ProtoDAC TDA1387 X8 project

[hifinet]

I am having some second thoughts about the 100R I/V resistor plus a preamp gain stage. Yes, there is more bass and better detail, but at the expense of some damage to the openness and soundstage. In general, if you can get by without a preamp gain stage, that is preferred. If you have the extra gain to use the 100R I/V resistor, you probably would be better off eliminating your preamp entirely and use a high quality pot, stepped attenuator, etc. and use the 420R I/V resistor. A voltage gain stage will always add some coloration.

With this DAC chip, there is not that much to improve regarding THD, which is about 0.01% with 420R and 0.006% with 100R.

The solution might be to add a buffer for better impedence matching. Talked about it months ago. A buffer tends not to color the sound.

I think that I should try four modules with 100R I/V. Distortion will still be at the 0.01% level, but output impedence will be lower. It will also keep the DAC relatively simple. Noise will be reduced. 3dB for each doubling. @eculcea in this post #681 used two modules stacked with 200R I/V resistors (2200uF times two decoupling caps) and found "a better and more detailed sound at the lower frequencies." That would be the expected result with better impedence matching.

[DRONE7]

Today I booted the "official" Protodac build that has been idle for some time. (Iv'e been using other Protodac builds ) and strangely it sounded like the audio was coming from 'underwater' !  indistinct and 'phasey' with some noise.

I swapped out the board for another and all good now but the original is definitely gone-burger.
This is the only board where I soldered the module (has been working fine for over 1 year) and I will replace it with pins and new module.

[thomaschan]

Does anyone know how to add an external Master Clock to the PI 4 and ProtoDAC? Frequency? 3.3V or 5V?

[hifinet]

Innomaker HiFi DAC HAT FOR RASPBERRY PI 4 3 B+ PI ZERO

Long thread . Ian Fifo project 

[hifinet]

Finally tried the Rhopoint 8G16D Econistor 100R I/V resistor. Green and shaped like a rocket with a cone on one end. Supplied by Farnell Ireland via Newark USA. Farnell stocks only 14 values of the Rhopoint. Same preamp setup as the 100R TX2575. These resistors sound very nice. Deeper soundstage, but it is not as large as the TX2575. I thought some of the diminished depth of soundstage with the TX2575 100R was due to the preamp. Some of it seems to be due to the resistor itself. These are not quite half the price of the TX2575. I think I still prefer the TX2575, but the decision is getting more difficult.

The next one will be the Rhopoint 5G10D in 350R. No preamp, back to the single module ProtoDAC.

Update: It may be that the preamp is breaking in. It is the MOFI Accuphase C3850 clone. I have fixed 100K load resistors on the input. PGA2310 volume control at the output. DC offset is <1mV. It is a NE5532-diamond buffer-VAS-diamond buffer with global feedback within the feedback loop of the NE5532. All transistors BC550/560. It could be a headphone amp. It sounds extremely good with the Rhopoint. I will need to go back and listen to the TX2575 again.

[neric34]

hi, i made a protodac and I try to enable it on Manjaro arm but it does not appear in the audio outputs. how to make it work with Manjaro?

I m very enthusiastic with the sound of the protodac!

[hifinet]

No support for Manjaro here. There is no enabling ProtoDAC. It does not identify itself to the OS. If you can have Manjaro output I2S to the GPIO, ProtoDAC will work. Set it up for a generic I2S DAC.

[neric34]

sorry for the wrong post...but if someone need, I ve found :



sudo nano /boot/config.txt

dtparam=audio=off
dtoverlay=rpi-dac

sudo reboot

sudo nano /etc/asound.conf

pcm.!default {
type hw
card 0
}

ctl.!default {
type hw
card 0
}

sudo reboot