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Reference DAC Module - Discrete R-2R Sign Magnitude 24 bit 384 KHz

Are there any obvious mods that I'm missing?
Adding a polymer to the 3.3v for the clock is very easy, you can use the block with all the vias, use those near the clock, see my mods.

Around the clock are also some smaller vias, I've used them to add some SMT caps and polymers to the back of the PCB.

The switcher for the FPGA is 1.2v
 
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Hi all, I write my problem here on this forum after writing an email to Soren's product support email describing my problem and getting absolutelly no answer for more than a week now;. I wanted to lower the DAC's output volume bacause my I2S source was too loud so I soldered a 10 k potentiometer on the DAC's pcb using the connection diagram description on the product's page and hifiduino's blog; my mistake was that I accidentally reversed the 3,3v and GND connection on the
potentiometer side so in a few seconds the 3.3v LDO from the board was blown away; I solderen another new one instead hoping that will solve my problem but was blown away again! so I measured the LDO points and found out that it's output was in short and that blew away the new regulator; the input was 20V (I am using +/- 15V to power the board), but it's output was in short with the GND pin; so I'm asking you all if you could give me some advice what to do next, because Soren seems like
doesn't care about after-buying support and doesn't respond to emails; thanks, I'm attaching a picture

An externally hosted image should be here but it was not working when we last tested it.
 
AS one who has modified my DAC board as much as anyone I never expected SOEKRIS to tell me how to fix something caused by my own negligence.

SOEKRIS has answered questions concerning mods I wanted to do but there was always his warning that one wrong move and your board is destroyed.

I am not aware of anyone who has time to try to walk anyone through a problem brought upon by negligence.

Modding products is great fun but as with any endeavour: education never comes cheaply and you have been educated.

You, more than likely, need a new board.
 
Hi all, I write my problem here on this forum after writing an email to Soren's product support email describing my problem and getting absolutelly no answer for more than a week now;. I wanted to lower the DAC's output volume bacause my I2S source was too loud so I soldered a 10 k potentiometer on the DAC's pcb using the connection diagram description on the product's page and hifiduino's blog; my mistake was that I accidentally reversed the 3,3v and GND connection on the
potentiometer side so in a few seconds the 3.3v LDO from the board was blown away; I solderen another new one instead hoping that will solve my problem but was blown away again! so I measured the LDO points and found out that it's output was in short and that blew away the new regulator; the input was 20V (I am using +/- 15V to power the board), but it's output was in short with the GND pin; so I'm asking you all if you could give me some advice what to do next, because Soren seems like
doesn't care about after-buying support and doesn't respond to emails; thanks, I'm attaching a picture

First, I would like to direct your attention to this statement on the soekris website:

"We do our best to respond to emails and phone calls in a timely manner, but please note that due to the small size of the company, we might not be able to respond immediately."

It is a DIY board so I like to give people and little time to fix problems themselfe.... You also didn't tell me about the 20V power (are you using 2x15V transformer ??), please note that the specs say:

"7-8V AC or +-7-15V DC max 5W"

That's not just for fun, there are several parts with absolute max specs at 18V to 19V, it's more likely that you have blown the regulator by overvoltage, and then the replacement.... The regulators themselfe are short circuit and temperature protected but overvoltage will kill them.... And often once a regulator blow it most likely with take sensitive stuff with them, like the FPGA....

Because I can't see how reversing GND and 3.3V to the volume pot should blow anything as that should just reverse the function....
 
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Try adding a polymer cap to the 3.3V rail near the clock, and since you removed the op-amps try supplying the board with +-5V and +3.3V directly. There's also the 1.8V switcher but you can power that with the 5V instead of directly, saves having an extra regulator and i've not seen any claims that upgrading the 1.8V did anything useful other than for completeness sake.

Thanks for the input guys.

"supplying the board with +/-5V and +3.3V directly" you mean directly at J2 in stead of J1? And then still +5V at J1 for the switcher?
 
Adding a polymer to the 3.3v for the clock is very easy, you can use the block with all the vias, use those near the clock, see my mods.

Danny, is this the clock cap, and what value are we talking about?

BwBMwQQ.jpg


I've already been considering replacing the ZLDO 17-33 reg with maybe a NewClassD UWB 3.3V reg. (goes by the name of DEXA Technologies in the US). Anybody know if this is compatible? Or will I need a SpakosLabs or a muzgDIY?
 
+1. Also the ability to configure a max volume limit (I.e. deliberately set an artificial ceiling). I remember several others asking for this not too far back in this thread.
Hi, back to new firmware possibilities.
Is it possible to get a firmware where it is not possible to adjust to +10dB? I have yet to find music where this is necessary. Every tune gets distorted.

0dB is more than enough :)
 
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I heave also a „randomly loses sync” issue. But in mine situation in 99% it is a power side issue..
since yesterday Soekris plays from battery and it is rock solid..
You heave add a solid power supply regulator.. mine simple toroid was not enough.. for quick I will add some CLC filter..
I try to figured out if it is grounding or AC/DC side..

Yes, now I do think it is indeed a power supply issue.

Tonight I was able to consistently replicate the problem, though I discovered it by accident. I have a big paper shredder plugged into the same AC outlet that my audio equipment plugs into. Tonight was the first time I've used this shredder in a while. Every time the shredder started shredding, the DAM would lose sync as described previously. (Now this doesn't explain why, without the shredder, it tends to happen right at the beginning of a song, but I'll ignore that for now.)

I am using a 30VA R-core transformer with dual 12V secondaries. Those secondaries go to a DIYINHK LT3042 +/- 15/12/9 regulated power supply, set to +/-9V. The LT3042 PSU powers my dual-mono dam1021 boards.

I'm assuming the shredder draws a fair amount of current, and therefore causes the mains to sag a bit. I would think there's enough capacitance in the chain to mask this, but apparently not.

Anyone have any hints as to how I might better insulate the power supply from AC mains fluctuations?

Thanks!
 
I made some progress.. I use all mine electronic skills (not a lot.. only hobby from a some years ago.. ;-) so I some can check if I do not make a some mistake.. )

With supply:
- I’m powering all audio equipment thru some serious filtering..
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(based on this project)

- between transformer and soekris I add a lot of capacitors + linear stabilizer (schottky diode, stabilizer LD1086v LDO type - transformer is 8V so I dont want to waste additional V), for quick mine scheme:
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So it loks like this:
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- Additionally I try to upgrade Input board.. I’m using board from some Onkio amplituner:


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- I replace cable with spdif signal for RG174 type..
- I add multiplexer (4051 type) – it works but I think that I do not chose its wisely because it limits spdif signal to 44,1 and 48khs (optical). Maybe someone tested different chip?

From yestorday everything loks ok.. no loosing sync issue.. I will test it in next days...
 
This isn't rocket science? I'm sure I'm a huge n0ob compared to most of you people but "regulated" should make the psu fairly immune to fluctuations in the grid. If for some reason there is a significant dip in the grid, there should be enough caps on hand to cover any short term demand.
I guess the only way to make the PSU absolutely bullet proof is to go against a big hifi taboo and use a smps with enough filtering?
I can't for the life of me see how a dac can put any real strain on the power supply? In my mind the sync issues must come from some other source? Is it possible that the shredder put out some kind of interference? The only time I've had issues with power was with an old amplifier of mine. The lights would go out in the room when I turned it on... Lots of big caps in that one, lol.
 
Pardon me if I'm being stupid now but since we're talking about the digital domain. The digital volume is just a matter of where in the shift register the data is located. Any amplification must thus be in the analogue domain?
Maybe it is so. Still every tune I have gets distorted at above approx +3dB using the digital volume built into the dam1021. It doesn´t matter what volume I use in the analog domain.
Others have reported the same several times.
 
That's really odd? To me that would imply either that the LSB becomes significant distortion wise or that some initial analogue stage is too weak and distorts? I guess if I were to pick one of the two I'd probably look at the analogue part?
I'm just throwing out a wild guess here but maybe full output signal pushes it right up to the rails of Vref? Tuning it down might just give it enough headroom vs Vref to stay clear of the issue?
 
But I have another "issue". Hopefully I am able to describe it..
My dam1021 is connected to a rpi. i2s direct and rs232 so I can control the dam via the rpi. I am using a serial program called minicom in the rpi distro.

The dam output to /var/ttyAMA0 - for instance when volume is changed via my 10k pot on the dam its volume is
Like this
tc@piCorePlayer:/$ cat /dev/ttyAMA0
V-22
V-22
V-23
V-24
V-25
V-25
and so on . Just like when entering the umanager via serial.

I want to be able to put this information to a small lcd screen connected to a rpi (but that is another question)

However first time after powercycle I do this "cat /dev/ttyAMA0" it goes "crazy" - flickering in the CLI and extreme distortion in the sound. I have to connect via serial program to the dam1021 first and the disconnect and the "cat /dev/ttyAMA0" puts out in correct manner and no problem.

Anyone else experienced this? And is it any explanation for this behaviour?
 
dac r2r soekris

Hi and thanks for your input, please follow my pictures because I made some new measurements, and maybe you'll be able
to point me out in the right direction with some measurements made an a working board to be able to localize my problem

this is my input voltage +/- 15V

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THIS IS MEASURED ON THE 3,3V LDO input

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this is the ohm-meter pins in short

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and this is the 3,3v LDO's output - it seems like it's in short-circuit although the traces are fine

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this is the way I tied up my potentiometer having the GND connection in the middle

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and this is the initial original picture which guided me for the potentiometer connection with the observation
that there is not noted on the pot side where is it's GND (on mine it was in the middle)

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and this is the way it was tied to the board when suddenly the 3,3v LDO was blown away; also the LED lamp on the board does not light up

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any information is welcome... maybe Soren could tell me if the FPGA could be replaced with a new one in case it is also damaged and what would be the cost?