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PecanPi - Next Generation Raspberry Pi DAC and Streamer

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Got it. Good luck with a new product.

One more thing, from your personal experience - is there could be any issues (ground loop/hiss/noise) if I connect unbalanced output of a DAC (RCA) with balanced input of Active speakers (XLR) or I shouldn't worry about it ?
 
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orchardaudio

orchardaudio

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Thread Starter #223
is there could be any issues (ground loop/hiss/noise) if I connect unbalanced output of a DAC (RCA) with balanced input of Active speakers (XLR) or I shouldn't worry about it ?
It is certainly doable, there is potential for issues depending on how the equipment is grounded internally.
 

rippie

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please note that i am a audio newbie; and evaluating if the pecanpi is something i can use in my setup.

I may/want to add a display+touchscreen to the RPi and set volume through the display (i dont like pots, its soooo 1980 :) ).
In my naivety I am thinking that to achieve best audio quality you want to attenuate the signal in or after the SRC4193, so to keep the best signal to noise ratio. you do want to avoid setting volume in the RPi.

-how do you program from the raspberry the SRC4193 digital volume attenuation?
-how is your potentiometer doing the volume attenuation?

could you (anybody) shed some light on this or best practices how volume control oughtta be and also regarding how it works with the pecanpi+RPi?
 
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orchardaudio

orchardaudio

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Thread Starter #225
please note that i am a audio newbie; and evaluating if the pecanpi is something i can use in my setup.

I may/want to add a display+touchscreen to the RPi and set volume through the display (i dont like pots, its soooo 1980 :) ).
In my naivety I am thinking that to achieve best audio quality you want to attenuate the signal in or after the SRC4193, so to keep the best signal to noise ratio. you do want to avoid setting volume in the RPi.

-how do you program from the raspberry the SRC4193 digital volume attenuation?
-how is your potentiometer doing the volume attenuation?

could you (anybody) shed some light on this or best practices how volume control oughtta be and also regarding how it works with the pecanpi+RPi?
There is not a way for the Rpi to control the SRC4193, the only way to do that is through the POT. The audio signal does not go through the pot, the pot only sets the attenuation level of the SCR4193.

The SCR4193 and the Rpi software volume control both functions in the digital domain so results will be very similar.
 

rippie

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the RPi could software control the the SRC4193 over the spi bus (but i assume its not connected by your answer).

i was just wondering if the digital domain in the RPi is the same digital domain as in the SRC4193 where the attenuation takes place. if the digital domains are different, the signal to noise ratio would be influenced right?

i'll take a look in the datasheet where/how the 4193 attenuation is done
 
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orchardaudio

orchardaudio

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Thread Starter #227
the RPi could software control the the SRC4193 over the spi bus (but i assume its not connected by your answer).

i was just wondering if the digital domain in the RPi is the same digital domain as in the SRC4193 where the attenuation takes place. if the digital domains are different, the signal to noise ratio would be influenced right?

i'll take a look in the datasheet where/how the 4193 attenuation is done
The spi bus is not connected to the Rpi. This is because as far as I can tell, there is no Linux driver available for the Rpi.

I don't know how the volume control is implemented in the Rpi software, and it may vary depending on the sw you pick.
 

rippie

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you are correct that there is no driver available, i have been searching. However i think i can manage to create a spi driver for it (i will build the whole OS for my hifi build).
it (=spi driver) only makes sense though if it would have a quality benefit, which i dont have the detailed knowledge for.

What i am guessing is that the RPi software will just lower amplitude for samples/data on the i2s. while the SRC4193 would attenuate in the last stages of the chip. if this is the case you would start noticing this in low volume settings. (see datasheet figures 1-38). if you attenuate at the end, you also attenuate the noisefloor, that would not happen if attenuation is done from RPi. is my preliminary thinking.
 
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