K&K Audio / Lundahl Transformers

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headphone transformer

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Hi,
I have just finished building my raven preamp, the amp sounds great with the amity power amps but does not have enough power to drive my sennhieser 650's. so I was wondering if there is a suitable transformer to step up the output to the headphones. or is this unfeasable?
regards
g brown

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Re: headphone transformer - drubrew 04:50:59 11/28/05 (0)
Ditto what Doug said above. This is a wonderful amp very clean and transparent. No added junk. No fatigue what so ever after long listening periods which is a hard thing to come buy these days. I spend about 8hrs a day with a pair of headphones on while doing Cadd design. So being able to take the headphones off at 5pm without having a serious migraine is important. I have used it with several pair of Grado's, all the Senn HD line and even the Sony Qualia. It is an amp that works well with all kinds of impedances, very versatile.
Thank You
Drew Baird
Moon Audio
308 Chrismill lane
Holly Springs, NC 27540
919-649-5018
Email: drubrew@bellsouth.net
Web: http://www.moon-audio.com
Re: headphone transformer - KevinC 04:12:52 11/22/05 (6)
Do you mean that you can't turn it up loudly enough? The output impedance is marginally low enough as it is, but won't withstand a step-up to get more output, if volume is your problem.

Kevin Carter
K&K Audio
www.kandkaudio.com
- Re: headphone transformer - G Brown 04:31:59 11/22/05 (5)
  Yes I can't get enough volume with the headphones. do you think I could use a seperate transformer for the output to headphones(switchable in and out of circuit). is there a suitable lundahl item?
  Best regards
  G Brown
  - Re: headphone transformer - KevinC 14:24:17 11/22/05 (4)
    There really isn't a way to do this without the additional gain to do it with. My new headphone preamp design uses a configuration similar to the Raven MkII, but with one differential pair (6H23pi) directly driving a second pair (6H30pi) loaded with an LL1689AM/PP connected for 9+9:1. This gives enough gain and very low output impedance ( <20 ohms).
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    - Re: headphone transformer - G Brown 15:47:43 11/22/05 (3)
      That sounds very interesting, do you have a schematic I could look at?
      Thanks
      G Brown
      - Differential Headphone Amplifier schematic - KevinC 10:13:41 11/24/05 (2)
        
        In Reply to: Re: headphone transformer posted by G Brown on November 22, 2005 at 15:47:43:
        
        Here is the schematic of the headphone amplifier. With the addition of some input switching it can be used as a preamplifier, as well. The overall gain is about 16dB as it is configured in the schematic. You can save some money by substituting the LL1689/PP (silicon iron core), but with some sacrifice of sound quality, of course. You can also use other input transformers like the LL1676 or LL1690 with very nearly identical results. I built the prototype in a Dyna FM-1 case with the Dyna power transformer (out of laziness). It is extremely quiet and has plenty of level for either my Sennheiser HD-600 or AKG K-271 headphones.
        I will let some of the guys here who have heard this comment (if they see this post) , but I find it to be wonderfully transparent and dynamic.
        With only the 6H30pi stage, the gain is woefully inadequate, so a direct-coupled input stage was necessary. To avoid the sonic evils of coupling caps, the two stages are directly coupled, but that requires some input stage plate voltage rebalancing as the input tubes are changed and perhaps as they age long term. I haven't found it necessary to make adjustments from month-to-month, so it appears not to be a big deal with good tubes.
        
        Kevin Carter
        K&K Audio
        www.kandkaudio.com
        http://www.kandkaudio.com/images/Differential_Headphone_Amplifier.pdf (Open in New Window)
        
        Re: Differential Headphone Amplifier schematic - Bergen4 14:06:37 11/25/05 (0)
        
        In Reply to: Differential Headphone Amplifier schematic posted by KevinC on November 24, 2005 at 10:13:41:
        
        I have heard Kevin's differential headphone amp and I think it's quite good. This is truly the best I have heard from an amp of this type, including solid state designs. No opamps for my headphones, please. My single ended (6SN7 directly coupled to 2A3's with Lundahl output transformers) is a different sound altogether. The tonal differences are not that great but in terms of presentation, the PP design has dynamics to die for. The leading transients are taut and fully integrated with the pace and flow of the music. The transistorized heaphone preamps I have spent time with seem to strip harmonics and trailing transients out leaving a more threadbare sound. Some people call this cleanliness or accurate but if it doesn't sound like music than it's wrong. You're missing something but not with this little differential amp. It's a mastering editor's dream tool. You don't miss a thing and at the same time the sound is capitivatingly real. The music seems to be to cut from whole cloth. There is a seamless quality to the sound. All the room sound is preserved and on good recordings I just want to hear more. I told Kevin not to leave me alone with his headphone amp because he may never see it again. Jokes aside, this is my next K&K Audio project. Good luck to you.
        
        Re: Differential Headphone Amplifier schematic - G Brown 15:56:59 11/24/05 (0)
        
        In Reply to: Differential Headphone Amplifier schematic posted by KevinC on November 24, 2005 at 10:13:41:
        
        Thanks for the schematic. I would be intrested to hear the opinions, of others who have herd this amp.
        regards
        G Brown

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