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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
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Old 19th February 2018, 11:42 AM   #7111
vodomore is offline vodomore  Canada
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Quote:
Originally Posted by soekris View Post
6K04 1% 0603. Your dam1021 is a rev1.
Thank you Soekris!
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Old 20th February 2018, 07:16 AM   #7112
tvicol is offline tvicol  Romania
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Default Asimetric output !!!

I have extracted schematic for V4 output.
As far I can see it has asymmetric gain, 1,5 for positive raw and 1 for negative.
While it is possible to drive a balanced line with an unbalanced signal, I suggest to change negative feedback resistor on inverted opamp to 1,86K. This will increase gain for negative rail to 1,5, therefore balanced signal will be symmetric.

Regards,
Tibi
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Old 20th February 2018, 08:18 AM   #7113
androa76 is offline androa76  Slovenia
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Hi
it is not asymetric... gain on inverted input is different formula as noniverted
Instead 619 (1,2pin) use bigger resistor in the same relation 1,24 kohm ( 6,7 PIN) on other output. But than your gain will be higher also on xlr output.
For my taste opa1602 (opa1622) is tooo soft sounded opamp...Soekris is soft and relaxed from default. Therefore for more dynamic sound i will use another opamp. Or different output stage. If you need just rca than the job is easier.
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Old 20th February 2018, 08:25 AM   #7114
tvicol is offline tvicol  Romania
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by androa76 View Post
Hi
it is not asymetric... gain on inverted input is different formula as noniverted
...
I know very well this and is still asymmetric.

Regards,
Tibi
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Old 20th February 2018, 10:13 AM   #7115
soekris is offline soekris  Denmark
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Quote:
Originally Posted by tvicol View Post
I have extracted schematic for V4 output.
As far I can see it has asymmetric gain, 1,5 for positive raw and 1 for negative.
While it is possible to drive a balanced line with an unbalanced signal, I suggest to change negative feedback resistor on inverted opamp to 1,86K. This will increase gain for negative rail to 1,5, therefore balanced signal will be symmetric.

Regards,
Tibi
Your schematic is wrong, the input to the inverting opamp is taken from the output of the non inverting opamp, so the balanced output is symmetric....
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Old 20th February 2018, 10:19 AM   #7116
tvicol is offline tvicol  Romania
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
Now make sense. Thank you, Soren !

Regards,
Tibi
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Old 20th February 2018, 10:30 AM   #7117
tvicol is offline tvicol  Romania
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
To conclude. This is V4 output.

Regards,
Tibi
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Old 20th February 2018, 11:30 AM   #7118
TNT is offline TNT  Sweden
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It's asymmetric in an other sense then as the distorsion of the neg side is the result of 2 OP amps but the pos is only from one?

And some delay....

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Old 20th February 2018, 11:39 AM   #7119
tvicol is offline tvicol  Romania
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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz
We can arguably debate this in all ways possible.
I'm not interested in balanced output, so from my point of view, schematic has the advantage that inverted opamp can be used as buffer for a "heavier" load.
Now back to mods.

Regards,
Tibi
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Old 21st February 2018, 12:56 AM   #7120
vodomore is offline vodomore  Canada
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Originally Posted by soekris View Post
....

Hi Soekris,



I have dam1021 rev1, and I'm trying to do the 16 caps mod.
Soekris DAC: Modding VRef | H i F i D U I N O


I found those holes in the PCB are very tiny, and around half of those holes were covered by PCB paint I guess and can't even put a single copper thread through it.


So, my question is, seems those holes are not connected to other parts, right? Can I expand those holes using a tiny drill bit?


Thanks!
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