Hi Jean-Marc
The power supply board is only capable of powering one PhiDAC. If you need to power more there are boards available on Aliexpress which will do the job with more output current, for example here , it should be able to handle 3 or 4 boards. The input to the board is +5V which often comes from a USB bus, the output is 9-10V.
For balanced outputs you need to run two PhiDACs in opposite phases. The phase switch on one needs setting to 180degrees, the other remains at 0degress. They both receive the same I2S signal. The DAC with the 180degree setting generates the negative audio phases (L-, R-) and the 0degrees DAC generates the positive ones (L+,R+). Powering - if from the supplied LM2662 boards - would be one power supply board per PhiDAC.
I hope this is helpful and gets you going.
The power supply board is only capable of powering one PhiDAC. If you need to power more there are boards available on Aliexpress which will do the job with more output current, for example here , it should be able to handle 3 or 4 boards. The input to the board is +5V which often comes from a USB bus, the output is 9-10V.
For balanced outputs you need to run two PhiDACs in opposite phases. The phase switch on one needs setting to 180degrees, the other remains at 0degress. They both receive the same I2S signal. The DAC with the 180degree setting generates the negative audio phases (L-, R-) and the 0degrees DAC generates the positive ones (L+,R+). Powering - if from the supplied LM2662 boards - would be one power supply board per PhiDAC.
I hope this is helpful and gets you going.
Hello,
I may need a bit of guidance for my PhiDAC commissionning. It is powered. The 2 LEDs are on. I could not borrow an Oscilloscope, But I have a multimeter. The Right channel looks alive: VDC is low: less than 5 mV and VAC is live and sensitive to volume changes. Unfortunatly, the Left channel looks wrong: VAC=0, and VDC is higher than the right channel: around 17-20 mV.
At C14, I get VDC = 2.1V and VAC fluctuating around 10-20 mV
I have the schematics, but not easy for me to determine what I should be looking for where.
Would you have in mind some relevant test points to track the signal along the Left channel ?
I tried to look at the board and have not identified bad solders...
Best regards,
JMF
I may need a bit of guidance for my PhiDAC commissionning. It is powered. The 2 LEDs are on. I could not borrow an Oscilloscope, But I have a multimeter. The Right channel looks alive: VDC is low: less than 5 mV and VAC is live and sensitive to volume changes. Unfortunatly, the Left channel looks wrong: VAC=0, and VDC is higher than the right channel: around 17-20 mV.
At C14, I get VDC = 2.1V and VAC fluctuating around 10-20 mV
I have the schematics, but not easy for me to determine what I should be looking for where.
Would you have in mind some relevant test points to track the signal along the Left channel ?
I tried to look at the board and have not identified bad solders...
Best regards,
JMF
I'd start out by checking DC levels on L channel as your C14 DCV seems too low, should be around half the supply (roughly 4V).
Working back from C14, is U9.1 also at 2.1V? Then check across C20 to see if that's the same. The start of the L channel signal chain is the 1387's pin 6 which should also have the same DCV.
Working back from C14, is U9.1 also at 2.1V? Then check across C20 to see if that's the same. The start of the L channel signal chain is the 1387's pin 6 which should also have the same DCV.
Hello Abraxalito,
I checked on the Right Channel, and I have 1.97V accross C26, so something similar to the Left Channel (2.15V). On the right channel (that seems to work, VDC at U5.1 and accross C8/C9 is consistent at about 2V.
On the left channel (presumed not to work). Output of U9.1 and accross C19/C20 is only 1.07V (1/2).
So voltage accross R30 is 1.07V <=> I imagine it is not good.
At DAC outputs C6/C7, I have 2V, and at C16/C17, I have only 1.05V.
DAC Vcc is 5.64V.
Do you confirm the voltage accross C26 and C14 should be about 4V, and not 2V (which would mean some issue on both channels)?
Can those measurements provide some usefull information to diagnose the issue?
Best regards, JMF
I checked on the Right Channel, and I have 1.97V accross C26, so something similar to the Left Channel (2.15V). On the right channel (that seems to work, VDC at U5.1 and accross C8/C9 is consistent at about 2V.
On the left channel (presumed not to work). Output of U9.1 and accross C19/C20 is only 1.07V (1/2).
So voltage accross R30 is 1.07V <=> I imagine it is not good.
At DAC outputs C6/C7, I have 2V, and at C16/C17, I have only 1.05V.
DAC Vcc is 5.64V.
Do you confirm the voltage accross C26 and C14 should be about 4V, and not 2V (which would mean some issue on both channels)?
Can those measurements provide some usefull information to diagnose the issue?
Best regards, JMF
VREF (the effective AC GND for the whole DAC) is set by D2 and D22 in series, the two yellow LEDs. A yellow LED is typically 1.9V so VREF therefore should be 3.8V.
Do check that U5 pin8 is 8V.
Correct, R30 should have practically no DCV across it.
Yes, both should be 3.8V (VREF) which should also be the voltage on R57 which filters the LED ref voltage.
Do check that U5 pin8 is 8V.
So Vref is 3.7V, accross D2 and D22;
U5 pin8 was 2.7V. There was a cold solder on L1, repaired now. Now I have about 4V along the Right channel signal line, which seems responsive. One thing OK now.
Then back to the left channel:
C14 is 2.2V,
U9.1 is at 1V (1/2 of at C14)
C20 is at 1V (1/2 of at C14)
1387's pin 6 is at 1V (1/2 of at C14)
U9 pin8 is 8V
All the group R39, R52, R40, R41 is at 8V
I rechecks the board and don't see other bad solders in the area.
Thanks so much for the help Abraxalito.
Best regards,
JMF
U5 pin8 was 2.7V. There was a cold solder on L1, repaired now. Now I have about 4V along the Right channel signal line, which seems responsive. One thing OK now.
Then back to the left channel:
C14 is 2.2V,
U9.1 is at 1V (1/2 of at C14)
C20 is at 1V (1/2 of at C14)
1387's pin 6 is at 1V (1/2 of at C14)
U9 pin8 is 8V
All the group R39, R52, R40, R41 is at 8V
I rechecks the board and don't see other bad solders in the area.
Thanks so much for the help Abraxalito.
Best regards,
JMF
As those voltages are all too low I'd like to see if U9.1 is working properly as it defines the voltage all the way back to the DAC.
Check pin2 and pin3 of U9.
I think that I have it. Possible bad solder on U9 pin 4. Did a small touch and now I have 4 volts along the signal line.
The Left Channel is "live" on the multimeter VAC, and sensitive to volume.
Thanks so much Abraxalito for having helped to look where I should.
I now have to solder some cinch and connect to amplifier and speakers.
Any other check you would advice before going "live" ?
JMF
The Left Channel is "live" on the multimeter VAC, and sensitive to volume.
Thanks so much Abraxalito for having helped to look where I should.
I now have to solder some cinch and connect to amplifier and speakers.
Any other check you would advice before going "live" ?
JMF
My PhiDACIplays Music 
Both channels...
I won't have the opportunity to do some critical listening tests in coming days, but what striked me on the first tracks I tried is the bass. Like if there was more bass than with any of my other DACs.
Thanks lot Abraxalito for the remote guidance for the trouble shooting. I have a second board built that I have to test. I hope I will be able to do it on my own.
JMF
Both channels...
I won't have the opportunity to do some critical listening tests in coming days, but what striked me on the first tracks I tried is the bass. Like if there was more bass than with any of my other DACs.
Thanks lot Abraxalito for the remote guidance for the trouble shooting. I have a second board built that I have to test. I hope I will be able to do it on my own.
JMF
As a result of focussing on complete systems for the past two months or so, there's now a new DAC (which I'm calling Abbado III out of sheer laziness) based on Abbado II but which incorporates a volume control and hence obviates the need for a preamp in a digital-only system. Just one of these new DACs followed by a poweramp is all that's required. I've wanted to incorporate a low-noise volume control in a DAC for quite some time but couldn't see an elegant way to accomplish that.
The latest DAC places the pot directly in parallel with the I/V resistor - this can only work well when the I/V resistor's a much lower value than the pot itself due to the fact that the I/V resistor is also the LC filter termination and needs to be a precise value. Pot resistance tolerances aren't tight enough to use a pot's track directly as I/V so the pot needs shunting with a much lower value fixed R to swamp its imprecise value and this can only be done when there's lots of DAC output current available. It can't work on 1-2mA output DACs (e.g. PCM56s) but an array of paralleled TDA1545As delivering 50mA total current works a treat as this allows an I/V resistor in the region of 100R and a 5k pot's tolerance doesn't much affect that when placed in parallel.
Here's the first generation Abbado III which I initially equipped with a 7th order plug-in filter :
The connection to the volume pot is top left, occupied by a sliver of perf-board in this shot. The biggest surprise on listening to this DAC was the improvement found from upgrading the 7th order filter to 9th order. Both wifey (who listened blind) and myself agreed that it made the music easier to understand and follow - the noisefloor is subjectively lower on the higher order one.
The latest DAC places the pot directly in parallel with the I/V resistor - this can only work well when the I/V resistor's a much lower value than the pot itself due to the fact that the I/V resistor is also the LC filter termination and needs to be a precise value. Pot resistance tolerances aren't tight enough to use a pot's track directly as I/V so the pot needs shunting with a much lower value fixed R to swamp its imprecise value and this can only be done when there's lots of DAC output current available. It can't work on 1-2mA output DACs (e.g. PCM56s) but an array of paralleled TDA1545As delivering 50mA total current works a treat as this allows an I/V resistor in the region of 100R and a 5k pot's tolerance doesn't much affect that when placed in parallel.
Here's the first generation Abbado III which I initially equipped with a 7th order plug-in filter :
The connection to the volume pot is top left, occupied by a sliver of perf-board in this shot. The biggest surprise on listening to this DAC was the improvement found from upgrading the 7th order filter to 9th order. Both wifey (who listened blind) and myself agreed that it made the music easier to understand and follow - the noisefloor is subjectively lower on the higher order one.
