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K&K Audio / Lundahl Transformers

1684 any info ?

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Hello Kevin,
LL1684 seems to be getting good comments from the Pimm/Dahl/Olson set on TubeDIY . I notice there's no datasheet as yet on the Lundahl site.
Any advice, or perhaps a quick technical summary ?
Oh, by the way, I tried to access some of the schematics for input/phase splitting info , on your K&K home page, but didn't have any success in accessing it .
Thanks in advance,
Mark J

Follow Ups:

Real story - LL1684 - KevinC 05:06:09 11/27/03 (0)
Well, I am embarrassed to write that the LL1684 IS NOT the 1+1:1+1 version of the LL1676 and LL1674. I shipped the first two pairs before I had seen the datasheet -- boy, was that stupid! If you have a driving impedance of 50 ohms or so, it will work well. Otherwise, you will experience roll-off.
The LL1684 was designed as the amorphous core version of the LL1588, which is normally used as a balancing output transformer after op amp type circuits. Those of you looking for output transformers for op amp output stages in DACs and CD players should look at this one.
A true 1+1:1+1 complement to the LL1676 is on the way sometime next year.

Kevin Carter
K&K Audio
www.kandkaudio.com
The data sheet is now online... - gdahl 10:25:31 11/21/03 (8)
...see link below.
Gary Dahl
"So many tubes, so little time..."
- LL1684 (Open in New Window)
- Ouch ! 150 ohm source... - IslandPink 07:35:14 11/24/03 (5)
  Gary, Kevin,
  Spec is given for 150 source impedance ;
  That could cause me a re-think .
  Is there any useful performance for 500 to 1000 ohm source impedance ?
  ( Load would be a pair of ECC99 sections as per Amity )
  Mark
  - Re: Ouch ! 150 ohm source... - KevinC 07:40:16 11/24/03 (4)
    Mark,
    I don't doubt that it will be fine with a 1K source impedance. I've used its mate, the LL1676, with such source impedances and still gotten great bandwidth at low distortion figures.
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    - Thanks, etc - IslandPink 13:57:00 11/24/03 (3)
      Ok Kevin, thanks for the reassurance.
      I also notice 1676 sheet shows good figures with 600 ohm source, so I imagine they're comparable .
      Mark
      - Re: Thanks, etc - KevinC 15:01:26 11/24/03 (2)
        
        In Reply to: Thanks, etc posted by IslandPink on November 24, 2003 at 13:57:00:
        
        Perhaps I was too hasty. Gary Pimm reports some issues with source impedance and phase splitting with the LL1684. The DCR is lower than one might expect for the "brother" of an LL1676, so maybe we should pause and see what Per Lundahl has to say. He is out of the office until the end of the week, but I have sent him an e-mail on the topic.
        Sorry for the hurry up and wait!
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        
        For the benefit of readers ... - IslandPink 10:32:06 11/28/03 (1)
        
        In Reply to: Re: Thanks, etc posted by KevinC on November 24, 2003 at 15:01:26:
        
        Kevin,
        I see the response from Per was that the 1684 was not ideally suited to the purposes of a HiFi input / phase splitting transformer, being more suited to coupling low-impedance equipment. Seems the 150 ohm source is serious advice. He did however suggest that a more easily driveable 1 : 1 + 1 amorphous transformer was on the way , yes ?
        regards,
        Mark
        
        For the benefit of amplifier builders... - KevinC 10:54:31 11/28/03 (0)
        
        In Reply to: For the benefit of readers ... posted by IslandPink on November 28, 2003 at 10:32:06:
        
        Well, one can never be sure of the outcome, but I have put a 1+1:1+1 amorphous core phase splitting transformer on my 2004 Lundahl Wish List with a very limited number of other items.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
- Re: Thanks, data sheet , phono Q etc - IslandPink 11:51:44 11/21/03 (1)
  Thanks Gary
  Must get adobe loaded at home - damn !
  Will have a look at work Monday. Should be able to order these in December. (Need to work on a beefier phono first anyway). What's your phono amp these days btw Gary (?) I saw you were keen on the Shelter 501, which is the next logical step , some time next year .
  How's the Aurora breadboarding going ?
  Mark
  - K&K Phono Preamp... - gdahl 13:43:21 11/21/03 (0)
    Hi Mark,
    I am using the K&K Phono Preamp, and am completely delighted with it. I posted a review on Audio Asylum--see the link below.
    My Aurora amps are actually switchable between Aurora mode (input, driver and output stage) and Amity mode (driver and output stage only). In the Aurora mode, the signal goes through a S&B TX-102 and then a single-ended input (line) stage, as shown on the schematic. The Amity input goes straight to an LL1676 and on to the driver grids.
    A few months ago, I settled on using the Amity mode driven by the Espressivo, because the Espressivo sounded more lively than the Aurora's own input stage. More recently, Lynn has found another tube that livens up the Aurora's first stage, so he is using the Aurora mode again (he is borrowing my turntable, phono amp and Auroras).
    If the new version of the Raven sounds better than the Aurora's input stage, I'll end up with the K&K Phono/Raven/Aurora combination. I am hoping that S&B successfully develops a phase-splitting TVC, which I would like to use at the input of the Raven.
    Lynn's work-in-progress amps are the DHT-driver Auroras. They will be built when the custom power supply iron arrives.
    Gary Dahl
    
    "So many tubes, so little time..."
    - K&K Phono Preamp Review on AA (Open in New Window)

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