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• Re: 845 or 300B - groverg 19:16:38 01/23/03 (5)
  In Reply to: 845 or 300B posted by herbet on January 23, 2003 at 18:15:20:

  The sonic difference, IMHO, is that the 845 plays music with an authority and reach that the 300B simply does not posses. The 300B can rock, but the 845 RUMBLES. Orchestral works, massed voices, organ and other difficult material come across with a spaciousness and breadth that the 300B simply can't muster. Most people are convinced when they hear a solo piano recording--the bottom end of the instrument is conveyed in an extremely convincing manner. It is also more neutral, tonally, than most 300Bs and, to my ears, better relays the unique properties of different recordings. It will also drive an amazing number of real-world speakers that the 300B can't touch. And it costs about $40--one of the best buys in audio, as far as I'm concerned.

  Technically speaking, the 845 demands high voltages, well-designed circuitry and difficult-to-source components to sound its best, though it will produce a pretty impressive 5 watts at lower voltages. Still, it's not an easy tube to work with.

  I use older ProAc Response 2's and they are very 300B-friendly, and I had a lot of fun with different 300B projects, all of them very satisfying in their way. But once I started working with the 845, I couldn't go back.
  
  

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  • Re: 845 or 300B - Jim Doyle 19:29:23 01/23/03 (4)
    In Reply to: Re: 845 or 300B posted by groverg on January 23, 2003 at 19:16:38:

    
    Grover - you may have seen my 845 inquiry here about a week ago.

    I decided to bite the bullet and order the basics to retrofit
    my sv811-10 amp to use a low voltage 845 with my 5K transformers.

    Do you have any experience to share with regard to interfacing
    issues (i.e. drivers) that will give better results?

    I have parts for a number of different topologies. I was going to
    start with interstage coupling since I have a pair of LL1660/10mA
    units on hand. In the 450-500V plate area, I'd need to swing
    about 100Vp-p on the interstage to get reasonable power out of the
    845. Wiring the interstage as 1:1.125 would require me to use a
    high-gain tube ; the 8532W, 6C45PI, 5842 are all options and tubes
    that I have a supply of. Wiring the interstage as 1:2.225 would
    allow me to do this with lower-gain, higher-current tubes such
    as 6N1P and 6SN7 which I also have on hand.

    What are your experiences with interstage coupling?

    Other options include not using interstages... There are numberous
    other topologies I could resort to include cathode following
    using 6BX7 or KT66.

    I'd love to hear about the choices and experiences you had with
    different driver designs and how you landed on driver that tickled
    your fancy.

    -- Jim

    
    
    
    

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    • Re: 845 or 300B - Maciek P 00:05:15 01/24/03 (1)
      In Reply to: Re: 845 or 300B posted by Jim Doyle on January 23, 2003 at 19:29:23:

      Hi,
      You can't use 5842 or 6C45p with LL1660/10mA and 1:1.125 ratio, because you need at least 15-20mA of the current to use them properly. LL1660/18mA or LL1660/30mA (excelent for 6C45p) is a good bet here. Using LL1660/10ma with 2:2.25 ratio is rather not a good idea because the driven tube will see 4 times bigger Rp of the driver, but you have a gap for 20mA and can use tubes like 5842 or 6C45p.

      MAciej
      
      

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      • Re: 845 or 300B - groverg 08:29:25 01/24/03 (0)
        In Reply to: Re: 845 or 300B posted by MaciekP on January 24, 2003 at 00:05:15:

        I agree, 15mA is about right for the 5842 in my experience. See, I don't know much about ITs :-).
        
        

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    • Re: 845 or 300B - groverg 21:01:01 01/23/03 (1)
      In Reply to: Re: 845 or 300B posted by Jim Doyle on January 23, 2003 at 19:29:23:

      Jim, I've only made a few stabs at IT coupling. Naturally the 845 loves it but I've never been able to get past the sound of the IT. Haven't spent a lot of money, though :-). That said, I think your best bet is to use the higher gain tube and a lower ratio. Step-ups get you into trouble and the 6N1P is a drab little tube, IMHO. The 6C45 has a lot more music in it. Frankly, I'd go with a 5842, it's pretty sweet with an IT.

      IMHO, a 6SN7 driving a triode-strapped KT88, simple RC-coupling throughout, might make you flip. I use parallel 6N7GT for more gain, and an EL34 driver, but it's the same idea. Nobody even looks at the 6N7GT but it has the most delicious harmonic signature.

      Hope this helps.
      
      

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      • 6N7GT - jeff mai 02:52:15 01/24/03 (0)
        In Reply to: Re: 845 or 300B posted by groverg on January 23, 2003 at 21:01:01:

        I absolutely second Grovers recommendation. I'm using it to drive 45s or 71As. Best sound I've gotten.
        
        

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