grounds in TDA1543 based dac

sparkle · 11th January 2004, 10:18 PM

Dear all!

Is there any sonic difference if you group
analogue grounds to analogue and digital
grounds to digital or if You connect them
together in one ground (o.k. I know that they
are (at the end) all connected together but
is there any sonic benefit of grouping grounds and then
connecting them together beside that You avoide
hum that way and that sort of things).
Could anyone explaine this to me please?

p.s. I have made my prototip dac around one ground
and have no problems with hum or anythinf unusual.
So I am wondering am I missing something in
sound of it.......

sparkle · 12th January 2004, 08:15 PM

anybody

ZERS · 13th January 2004, 02:34 PM

Hi,

The digital grounds and analogs one are qite different and the noise isn't the same.

Pratically, both must be shared on PCBs and the connexions between us must be done through a 100k (or more) resistor.

The "signal" within each of grounds has not the same nature and it's clear that the noise in the analog ground disturbs the digital part.

In terms of sounds, the sounds looks less clear.

Hope is help

sparkle · 13th January 2004, 07:43 PM

We'll try it and let You now- when I take a look on my pcb I have my grounds separated but connected with one tiny path with each other. I will cut that path and try with 100k in there to connect them
thanks
daniel

sparkle · 13th January 2004, 08:58 PM

Dear ZERS

I have separated all my digital grounds from analogue ones with 100k as U suggested. I could hear, in my speakers, that my dac was oscilating .
Turned down to 10k - oscilations were less to hear. Disconected the resistor- no oscilations. I will leave it separated with no resistor only connected with a tiny wire.
Best regards
daniel

ZERS · 13th January 2004, 10:39 PM

this is quite surprising.

It must depe,d on the way the PCB is built.

Isprièavam se!

guido · 15th January 2004, 11:02 AM

General rule for DAC/ADC grounds:

Connect analog and digital gndplanes at the DAC/ADC, if not possible (more than one DAC, other reasons):

Connect analog and digital gnd pins to ANALOG ground.

Connect analog and digital together at the DAC/ADC as short track as possible. Any restistance between analog/digital would generate a voltage difference between analog and digital gnd pin.

Any voltage between those pins is then also present on the output!

Got this from an analog devices application note, together with the technical background. Not shure this applies for all DAC's/ADC's, check the datasheet.

E.g. this is stated in the BB PCM63, page eight

http://focus.ti.com/lit/ds/symlink/pcm63.pdf

So NOT the way elektuur did it in their first DAC.....

GuidoB

sparkle · 15th January 2004, 07:54 PM

Thanks- I was a little suspicious about that 100k resistor as ZERS and I have comented via mail but what a heck I give it a try to see what happens. It was not very nice to hear- as expected.....

daniel

11th January 2004, 10:18 PM	#1
sparkle diyAudio Member Join Date: Oct 2003 Location: middle of nowhere...	grounds in TDA1543 based dac Dear all! Is there any sonic difference if you group analogue grounds to analogue and digital grounds to digital or if You connect them together in one ground (o.k. I know that they are (at the end) all connected together but is there any sonic benefit of grouping grounds and then connecting them together beside that You avoide hum that way and that sort of things). Could anyone explaine this to me please? p.s. I have made my prototip dac around one ground and have no problems with hum or anythinf unusual. So I am wondering am I missing something in sound of it.......

15th January 2004, 11:02 AM	#7
guido diyAudio Member Join Date: Mar 2002 Location: diepe zuiden	General rule for DAC/ADC grounds: Connect analog and digital gndplanes at the DAC/ADC, if not possible (more than one DAC, other reasons): Connect analog and digital gnd pins to ANALOG ground. Connect analog and digital together at the DAC/ADC as short track as possible. Any restistance between analog/digital would generate a voltage difference between analog and digital gnd pin. Any voltage between those pins is then also present on the output! Got this from an analog devices application note, together with the technical background. Not shure this applies for all DAC's/ADC's, check the datasheet. E.g. this is stated in the BB PCM63, page eight http://focus.ti.com/lit/ds/symlink/pcm63.pdf So NOT the way elektuur did it in their first DAC..... GuidoB __________________ GuidoB

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12th January 2004, 08:15 PM	#2
sparkle diyAudio Member Join Date: Oct 2003 Location: middle of nowhere...	anybody

13th January 2004, 02:34 PM	#3
ZERS diyAudio Member Join Date: Jan 2004 Location: LYON	Hi, The digital grounds and analogs one are qite different and the noise isn't the same. Pratically, both must be shared on PCBs and the connexions between us must be done through a 100k (or more) resistor. The "signal" within each of grounds has not the same nature and it's clear that the noise in the analog ground disturbs the digital part. In terms of sounds, the sounds looks less clear. Hope is help

13th January 2004, 07:43 PM	#4
sparkle diyAudio Member Join Date: Oct 2003 Location: middle of nowhere...	We'll try it and let You now- when I take a look on my pcb I have my grounds separated but connected with one tiny path with each other. I will cut that path and try with 100k in there to connect them thanks daniel

13th January 2004, 08:58 PM	#5
sparkle diyAudio Member Join Date: Oct 2003 Location: middle of nowhere...	Dear ZERS I have separated all my digital grounds from analogue ones with 100k as U suggested. I could hear, in my speakers, that my dac was oscilating . Turned down to 10k - oscilations were less to hear. Disconected the resistor- no oscilations. I will leave it separated with no resistor only connected with a tiny wire. Best regards daniel

13th January 2004, 10:39 PM	#6
ZERS diyAudio Member Join Date: Jan 2004 Location: LYON	this is quite surprising. It must depe,d on the way the PCB is built. Isprièavam se!

15th January 2004, 07:54 PM	#8
sparkle diyAudio Member Join Date: Oct 2003 Location: middle of nowhere...	Thanks- I was a little suspicious about that 100k resistor as ZERS and I have comented via mail but what a heck I give it a try to see what happens. It was not very nice to hear- as expected..... daniel