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K&K Audio / Lundahl Transformers Welcome! Need support, you got it. Or share youe ideas and experiences. |
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In Reply to: RAKK question posted by Max Dissipation on June 21, 2004 at 21:30:38:
Actually there is a very specific reason to use a separate transformer for the DAC ouput that is unrelated to gain. The current outputs from the DAC "sit" at a potential of 1/2 V supply due to the unipolar power supply and the need to swing the signal "up" and "down". In order to dispense with this DC offset without saturating the transformer, it is connected to the differential outputs with the two primary coils oriented in reverse "phase" relative to each other so that the DC flux component in the core cancels, while the out-of-phase AC signal drive actually adds. Another way to do this would be to use DC blocking capacitors, but this is sonically unacceptable. The obvious differential connection of the transformer across the differential current output terminals doesn't work; it causes the DAC output stage to oscillate. So we use the trickier connection that works just fine. The frequency response of this DAC/transformer combination is down only 0.75dB at 10Hz relative to 1kHz, so the DC cancellation "trick" works nicely.
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Follow Ups
- Re: RAKK question - KevinC 04:23:37 06/22/04 (1)
- Re: RAKK question - Max Dissipation 04:42:53 06/22/04 (0)
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