ProtoDAC TDA1387 X8 project

[Lolkapies]

And another photo of the working set.
This project: 
https://www.pcbway.com/project/shareproj...db17b.html
works without problems, I used a jumper on R8 to draw power from Kali. Without the jumper you can power independently.

[hifinet]

Than you for sharing your builds.

This PCB looks very nice. Excellent layout and dual layer ground planes with many vias. Not sure if it makes any difference in sound quality, but a very nice PCB. It also has some spots for film decoupling caps for the power supply. Multiple pads for the output coupling caps, but the maximum span is not as long. Sells as a complete kit from the UK. The price for the kit is quite high, considering the I/V resistors are not metal foil (which are by far the most expensive parts of ProtoDAC). Maybe he sells the PCB only.

[eculcea]

I am gathering the pieces for the ProtoDac.
I have a HifiBerry Digi 2Pro laying around and I was wondering if I could use this as a reclocker. I read somewhere it is possible but I didnt see a detailed description on how this could be done. IanCanada reclocker is of course much better but, I figured HifiBerry Digi 2Pro while not a great reclocker is still better than what you get from the RPI.

[hifinet]

I am gathering the pieces for the ProtoDac.
I have a HifiBerry Digi 2Pro laying aroung and I was wondering if I could use this as a reclocker. I read somewhere it is possible but I didnt see a detailed description on how this could be done. IanCanada reclocker is of course much better but, I figured HifiBerry Digi 2Pro while not a great reclocker is still better than what you get from the RPI.

I have no personal experience with the Digi2 Pro, but I think it might work as a reclocker for ProtoDAC. Assuming that the topside GPIO of Digi2 Pro carries reclocked I2S on pins 12, 35 and 40. If the Digi2 Pro works with Moode (although Digi2 Pro is not in the named I2S device list), and the topside GPIO carries I2S, it should work as a reclocker for ProtoDAC.

[Lolkapies]

I know the recommended range for C1 and C2 is 4.7 to 10uF. I want to try better quality capacitors, smaller values are cheaper. Can I use 1uF or less? How will it affect the sound? I have 200mV/47k ohms at the input to the amp.

[hifinet]

I know the recommended range for C1 and C2 is 4.7 to 10uF. I want to try better quality capacitors, smaller values are cheaper. Can I use 1uF or less? How will it affect the sound? I have 200mV/47k ohms at the input to the amp.

If your input impedence is 47k, you can go much lower. The C1 and C2 caps form a high pass filter with the input resistance. There is more info in post 429 . You can pick a corner frequency close to the desired cutoff (for example, 20 Hz), but undesirable phase shift is highest. With 1uF and 47k, the cutoff frequency is 3.386Hz and the phase shift at 20 Hz is 9.61 degrees. I have used 3.3uF with standard solid state 10k input impedence, and it sounds very good. I usually do this to get the size of the cap smaller (with the Jantzen Superior-Z, which is still quite large).

High pass filter calculator

[DRONE7]

If your input impedence is 47k, you can go much lower.

Yes, 47k is standard for many/most S/S pre-amplifier inputs and 10k for many power amplifier inputs and/or valve circuits.

2.2uF  will be fine into following 47k load and well worth experimenting using the calculators for lower.


https://www.redcrab-software.com/en/Calc...ass-filter

https://www.learningaboutelectronics.com...hp#answer1

[Lolkapies]

Thanks for the advice. 
Is it necessary to go below 2Hz or will a little below 20Hz be enough? My speakers operate between 35Hz and 20kHz and the amp operates between 20Hz and 20kHz.

[hifinet]

The reason to go below 20Hz is to limit phase shift in the audio band.

As stated in post 429, using a 1uF cap at 10k Ohm impedence, the corner frequency is 15.915Hz, but phase shift at 20Hz is 38.51 degrees (at 30Hz it is 27.95 degrees, at 50Hz it is 17.66 degrees). Just take these factors into consideration.

The main reason to choose a corner frequency much lower than 20 Hz is to limit phase shift in the audio band.

[Lolkapies]

What angle should be set for 20Hz? 45 degrees?