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Old 19th May 2019, 12:07 PM   #2091
Zoran is offline Zoran  Serbia
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Join Date: Jan 2004
Location: Belgrade
Originally Posted by Radian View Post
Hi Zoran,
would you mind drawing a simple sketch of your balanced Filter?

Greets, Klaus
Hi Klaus
I used settings from picture butt, hat is for SE. And with 1/2 value of L added in booth lines for balanced. I use butt, but You can use Bessel. Try to get values close to standard. Will be useful to know the internal resistance of the source. For the termination I suggest to measure. IfYou are win user You have great soft called ELSIE for designing filters. I find this online calc tool very helpful
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Old 20th May 2019, 06:51 AM   #2092
xx3stksm is offline xx3stksm  Japan
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Join Date: Jun 2017
Location: Hokkaido(north area)
The Best DAC is no DAC
Originally Posted by mmerrill99 View Post
What are your best guesses as to why DSD is less prone to this - less bursty underlying processing?
Artifact caused by tough input signal strongly depends on PCB quality and DAC technology. The ideal DAC doesn't generate artifact even if the input is real music, which has significant amplitude change in many frequencies, where ordinary one fails to output the same waveform as the input. The 1st pic is pcm1794 in PCM mode. The 2nd is pcm1792 in PCM mode. The difference is probably the PCB structure. Both are 6bit DSM. The 3rd harmonics around 1.5kHz is the consequence of accuracy error in 6bit DAC inside the chip. It's not easy for the chip to keep high accuracy to prevent 3rd order distortion even if it is well-designed.

The 3rd pic is pcm1792 in DSD128. Pcm1792 has dedicated converter from DSD to analog(67-taps analog FIR). It's superior to PCM mode because no accuracy error exists in DSD(1bit DSM) though some 3rd order still remains. I don't know where 879.89Hz(2x440Hz) comes from, maybe internal distortion inside the chip or external I/V converter. Anyway, DSD mode is usually superior to PCM mode in modern chips, ESS too. I guess pcm1792 can't make the best of DSD mode because of its architecture. Single low supply voltage forces pcm1792 to have a current output and a user to design distortion-free I/V stage. Recent high output current to ensure high SNR makes the design far difficult. I would recommend the best I/V is no I/V. No I/V topology, as well as no DAC, is the ultimate. Discrete no DAC topologies like Chord or PS audio, i.e., FPGA and discrete transistors.

The 4th pic is current my DAC, where FPGA and DAC chip(AD9717) are used for 2bit DSM with 4-taps analog FIR. It's not ideal because the best is FPGA and transistors in DSD(1bit DSM) to achieve low noise floor fluctuation. I'm now under construction what is the best conversion from digital to analog without I/V by transistors. FPGA has already finished successfully because the digital domain is easier to design than the analog domain. Once you have fixed it, you have no problem forever. Emitter coupled circuit like ECL with 16-taps, is a major candidate now.
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