Thank you.
Would a good power bank be considered safe for powering the Pi through GPIO?
Alex,
See my post #106 in this thread here: http://www.diyaudio.com/forums/digi...ry-dac-pro-hw-mods-anybody-3.html#post4626613
Note that there you need to make sure to feed 3.3v to both the DAC digital V input and to the clocks, I had to add a jumper to make that happen. Details in the fourth picture I posted.
Greg in Mississippi
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Hi Greg,
I saw that post but didn't know you had powered 3.3V external already.
I can see the traces which you did cut, and the jumper-wire.
In my case, I cut off the header pins 1 and 17 from RPI which are 3.3V.
Those 2 pins are shorted on DAC+Pro (I measured this), so if I feed Pin 1 on DAC+Pro with 3.3V this also should power the clocks, or am I mistaken?
Thanks for your help!
Btw, I'm using it for I2S signal only, not using the dac part.
Regards,
Alex
I saw that post but didn't know you had powered 3.3V external already.
I can see the traces which you did cut, and the jumper-wire.
In my case, I cut off the header pins 1 and 17 from RPI which are 3.3V.
Those 2 pins are shorted on DAC+Pro (I measured this), so if I feed Pin 1 on DAC+Pro with 3.3V this also should power the clocks, or am I mistaken?
Thanks for your help!
Btw, I'm using it for I2S signal only, not using the dac part.
Regards,
Alex
Yes, Pin1 and Pin17 both have 3.275V and it's within spec of ExpressO tcxo's
which is +/- 5% of 3.3V
I will try this, it could be that the very tiny traces on DAC+Pro induce a resistance which results in a lower voltage on TCXO's.
Since I didn't cut traces on DAC+ Pro but cut pins 1 and 17 from RPI itself,
and powered pin1 on DAC+ Pro (which is shorted with pin 17) this logically should work.
But since my 3.3V is lower, 3.275V, it could be that resistance of traces on
DAC+ Pro renders the voltage out of the 3.3V +/- 5% spec of ExpresssO tcxo's
which is 3.135V.
I will try powering them directly and report back.
I was wondering the other day if just cutting the PI 3.3V pins
and than just using the analog regulator 3.3V with a bridge for
also powering the digital side of the DAC and the clocks would make sense.
Perhaps there is a chance that this is better than using the PI 3.3V.
Just one quality 5V would be required for the entire DAC.
Obviously this will not be as good as having separate supplies/regs for everything.
It can be established quite easily though -- if the reg can supply the required current !?!?
and than just using the analog regulator 3.3V with a bridge for
also powering the digital side of the DAC and the clocks would make sense.
Perhaps there is a chance that this is better than using the PI 3.3V.
Just one quality 5V would be required for the entire DAC.
Obviously this will not be as good as having separate supplies/regs for everything.
It can be established quite easily though -- if the reg can supply the required current !?!?
I finally managed to feed DAC+Pro external with 3.3V.
Indeed the bridge wire from pin 17 to 3.3V next to TCXO did the trick, soldered it
to the cap, just as Greg did in post 106. This works!
It gained in SQ again, very happy with it.
BUT:
It's sad they use ExpressO TCXO's which we can not exchange with better ones,
at least, not that easy.
Since the ExpressO TCXO's are switched on and off from software (driver), we can't
use normal TCXO's like the NDK NZ2520SD which I am very fond of.
ExpressO FXO-HC73 which are used for DAC+Pro have very mediocre specs.
They have not so good Phase noise performance
ExpressO FXO-HC73 NDK NZ2520SD
1Hz ??? -85 dB
10Hz -65 dB -113 dB
100Hz -100 dB -140 dB
1kHz -120 dB -153 dB
10kHz -120 dB -157 dB
100kHz -125 dB -158 dB
This is why I prefer NDK NZ2520SD.
Maybe I will create a double relais board which will take use of the ON/OFF signal
to trigger the relais to use. In that case I could use the NDK's.
Indeed the bridge wire from pin 17 to 3.3V next to TCXO did the trick, soldered it
to the cap, just as Greg did in post 106. This works!
It gained in SQ again, very happy with it.
BUT:
It's sad they use ExpressO TCXO's which we can not exchange with better ones,
at least, not that easy.
Since the ExpressO TCXO's are switched on and off from software (driver), we can't
use normal TCXO's like the NDK NZ2520SD which I am very fond of.
ExpressO FXO-HC73 which are used for DAC+Pro have very mediocre specs.
They have not so good Phase noise performance
ExpressO FXO-HC73 NDK NZ2520SD
1Hz ??? -85 dB
10Hz -65 dB -113 dB
100Hz -100 dB -140 dB
1kHz -120 dB -153 dB
10kHz -120 dB -157 dB
100kHz -125 dB -158 dB
This is why I prefer NDK NZ2520SD.
Maybe I will create a double relais board which will take use of the ON/OFF signal
to trigger the relais to use. In that case I could use the NDK's.
Yes theoretically the NDK series have better speqs , special in phase noise area ,
practical the expresso series ... listed beter , more black background , faster and relaxing micro-dynamics , imho its the second better choice after the King series of Crystek ( but cost almost one HAT board ... )
and some more .. the separate voltage regulator for oscillator its really GOOD idea !
practical the expresso series ... listed beter , more black background , faster and relaxing micro-dynamics , imho its the second better choice after the King series of Crystek ( but cost almost one HAT board ... )
and some more .. the separate voltage regulator for oscillator its really GOOD idea !
I do not understand this statement, can you explain?
The Dac+ uses the enable/disable pin to activate the required clock, why can't you substitute your preferred one?
I am surprised! Even the NDK NZ2520SD has this feature! How could I not notice this.....
I will try difference between Expresso and NDK NZ2520SD (I am absolutely not convinced Expresso would sound better) so I will try this!!
Thanks for pointing me in the right direction
