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USB to I2S 384Khz - DSD Converter

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s3tup

s3tup

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Joined 2004
s3t.it/audio/
^ What they said plus check the series resistor values on the board. For twisted pair they should be circa 70-90ohm (plus source resistance of the driver) to match the Ethernet's 100ohm impedance.
The better way is to use proper differential signaling techique - whether it's use of bare LVDS or transformer coupled (as used in Ethernet).
 
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merlin el mago

merlin el mago

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Joined 2009
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Hercules said:
It took me 15 mins to rewire them, as it's all solid core, need a tweezers to hold the wire, as the RJ45 socket is PCB type, quite hard to avoid short of wires.
Click to expand...

Have you seen your pcb & clock are broken?
 

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syklab

Member
Joined 2009
s3tup said:
^ What they said plus check the series resistor values on the board. For twisted pair they should be circa 70-90ohm (plus source resistance of the driver) to match the Ethernet's 100ohm impedance.
The better way is to use proper differential signaling techique - whether it's use of bare LVDS or transformer coupled (as used in Ethernet).
Click to expand...

Hi,
How do you turn the data, Bclk and Frame sync SE signal into differential signal?

Thanks
 
C

crobbins5421

Member
Joined 2007
I2S Grounding Questions

Please comment:

1. If I use a 3.3V to 5V I2S buffer, I don't physically attach those the ground wires to the signal wires do I? If not, where would the ground wires run?

2. On my DAC board there's only BCK, DATA, and FS. The nearest grounding point on the DAC board is 5 inches away.

Thanks
 
H

hochopeper

Member
Joined 2009
crobbins5421 said:
Please comment:

1. If I use a 3.3V to 5V I2S buffer, I don't physically attach those the ground wires to the signal wires do I? If not, where would the ground wires run?

2. On my DAC board there's only BCK, DATA, and FS. The nearest grounding point on the DAC board is 5 inches away.

Thanks
Click to expand...

I don't understand what you're suggesting in your 1st question.

For your 2nd question, if you must use that DAC, then the best alternative is to scrape some soldermask off and expose some of the copper from the ground plane.
 
C

crobbins5421

Member
Joined 2007
I use the TDA1541A chip in my DAC. It uses 5V logic.

To use the Amanero board, I need a 3.3V to 5V level shifter like this:

So...I just run the I2S sigal grounds to the power ground on the level shifter?

Also, shouldn't the signal wires be the same length as the ground wires?...
 

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s3tup

s3tup

Member
Joined 2004
s3t.it/audio/
syklab said:
Hi,
How do you turn the data, Bclk and Frame sync SE signal into differential signal?

Thanks
Click to expand...

Use the RS-485 or LVDS transmitter/receiver ICs...



For level shifting you could use TTL-compatible CMOS ICs such as HCT series.

Throw-in a reclocker near the DAC which will reclock data, BCLK, LRCLK lines with MCLK clock. Make the MCLK connection the best you can.

But TDA1541 doesn't require 5V level logic signaling - it's kinda weird as per HtP/ecdesign threads. Use these attenuators recalculated for 3v signaling and be happy, or use the 3v directly.
 
S

smanz

Member
Joined 2008
crobbins5421 said:
I use the TDA1541A chip in my DAC. It uses 5V logic.

To use the Amanero board, I need a 3.3V to 5V level shifter like this:

So...I just run the I2S sigal grounds to the power ground on the level shifter?

Also, shouldn't the signal wires be the same length as the ground wires?...
Click to expand...

I think a better solution is to use a digital isolator as the IL 175. Thus also break ground loops. You just have to connect VD1 to 3.3V (Amanero side) and VD2 to 5V (TDA1541 side)

All wires must be the same length.

Regards
 
qusp

qusp

Member
Joined 2009
smanz said:
I think a better solution is to use a digital isolator as the IL 175. Thus also break ground loops. You just have to connect VD1 to 3.3V (Amanero side) and VD2 to 5V (TDA1541 side)

All wires must be the same length.

Regards
Click to expand...

yes they should ideally, if its all being reclocked a bit of difference wont cause a big problem. I didnt mention it on the previous page as it seemed like I already had my work cut out getting a ground for each signal =) plus it sounded like there was a long cable afterwards, so 20mm probably wasnt a big deal in the greater scheme of things. ribbon cable is a good way to assure the same length though so I just suggested that.


more general stuff for the thread

when twisted pear suggest twisted pair can be used, they mean actual twisted pair cable, not home twisted silver wire, but 100ohms ethernet cabling, I favor Belden Cu in PTFE network cable, but yes HDMI is a better cable construction IMO.

I tell you what though, nothing beats not needing to drive a long cable to your dac in the first place.... just use an isolator and reclock locally at the dac if you can. people really shouldnt be treating this like a separate peripheral, its part of the dac, it should be as close to the dac as possible, you should not use one of these HDMI or teleporter things just to enable you to install it somewhere you have enough room for your shunt regs... the thing is tiny, you should have room for it in any dac, putting it in another case just so you can use a low noise power supply is walking *** backwards
 
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