None taken! It's really for the best as it's certainly safer to be thorough than otherwise, especially when describing a schematic by looking at a pcb. That's regardless one's experience level.
You've certainly been busy with this board!
You've certainly been busy with this board!
Would this one fit the bill? - its just over $40 : https://item.taobao.com/item.htm?sp...6BaMG6b&id=12809416535&ns=1&abbucket=3#detail
abraxalito, Yes, thank you! It is exactly the right thing. An SRC4392 is rated for harmonic distortion down at -140dB. Don't know how you found it, but good work. I will have to see if I can figure out how to order one to try.
Mark,
Did you put small resistors -2 Ohm or so - between dac and opamp? I found that doing so halves the distortion. 6dB improvement for the price of two resistors, not bad.
Did you put small resistors -2 Ohm or so - between dac and opamp? I found that doing so halves the distortion. 6dB improvement for the price of two resistors, not bad.
Haven't tried it yet, too many things going at once. But, I will. Very interesting observation.
A question for you: when you say 2 small resistors halve the distortion, I assume you mean 2 per channel? If not, I may be missing something.
Looks like that was for a version 1.04 DAC. The current version appears to be 1.06.
Regarding use of a controller, the 1.06 DAC doesn't seem to need one. It appears to adjust automatically to the input stream with the user only needing to select a hardware input using the jumpers, or maybe using a switch instead which has been wired up to the jumper posts.
Hi Mark
Yes, two per channel between the DAC and the opamp, so one for the + and one for the - dac output. I was very surprised with the results; will post measurements, time willing. But I couldn't go below 2.7 Ohm because the board froze for unrelated reasons. Some further experimentation may be required to find the optimum point.
I also tested this with the 9018 board, but in that case any resistance added in the path between opamp and dac produces more distortion.
Yes, two per channel between the DAC and the opamp, so one for the + and one for the - dac output. I was very surprised with the results; will post measurements, time willing. But I couldn't go below 2.7 Ohm because the board froze for unrelated reasons. Some further experimentation may be required to find the optimum point.
I also tested this with the 9018 board, but in that case any resistance added in the path between opamp and dac produces more distortion.
Hi Androa
I don't think it matters so much, all you need is a good reservoir of electrons. I will check the datasheet and get back to you
I don't think it matters so much, all you need is a good reservoir of electrons. I will check the datasheet and get back to you
I am thinking about the Vref. How about changing the resistor divider with a Vref IC ? I think that could improve THD
Vref should work best at the quiescent, or 1/2 of full scale in this case, DAC output voltage. That, in turn, is dependent on AVCC whatever it happens to be.
It is not so important for Vref to be at an exact, pre-determined, fixed reference voltage.
It is not so important for Vref to be at an exact, pre-determined, fixed reference voltage.
Agreed but its important not to fluctuate . I will do some tests this week using the TI VREF monolithic ICs
This is an interesting link in regards with Vref and THD impact (for ADC)
http://www.ti.com/lit/wp/slyy097/slyy097.pdf
This is an interesting link in regards with Vref and THD impact (for ADC)
http://www.ti.com/lit/wp/slyy097/slyy097.pdf
Could someone show me the easiest way to put the Dac in current mode?
I followed the advice of Madds1 post # 355 but the indicated resistance seems irrelevant, I tried all the values between 0 and 3.2M.
I'm a beginner, could you show some images too?
Any suggestions?
I followed the advice of Madds1 post # 355 but the indicated resistance seems irrelevant, I tried all the values between 0 and 3.2M.
I'm a beginner, could you show some images too?
Any suggestions?