Noise from HDMI port, Pi2, HiFiBerry DAC+ [SOLVED]

PeteB

Edit (6-6-2016): Time to put this to rest...

*****

I've had some issues with noise on the outputs of the DAC+. I was finally able to trace it to noise conducted over the HDMI port when the cable is connected. I would be grateful for any information or links on how to keep this from happening.

With the HDMI cable, I get around 80db in actual use, equivalent to 14-bit useful resolution. Without the cable I get close to the expected 100~110 db dynamic range. I would like to do better.

See below for some screen grabs from RMAA. I also have similar results from another tool called "Daquarta" I can post later.

The DAC+ results are very good, when tested with the HDMI cable unplugged, so I do not suspect a hardware problem.

In the pics, the white trace is a test with HDMI unplugged. The green trace shows the effects of the noise with HDMI connected. The graphs are on a logarithmic scale, so the difference does not look like much, but it is significant.

dunghnguyen

I am not fully aware what you have done on the analysis but it looks meaningful for the improvement (if any). For me, I just don't plug the HDMI haha... I love Rune with DAC+ a lot...its sounds are really nice

hondagx35

Hi Pete,

is this with a regular monitor or TV plugged in the HDMI?
I'm asking, because with my small TFTs (waveshare, ODROID) i can't measure any noise.

Frank

PeteB

@dungnguyen: I have recorded amazingly good results with the DAC+, when under ideal conditions, and when testing at 44.1K, 48K, 96K (I have nothing that will reliably measure above that). Unfortunately, there is this noise susceptibility, which can sometimes make the test results much worse.

@[deleted]: I do not own any small TFTs. In this test I used an LCD TV. Other tests with a new-ish Viewsonic HDMI LED monitor were similar. I believe the HDMI is conducting noise from other sources (note the peak at 60Hz - well, 50Hz in your case). The TV/monitor is only a small contributor to the noise. This can be shown by leaving the TV connected to power and to the HDMI port, and disconnecting or turning off everything else.

dunghnguyen

@[deleted]: thanks for your analysis as well as advice. For my ear, I cannot recognize any noise with or without hdmi port connected. Thanks God for that so that I can still listen DAC+ ...I luv it much ...play from Pi 2 signal out via USB to DAC SMSL M8 decoded perfectly.

rikardo1979

always use good quality cables

All this is comming from your cable as its like an long aerial

PeteB

rikardo1979 wrote.... All this is coming from your cable as its like an long aerial

Not in this case. You are correct about using good cables of course, but the noise is not RFI or EMI (I tested for that).

Here is why I know how the noise is being conducted by the HDMI cable:

If I disconnect the cable at either end, the noise goes away. Same result if I leave the cable connected and the TV (or monitor) turned on and plugged into the wall socket, and I simply turn off or unplug all possible noise sources. If the cable acted like an aerial, akin to an un-terminated scope probe for example, then some noise would remain if I left the cable connected to the pi, and disconnected at the TV. The noise would also change if I moved the cable, or if I made a loop and rotated it.

It is definitely noise from various sources, conducted over the HDMI cable and through the HDMI connector. I can induce varying amounts of noise. With all noise sources removed, the results are quite good.

With RMAA and a 24-bit sound card input, 0.004% THD and -100db A-weighted noise is at the limit of the hardware.

With calibrated inputs and better software, I can measure down to 0.002% THD (0.001% would be perfect score for the DAC+).

PeteB

Test with an external USB 24-bit soundcard, and software calibrated to the sound card inputs:

Test conditions:
--------------------
test signal: 984.350Hz, 48KHz-16 bit wav file, 50% FS, 1.01Vrms measured at the DAC+ output
source: RuneAudio, HW volume control (or disabled) at 100, HiFiBerry DAC+ I2S
input: SB X-Fi HD, ~12k-ohm impedance, 96K-24bit resolution
software: Daquarta for Windows v9.10, calibrated to sound card inputs at 1V rms

Disclaimer: Everything was adjusted to give the best results. Distortion and noise would be higher in normal use, with normal recorded music, and at normal listening volumes.

@Rikardo: Same interconnect cables used for this test, except HDMI cable NOT plugged, and a shorter better quality RCA cable (still under $10...

)

@[deleted]: If you keep noise sources away from your Pi, and use your battery bank with no connections to the mains except your power amp, you should be able to come close to the same low noise and THD.

rikardo1979

PeteB wrote
rikardo1979 wrote.... All this is coming from your cable as its like an long aerial
Not in this case. You are correct about using good cables of course, but the noise is not RFI or EMI (I tested for that).

Here is why I know how the noise is being conducted by the HDMI cable:

If I disconnect the cable at either end, the noise goes away. Same result if I leave the cable connected and the TV (or monitor) turned on and plugged into the wall socket, and I simply turn off or unplug all possible noise sources. If the cable acted like an aerial, akin to an un-terminated scope probe for example, then some noise would remain if I left the cable connected to the pi, and disconnected at the TV. The noise would also change if I moved the cable, or if I made a loop and rotated it.

It is definitely noise from various sources, conducted over the HDMI cable and through the HDMI connector. I can induce varying amounts of noise. With all noise sources removed, the results are quite good.

With RMAA and a 24-bit sound card input, 0.004% THD and -100db A-weighted noise is at the limit of the hardware.

With calibrated inputs and better software, I can measure down to 0.002% THD (0.001% would be perfect score for the DAC+).

in this case you have few options

get new TV which dont push noise over HDMI - very expensive option

dont use HDMI in HiFi - highly recommended

dont use this measuring software, so you would not know (if the noise is not audible) - best solution

PeteB

rikardo1979 wrote
get new TV which dont push noise over HDMI - very expensive option

dont use HDMI in HiFi - highly recommended

dont use this measuring software, so you would not know (if the noise is not audible) - best solution

Hi Rikardo,

1 - I tried only the one TV, but a couple HDMI monitors, same results.
2 - Yes, I really prefer headless anyway, and I am looking into a 2-line display.
3 - Bbbbut: my other software is even more sensitive than this middlin' sound card! How can I live with myself if I don't solve this?

Ok, seriously, it is audible with plain vanilla 55-ohm AKG headphones, and a middling headphone amp, IF I use the hardware volume control at normal listening levels. If I don't, not audible, so I can make it go away by pushing the noise down. Still, it is annoying to be limited to about 14 bits resolution when you are playing 24-bit material...

The best solution for now is to keep all noise sources away. The TV is not the source, the HDMI is just the conduit to the noise. If you look at the graphs above closely, you will notice a 60 Hz (mains freq) peak on the green trace. By contrast my rotating disk drive only adds a tiny bit of noise, and the stock p/s only a little bit more.

edit:

Anyway, this is supposed to be a software forum, so I will do my best to stick to that from now on...

rikardo1979

PeteB wrote
rikardo1979 wrote
get new TV which dont push noise over HDMI - very expensive option

dont use HDMI in HiFi - highly recommended

dont use this measuring software, so you would not know (if the noise is not audible) - best solution
Hi Rikardo,

1 - I tried only the one TV, but a couple HDMI monitors, same results.
2 - Yes, I really prefer headless anyway, and I am looking into a 2-line display.
3 - Bbbbut: my other software is even more sensitive than this middlin' sound card! How can I live with myself if I don't solve this? [emoji38]

Ok, seriously, it is audible with plain vanilla 55-ohm AKG headphones, and a middling headphone amp, IF I use the hardware volume control at normal listening levels. If I don't, not audible, so I can make it go away by pushing the noise down. Still, it is annoying to be limited to about 14 bits resolution when you are playing 24-bit material...

The best solution for now is to keep all noise sources away. The TV is not the source, the HDMI is just the conduit to the noise. If you look at the graphs above closely, you will notice a 60 Hz (mains freq) peak on the green trace. By contrast my rotating disk drive only adds a tiny bit of noise, and the stock p/s only a little bit more.

edit:

Anyway, this is supposed to be a software forum, so I will do my best to stick to that from now on...

im with you. I dealing with noise myself at the moment.
I just got few LPS units. One for RaspDAC, one dual unit for my TT and phono stage.
Now I found that one of the cheap PSU s for Raspberry is pushing a lot of noise back to grid.
So I need to buy another LPS

...
More money to spend [emoji12]

OP2

PeteB

@Rikardo:

You could get something like this, plus an adapter for microusb:

http://www.mouser.com/ds/2/260/gs25a-spec-767496.pdf

It is not an LPS, but these were designed for medical instruments, and they meet fairly strict specs, even the commercial version meets the FDA specs. Less than 50 mV ripple. I have used them on the job, there are several manufacturers, all with good specs, for around $20 in quantity one.

I just tested one of these against an old HP filtered supply, and they test almost the same, within my ability to measure, so I got it for one of my two Pi 2 combos. Clean power on a <$20 budget. I am sure there is a Euro version of the same thing, your regs are stricter than US.

As a plus, they are 4-amp supplies, and their load regulation is very tight. I use it with the Pi that has a WD hard drive attached. It never deviates more than 100mV from 5V, even if the spec says +/- 5%. 80% or 85% efficiency, depending on what you pay for, and meet all EMC guidelines. Few of the RPi supplies can come close to that (nobody can for under $10, which is what the pi market demands).

Pete

rikardo1979

PeteB wrote@Rikardo:

You could get something like this, plus an adapter for microusb:

http://www.mouser.com/ds/2/260/gs25a-spec-767496.pdf

It is not an LPS, but these were designed for medical instruments, and they meet fairly strict specs, even the commercial version meets the FDA specs. Less than 50 mV ripple. I have used them on the job, there are several manufacturers, all with good specs, for around $20 in quantity one.

I just tested one of these against an old HP filtered supply, and they test almost the same, within my ability to measure, so I got it for one of my two Pi 2 combos. Clean power on a <$20 budget. I am sure there is a Euro version of the same thing, your regs are stricter than US.

As a plus, they are 4-amp supplies, and their load regulation is very tight. I use it with the Pi that has a WD hard drive attached. It never deviates more than 100mV from 5V, even if the spec says +/- 5%. 80% or 85% efficiency, depending on what you pay for, and meet all EMC guidelines. Few of the RPi supplies can come close to that (nobody can for under $10, which is what the pi market demands).

Pete

nice one, thanks for info. I may get this cheap solution for the RPi which is running Kodi and is hooked only to AVR. This is going to be good for that

For my HiFi gear I have these two now

9V/5.5A for Audiophonics RaspDAC I-Sabre V3 DAC ES9023 TCXO

this one is to feen my TT and phono stage 12V+18V/1A each

dunghnguyen

@[deleted]: tks for your share about the mouser adapter. It looks good for people using Pi.

rikardo1979

dunghnguyen wrote@[deleted]: tks for your share about the mouser adapter. It looks good for people using Pi.

good for RPi but with RPi 3 I would be careful especially with DAC boards like I-Sabre V3. The RPi 3 on its own needs 2.5A minimum, but in my case I ended up using 5.1V/3A to get rid of the under voltage problem! And this is without anything else plugged into it!

With older RPi 2 you should be safe with this PSU.

So my personal preference is RPi 2 with this DAC and I using this overkill LPS at top to make sure is stable and solid as tank

I just like my music

rastus

PeteB wroteI use it with the Pi that has a WD hard drive attached.

Brother, the Pi with the DIGI+ or the Pi with the DAC+? Don't really know why I'm asking, just curious is all.

rastus

rikardo1979 wrotegood for RPi but with RPi 3 I would be careful especially with DAC boards like I-Sabre V3. The RPi 3 on its own needs 2.5A minimum, but in my case I ended up using 5.1V/3A to get rid of the under voltage problem! And this is without anything else plugged into it!

Correct me if I'm wrong, but I was of the assumption that more amps (A) than needed was OK (but not less than needed), and that too much or too little volts (V) was dangerous. The reason I ask is... you ended up getting 5.1V/3A and (if my assumption is correct) you could've went higher, to say 5.1V/4A or 5.1V/5A.... unless of course your running a powered USB hub, which would mean you wouldn't need the extra amps.

rikardo1979

rastus wrote
rikardo1979 wrotegood for RPi but with RPi 3 I would be careful especially with DAC boards like I-Sabre V3. The RPi 3 on its own needs 2.5A minimum, but in my case I ended up using 5.1V/3A to get rid of the under voltage problem! And this is without anything else plugged into it!
Correct me if I'm wrong, but I was of the assumption that more amps (A) than needed was OK (but not less than needed), and that too much or too little volts (V) was dangerous. The reason I ask is... you ended up getting 5.1V/3A and (if my assumption is correct) you could've went higher, to say 5.1V/4A or 5.1V/5A.... unless of course your running a powered USB hub, which would mean you wouldn't need the extra amps.

yes, thats all correct

so to be able to run RPi 3 and not suffer under voltage issue (rainbow square in top right corner of the screen), you need more powerful PSU.
You can run RPi 2 with PSU 1A and you good where for RPi 3 you need at least 2.5A!!! (in my case 2.5 was not enough so ended up using 3A!)
So in theory you using more to get same

as to play audio (thats why we here, to have an audio solution) you do not need CPU power of new RPi 3.
So you can use older RPi with smaller, cheaper power supplies

PeteB

Voltage:
----------
The Pi is specified for 5V +/- 0.25V... (5%). The Pi by itself can run on a wider range, but many USB devices can't.
If the voltage drops too low, the Pi has a circuit to detect it and will not run.
If the voltage is too high, there is a risk of damage to the Pi circuitry, or a USB dongle, or a memory device.

As the load on a typical power supply increases, the voltage drops a little, and vice versa. At no load it is a bit higher, at full load a bit lower. This is called load regulation. A cheap 5V supply has poor load regulation, and may measure only 4.7~4.8V at the USB port, too low for some WiFi dongles. The voltage also drops a bit in the typical cheap supply cable.

The reason why some people use 5.1V~5.3V power supplies is to compensate for poor load regulation. They are counting on the voltage drop from a cheap regulator to bring the voltage down to 5V at the Pi. This is a common practice, but not a good one. A good 5V 2A supply should measure 5.0V at 50% load, which is typical after startup. Unfortunately a "good" wall-wart would cost over $10, not the $5~6 most Pi owners are counting on.

6V is definitely too high for a direct connection.

The reason why we have 6~7V, or even higher supplies is because some Pi DACs and Pi Amps regulate this higher voltage down to 5V, filter it, and supply the Pi through the 40-pin connector. This way the Pi DAC or the Pi Amp gets clean power, and the Pi gets a separate power supply that does not add noise to the DAC or Amp. This is a good solution (like Audiophonics uses), much better than supplying the DAC through the Pi, but more expensive.

Current:
----------
A direct connect linear supply can be rated at anything over 2 Amps, no matter what, it will supply clean power if designed and filtered correctly. Running a 10-amp supply at 1 amp will do no harm

A direct connect SMPS should be rated at over 2 Amps, but less than 10. Some SMPS supplies need about 10~20% load to meet their noise specs. So a 10 amp SMPS will work safely at 1 amp of less, but it may not meet its stated regulation or noise limits at a low current.

rastus

Very nice explanation PeteB, thank you.... and I do mean that, thank you brother. Makes sense to me.