ProtoDAC TDA1387 X8 project

[hifinet]

I'm ordering parts/PCBs for the two SMPS filters. One question I have regarding using the filters is their effect on the dynamic response of the SMPS. Instantaneous power delivery. Yes, the noise may be gone, but possibly at the expense of dynamic response. The ultracap supply has macho dynamic response, but it needs continuous charging. An issue of UC charging is that the current needs to be limited. I have read that the LT1963 (and others like LT3042) can survive UC charging. Some things in the planning stages.

[varunach]

@hifinet quick question- How does clocking/re-clocking work with ProtoDAC? Typically if you are using a re-clocker like FifoPi the DAC is better run in SYNC mode, for which there is a wire that connects between the reclocker and the DAC (Master clock MCLK terminals on both). But there is no such MCLK terminal on ProtoDAC. In that case is it running in asynchronous mode. Curious how it is getting the clock signal from Allo or Fifopi

[Tim Curtis]

@hifinet quick question- How does clocking/re-clocking work with ProtoDAC? Typically if you are using a re-clocker like FifoPi the DAC is better run in SYNC mode, for which there is a wire that connects between the reclocker and the DAC (Master clock MCLK terminals on both). But there is no such MCLK terminal on ProtoDAC. In that case is it running in asynchronous mode. Curious how it is getting the clock signal from Allo or Fifopi

The ProtoDAC simply receives data thats already been clocked upstream for example by Raspbery Pi itself or by a reclocker inbetween the Pi and the ProtoDAC. The data includes the clock signal and the DAC locks to that signal for its timing.

The IanCanada DAC boards are based on ESS 9028/38 chips and provide on-board re-clocking via a dedicated clock module. These boards by default can be used without a reclocker but if an IanCanada reclocker is used it provides an option to use its clock module instead of the DAC on-board module. This is done by removing the DAC on-board clock module and then connecting to the reclocker clock module via a coax cable.

There are some other subtleties in the ESS chip having to do with bypassing its integrated Jitter Eliminator (an Aschronous Sample Rate Converter or ASRC) which in effect is redundant to an external reclocker like the IanCanada FIFOPi. I think this is mentioned in one of the IanCanada documents.

[OnkelPH]

@hifinet quick question- How does clocking/re-clocking work with ProtoDAC? Typically if you are using a re-clocker like FifoPi the DAC is better run in SYNC mode, for which there is a wire that connects between the reclocker and the DAC (Master clock MCLK terminals on both). But there is no such MCLK terminal on ProtoDAC. In that case is it running in asynchronous mode. Curious how it is getting the clock signal from Allo or Fifopi

The ProtoDAC simply receives data thats already been clocked upstream for example by Raspbery Pi itself or by a reclocker inbetween the Pi and the ProtoDAC. The data includes the clock signal and the DAC locks to that signal for its timing.

The IanCanada DAC boards are based on ESS 9028/38 chips and provide on-board re-clocking via a dedicated clock module. These boards by default can be used without a reclocker but if an IanCanada reclocker is used it provides an option to use its clock module instead of the DAC on-board module. This is done by removing the DAC on-board clock module and then connecting to the reclocker clock module via a coax cable.

There are some other subtleties in the ESS chip having to do with bypassing its integrated Jitter Eliminator (an Aschronous Sample Rate Converter or ASRC) which in effect is redundant to an external reclocker like the IanCanada FIFOPi. I think this is mentioned in one of the IanCanada documents.

I’ve the latest fifopi Q7 ll, do I have to select an other HAT , than ProtoDAC in the system settings, to get it to work correctly?

[Tim Curtis]

For the Q7 select "ProtoDAC TDA1387 X8"

[hifinet]

Thanks for the great info, Tim.

The Allo Kali has status LEDs that indicate Full, Lock (blue) or Empty, the bitrate and the clock being used. Are there any status LEDs on the Q7 or MA?

Answering one of my own questions. Q7 II has output format LEDs: DSD or I2s. It also has output status LEDs : Empty and Lock
Power LED and Input LEDs for I2S, DSD or DoP.

The MA manual says to use a PCM5122 I2S device. Would the ProtoDAC TDA1387 X8 setting be used with the MA?

[Tim Curtis]

Thanks for the great info, Tim.

The Allo Kali has status LEDs that indicate Full, Lock (blue) or Empty, the bitrate and the clock being used. Are there any status LEDs on the Q7 or MA?

Answering one of my own questions. Q7 II has output format LEDs: DSD or I2s. It also has output status LEDs : Empty and Lock
Power LED and Input LEDs for I2S, DSD or DoP.

The MA manual says to use a PCM5122 I2S device. Would the ProtoDAC TDA1387 X8 setting be used with the MA?

As of moOde 8.3.7 you would select "ProtoDAC TDA1387 X8 (FifoPiMa)" which would load the hifiberry-dacplus driver which provides Master Mode support. For < version 8.3.7 choose "HiFiberry Dac+" or "HifiBerry DAC+ Pro" both of which load the hifiberry-dacplus driver.

[GoreMaker]

I'm REALLY interested in using this as a basis to make a base board for a Pi CM4 that includes an input DC/DC converter and screw terminals for the GPIO for simpler integration into really small custom-built music players. Are there any routing concerns for the traces that I should keep in mind to minimize induced noise?

[hifinet]

First, I am not the expert to answer your specific questions.

Some things that I have discovered. DC/DC converters are very noisy. Pre-DC/DC converter RFI filtering is an absolute necessity. Use SMPS filters and LDO linear regulators after DC/DC converters and before ProtoDAC, if you plan to power ProtoDAC that way. Allo used more than 30 LDOs and zero switching elements on board in their excellent USBridge Sig !! I am considering a LifePO4 battery supply for ProtoDAC. The quality of the ProtoDAC power supply is extremely important for sound quality. The PurePi 5V ultracap supply needs a snubber (2R7 and 1uF film or even larger) before supplying ProtoDAC. The noise to be concerned with is conducted noise in power and data connections (I2S). EMI/RFI to ProtoDAC is less of a concern.

[hifinet]

I have a bunch of Icepower 200AC modules (200W mono into 4 Ohms) that I plan to sell inexpensively. I am working out a good way to power them before selling them. The 200AC sound excellent (and they are tiny, 1mm wider than a HAT and 107mm long; and no heat) , but the problem has been dealing with the switching noise from the supplies. I am using a 2000W industrial PFC 48V SMPS (95% efficient) used in cell towers. Cheap, high capacity and it is CAN BUS programmable, so that was interesting and fun.

The 200AC also needs +12V and -12V for the front end. Started with a cheap DC-DC converter without RF filter. Bad. Too noisy. Much better with a Pre-RF filter. It still needs more noise reduction. Adding LDOs. The nice thing about SMPS is compact/light weight. I think it can work with adequate SMPS filtering. 

theslowdiyer built one with a linear power supply.