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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

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K

kumori

Member
Joined 2011
kenneth_obee said:
I connect AES SPDIF to two dam dacs in parallel running balance mode. I use SPDIF1+ and SPDIF1- and GND as connection. It can lock the signal in normal case, however, when I switch on/off the lights in home such as the lamp in toilet or kitchen, it will loss signal and muted for 1/2 second until it can relock again.
Does anyone know what would be the cause and how to solve it? Thanks.
Click to expand...

This is maybe an AC bounce due to different potentials in different hifi boxes. (probably Computer and DAC). Try to connect all the grounds together (bridge the isolation), so that all boxes (and sections) run on the same reference potential. See if the problem still exists then.
 
K

kenneth_obee

Member
Joined 2010
kumori said:
This is maybe an AC bounce due to different potentials in different hifi boxes. (probably Computer and DAC). Try to connect all the grounds together (bridge the isolation), so that all boxes (and sections) run on the same reference potential. See if the problem still exists then.
Click to expand...
Thanks for your reply.

The DAC is connected with CD player thru SPDIF (AES) connection. How can I make sure the grounds are connected?
 
N

normundss

Member
Joined 2009
kenneth_obee said:
I connect AES SPDIF to two dam dacs in parallel running balance mode. I use SPDIF1+ and SPDIF1- and GND as connection. It can lock the signal in normal case, however, when I switch on/off the lights in home such as the lamp in toilet or kitchen, it will loss signal and muted for 1/2 second until it can relock again.
Does anyone know what would be the cause and how to solve it? Thanks.
Click to expand...

I guess you are trying to run SPDIF over balanced XLR connection, not actual AES/EBU signaling? AES3 uses higher voltages than SPDIF and could potentially damage the FPGA chip unless you use an appropriate transformer or other level matching circuit.

Do you use an isolation transformer on SPDIF input?
Have you biased the SPDIF inputs with 1.2V DC?
Does the problem happen with only one dac connected?
 
K

kenneth_obee

Member
Joined 2010
normundss said:
I guess you are trying to run SPDIF over balanced XLR connection, not actual AES/EBU signaling? AES3 uses higher voltages than SPDIF and could potentially damage the FPGA chip unless you use an appropriate transformer or other level matching circuit.
Click to expand...
Yes, it is just SPDIF over balance XLR connection.

normundss said:
Do you use an isolation transformer on SPDIF input?
Click to expand...
No I don't, just connect the + of XLR to SPDIF1+, - of XLR to SPDIF1-, GND of XLR to GND of dam, parallel three wires to two dam cards (for bal-left and bal-right)

normundss said:
Have you biased the SPDIF inputs with 1.2V DC?
Click to expand...
No

normundss said:
Does the problem happen with only one dac connected?
Click to expand...
Never tried, as my friend only get one source (CDP) one digital output(SPDIF over XLR). I tried the Amanero at my home and there was no problem.
 
S

soekris

Member
Joined 2009
soekris.dk
Paid Member
kenneth_obee said:
Yes, it is just SPDIF over balance XLR connection.

No I don't, just connect the + of XLR to SPDIF1+, - of XLR to SPDIF1-, GND of XLR to GND of dam, parallel three wires to two dam cards (for bal-left and bal-right)

No

Never tried, as my friend only get one source (CDP) one digital output(SPDIF over XLR). I tried the Amanero at my home and there was no problem.
Click to expand...

Shouldn't really work at all, trafo is needed and spdif- need to be biased. You also need to limit maximum voltage input as real AES can overload the input, use a voltage divider.
 
S

soekris

Member
Joined 2009
soekris.dk
Paid Member
shacker said:
I have a new issue on 1.04 firmware. My DAC won't automatically switch sources between SPDIF and USB(I2S) as it was on 0.99. When both SPDIF and USB signals are available and DAC is playing from USB, when I disconnect USB cable it won’t switch to SPDIF. Power cycle is required. Then it’s playing from SPDIF. I’m connecting USB cable, start playing something by USB, then turn off SPDIF source and again – it won’t switch to USB without power cycle. I don't have source selector connected, only auto mode.

Could somebody confirm this?
Click to expand...

Yes, found the bug, version 1.05 will be out soon.
 
S

spikestabber

Member
Joined 2015
Hi Søren quick question, what it is purpose of the 10R resistors on the LME49724 output? If I am using the buffers solely for headphones are they really required?

Cheers.

From the datasheet; though it shouldn't apply to my application?

"Although the LME49724 can drive capacitive loads up to 100pF, cable loads exceeding 100pF can cause
instability. For such applications, series resistors are needed on the outputs before the capacitive load."
 
Last edited:
S

soekris

Member
Joined 2009
soekris.dk
Paid Member
spikestabber said:
Hi Søren quick question, what it is purpose of the 10R resistors on the LME49724 output? If I am using the buffers solely for headphones are they really required?

Cheers.

From the datasheet; though it shouldn't apply to my application?

"Although the LME49724 can drive capacitive loads up to 100pF, cable loads exceeding 100pF can cause
instability. For such applications, series resistors are needed on the outputs before the capacitive load."
Click to expand...

Don't your headphones have a cable ? Cables are capacitive loads....
 
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