Hi Nick!
Thank you for the explanation!
However, there is one problem: 2,78 V DC output of the opamp. How to reduce this voltage to zero without the use of a capacitor?
Regards!
I wanted to let you know that i have my Najda up and running.
I compared it to my Audio-GD DAC-19 (2x Burr Brown 1704 dacs) and i am quite happy to say that the Najda sounds superior to the Audio-GD.
There was no burn-in time, just out of the box and using pass through 96Khz.
At this pont i am using the Najda also as preamp and have integrated my sub <80Hz and the mains >80Hz (L4R).
The Audio-GD dac is for sale
I compared it to my Audio-GD DAC-19 (2x Burr Brown 1704 dacs) and i am quite happy to say that the Najda sounds superior to the Audio-GD.
There was no burn-in time, just out of the box and using pass through 96Khz.
At this pont i am using the Najda also as preamp and have integrated my sub <80Hz and the mains >80Hz (L4R).
The Audio-GD dac is for sale
Hi,
I've completed my second set of Najda and the challenge was this time:
1U cabinet, external low jitter clock ready, WaveIO USB board, Najda symmetrical input expansion board ready, optimization of cabling in the minimum allowable place.
Here are low resolution pictures of the front, back and top
I choose a slimline 1U 230 mm deep with silver 10 mm front panel from Modushop cabinet which is very nice to work with. I also use their new digital printing offer. Of course, milling on both sides of the front panel, back panel milling and digital printing had a cost (about 300 €) but I like the result.
Note that I had some minor problems that I will describe in a subsequent post
JC
I've completed my second set of Najda and the challenge was this time:
1U cabinet, external low jitter clock ready, WaveIO USB board, Najda symmetrical input expansion board ready, optimization of cabling in the minimum allowable place.
Here are low resolution pictures of the front, back and top
I choose a slimline 1U 230 mm deep with silver 10 mm front panel from Modushop cabinet which is very nice to work with. I also use their new digital printing offer. Of course, milling on both sides of the front panel, back panel milling and digital printing had a cost (about 300 €) but I like the result.
Note that I had some minor problems that I will describe in a subsequent post
JC
Attachments
I would like to warn people interested in such a nice cabinet (Slimline with 10 mm front panel) that there are some milling made on the inside of the front panel which are undocumented in the original dxf files that could be downloaded from the web site. You can see on the picture were the arrows are !
So, I was not able to fix correctly my navigation panel but Modushop handled the situation quite nicely. I designed a small work around part that correct the problem (see the closup). They made it very quickly and sent it to me for free.
Note that, on my request, they have put today in the download section of the web site a new file with all updated 1U, 2U, 3U & 4U 10 mm front panel to avoid future problem.
Also, I had a small problem with the "SPDIF" marking on the front plate, part of the "F" is broken. Apparently it was a local problem with the primer used before the digital printing. Beside this, I don't have any other problem with the new digital printing so I think that the price requested (25€) is by far more affordable than the engraving which stays of course more "eye catching"
So all in all, I'm very satisfied by this cabinet. Now, I'm waiting for Nicolas to have new set of expansion board available and of course updated software that will allow mixed IIR/FIR, external clock, and decimation.
I know that he is working hard on this kind of things for another Pro audio and that, at the end, we will benefit from his work for our nice Diy Najda board but when is another question...
JC
Attachments
Yes, this is a C-R-L-C filter I designed. The idea was, beside further filtering the TDK SMPS, to provide some kind of isolation with other devices. In addition, on the 5V side, the double choke provide some separation on the ground side too. It could be specially interesting, if your SMPS doesn't provide separate ground between output voltages.
For the Najda board, R = 0 to avoid too much drop-out voltages and chokes values according to the current outputs (2 x 4.2 mH for the 5V, 2 x 15 mH for +/- 12V)
For the external low jitter clock, I cut a pcb in half and use 47 Ohms and 2 x 47 mH). With those values, I'm under 1 mV peak to peak of residual noise.
JC
I designed this filter not specifically for the Najda board but to be usable in future projects I will have.
In general, it is better to let the designer choose where to join the digital and analog ground. For Najda, Nicolas did it on the main board through a 0 Ohms resistor. By using common mode dual chokes for the 5V digital you provide some kind of isolation of the digital ground from the SMPS. But the main purpose of this filter is to filter the residual high freq noise from SMPS.
JC
I would not go below let's say 4.9 V for the digital line. I did some successful tests at 4.85V but this depends on too many factors.
On the analog side, no real problem here, though you must have a margin for the 2 low power linear regulators around the volume control IC which should be at about 8V so I would say not lower than 10.5 or 11V.
JC
Ins and outs of it all
Hope'n for a little help and advice. I would snatch up a Nadja board in a heartbeat but for the fact that it is unbalanced. My intent is to slide it in between my pre-pro (balanced) and eight active drivers , who's amps are also balanced, to take advantage of the filters for a digital crossover. I believe I have away to introduce analog input via the I2S port, but short of adding 8chs of additional DAC's, is it possible to use the DACs that are available on the Nadja and end up with balanced outputs? BTW this all started with a pair of MiniDSP 2x4's that I offed, I felt there was something better, too noisy, hard to get the gain structure right. I'm sure most of you are getting a good chuckle bout now, but I'm just getting my head around this digital thing.
Thanks
JBS
Hope'n for a little help and advice. I would snatch up a Nadja board in a heartbeat but for the fact that it is unbalanced. My intent is to slide it in between my pre-pro (balanced) and eight active drivers , who's amps are also balanced, to take advantage of the filters for a digital crossover. I believe I have away to introduce analog input via the I2S port, but short of adding 8chs of additional DAC's, is it possible to use the DACs that are available on the Nadja and end up with balanced outputs? BTW this all started with a pair of MiniDSP 2x4's that I offed, I felt there was something better, too noisy, hard to get the gain structure right. I'm sure most of you are getting a good chuckle bout now, but I'm just getting my head around this digital thing.
Thanks
JBS