Tube DIY Asylum

• Well basically... - Nickel Core 12:41:22 05/07/07 (5)
  In Reply to: Born to Leggo!!! posted by richardl on May 7, 2007 at 11:52:21:

  ...what you see is a integrated SET amp.

  3 stages, input xfrm-> PEC Pot-> Aa-> cap-> 10Y-> cap-> 300B

  First stage has series battery bias, second stage cathode bias, third stage fixed bias.

  First stage CCS loaded, second stage L loaded.

  Filaments via a VCCS for the first two stages, third stage AC.

  PSU:

  First and second stage: CLC one per channel (6X4 rectified)
  Third stage LCLC one per channel (GZ37 rectified, the OPT size chokes you see on the back are 10H / 5R chokes).
  Fixed bias, CLC one per channel (6X4 rectified)

  Each filament / VCCS combo has its own transformer (there is another rather large heater/filemament transformer inside the amp you can't see).

  Aa runs @ 185V / -3.6V bias
  10Y runs @ 340V / -26V bias
  300B runs @ 450V / -90V bias

  You see a humpot too besides the 10Y's because I want to check if i can get away with AC on the driver too.

  Basically this a breadboard on which I want to try a few things for a slightly over the top integrated amp (with phono-stage) I'm currently building.

  The rest of the system:

  AN-Lexus sig. speaker rewired with AN-Vx and upgraded with hemp drivers
  AN-TT Three reference with RS-A1 arm and Kondo-IOJ
  AN-S8 step-up
  DIYHifi LCR Cole Riaa
  All interconnects are AN-SOGON

  
  Regards,
  Nickel Core

  
  
  

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  • AC on 300B - zarniwoop 14:08:28 05/07/07 (3)
    In Reply to: Well basically... posted by Nickel Core on May 7, 2007 at 12:41:22:

    have you checked what kind of hum you get with AC heating on the 300b? I am soon going to try some cancellation methods to get mine down lower than it is currently. this is also a 3stage 300b amp, but only 2 are dht (choke loaded 6b4g driver).

    
    
    

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    • Re: AC on 300B - drlowmu 21:35:18 05/07/07 (1)
      In Reply to: AC on 300B posted by zarniwoop on May 7, 2007 at 14:08:28:

      hello zarniwoop !

      an idea. why not sub in a 2a3 for the 6B4G so you can run your driver on AC at 2.5 VAC / 2.5 A.

      that should sound even better than a DCed Ef 6B4G I would guess.

      jeff medwin
      
      

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      • Re: AC on 300B - zarniwoop 07:12:38 05/08/07 (0)
        In Reply to: Re: AC on 300B posted by drlowmu on May 7, 2007 at 21:35:18:

        hi,
        Even with a 2a3 I doubt it would work to use AC heating. In theory, the hum from the two ac-heated dhts should cancel somewhat when they are coupled in series as common-cathode stages. guess the driver overwhelms that effect since its amplified further.

        i'm going to try to stay with AC on the 300B. I still maintain that its not possible to get a really quiet amp with AC heating dhts (in SE) without some tricks. Maybe at 2.5v its tolerable.
        
        

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    • Re: AC on 300B - Nickel Core 14:11:02 05/07/07 (0)
      In Reply to: AC on 300B posted by zarniwoop on May 7, 2007 at 14:08:28:

      Well, with the 10 turn hum pots I'm able to get down to unhearable hum level at my listening position with my 97dBA speakers (you can feel some 50hZ hum when touching the cones though).
      
      

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  • Very nice. - richardl 13:27:06 05/07/07 (0)
    In Reply to: Well basically... posted by Nickel Core on May 7, 2007 at 12:41:22:

    I am sure it will be beautiful in a chassis too.
    
    

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