Bedroom System

Discussion in 'DIY' started by Mike B, Dec 8, 2012.

  1. claud

    claud Well-Known Member Donor

    Joined:
    May 8, 2007
    Messages:
    2,689
    Likes Received:
    258
    So, it takes two 300Bs. What are the other tubes it uses? They look to be 9 pins ones. Are they all input tubes?
     
  2. Mike B

    Mike B Bronze Member Donor Top Poster

    Joined:
    May 18, 2007
    Messages:
    16,828
    Likes Received:
    502
    Each 300B uses a whole 12AU7 (both triodes in parallel) as a driver. The one in the middle is a 12AT7 (substituted by me for original design of 12AX7) which serves as the preamp for both sides. The amp will reach max output with only 300 mV as designed and I have a preamp good for 1.6 volts driving it so substituted the lower gain (and better sounding) 12AT7.

    Now if only those Western Electric's would ship...
     
  3. claud

    claud Well-Known Member Donor

    Joined:
    May 8, 2007
    Messages:
    2,689
    Likes Received:
    258
    What 12AU7s are you using? What about the 12AT7? What brand. Did you mean that you changed the amp to use 12AT7 instead of 12AX7 or can it use either?
     
  4. Mike B

    Mike B Bronze Member Donor Top Poster

    Joined:
    May 18, 2007
    Messages:
    16,828
    Likes Received:
    502
    I'm using RCA clear tops for the 12AU7s and and a Valvo E180CC for the AT7. Yes, the amp can use pretty much anything in the "12A" family depending on how much input sensitivity you need or want. I have run a 12AX7 (Sovtec long plate) and it works fine, but that Valvo sounds better.
     
  5. claud

    claud Well-Known Member Donor

    Joined:
    May 8, 2007
    Messages:
    2,689
    Likes Received:
    258
    Did you try any thing else for the 12AU7s? Could you hear a difference with the RCAs? I am just curious as to which tubes make a difference in your amp if upgraded.
     
  6. Mike B

    Mike B Bronze Member Donor Top Poster

    Joined:
    May 18, 2007
    Messages:
    16,828
    Likes Received:
    502
    The clear tops were a noticeable improvement over the Electro Harmonics that came with my "tube kit" and that Valvo was the one that sounded best in the Stereomour I ran before. I find little difference between the Gold Lion and EH versions of 300B. Look the same and made in the same factory I believe.
     
  7. claud

    claud Well-Known Member Donor

    Joined:
    May 8, 2007
    Messages:
    2,689
    Likes Received:
    258
    Have you thought about trying Sophia , EML or the KR 300Bs. If you search the "Tubes" forum at Audio Asylum you might find something better. Which ever is the amp's input tube would make the most difference in tube rolling.
     
  8. Carl V

    Carl V Bronze Member Donor Top Poster

    Joined:
    May 8, 2007
    Messages:
    12,021
    Likes Received:
    774
    Once upon a time RAM tubes were well curated. I had some of Rogers musical design amps RM-9 & rm-10. I really liked his low powered emission tube designs. Sadly he just passed away this year.

    tubes can be so nice, so frustrating, so variable.
     
  9. Mike B

    Mike B Bronze Member Donor Top Poster

    Joined:
    May 18, 2007
    Messages:
    16,828
    Likes Received:
    502
    That Valvo was magic with the Stereomour and I think the gain factor was around 50 as compared to a 12AX7 which is around 100. So half the gain and I need 600 mV for full output and with over twice that available no problem. It was magic again when I put it in the Elekit. That is the input tube and I liked it so much I bought a spare as it's long obsolete. The preamp is Elekit too, a TU8500 which also gets rave reviews. I've got a couple of clear tops in there too. It's a mix of SS and valves with the bonus of a phono stage with both MC and MM inputs. Amazing - :)

    As far as the 300B goes, I have my pre-order in with Western Electric and until a couple more years go by and the Gold Lions need replacing I'mma just gonna wait.
     

Share This Page