Good evening, I am trying to build an R2R DAC I purchased from AudioPhonics, and this is the one. My problem is that in the single-ended configuration, I have a positive output from the channels, but following the schematic, I need to connect it to the negative input of the operational amplifier, which results in a negative voltage on the RCA outputs. Can someone help me understand where I might be going wrong? Thank you very much!
https://www.audiophonics.fr/en/dac-...2023-r2r-dac-module-24bit-384khz-p-17986.html
https://www.audiophonics.fr/en/dac-...2023-r2r-dac-module-24bit-384khz-p-17986.html
Thank you very much for the response. I have two more questions: The power supply for the OPA134 needs to be dual, correct? Also, I plan to connect it to the Buffer Preamp B1 by Nelson Pass. Should I maintain the signal inversion all the way to the power amp? Can I also connect this DAC to the Naim Nait XS3 without any issues?
In engineering there are usually alternatives. Op amp circuits CAN be made to run on a single supply.
Your circuit is probably dual supply, but do you have an actual complete schematic diagram?
There is no signal inversion at your board's single ended outputs.
The IC has one inverting and one non-inverting output. This IC was originally intended for a balanced mono circuit.
But it can be used for a single ended stereo circuit, as shown. Then the left side must use an inverting op amp circuit.
The B1 is also non-inverting. with DC blocking at both input and output.
The Naim is also non-inverting, with DC blocking at the input.
Your circuit is probably dual supply, but do you have an actual complete schematic diagram?
There is no signal inversion at your board's single ended outputs.
The IC has one inverting and one non-inverting output. This IC was originally intended for a balanced mono circuit.
But it can be used for a single ended stereo circuit, as shown. Then the left side must use an inverting op amp circuit.
The B1 is also non-inverting. with DC blocking at both input and output.
The Naim is also non-inverting, with DC blocking at the input.
I followed exactly the schematic provided on the website, and I powered the OPA with a dual supply. I thought it was incorrect for it to have a negative output.
If your board is wired exactly like the diagram, it does not invert either channel.
Is there a wrong setting on your scope?
Try connecting both probes to just one channel's output. Do both look the same?
Is there a wrong setting on your scope?
Try connecting both probes to just one channel's output. Do both look the same?
Thank you so much, Rayma, you’re really kind to help me.
When I connect the probes to the DAC output, both channels show a positive value. However, when I connect the dual power supply, the output on the RCA is negative.
Testing with the multimeter, I find a voltage of -1.4V on the RCA outputs.
When I connect the probes to the DAC output, both channels show a positive value. However, when I connect the dual power supply, the output on the RCA is negative.
Testing with the multimeter, I find a voltage of -1.4V on the RCA outputs.
I don't understand. Can you be more clear? Do you mean there is negative DC voltage, not negative AC (signal)?
This circuit should never be able to have DC voltage on the outputs of either polarity.
There should be DC blocking capacitors there. Value should be about 10uF 35V bipolar. Do you not have them?
Can you draw a complete circuit diagram of what you are measuring?
If you are using the diagram above, that is more of a conceptual diagram, not an actual schematic.
What is the DC voltage output of each channel, at the DA-7 outputs?
This circuit should never be able to have DC voltage on the outputs of either polarity.
There should be DC blocking capacitors there. Value should be about 10uF 35V bipolar. Do you not have them?
Can you draw a complete circuit diagram of what you are measuring?
If you are using the diagram above, that is more of a conceptual diagram, not an actual schematic.
What is the DC voltage output of each channel, at the DA-7 outputs?
I wouldn't know how to explain myself better. I don’t have the DAC with me right now, but tomorrow I can upload some photos from the oscilloscope.
Probably the DA-7 left channel has +1.4V DC output, since it is single supply.
Then the left channel op amp, which has a gain of -1 (unity gain, inverting) will output -1.4V DC.
Then the left channel op amp, which has a gain of -1 (unity gain, inverting) will output -1.4V DC.
ryma
go look at the product page he quoted, it is not so straight forward as it seems and I don't think he can explain any better what is wrong. There is no schematic at all. Picture of the POT and other paraphernalia has nothing to do with it, I don't know why he is showing it. He must first establish that the DAC is operational as he wants to apply it. There is a number of solder links he has to configure. There is some interpreting to be done. I don't do DAC, have not tried to, 50 bucks for a topping is my goto DAC
go look at the product page he quoted, it is not so straight forward as it seems and I don't think he can explain any better what is wrong. There is no schematic at all. Picture of the POT and other paraphernalia has nothing to do with it, I don't know why he is showing it. He must first establish that the DAC is operational as he wants to apply it. There is a number of solder links he has to configure. There is some interpreting to be done. I don't do DAC, have not tried to, 50 bucks for a topping is my goto DAC
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Unfortunately, this link is all I have; I can't find any other schematic or information about it.
It seems like they sel the raw dac then you are left to configure it to your need and ad to it what is needed externaly
I guess he can do some simple signal polarity measurements with a scope and see if the left channel of the DA-7
does indeed invert the signal polarity, while the right channel does not invert polarity.
If so, the right channel op amp must be a non-inverting unity gain circuit (signal applied to the positive input).
But also he likely needs DC blocking capacitors at the outputs of the DA-7, about 10uF at 35VDC.
Also there must be main output DC blocking capacitors as well, even if the power amp has them at the inputs.
does indeed invert the signal polarity, while the right channel does not invert polarity.
If so, the right channel op amp must be a non-inverting unity gain circuit (signal applied to the positive input).
But also he likely needs DC blocking capacitors at the outputs of the DA-7, about 10uF at 35VDC.
Also there must be main output DC blocking capacitors as well, even if the power amp has them at the inputs.
