Hi, I built a PCM2707 based USB DAC, but WinXP don't recognize it 
.
It says "usb device can't be recognized due to malfunction", or something like
.
Attached is the schematic. 2707 is used in self powered mode, feed by two LDO regulators. Voltages on the regulators are ok, but pin 32 (Vcom) is 0V.
I can't believe I've killed the PCM2707, because I soldered it very carefully.
Any hint on what may be wrong? TIA.
.It says "usb device can't be recognized due to malfunction", or something like
.Attached is the schematic. 2707 is used in self powered mode, feed by two LDO regulators. Voltages on the regulators are ok, but pin 32 (Vcom) is 0V.
I can't believe I've killed the PCM2707, because I soldered it very carefully.
Any hint on what may be wrong? TIA.
Attachments
Hi Akira386.
I took a look and compared your schematic to my schematic. I use the PCM2706 in the I2S mode so there are differences but from what I see yours should work.
Have you had your circuit working as a prototype so you know it will work? Or maybe this is your first prototype.
Could it be that one of the pins is not soldered? I would guess you have checked continuity with a meter already.
If you have a scope check to see if you have any signal on the clock pins. If you do then you know the chip is not dead. If you don't then it tells you nothing.
When I prototyped my DAC I ended up with two or more dead DAC chips. I never knew why and I still don't. I was pretty careless and prototypes had wires everywhere so that is the nature of prototyping. But on production DAC board I have not had a single failure in 7 dacs and I take no precautions with what order I plug in the mains or USB cable or how long the DAC sits with out a USB connection.
What I suggest is that if you have nothing left to try then you replace the DAC chip. I have done this many times. A few times I have soldered the PCM2707 in the wrong way and replacing chips on prototypes. First apply extra solder to the pins. Take a sharp utility blade and cut the pins at the chip body. Clean up with desoldering wick and solder in a new chip. Careful as too much heat to the pads will make them lift. But even then you can fix it with jumper wires. Don't give up. You are very close
Let me know if I can be of any further assistance.
I took a look and compared your schematic to my schematic. I use the PCM2706 in the I2S mode so there are differences but from what I see yours should work.
Have you had your circuit working as a prototype so you know it will work? Or maybe this is your first prototype.
Could it be that one of the pins is not soldered? I would guess you have checked continuity with a meter already.
If you have a scope check to see if you have any signal on the clock pins. If you do then you know the chip is not dead. If you don't then it tells you nothing.
When I prototyped my DAC I ended up with two or more dead DAC chips. I never knew why and I still don't. I was pretty careless and prototypes had wires everywhere so that is the nature of prototyping. But on production DAC board I have not had a single failure in 7 dacs and I take no precautions with what order I plug in the mains or USB cable or how long the DAC sits with out a USB connection.
What I suggest is that if you have nothing left to try then you replace the DAC chip. I have done this many times. A few times I have soldered the PCM2707 in the wrong way and replacing chips on prototypes. First apply extra solder to the pins. Take a sharp utility blade and cut the pins at the chip body. Clean up with desoldering wick and solder in a new chip. Careful as too much heat to the pads will make them lift. But even then you can fix it with jumper wires. Don't give up. You are very close
Let me know if I can be of any further assistance.
Member
Joined 2002
Maybe the problem is related to timing. In my DAC the PCM2706/7 is powered from the mains. The PCM2707 has power long before the USB connection is made. But in Akira386's case it is happening at the same time.
I also do not have a problem if I disconnect the mains power first and then disconnect the USB cable or connect the USB cable before the mains.
But come to think of it... I have a prototype (looking at it right now, just plugged it in and it works) that is rigged in self power mode but gets power from the USB bus. Same as Akira386.
The mystery continues....
I also do not have a problem if I disconnect the mains power first and then disconnect the USB cable or connect the USB cable before the mains.
But come to think of it... I have a prototype (looking at it right now, just plugged it in and it works) that is rigged in self power mode but gets power from the USB bus. Same as Akira386.
The mystery continues....
Thank you for the input, guys!
Measuring from the GND, it has 3V in the XTI and 3.3V in the XTO 
.
Maybe it is time to replace the PCM.
Thank you for the suggestion and incentive, Brent.
akira
It's my first prototype, Brent. I was confident that it would work, it is so simple, but...Brent Welke said:
The only instrument I have is a DMM...
Measuring from the GND, it has 3V in the XTI and 3.3V in the XTO .This is what I fear..
Maybe it is time to replace the PCM.
Thank you for the suggestion and incentive, Brent.
John, the LDO regulators are powered by the USB bus, so it is impossible to provide power to the PCM while dettached.jkeny said:
akira
I don't know how sensitive the crystal is to heat, I use a SMD clock oscillator, but I know that if the clock is not running you get the exact same problem you describe with Windows saying "Unrecognized USB Device"
The fact that you measure voltage at the crystal also tends to make me think the crystal is not functioning
The fact that you measure voltage at the crystal also tends to make me think the crystal is not functioning
I removed the PCM following Brent's advices, and luckily no track came off.
But with a new PCM in place, thing got worse. Now, Windows does not detects it.
3.3V is presente on Vdd, Vccp, VccR, VccL, Fsel and Test. Everything seems ok, but no sinal of life.
Vcom is 0V, and so is SSPND..
Very intriguing. Have I made a PCM killing board?
Next I will try to replace the crystal
.
But with a new PCM in place, thing got worse. Now, Windows does not detects it.
3.3V is presente on Vdd, Vccp, VccR, VccL, Fsel and Test. Everything seems ok, but no sinal of life.
Vcom is 0V, and so is SSPND..
Very intriguing. Have I made a PCM killing board?
Next I will try to replace the crystal
.Akira,
I have a similar non working PCM2706 board (AW-D3 kit) but mine never output I2S or SPDIF (there is a jumper on board to wsitch between modes) although internal DAC output was fine.
This output has now been reduced to very low volume even though I made no changes to the board. However, XP still recognises the DAC USB connection.
These chips seem temperamental
John
I have a similar non working PCM2706 board (AW-D3 kit) but mine never output I2S or SPDIF (there is a jumper on board to wsitch between modes) although internal DAC output was fine.
This output has now been reduced to very low volume even though I made no changes to the board. However, XP still recognises the DAC USB connection.
These chips seem temperamental
John
Funny story - maybe?
I wondered what the analogue output sounded like on the PCM2707 vs. the TDA1543 so I prototyped it up one day and could only get a very small signal out. I spent 10 or more hours over a few days until finally one day I noticed the PCM2707 output is controlled by the computer's volume control setting. I did not expect this. You have to set Windows to default to the USB device before the volume control will affect it. This may not be your problem but my story may help someone.
I wondered what the analogue output sounded like on the PCM2707 vs. the TDA1543 so I prototyped it up one day and could only get a very small signal out. I spent 10 or more hours over a few days until finally one day I noticed the PCM2707 output is controlled by the computer's volume control setting. I did not expect this. You have to set Windows to default to the USB device before the volume control will affect it. This may not be your problem but my story may help someone.
Brent,
I had the default device set to USB DAC always but sound has gradually gone too low.
BTW how did the PCM2707 internal DAC compare to TDA1543 sound? haven't been able to get I2S working so have no comparison but when PCM was working properly I was impressed with the PCM analogue out.
John
I had the default device set to USB DAC always but sound has gradually gone too low.
BTW how did the PCM2707 internal DAC compare to TDA1543 sound? haven't been able to get I2S working so have no comparison but when PCM was working properly I was impressed with the PCM analogue out.
John
Perhaps these are being caused by ESD damage.
It is known that ESD damage can cause latent failure. ESD wounds the component to the point where it still works, but over time it eventually fails.
And some delicate semiconductor junctions can be damaged by ESD as low as 10V.
Just a possibility.
akira
I didn't put in any effort to perfect the PCM2707's output. But what I heard didn't excite me. I am sure it would compare well to an iPod. With an oscillator clock, good power supply and tweaking it would probably be better then any small store bought USB DAC/player on the market.
However I doubt anyone will be addicted to the PCM2707's sound. For many (me included) the NOS TDA1543 sound is addictive like a drug.
I replaced the crystal, but no effect. It was not the culprit.
Then I replaced the PCM (again) and now it worked! Windows recognized it as USB audio device.
After much trouble, finally it's working.
Thank you for the assistance!
I had no time to listen to it carefully, but the first impression is that it sounds not so good as my reference, a modified Optoplay. Not bad for a monolithic chip, I think.
Next, maybe I'll build a PCM2707 -> I2S -> TDA1543 one.
akira
Then I replaced the PCM (again) and now it worked! Windows recognized it as USB audio device.
After much trouble, finally it's working.
Thank you for the assistance!
I had no time to listen to it carefully, but the first impression is that it sounds not so good as my reference, a modified Optoplay. Not bad for a monolithic chip, I think.
Next, maybe I'll build a PCM2707 -> I2S -> TDA1543 one.
akira
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