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Re: Which Output Transformer ?

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In Reply to: Which Output Transformer ? posted by akltam on September 05, 2003 at 01:33:57:

The LL1623/PP at 3K will work well. Recently one of my local audio friends built a PP parallel fixed bias amplifier similar to your description and used an LL1679/PP connected for 2.6K primary. It sounds really nice. We have auditioned it will EL34, 6550C, KT88 and 6L6GC outputs and all work well. If you are interested in the schematic, I can e-mail it to you, once I know your e-mail address.

Kevin Carter
K&K Audio
www.kandkaudio.com

Follow Ups:

Is this 1679 a new output transformer ? - akltam 07:31:42 09/05/03 (24)
It seems to me that this 1679 is new. is it ?
I have changed the security of my moniker name to allow receiving emails. I would love to look at the schematics of that amp using 1679 as I have not finalised any design yet. All I know is that it will be 2 pairs of somthing like EL34 or 6550.
I am now in fact looking up all the theories behind tubes like the williamson, SRPP, long pair tail ...etc. It is very interesting but giving me some headache to decide what to use.
Thanks in advance.
Alan
- Link to KT88 Monoblock amp - KevinC 08:54:10 09/05/03 (23)
  Take a look here to see the final circuit of the P-P parallel EL34/KT88/6L6GC monoblock amplifier that was expertly built by Joe Rosovitz and designed by me.
  http://hometown.aol.com/kevinc927/images/KT88monoblockamp.pdf
  
  Kevin Carter
  K&K Audio
  www.kandkaudio.com
  - http://hometown.aol.com/kevinc927/images/KT88monoblockamp.pdf (Open in New Window)
  - KT88 Monoblock amp picture - KevinC 06:14:06 09/06/03 (12)
    Here is a picture of one channel of Joe's monoblock amplifier. The top plate is chrome plated aluminum and the chassis is African lacewood custom manufactured by a local high end cabinet shop. The knobs were turned out of the same wood by me.
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    - http://hometown.aol.com/kevinc927/images/KT88monoblock.jpg (Open in New Window)
    - Re: KT88 Monoblock amp picture - akltam 08:33:48 09/06/03 (9)
      Kelvin,
      You have post before that you are considering having a PCB for a tube power amp. Will you be considering doing this one as the driver PCB. You have this for this 2 pairs, also for your 300B.
      DIYer can choose the implementation as they like, but they can alway start with the board, What do you think ?
      IMHO.
      Alan
      - Amplifier Kit - KevinC 05:18:17 09/07/03 (8)
        
        In Reply to: Re: KT88 Monoblock amp picture posted by akltam on September 06, 2003 at 08:33:48:
        
        I was contemplating using this driver circuit for the monoblock version of the kit and a single-ended adaptation for the stereo version.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        Re: Amplifier Kit - hpsxr 16:46:20 09/08/03 (3)
        
        In Reply to: Amplifier Kit posted by KevinC on September 07, 2003 at 05:18:17:
        
        Hi !
        When you write:
        "Version 2: SE input transformer coupled to PP output stage (300B), cathode bias. Capable of 18 watts.
        Monoblock amplifier kit
        Same versions as above but with twice the power and PP input as well as output"
        Is a 300B PPP ? Could you post details of the 300B PPP?
        Thank You
        Hugo
        
        PP Parallel 300B Amplifier Circuit - KevinC 18:32:38 09/08/03 (2)
        
        In Reply to: Re: Amplifier Kit posted by hpsxr on September 08, 2003 at 16:46:20:
        
        Here is a link to the circuit.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        http://hometown.aol.com/kevinc927/images/PPparallel300Bamp.pdf (Open in New Window)
        
        Re: PP Parallel 300B Amplifier Circuit - hpsxr 19:38:16 09/12/03 (0)
        
        In Reply to: PP Parallel 300B Amplifier Circuit posted by KevinC on September 08, 2003 at 18:32:38:
        
        Is possible see details of your super-amp that used 2A3 driver tubes instead of 6BX7GT ?
        Thank You
        Hugo
        
        Thank You - hpsxr 05:01:47 09/09/03 (0)
        
        In Reply to: PP Parallel 300B Amplifier Circuit posted by KevinC on September 08, 2003 at 18:32:38:
        
        ...
        
        Re: Amplifier Kit - hpsxr 10:13:01 09/07/03 (3)
        
        In Reply to: Amplifier Kit posted by KevinC on September 07, 2003 at 05:18:17:
        
        Hello !
        K&K Audio have a GREAT Line Stage.
        Why lose that type of input stage in the new amplifier ?
        Thank You
        Hugo
        
        Re: Amplifier Kit - KevinC 14:37:37 09/07/03 (2)
        
        In Reply to: Re: Amplifier Kit posted by hpsxr on September 07, 2003 at 10:13:01:
        
        If you were interfacing the PP Line Stage to the PP amp, you could easily omit the amplifier input transformer and go directly to the 6SN7GT grids.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        Re: Amplifier Kit - hpsxr 14:47:15 09/07/03 (1)
        
        In Reply to: Re: Amplifier Kit posted by KevinC on September 07, 2003 at 14:37:37:
        
        We could omit the LL1667/5mA with your's current source in the input stage.
        
        Re: Amplifier Kit - KevinC 15:48:38 09/07/03 (0)
        
        In Reply to: Re: Amplifier Kit posted by hpsxr on September 07, 2003 at 14:47:15:
        
        Yes, that will work, but you lose the balancing action of the P-P choke in the process.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
    - Re: KT88 Monoblock amp picture - akltam 08:16:03 09/06/03 (1)
      Kelvin,
      Please show me the inside of this amp. I don't see the lundahl around.
      It is so professional.
      Thanks.
      Alan
      - Re: KT88 Monoblock amp picture - KevinC 05:19:05 09/07/03 (0)
        
        In Reply to: Re: KT88 Monoblock amp picture posted by akltam on September 06, 2003 at 08:16:03:
        
        That's a Lundahl LL1679/PP under the black transformer cover.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
  - Re: Link to KT88 Monoblock amp - akltam 20:29:24 09/05/03 (1)
    Kelvin,
    Thank you.
    Very nice and interesting schematics. There seems to be little compromise in your design. Choke loaded driver tubes, Separate transformer for the negative grid bias and with choke. All transformer couple. Very Very Interesting !
    This animal needs a very big chasis and so many transformer around. It will be interesting to see the real thing. Any pictures ?
    Do you know how many sections are there in 1679 ?
    Hey, one other thing, there seems to be NFB ? is it ?
    Thanks.
    Alan
    - Re: Link to KT88 Monoblock amp - KevinC 05:32:41 09/06/03 (0)
      I will post a picture shortly. The chassis for each channel is 16" x 20", so they aren't small, but not crazy-big either.
      I don't know haow many sections the LL1679 has. If there is any global NFB, it is unauthorized!!!! No, there is no global feedback used. In my experience, that is the quickest way to rob the music of vital harmonic info.
      
      Kevin Carter
      K&K Audio
      www.kandkaudio.com
  - Re: Link to KT88 Monoblock amp - drlowmu 14:12:27 09/05/03 (7)
    Kevin,
    That certainly is a very nice (final) P-P-P circuit.
    Nice design work.
    Jeff Medwin
    - KT88 Monoblock amp woulda's - KevinC 15:53:52 09/05/03 (6)
      Thanks, Jeff. If we were to buikd this again, we would use an LL1660S/PP interstage. I have used it in a PP300B amp that sounds really exceptional. It just didn't exist when we started the KT88 amp.
      
      Kevin Carter
      K&K Audio
      www.kandkaudio.com
      - Re: KT88 Monoblock amp woulda's - sinewave 10:26:00 09/06/03 (2)
        
        In Reply to: KT88 Monoblock amp woulda's posted by KevinC on September 05, 2003 at 15:53:52:
        
        According to the RCA tube Manual the 6BX7 has a hi-mu section and a low-mu section, this seems to be an unusal use of this tube in a balanced push pull circuit, why use this tube instead of another 6sn7 or 6SL7?
        
        6BX7GT driver - KevinC 10:46:22 09/06/03 (1)
        
        In Reply to: Re: KT88 Monoblock amp woulda's posted by sinewave on September 06, 2003 at 10:26:00:
        
        The RCA tube manual that you have is incorrect. You are the second person to make that comment to me recently; you must both have the same tube manual edition. A 6BX7GT has two identical triodes, both low mu, low Rp. I use it instead of a 6SN7GT, because I have demonstrated to my satisfaction that a low Rp tube is the best output stage driver. Whether it's a 2A3, 45, 6BX7GT, or a even a 5687/ECC99/7119, the low plate impedance seems necessary to control the output tube grid. Low Rp drivers make amplifiers sound more powerful and cleaner, all other things being equal. It really isn't a small thing.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        Re: 6BX7GT driver - sinewave 14:58:34 09/06/03 (0)
        
        In Reply to: 6BX7GT driver posted by KevinC on September 06, 2003 at 10:46:22:
        
        After checking both GE and Sylvania tube manuals, it would appear that you are correct.
      - Re: KT88 Monoblock amp woulda's - Max Dissipation 05:54:03 09/06/03 (2)
        
        In Reply to: KT88 Monoblock amp woulda's posted by KevinC on September 05, 2003 at 15:53:52:
        
        Hi Kevin
        Could you post details of the 300B PP?
        Many thanks
        Max
        
        PP 300B amp schematic - KevinC 07:54:25 09/06/03 (1)
        
        In Reply to: Re: KT88 Monoblock amp woulda's posted by Max Dissipation on September 06, 2003 at 05:54:03:
        
        Here it is.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        http://hometown.aol.com/kevinc927/images/PP300Bamp.pdf (Open in New Window)
        
        Thanks! - Max Dissipation 10:18:01 09/06/03 (0)
        
        In Reply to: PP 300B amp schematic posted by KevinC on September 06, 2003 at 07:54:25:
        
        Thanks Kevin
        Looks tasty

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