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Re: UltraAnalog D20400A?

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In Reply to: UltraAnalog D20400A? posted by danlaudionut on December 04, 2003 at 00:29:31:

I have never had my hands on a unit that uses the Ultranalog DAC. It also appears from what little info is available that SF used dual stereo DACs in differential mode in this unit. Assuming that it is voltage output,the voltage level is high (1-2vRMS at 0dBfs)and the output impedance is low (1-100 ohms), then you can employ a range of transformers to couple to the outside world. You could use a circuit similar to that used at http://beggingdogrecords.tripod.com/DAC.html. It worked out nicely for him.

http://beggingdogrecords.tripod.com/DAC.html (Open in New Window)

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1540??? - nc 20:32:34 12/04/03 (3)
If I am going to do a balanced connection between DAC outputs directly to an Aurora input (L+, L-, R+, R-, ground to the schematic @ http://www.nutshellhifi.com/aurora.gif). No phase splitting is required, as the signal is balanced all the way through. Which transformer will you recommend to replace the 1544a in the schematic?
- Re: 1540??? - KevinC 07:12:25 12/05/03 (1)
  Let me clarify some topological points. You are planning to take a balanced signal out of the DAC and directly into a two stage fully push pull amp with an intervening volume control? Something like the Aurora, but with only two stages?
  If the output of your DAC is 2vRMS at 0dBfs, then I would be concerned about being able to drive the amp to full output. I think that the Aurora as it is on the link that you gave would be a more appropiate solution, if I understand your goals properly. In spite of bringing a balanced signal out of the DAC, I would still use an input transformer like the LL1544A or LL1676. They provide a substantial measure of common mode noise rejection that the audio circuit alone does not.
  - 1540??? - nc 09:15:30 12/05/03 (0)
    Thanks for the reply. Yes I will use pentode drivers and attempt (no guarantee that it is going to work) to use only two stages of amplification. I can always add another stage if required, and I am just inspired by the Gary Pimm's single driver thread at the Tube DIY forum. I do fully intend to use a transformer between the DAC output and the driver stage. I am just not sure which one will be better since I do not need to split signal. Thanks for the suggestion of 1676, which looks good for my use here.
- 1540??? - nc 00:13:57 12/05/03 (0)
  I guess I should add that the DAC will be Cirrus CS43122, voltage out, similar to the CS4396 as linked in the previous message. I am just thinking of building a balanced-PP amp with a total of 2 stages of amplification.

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