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Signalyst DSC1
Signalyst DSC1
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Old 27th November 2014, 10:40 PM   #31
LeonBernieniv is offline LeonBernieniv  China
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Quote:
Originally Posted by Signalyst View Post
In this picture there is still missing PSU feed for IC1/IC2 that is normally coming from the Amanero +3.3V output...

I tried to make a clarifying picture

(the DSC1 PSU board has suitable 3.3V output for the purpose)

Yes, I understand you point out. Perhaps the power circuit and the signal circuit should be consider in next layout. Expect Dsc-2.0.
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Old 27th November 2014, 11:00 PM   #32
Signalyst is offline Signalyst  Finland
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Quote:
Originally Posted by LeonBernieniv View Post
Yes, I understand you point out. Perhaps the power circuit and the signal circuit should be consider in next layout. Expect Dsc-2.0.
I think I can add separate power connector for the 3.3V, but for the signals I prefer to have a direct plug-on daughter card for the interface instead of wires... I was thinking to add place for JLSounds OEM or I2SoverUSB board too. Or maybe just two PCB variants.
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Old 27th November 2014, 11:19 PM   #33
LeonBernieniv is offline LeonBernieniv  China
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Any improvement on dem like you said in blog?
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Old 27th November 2014, 11:37 PM   #34
LeonBernieniv is offline LeonBernieniv  China
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And ad844 for IV looks overwhelmed, lm6181 is the good one in use.
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Old 29th November 2014, 12:39 AM   #35
Signalyst is offline Signalyst  Finland
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Quote:
Originally Posted by LeonBernieniv View Post
And ad844 for IV looks overwhelmed, lm6181 is the good one in use.
It should be quite easy to experiment with different ones. LME49713 has also been proposed and I will probably try it out (TO-99 version can be fitted).

But I kind of regret not sticking to AD797 for the filter stage, I've had very good results with it in previous designs. So mayble I'll go to single ones in the next version for more flexibility. I also realized later that duals used this way will limit the filter performance somewhat. AD797 needs a bit more complex and different surrounding design.

I'm not sure if I should also switch to SOIC-8 versions at the same time, but that makes socketed approach harder for those who would like to easily swap & compare. Opinions on this?
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Old 29th November 2014, 02:15 AM   #36
LeonBernieniv is offline LeonBernieniv  China
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49713 is suitable certainly but still prone to clipping in case of a large current swing. Preferably Rf should be less than 1K.
About filter, GBWP and Ib are two important considerations.
You decide.
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Old 29th November 2014, 11:42 AM   #37
Terry Demol is offline Terry Demol  Australia
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Quote:
Originally Posted by Signalyst View Post
It should be quite easy to experiment with different ones. LME49713 has also been proposed and I will probably try it out (TO-99 version can be fitted).

But I kind of regret not sticking to AD797 for the filter stage, I've had very good results with it in previous designs. So mayble I'll go to single ones in the next version for more flexibility. I also realized later that duals used this way will limit the filter performance somewhat. AD797 needs a bit more complex and different surrounding design.

I'm not sure if I should also switch to SOIC-8 versions at the same time, but that makes socketed approach harder for those who would like to easily swap & compare. Opinions on this?
SOIC-8 to DIL8 mini pcb adaptors are an option and easily available.

797 has stability problems if not treated carefully. The real advantage of 797
is very low CM distortion so if your circuit has either inverting config and or
low source impedances you may get as good performance with other opa's.

Refer Samuel Groners opamp measurement paper.

Have you done any distortion measurements on this DAC. I am interested
where the linearity bottle necks are with this design. I am guessing with
DSD128 and higher it should measure very well.

T
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Old 1st December 2014, 08:45 PM   #38
Signalyst is offline Signalyst  Finland
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Originally Posted by zenelectro View Post
797 has stability problems if not treated carefully. The real advantage of 797 is very low CM distortion
I know, I've been using it for long time in various DACs. It has also good GBWP suitable for active filters even in MFB type setup.

Quote:
Have you done any distortion measurements on this DAC. I am interested
where the linearity bottle necks are with this design. I am guessing with
DSD128 and higher it should measure very well.
Yes, I have done some. These results are with the modifications I posted earlier:
Preliminary measurement results for the DSC1 DAC - Blogs - Computer Audiophile
More DSC1 measurement results - Blogs - Computer Audiophile

DSD256 is optimal rate for this as it is now.

I know how to improve this further. But I'll make a new board for those improvements. I'm quite happy with the result for first board iteration. Especially how it sounds... Full design in one month on my "free" time.
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Old 25th December 2014, 09:13 PM   #39
mcluxun is offline mcluxun  United States
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Click the image to open in full size.
Amanero blows my XMOS out of water.
Waiting on my usb b to a panel mount and right angle cable to finish it.
love the sound so far.
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Old 26th December 2014, 12:57 AM   #40
mcluxun is offline mcluxun  United States
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Also I went back to check on the source of noise.
It turns out my 5V supply is very malfunctioning (30-50mV AC can you believe that?).
I swapped in a SSLV. Problem solved.
Click the image to open in full size.
 

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