K&K Audio / Lundahl Transformers

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K&K Audio / Lundahl Transformers

Current Source for PCM1794a DAC

95.147.213.3

Hi,
I was perusing your website and noticed in your digital section where you discuss your MKIV RAKK DAC that you say:
"Each of these DAC chips is receiving reference current from a new reference current source that we have developed, which is responsible for a dramatic improvement in sound quality"

I have a very tweaked DAC based on the PCM1794a (it's the DDDAC 1794NOS kit) and would love to try a current source for the reference current. Currently, I'm using a resistor as per the datasheet.

I guess my question is, would you be prepared to share the information about how you achieved the current source?
Maybe you would be interested in producing a small 2 pin CCS module which can be used in place of the resistor? I can see that would be a popular product if the results are good as you suggest.

thanks in advance,
James

James

Follow Ups:

RE: Current Source for PCM1794a DAC - DWJames 08:08:24 08/14/14 (3)
Thanks guys.
Dave, I can respect that you want to protect your hard work. Any teeny pointers in the right direction you could pass my way would be gratefully received, but I understand if you want to keep it under your hat.

JKT, from what I've read so far, a J-FET seems to be the simple and easy choice for now, thanks

James
- RE: Current Source for PCM1794a DAC - Dave Davenport 19:18:47 08/14/14 (2)
  James,
  
  I would suggest that you go with what JKT has proposed.
  
  Dave
  - RE: Current Source for PCM1794a DAC - KevinC 08:21:26 08/16/14 (1)
    You might try a couple of different types of JFETs for this to see what sounds the best. For example, a high transconductance 2SK170 and a low/med 2N3819.
    
    Kevin Carter
    K&K Audio
    www.kandkaudio.com
    - RE: Current Source for PCM1794a DAC - DWJames 01:24:23 08/18/14 (0)
      Thanks guys, that's great :)
      James
RE: Current Source for PCM1794a DAC - Dave Davenport 09:14:36 08/13/14 (1)
James,

You have a sharp eye and a keen intellect in spotting that and assessing its worth. It is not just a simple CCS like we use elsewhere but an innovative design that took quite a bit to develop. This is only one of the several "secrets" that make the RAKK dac such an outstanding performer.

I choose to disclose the existence of a few of the innovations and choose to not disclose others. However, it would be foolish of me to give away the competitive edge of the RAKK dac by revealing the details of the innovations.

Dave
- RE: Current Source for PCM1794a DAC - JKT 15:16:33 08/13/14 (0)
  You could replace the resistor with a simple JFET current source like the earlier RAKK DACs (1-3). Sounds better than a resistor, but not as good as the new one in the Mark IV.

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