA970BL (B&D).
     
  8. elnaldo

    elnaldo Addicted Member

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    Down here we use the BC550-BC560 and BC549-559 (Higher voltage ).

    Both are low noise, I think still in production (fairchild)
     
  9. dr*audio

    dr*audio Fish fingers and custard! Subscriber

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    2SA970 here. I still have a few 2SC2240 left, but I guess I'm going to have to make a mass buy of the KSC1845. You can also use 2N5087 but the basing is EBC. NEVER buy components on E-Bay, you're probably going to get counterfeit parts.
     
  10. jblmar

    jblmar JBL & marantz

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    Tom B,
    We're not located too far away.
     
  11. jblmar

    jblmar JBL & marantz

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    Mouser or Digikey, among some other vendors are very reliable. Overall matching of HFE is most important for matching the differential pair.
     
  12. gslikker

    gslikker Super Member

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    Opinions about 2N5088 if high impedance (TT input) and low voltage?
     
  13. EchoWars

    EchoWars Hiding in Honduras

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    Hmmm. Not bad. But that low voltage is going to really limit its usefulness.
     

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