100dB might not easily be achievable in practice despite what a sim will show you. That's because down at that level component parasitcs conspire to raise the feed-through. I don't worry about phase because speakers aren't too hot at preserving it. Whereas I do worry about bandlimiting and consistently find narrower bandwidths sound cleaner.
Just as a recent example of this - just this week I installed a 2nd order low pass after the post-DAC amp I have, which itself is following a very steep filter. The perceived noise floor dropped, even though that new LC filter is in practice predominantly filtering out the post-amp's own noise contribution. So my answer to your question to me is 'Yes, for sure' 🙂
Just as a recent example of this - just this week I installed a 2nd order low pass after the post-DAC amp I have, which itself is following a very steep filter. The perceived noise floor dropped, even though that new LC filter is in practice predominantly filtering out the post-amp's own noise contribution. So my answer to your question to me is 'Yes, for sure' 🙂
I can understand those parasitics. I built a theorectically, well simulated multi-stage LCR board for cleaning up SMPS noise and it was beaten by some low frequency ferrite rings in terms of sonic improvement .
But I have no plan to put ferrite beads/rings at the DAC balanced outputs of PCM1795 as I always found ferrites on signal wires make the sound unnatural, maybe it was psychological. Inductors would only dump the noise from the signal to ground with almost no loss.
But I have no plan to put ferrite beads/rings at the DAC balanced outputs of PCM1795 as I always found ferrites on signal wires make the sound unnatural, maybe it was psychological. Inductors would only dump the noise from the signal to ground with almost no loss.
My plan to further upgrade my UD7007 blu ray player, which we had some discussions some months ago in another thread, will be executed next week. Parts will be arriving next Monday.
I have followed your advice to use the LM6171 for IV, and have now selected AD8620 for LP filter.
The only thing differs from what we previously discussed is that while 10pF across the feedback resistor for the LM6171 should work well for the opamp, I think I will stick with the original schematic of using 1nF. I understand that we don't need that much capacitance for stability but the RC there is to provide a first order low pass function, without it, the attenuation of noise will be reduced substantially and the fillter will be reduced to 3rd order from 4th order.
I have followed your advice to use the LM6171 for IV, and have now selected AD8620 for LP filter.
The only thing differs from what we previously discussed is that while 10pF across the feedback resistor for the LM6171 should work well for the opamp, I think I will stick with the original schematic of using 1nF. I understand that we don't need that much capacitance for stability but the RC there is to provide a first order low pass function, without it, the attenuation of noise will be reduced substantially and the fillter will be reduced to 3rd order from 4th order.
Empirically the larger capacitors there sounded worse (reduced soundstage depth) to me. Have a play and see what you find for yourself. I don't have a cogent technical reason for why smaller sounds better yet, but I'm hopeful 🙂
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