I have recently purchased a second hand PS Audio ultralink Dac. Since I am using powered speakers, I do not have a preamplifier at the moment. So I tried connecting the XLR outputs of the Dac to the powered speakers and varying the input level on the back of the powered speakers for checking. I can hear a kind of distortion from the tweeters (like the tweeters have been torn and distorted ). When I connect the speakers to another system, they play perfectly fine
Since it's exactly the same in both channels, is it a problem in the power supply of the Dac or something like a DC offset at the XLR outputs of the Dac? And if it's the DC offset, how do I measure it? Also, are the speakers at a risk due to this?
Thank you
Since it's exactly the same in both channels, is it a problem in the power supply of the Dac or something like a DC offset at the XLR outputs of the Dac? And if it's the DC offset, how do I measure it? Also, are the speakers at a risk due to this?
Thank you
Speakers could potentially be at risk, depending. From your description, seems like the unit might be broken. Do you have an oscilloscope to check for gross problems? Even with only a DVM you could play back a sine wave and measure the voltage. Higher voltage than your speakers are able to accept? Also, if you know how you could also use a soundcard to look for distortion products at the dac outputs. Again, you would have to watch signal levels to make sure they are compatible. Otherwise you might contact PS Audio to see if they can help.
I do not have am oscilloscope but do have a decent DVM . From what I understood, I need to play a sine wave (400Hz??) in Mono and set the meter on AC and check with the probes at the output ? What should I look for ?
Maybe the DAC output is just too high and the vol pot on the speakers is not right at the iinputs.?
Try an external pot between the dac and speakers.
Try an external pot between the dac and speakers.
The volume pot at the speakers is at the default 0 position. The speakers play perfectly well with other preamps . Also the distortion I mentioned above is when u r a little close up to the speakers or if the volume is high.
None of this tells you whether the DAC output is not much higher than your other preamps and overloading the input of the speakers.
Ok. So you suggest i borrow a preamp and try the Dac with it ?? Just hoping there is no risk to the borrowed preamp and/or the speakers itself ?
Yes, insert a preamp between the speakers and DAC. Maybe check the DAC output with a multimeter for DC?
To measure DC offset at the Dac output, I set the Multimeter to DC and measure the Left and Right channels independently? What reading to expect for a good working unit ?
Just opened the unit to check for any anomalies. The pcb is very well laid out. Upon inspection, I found out that the XLR outputs have a nasty dry solder joint on one channel. The positive wire is barely seated in the terminal without any solder. Wondering how there was distortion in both channels though.
The soldering looks very bad generally so wouldn't be surprised if there are not dry joints on the underside too.
You mean on the underside of the pcb where the red and green wires are attaching ? I will redo the xlr wiring on both left and right outputs tonight and see if it fixes the problem. Else I may have to check for dry joints elsewhere too as you rightly said. Will revert. Thank you and I really appreciate your time and help
Re-soldered all connections. The other channel too had many dry solders as well as the Coaxial RCA Jacks. I intend to connect the unit this evening. Before I hook them up to the speakers, I want to check for any DC at the output terminals of the Dac. So I should essentially put the meter on DC and play a music file and check with Pin 2 and Pin 3 of the XLR outputs for the reading to be close to 0 Volts correct? Or should it be done without playing any source with just the Dac powered up ?