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    vta resistors

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    kost

    Posts : 33
    Join date : 2009-05-12
    Age : 52
    Location : athens

    vta resistors

    Post by kost on Wed Nov 18, 2009 8:03 am

    Hi

    I am thinking to lower the VTA output and this is a good chance to replace the resistors with better quality ones.
    Any suggestions? Riken, kiwame or...?

    cheers

    kost

    Bob Latino
    Admin

    Posts : 2378
    Join date : 2008-11-26
    Location : Massachusetts

    Re: vta resistors

    Post by Bob Latino on Wed Nov 18, 2009 9:43 am

    Kost,

    The resistors supplied with the VTA driver board are 1% precision metal film resistors. Both channels will have perfect balance if you use the stock supplied resistors that come with the board. Metal film resistors are also very quiet. Their use is one of the main reasons why the random noise level of a VTA boarded ST-70 amp is very low. The use of other than the suppled resistors could give unpredictable results with respect to the board's sound quality.

    Another option you could try is to selectively replace resistors that are directly in the signal path and see if you feel that the change has a positive influence on the amp's sound quality. You can check your VTA board schematic and I am sure you can figure out which resistors these are. Understand that replacing a 15 cent resistor with a $4.00 Riken resistor or a $1.00 Kiwame resistor doesn't automatically gain better sound quality. Realize also that replacing all the 40 or so resistors on the VTA driver board with $1.00+ resistors could get pretty expensive.

    Bob

    Brinkman

    Posts : 14
    Join date : 2009-01-01

    Re: vta resistors

    Post by Brinkman on Wed Nov 18, 2009 4:03 pm

    This is one of the rare occasions where a compromise is optimal. By compromise I mean only replace a few resistors rather than all. Specifically, I'd replace the grid resistors (R1/R2, R33/R34, R35/R36) with carbon composition types. By the way, the Kiwames are rumored to be re-branded KOA/Speer resistors which can easily be obtained more affordably via Mouser.

    Additionally, the plate load resistors (R11/R12, R19/R20, R21/R22) could be upgraded to non-inductive wirewound types such as Mills. All these suggestions are per Morgan Jones' excellent book, Valve Amplifiers. And I really mean excellent. It's awesome.

    Otherwise, if all I had was the PC board and no parts, I'd get PRP resistors for the rest of the metal films. They are inexpensive (to an audiophile) 1% metal film resistors which a lot of folks swear by. It's probably hype, but it helps tweakers sleep at night, so it's okay. Also, you can chase your tail experimenting with the coupling capacitors (C5/C6, C7/C8). I'm currently using Jensen paper-in-oils, but on a different driver board. I still enthusiastically recommend the VTA board though.

    Have fun.

    Luddite

    Posts : 235
    Join date : 2009-02-04
    Age : 66
    Location : Texas

    Re: vta resistors

    Post by Luddite on Wed Nov 18, 2009 4:39 pm

    All these suggestions are per Morgan Jones' excellent book, Valve Amplifiers. And I really mean excellent. It's awesome.

    Speaking of Morgan Jones, I built a headphone amplifier six years ago based on a modified Morgan Jones design (rumored to be a reverse engineered EAR). This amplifier uses the Russian military 6N1P tubes in place of 12AX7's. Oustanding performance with my Sennheiser HD-580 headphones!

    Charlie

    Brinkman

    Posts : 14
    Join date : 2009-01-01

    Re: vta resistors

    Post by Brinkman on Wed Nov 18, 2009 5:27 pm

    I actually just came across that amplifier schematic the other day. Apparently someone implemented some John Broskie/TubeCAD tweaks to the power supply as performance upgrade. Looks really interesting, but headphones (and the associated amp) are more of a solution in search of a problem for me.

    But if I was inclined to build one, that one would be on my short list!

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