Replies: 15 comments 14 replies
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Thanks for the report. Are you sure about the address? This documentation suggests that it uses the
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Sorry you are correct.
I used “27” for a LCD I added.
The Geekworm x950 worked right off the bat.
Sent from a fancy digital device...
… On Jul 19, 2021, at 9:55 AM, Dale Whinham ***@***.***> wrote:
Thanks for the report.
Are you sure about the address? This documentation suggests that it uses the iqaudio-dacplus devicetree overlay under Linux, which uses 0x4c as its I2C address, the same as the IQaudIO Pi-DAC Pro listed in the Wiki.
0x27 sounds more like an LCD address.
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While the X950 appears to be working correctly I note two issues... The output, both the headphone amp and the phono plugs exhibit a good amount of distortion and popping and clicking. I have a 20x4 LCD screen connected too and when I disconnect power to that screen from the PI the X950 volume drops significantly and the distortion decreases but does not go away... it is still annoyingly prevalent. Could the default gains be too high? Which setting controls that? BTW: That dovetails to a question. Is there any way to set the initial power-up volume level to something other than 100? Even 20 is extremely high on the X950 (leading back to the possibility of the initial gains being too high for the X950. ) Thanks! |
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This sounds like a ground loop issue, or electrical noise from the LCD's backlight, or a noisy PSU, try using alternative PSUs or using it away from other equipment.
Not usually, they're the defaults used by PC Munt/FluidSynth and most users find this well balanced.
No; only the gain settings as above, which basically determine how loud 100 will be.
I think there's probably some kind of issue with your DAC, this hasn't been the case for the DACs that have been tested previously. The PCM51xx does have internal controls via the i2c control interface, so it may have an internal default gain that is set too high at the DAC level. I would test the DAC under Linux to see if the distortion is present there. Also make sure the outputs you are using aren't too hot for the equipment you're feeding - e.g. using a headphone amp into speakers expecting line level will almost certainly be super distorted and may even blow your speakers. |
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I isolated the problem down to the LCD display. I noticed that as I increased the baud rate to the display the distortion would start to disappear. Once I hit 1000000 there was no distortion, but I kept getting pops and static like a vinyl record with light scratches. I disabled the LCD display in the configuration settings and left it in circuit... and voila! Absolutely perfect sound!!! BTW: This is pretty darned impressive... It is impossible to tell it apart from my real SC-55 when using a good soundfont. Anyway with the 20x4 LCD in circuit but disabled no issues. That points to no issues with the power supply itself. It could be something with the LCD's electronics causing the popping noises or voltage draw surges?? Does the PCM5122 I2S work well with an I2C 20x4 display normally? If so I'll just order a new display. Thanks! |
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More investigation: The higher I drive the baud rate the fewer pops or ticks I hear. I pushed the rate to 1500000 but the pops were still present. I tried lowering it down to 200000 and the output was badly distorted. So next I took it back to 1000000 and while I was playing a GM Midi tune I completely disconnected the LCD display. The pops and clicks continued! Doesn't that point to an issue with the drivers for the display or at least in the handling of the I2C communication? Thanks! |
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Could you attach your config file please? |
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Attached. I tried with no display attached, using this configuration with the same results. I also tried another LCD identical to the first with the same results. When the display is set to "none" all of the pops disappear completely. Thanks. |
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Okay, it looks fine, except: sample_rate = 44000This is... weird. Make it You haven't mentioned anything about what Pi you're using, which model? |
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I am using a brand new 8gb PI 4.
Thanks
… On Jul 21, 2021, at 10:53 AM, Dale Whinham ***@***.***> wrote:
Okay, it looks fine.
You haven't mentioned anything about what Pi you're using, which model?
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Ok. You're responding by email so you won't see the edits to my reply - check your samplerate, it is nonstandard. The DAC may accept it but it should be corrected to 44100 or 48000. I will retest Pi 4 with my iQAudio DAC when I get some free time, which is the closest DAC to this one (same chip). If I can't reproduce the issues you describe then I will just have to mark the X950 as incompatible. |
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Yeah I set that rate while attempting to find something that worked.
I had the same problem with other rates.
I will try another I2S DAC to see if the X950 is at fault.
I will also try a different LCD though the issue occurs only when the I2S LCD driver is enabled, even if no display is connected.
The 950 itself works fine with the LCD driver disabled.
Sent from my portable device.
… On Jul 21, 2021, at 11:08 AM, Dale Whinham ***@***.***> wrote:
Ok. You're responding by email so you won't see the edits to my reply - check your samplerate, it is nonstandard. The DAC may accept it but it should be corrected to 44100 or 48000.
I will retest Pi 4 with my iQAudio DAC when I get some free time, which is the closest DAC to this one (same chip).
If I can't reproduce the issues you describe then I will just have to mark the X950 as incompatible.
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Btw is your DAC using I2S as well?
I was considering trying a GPIO LCD next.
Sent from my portable device.
… On Jul 21, 2021, at 11:08 AM, Dale Whinham ***@***.***> wrote:
Ok. You're responding by email so you won't see the edits to my reply - check your samplerate, it is nonstandard. The DAC may accept it but it should be corrected to 44100 or 48000.
I will retest Pi 4 with my iQAudio DAC when I get some free time, which is the closest DAC to this one (same chip).
If I can't reproduce the issues you describe then I will just have to mark the X950 as incompatible.
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All external DACs that mt32-pi can use are using I²S for audio sample data. Most DACs (e.g. PCM5102A) need zero configuration, they just receive the samples and output audio. Some less commonly-used DACs are based on the PCM5122/PCM5242 (such as your X950 and my iQAudio), and are more advanced. These are also connected to I²C for control of their mixers/DSPs (note C not S). In mt32-pi, a "magic poke" via I²C has to be done at startup to wake up and un-mute these DACs, but that's the only time the DAC is communicated with via I²C. Afterwards, only audio is sent, like all other DACs. In other words, beyond the "magic poke", there's no functional difference. There is a chance that the I²C LCD traffic is somehow upsetting the DAC, but I don't know why until I investigate. My PCM5242 DAC has been used together with no problems alongside I²C LCDs since the early days of mt32-pi almost a year ago, but there could be a regression as I don't use this DAC very often. I wouldn't rush to switch to GPIO LCD just yet, it's an even less-tested configuration and I'm even considering deprecating it. |
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Tested v0.10.0 with my iQAudio Pi DAC Pro which needs I²C initialization together with a 4x20 I²C LCD on a Pi 4 4GB. Everything is working perfectly with no audio distortion, config file was all left at defaults except for what's necessary to enable the hardware. It's extremely unlikely I'll be able to debug what's wrong with the X950 unless I can get one in front of me. |
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Thanks for trying! I will test with another DAC tonight. |
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So I hooked up a brand new Innomaker DAC and got exactly the same results... with the baud rate for the LCD update set to 1000000. As long as the hd44780_i2c driver is enabled popping and static show up at a rate of maybe once or twice every 3-4 seconds. When I disable the hd4470_i2c driver or switch to either hd44780_4bit, sh1106_i2c, ssd1306_i2c or none, there are absolutely no pops or clicks, with the above baud rate. The display itself doesn't matter. I can have it completely unplugged and the above is true. So I've eliminated the display, power & the DAC and the only constant is the hd4470_i2c driver. Then I tried lowering the baud rate to the display back to the default of 400000 and NO POPS or STATIC on the Innomaker board, with or without the display connected. (Edit: I was wrong... the pops now occur maybe once or twice every 30 seconds or so, though MUCH better than before...) The hd4470_i2c driver seems to be the issue. I guess I can either use the Innomaker board and set the baud rate to the default 400000 or use the Geekworm board with the _4bit display or any of the others... though my preference is the 80x4 display. The Innomaker board lit talks about their dual clock reference, something the X950 does not talk about. Could that be the difference? Thanks! |
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I've re-tested again, with all the DACs I have, 1000000 I2C baud, and the 20x4 LCD. I don't get any clicks or pops, ever, with the hd44780_i2c driver, with or without an LCD connected. Sorry, but I just can't reproduce the issue and I've spent hours trying different combinations. At this point the only difference is the 8GB Pi 4, I don't have one of those for testing, only the 4GB version, but I can't see how that would make any difference. How long are your wires for the LCD? I2C is not designed for long runs and interference can easily corrupt the data and cause all sorts of problems, so you should always use the shortest wires possible. I am pretty sure you are experiencing hardware issues. |
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I have one last idea, you could try removing the following lines from # Optimized frequency settings for lower energy use/temperature on Pi 4
arm_freq=600
arm_freq_min=100
gpu_freq=100
over_voltage=-16
over_voltage_min=-16These apply an underclock and and undervolt on Pi 4 to (dramatically) reduce the temperature, maybe your Pi doesn't like these particular settings. |
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Well Shazaam! I tried a brand new out of box PI 4 - 4GB. (Note: The one I was using is also brand new.). ( Edit: also tried another PI 4 - 8GB with the same positive result. ) The popping/static disappeared completely using the Innomaker board. The thing to try next is to re-install the X950 and seeing if the distortion occurs at 400000 baud, if the 1000000 baud cures it again, and if there is any popping or static noise. I will try this next just to investigate.... (Edit: Confirmed popping/static is back on the new PI 4 4GB using the hdd4470_i2c driver AND the X950. Distortion still exists at 40K Baud, I can hear none at 1000000. No issues nor popping/static using any other driver... so the X950 works fine as long as you do not use the i2C LED character display. Back to the Innomaker board for me! ) BTW: I noticed that the hd4470_i2c address specified in the configuration has no effect on anything. Is it even needed? I don't understand why only the hd4470_i2c driver causes problems with the first PI 4, yet the other I2C drivers do not. With either DAC board the volume is waaaay too loud when things come up. I have to dial the volume down to 10-12 to avoid breaking my ear drums using headphones. I already have the gains set to 0.1 for everything which is the lowest the config file states works. Sorry to have dragged you down this rabbit hole. I'm sure the last thing you wanted was to be doing "tech support"! It is appreciated though. |
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Still very suspicious of the power supply; this reeks of typical electrical noise/interference issues caused by poor quality PSUs, bad wire shielding, etc. Just because it only happens with one LCD driver and not the others doesn't mean it's the software. The pattern of accesses over I2C the Pi does is different for each of the LCD drivers. There's a "burst" of data every 1/60th of a second to update the screen, which will cause a CPU core to suddenly draw more current and cause a bit of electrical noise. The higher the baud, the faster the burst, the greater the load. If the PSU is delivering a noisy, ripply supply, this extra load may cause a spike of noise bad enough to upset the I2S audio stream going to the DAC and cause an audible pop. Suggest you retest everything with the official Pi PSU or at least something branded that can deliver a good 3A+ of current.
Not sure what you mean here? The config has
See theory above. Random weirdness is very often a strong sign your PSU is bad. One Pi unit might have enough slight manufacturing differences to deal with it, another may not. Honestly, I have lost count of the number of times that people have rushed to me claiming there is a "bug" with mt32-pi, when in fact they were using some weak Samsung phone charger from 2006, and the "bug" magically disappeared when upgrading to and approved PSU. mt32-pi can and will stress your Pi and PSU in ways that Linux does not.
Try this kernel (with all the config gains back to default): It sets the analog gain of the PCM5122 to -6dB at the hardware level, and so it should be quieter than the v0.10.0 release. If it fixes your loudness issue, I'll add a new config option to control it.
No problem. Not going to lie, this is the worst part of leading a project alone that suddenly blew up and got hundreds of users. My email, Twitter and Discord get swamped on a daily basis and I basically have to ignore half of the messages I get. |
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Re: Power That was one of the very first things I suspected but I tried with a bench power supply @ 5A with the same results throughout. The thing is that two other PI 4's are not exhibiting the popping issue nor distortion issue at all with the Innomaker DAC, only with the X950 do both occur and then only when the particular LCD driver is enabled. In this case it may be the original PI itself causing the popping static noise with the Innomaker. On all three if I use any of the other three drivers no problems. Also the baud rate distortion is consistent... And since the results are the same with and without the displays connected, something about that driver is fouling up the X950 on all three PI's I've tried I've even hooked up a 4Bit 20x4 LCD and that works fine with the X950... as well as a 1.3" graphical display. I am happy with how the Innomaker works on the other three PI's with the LCD display. Should you wish to pursue it, e-mail me your shipping address and I'll send you a X950 via Amazon. RE: I2C address.... Sorry I meant the DAC driver not the LCD driver address... i2c_dac_address = 4d <--- I can put anything here and it works, or delete the line altogether. Re: Kernel Thanks!! I'll give that a shot and report back. EDIT: That is MUCH better! I made up a nice case for the whole Innomaker & LCD setup that I will post on Thingiverse once I get the bugs out. Thanks again!!! |
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Alright, I believe you. :) You must understand though, I needed to eliminate this possibility as it has caused so many problems in the past (and continues to do so in certain setups, e.g. MiSTer).
The unfortunate situation is that I have in front of me a Pi 3B, 3B+, 3A+, 4, and CM4, with three different models of DAC, and two different models of HD44780 I2C display, one 4x20, the other 2x20 and not a single combination of any of this hardware can reproduce the problem you are describing with any I2C baud rate. The driver has existed mostly unchanged for well over a year now and you are the very first person to report this problem. I have seen many, many, many mt32-pi builds with HD44780 I2C displays being used with a DAC "in the wild" with no reported audio problems, so... I'm at a complete loss. I would have also suspected the LCD itself, maybe the backpack was behaving differently, but you are saying that it occurs without any LCD wired, so... I have no idea.
This is very kind of you - I would like to get to the bottom of what's going on here as it does seem like a nice DAC kit. I couldn't find a way to see your email address on GitHub, but what I have done is added the X950 to my Amazon wishlist. I'm not 100% sure I've chosen the same one as yours but the photographs of the DAC PCB and chassis seem to match your link (I'm in the UK so the Amazon listing is a little different). Failing that, my email is daleyo at gmail ^dot^ com.
Ahah, okay. So this is going back to my earlier comment about some DACs needing a magic poke. If your DAC works with If the DAC is silent at startup, and needs initialization, The PCM5122 can be configured in two ways depending on how the manufacturer wired the chip: software (via i2c, hence the i2c address and init), or "hard-wired" (pins on the chip set high or low). My guess is that your DAC is hard-wired and doesn't need any initialization.
My guess is that since your DAC may be hard-wired, the kernel will have no effect. I think the X950 definitely needs more research. |
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My guess is that X950 have pull-up resistors on I2C bus with bad values. So RPi4 just can't reliable operate this bus when this DAC connected. Try to remove them. Because RPi has it's own pull-up resistors and typical add-ons for RPi doesn't need them: https://raspberrypi.stackexchange.com/questions/49815/why-many-raspberrypi-add-on-has-pull-up-resistors Good practice is to have empty traces for pull-up resistors. So that everyone who actually needs them could calculate a proper value and solder those resistors. |
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TheMadLynx: That's interesting... I'll have a look. Dale: I sent you an e-mail. Thanks! |
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On thing I forgot to mention is that throughout all of this is that I've been sending midi output to the MT-32 Pi via Ethernet/RTP. I don't know if that has any relevance. |
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Thanks again for sending the X950! I received it today, and I immediately set it up with:
Unfortunately I can find no problems at all with this DAC, it sounds as good as all of the other DACs I have tried with no changes to the software. I can't detect any popping. Using a pair of headphones directly into the HP AMP port was loud, as of course it's driving my headphones (ATH-M50x) at full volume - this is no surprise - but not distorted. Faster baud rate of 1000000 is also fine. The following video shows the DAC working, with audio recorded via a USB mixer: At this point, I have no further suggestions other than the possibility that your particular DAC may be partially faulty. If there are any specific MIDI examples/games you want me to try, fire away. |
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At least we now know it works! I agree that the most likely thing is I got a bad DAC, especially since I have no such problems with the Innomaker. Thanks again! |
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Yes, I am confident enough to add this to the wiki (as per the original purpose of the thread(!)). It may be worth cleaning the GPIO pins of your Pi and the DAC's GPIO connector with IPA and a toothbrush to see if that helps, and also look carefully for poor solder joints or shorts on your board, especially around the PCM5122 chip. Failing that, Amazon should be able to exchange/refund it for you without much fuss especially if you have Prime. Anyway; the kit itself is very nice, particularly the case - I can see why you chose it! |
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MT-32pi works great with the Geeekworm x950.
i2S address = 27
https://www.amazon.com/gp/product/B096V62P2W
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