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  1. Old Comment
    marc brown's Avatar

    First Watt B1 clone

    Nice B1! Where did you source your relay selector?
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    Posted 18th April 2016 at 09:13 PM by marc brown marc brown is offline
  2. Old Comment
    abraxalito's Avatar

    Rant on the SET critics

    Headphones are very efficient - about 100dB/mW. Since I've built a bal SE amp for mine, there's really no going back to classAB. All else is gaslight, so even though I've not heard a valve SET amp I understand where you're coming from.
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    Posted 7th April 2016 at 02:35 AM by abraxalito abraxalito is offline
  3. Old Comment
    abraxalito's Avatar

    Mighty mite balanced SE classA headphone amp

    No direct side-by-side comparison with it - I plan to go back again to the BBftB amp and listen to them both with the same phones. But I really like the simplicity of this new one, and it gets out of the way of the music in a way I'm not sure I've heard before. Really enjoyable.
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    Posted 6th April 2016 at 05:47 AM by abraxalito abraxalito is offline
  4. Old Comment

    Mighty mite balanced SE classA headphone amp

    any comparison with your other headphone amp?
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    Posted 6th April 2016 at 02:22 AM by jambul jambul is offline
  5. Old Comment
    rjm's Avatar

    Matching JFETs

    Please use ver. 1.2. I was an idiot and forgot to divide by V_gs0 for the transconductance in 1.1.
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    Posted 5th April 2016 at 01:57 AM by rjm rjm is offline
  6. Old Comment

    Matching JFETs

    Thank you very much!
    I am sure it will be useful in my next project. I will try to build an amplifier without feedback. I am still waiting for parts, but I will try to measure the component I have on hand using your methodology.
    Again, thank you for sharing with the DIY community.
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    Posted 5th April 2016 at 12:22 AM by BaffleChallenged BaffleChallenged is offline
  7. Old Comment
    rjm's Avatar

    Matching JFETs

    Thanks for your input. I've uploaded a revised spreadsheet that hopefully clarifies some things. I've added an extra line where can now calculate the transconductance at a given current.

    The table in the supermatched jfets post uses the same calculation as the worksheet posted here, but then goes an extra step and says "ok, now for the R_source used in the actual circuit where you are going to use this jfet, what is the transconductance?" That's a different value (usually) from the test values R_source1 and R_source2 used here.
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    Posted 4th April 2016 at 11:58 PM by rjm rjm is offline
  8. Old Comment
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    Posted 4th April 2016 at 11:35 PM by rjm rjm is offline
  9. Old Comment

    CrystalFET Phono Stage

    How / where can I order the kit?
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    Posted 4th April 2016 at 05:08 PM by richandy richandy is offline
  10. Old Comment

    Supermatched JFETs

    Hi!

    I re-checked my measuring setup once again, even if it is really simple. Just because the pressure, with which the JFets are pressend on the heatsink, changed I_D.

    I found out that my cables for measuring, even if they are quality Hirschmann cables, had a slightly corrosion on the connectors. I cleaned them, and got reliable measurements. One mystery solved.

    Edit:
    I'll do also the math with your procedere, and see how it varies. I hope that the difference will be just of academic nature, so I'll safe lot's of time in the future!
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    Posted 4th April 2016 at 12:58 PM by Murdoc Murdoc is offline
  11. Old Comment

    Matching JFETs

    Hi, I am a bit confused by your table, on the left, under constants, you have R1,R2,R_Source, all of different values. In your previous blog entry, you provide a spreadsheet where 2 resistor are used to calculate vgs_0 and idss.
    first question:
    How does R_source fit in the picture???
    second question:
    can we modify the provided spreadsheet to include the calculation of g_m?
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    Posted 4th April 2016 at 12:33 PM by BaffleChallenged BaffleChallenged is offline
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