Hello,

I populated all the the boards (list below) and installed the Tridents (yes, i removed the ferrites) and everything worked from first power on. Beautiful sound!!!

HOWEVER, now (around after a week) when i readjusted (matched) the output Placid BP voltages, and powered off the DAC and put on the cover of the DAC's casing the DAC stopped playing music after next power on.

After looking into the DAC again i noticed that one of the AVCC's leds was not lit. The voltage between IN and GND is 5.30V on both sides of the AVCC, which is the voltage Placid is set to. The output voltage between OUT and GND is 0.85V on both sides. That does not look right, does it?

The Placid was set to 0.5V accross R8, however i have tried several different options now (0.5V being the highest) - 0.36V, 0.47V, 0.48V - but it does not help. The Tridents have all the leds lit. I also measured the voltage across Placid's R3 and it seemed to be really high, around 0.180V. Could this have been the problem, or is it just a symptom of power not drawn by some part of the DAC?

I have my own control software that is reading/writing the DAC registers and at least according to I2C registers the DAC chip locks to the signal and i can get the PLL frequency, adjust volume, etc. I also tried disconnecting the I2C interface and using the DAC's own firmware chip, but this does not help either. The Lock led is very dim and the DAC does not go through the automute led at boot like it used to when it worked.

I tried with another DAC and there was sound.

Any ideas how to continue from here? Could the problem be somewhere else than the AVCC module? And if it is, what shall we do?

Input device: M2Tech Hiface (spdif)
Output device: Hypex UcD400HG HxR modules (balanced)

DAC configuration:
Buffalo II board
2x Placid BP (+15V,-15V, ~0.15V ccs voltage per rail, dual powered)
1xPlacid (5.30V
IVY III (jumpers not soldered)

Also is it possible to power the DAC's AVCC with a Placid? just to try out if the DAC works ok without the AVCC. I got one extra, however it's very early version and does not go below 5.8V by default and the output voltage seems to change a lot more relative to the warmth of the module, compared to newest version.

If 0.470V CCS on Placid procudes 50-60ma shunt (which is the overhead specified in the manual), then 500ma would produce 80-90ma? If that is the case, some 100ma part is not working, since the placid is now shunting 180ma.

I'll test the AVCC module tomorrow and report back.

The AVCC module seems to work connected straight to Placid. Both leds were lit regardless of which side was powered. Should that be the case? Sounds kinda weird (in sense of symmetry) that one voltage input lits both sides.

However, i could not measure the output voltages properly on both sides yet. The other side output was around 3.3-3.48V but the other side only gave occasional voltage bursts. I'll confirm the voltage on that side of AVCC later. My multimeter needs steady connections to for measurement, which requires some soldering extra wires to the AVCC module.

ps. when connected to dac, the led of the faulty side is not completely dark, but very dim.

Edited by user Wednesday, June 1, 2011 9:08:44 AM(UTC)  | Reason: Not specified

I finally had the time and energy to the do the measurements. I attached AVCC straight to Placid again and ensuring proper connections with my multimeter. That resulted steady 3.50V output on both sides, with both leds lit. Result: the AVCC works.

After that i started wondering if the AVCC had good connection to the placid when attached to BII. I found one VDD_IN header pin that i could not measure properly so I re-soldered it along with all the other AVCC pins, just in case. But still no go, only one led was lit.

But, after fiddling around a while, I noticed by accident that when i detach the the VDD_XO Trident from the BII, both leds are lit in AVCC. So, maybe the problem is the VDD_XO after all? I did not find any shorts in the connections or broken resistors in the Trident module. Both leds are lit in the VDD_XO module. Just in case, i re-soldered the header pins and the trident resistor. Still no go.

Then i remembered i tried with several different shunt values on the placid last time. I checked the shunt voltage and it was 0.35V. I started raising it and at .4V the other led light up on the AVCC! I raised it to 0.47V.

So, you know what, it works again! I don't know what the original problem was, but I managed to fix it somehow. Maybe it was a bad connection somewhere. I just wish i had the time to do this several weeks earlier.

pictures could help spot your problem.

That is typically a sign of lack of current from the placid. Try increasing it a bit, or try *only* powering the avcc module. Do not power anything else with the Placid.

That is exactly what i am doing in the pictures. 0.47V ccs voltage should be more than enough. The AVCC is that small thing on top the white cardboard in the overview picture. The whole thing is there just because i am too lazy to get the Placid and the trafo out.

Or how high should/can i go with the CCS?

Edited by user Wednesday, July 20, 2011 5:01:49 PM(UTC)  | Reason: Not specified

Also while only powering the AVCC mmodule back the CCS current from the placid down to say 200ma

I noticed in the picture of both LEDs lit, you are holding the AVCC by it's connectors. Does placing pressure on those connectors make a difference?

Did not help. I have also measured the resistances between the header pins and they are not shorted. I could try soldering the wires straight to the header pins.

By the way. What would happen if i powered both sides from the one 3.50V output that works? Too much power draw or stress to one side of avcc? Too long wires?

Edited by user Wednesday, July 20, 2011 6:22:35 PM(UTC)  | Reason: Not specified