Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 Khz - Page 712

vodomore · 19th February 2018, 11:42 AM

Quote:

Originally Posted by soekris

6K04 1% 0603. Your dam1021 is a rev1.

Thank you Soekris!

tvicol · 20th February 2018, 07:16 AM

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

androa76 · 20th February 2018, 08:18 AM

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.

tvicol · 20th February 2018, 08:25 AM

Quote:

Originally Posted by androa76

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

soekris · 20th February 2018, 10:13 AM

Quote:

Originally Posted by tvicol

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....

tvicol · 20th February 2018, 10:19 AM

Now make sense. Thank you, Soren !

Regards,
Tibi

tvicol · 20th February 2018, 10:30 AM

To conclude. This is V4 output.

Regards,
Tibi

TNT · 20th February 2018, 11:30 AM

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....

//

tvicol · 20th February 2018, 11:39 AM

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

vodomore · 21st February 2018, 12:56 AM

Quote:

Originally Posted by soekris

....

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!

20th February 2018, 10:19 AM	#7116
tvicol diyAudio Member Join Date: Jan 2005 Location: Bucharest	Now make sense. Thank you, Soren ! Regards, Tibi __________________ https://evotronix.eu

20th February 2018, 11:30 AM	#7118
TNT diyAudio Member Join Date: Apr 2003 Location: Sweden	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.... // __________________ More distortion to the people! Timing . . . . is paramount.

20th February 2018, 11:39 AM	#7119
tvicol diyAudio Member Join Date: Jan 2005 Location: Bucharest	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 __________________ https://evotronix.eu

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20th February 2018, 08:18 AM	#7113
androa76 diyAudio Member Join Date: Mar 2007 Location: Maribor	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.