Makes perfect sense, was what I suspected but now I know for sure. My DMM registers no discrepancy between the two signal outputs.
Thanks guys! I was about to shell out for output transformers, but now I can spend that on another deck and 8 shunt regulators.
Do I need to float the ground at the DAC end, or can I just take the 3 pins straight through the XLR cable to the amp? The ground on the amp XLR is connected to mains earth as per manufacturers instructions.
Thanks guys! I was about to shell out for output transformers, but now I can spend that on another deck and 8 shunt regulators.
Do I need to float the ground at the DAC end, or can I just take the 3 pins straight through the XLR cable to the amp? The ground on the amp XLR is connected to mains earth as per manufacturers instructions.
Well I took a gamble and plugged my £5000 speakers into the nCore amps.
The result? Background noise is the same, didn't think to measure the offset before removing the caps but i have a suspicion that it was there previously.
The other result? With no capacitors in the way it sounds even clearer!
Also there is no sign of any ground loop problems i.e. no low frequency residual noise whatsoever.
So the question is now "What may be causing this 130mV offset between +ve & -ve, and what can I do about it?"
This DAC is still on a wooden board and the XLRs are connected with some cheap cable and bad soldering as I just hacked it back together quickly to test this out. Could it be that level of voltage difference is caused by a poor connection somewhere?
I'm actually getting 130mV on one amp and 150mV on the other.
The result? Background noise is the same, didn't think to measure the offset before removing the caps but i have a suspicion that it was there previously.
The other result? With no capacitors in the way it sounds even clearer!
Also there is no sign of any ground loop problems i.e. no low frequency residual noise whatsoever.
So the question is now "What may be causing this 130mV offset between +ve & -ve, and what can I do about it?"
This DAC is still on a wooden board and the XLRs are connected with some cheap cable and bad soldering as I just hacked it back together quickly to test this out. Could it be that level of voltage difference is caused by a poor connection somewhere?
I'm actually getting 130mV on one amp and 150mV on the other.
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Yes it really is 0.2mV. I guess that someone spent some time getting those screws tuned in just right.
Yesterday when I measured the offset at the output of the DAC (and declared it to be zero) I had the meter set on 200V rather than 200mV so it wasn't registering anything.
Have just checked those outputs again, and I found a stable 6.5mV offset on the right channel, but the left is fluctuating wildly between about 80 and 125mV.
So all those values again:
Ncore unconnected - 0.2mV left, 0.3mV right
Ncore connected - 128.5mV left, 148.2 mV right
DAC outputs - 80 to 125mV left, 6.5 mV right
Yesterday when I measured the offset at the output of the DAC (and declared it to be zero) I had the meter set on 200V rather than 200mV so it wasn't registering anything.
Have just checked those outputs again, and I found a stable 6.5mV offset on the right channel, but the left is fluctuating wildly between about 80 and 125mV.
So all those values again:
Ncore unconnected - 0.2mV left, 0.3mV right
Ncore connected - 128.5mV left, 148.2 mV right
DAC outputs - 80 to 125mV left, 6.5 mV right
Just had an second look at the values you posted. Think for the left channel they can't be correct.
For an unmodified ncore the measured DC offset at the output should be around 20 times higher than at the input but your values for input and output on the left channel are almost the same.
For the right channel they make sense.
For an unmodified ncore the measured DC offset at the output should be around 20 times higher than at the input but your values for input and output on the left channel are almost the same.
For the right channel they make sense.
Ok thankyou, will do.
I assume that this fluctuation is on the DAC itself rather than in the cabling, and that its nothing to do with the mainboard so will narrow my search to the left half of the DAC board.
On first inspection it appears that the ground pin from DAC to mainboard on the left channel doesn't have any solder on it at one end! Will need to disassemble a little further to check if it's no solder, or just not as much as the others. I was pretty diligent when building the deck but something is definitely amiss here.
I assume that this fluctuation is on the DAC itself rather than in the cabling, and that its nothing to do with the mainboard so will narrow my search to the left half of the DAC board.
On first inspection it appears that the ground pin from DAC to mainboard on the left channel doesn't have any solder on it at one end! Will need to disassemble a little further to check if it's no solder, or just not as much as the others. I was pretty diligent when building the deck but something is definitely amiss here.
Well I measured the left channel at the DAC again. The oscillation has stopped and it is now reading 6.4mV which would make more sense.
I guess that ground is actually connected ok, and that I was not diligent enough with the probes on the DMM previously.
Thanks for helping me to try and understand this. I still don't (LOL) so can one of you just confirm that an offset on the output of the amps of between 130 and 150mV is ok?
I guess that ground is actually connected ok, and that I was not diligent enough with the probes on the DMM previously.
Thanks for helping me to try and understand this. I still don't (LOL) so can one of you just confirm that an offset on the output of the amps of between 130 and 150mV is ok?
Don't know also. Maybe it has an effect on sound quality, but don't think it will do any harm to the speakers.
If you will lower the gain of your setup because of the hissing problem the DC offset will also become lower.
You can also try to exchange the IV resistors you have build in. Use the best matching for one channel.
If you will lower the gain of your setup because of the hissing problem the DC offset will also become lower.
You can also try to exchange the IV resistors you have build in. Use the best matching for one channel.
Hello
Have just received the 4 deck pcm1794 dac from Doede..
use 5 hours to make it together,,,soldering is realy nice and easy ...top class print
have listening a little from my Pc to dac ....without the extra 5v supply to Waveio ,,and 8m usb cable with an extender boks ,,output is mindorf silcer in oil,,(have Cinemag in order )
without saying to much before 50 hours playtime...i will say one thing..i am totally blown away....(return with more about the sound)
I can see there are some advised against the I_V resistor ..more good ideas ???
best Bjarne
Have just received the 4 deck pcm1794 dac from Doede..
use 5 hours to make it together,,,soldering is realy nice and easy ...top class print
have listening a little from my Pc to dac ....without the extra 5v supply to Waveio ,,and 8m usb cable with an extender boks ,,output is mindorf silcer in oil,,(have Cinemag in order )
without saying to much before 50 hours playtime...i will say one thing..i am totally blown away....(return with more about the sound)
I can see there are some advised against the I_V resistor ..more good ideas ???
best Bjarne
Bjarne,
Now playing since a week with Audio Note tantalum 2w non magnetic resistors. Before this I tried the standard supply and Allen Bradley.
These tantalums are in my opinion the very best resistors in this spot, try them, you will be amazed of the detail, clarity and energy boost they add.
Regards,
Now playing since a week with Audio Note tantalum 2w non magnetic resistors. Before this I tried the standard supply and Allen Bradley.
These tantalums are in my opinion the very best resistors in this spot, try them, you will be amazed of the detail, clarity and energy boost they add.
Regards,
