StanleyB1
Banned - Shares IP addresses with DC Lee Herandu
- Joined
- Jul 11, 2008
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Quote:
My 1st advise would be to subject that transformer circuit to a frequency sweep test so that you can get an idea of the drop off at the sub 100Hz and post 20KHz region. If you are using a delta sigma DAC chip, then you shouldn't have to lose sleep about anti-aliasing noise, so don't go heavy on the filtering. You may not need any extra filtering at all. But keep the transformer away from other parts by at least 2cm if possible, and away from opamps or transistors that give off noticeable heat. Transformers change their sound with temperature fluctuations. By giving it enough space to 'breath' and stabilize its core temperature, you can even out any nasty tonal variations between winter and summer listening.
I find it useful to insert a Zobel network in the secondary side of legs of the transformer in order to combat any phase reversal or frequency dependent loading effect. But this partly depends on the input circuit design of the following amplifier the DAC is plugged into.
Just don't fit any resistors in series with the transformer output. It will kill low level detail, make the DAC sound dark, and strangle the dynamics.
Same way, don't fit a DC blocking cap in series. Transformers don't pass DC
, so avoid adding any unneeded obstacles to the sound path.
| Originally Posted by regal /img/forum/go_quote.gif I am building a passive I/V w/step-up transformer as a filter like used in the AudioNote DAC's, what are your opinions of this technique? |
My 1st advise would be to subject that transformer circuit to a frequency sweep test so that you can get an idea of the drop off at the sub 100Hz and post 20KHz region. If you are using a delta sigma DAC chip, then you shouldn't have to lose sleep about anti-aliasing noise, so don't go heavy on the filtering. You may not need any extra filtering at all. But keep the transformer away from other parts by at least 2cm if possible, and away from opamps or transistors that give off noticeable heat. Transformers change their sound with temperature fluctuations. By giving it enough space to 'breath' and stabilize its core temperature, you can even out any nasty tonal variations between winter and summer listening.
I find it useful to insert a Zobel network in the secondary side of legs of the transformer in order to combat any phase reversal or frequency dependent loading effect. But this partly depends on the input circuit design of the following amplifier the DAC is plugged into.
Just don't fit any resistors in series with the transformer output. It will kill low level detail, make the DAC sound dark, and strangle the dynamics.
Same way, don't fit a DC blocking cap in series. Transformers don't pass DC
