Nevermind... just had to supply the isolators with 3.3v and this was sorted... but it appears I might have botched this board somehow... I get no sound from the right channel for some reason
Edit: Really strange behavior from this board... on power cycle it won't detect the source again and the Rev goes back to FF until I remove the unbuffered outputs and put it back in again?
Managed to pull the pad from J7 for one of the outputs
(probably from removing the opamps. Tapping it straight from the capacitor and it's working now.Problem is now the fpga sometimes goes to Rev. FF and won't detect inputs sometimes... any ideas on what I should be looking at Soren?
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I have my dac on loan, so can't add pictures right now.
Ref-Ds power 3.3v iso on Dam and 5v clean side on JLsounds I2S. BiB powers Dam through main power jack at +/-11V. Haven't gotten the time to remove the bridge or onboard caps yet.
Ok... after some probing I think I have the same issue as wineds for this board (funny since I took care to use kapton tape for this board).
I've since used kapton to cover the resistors and capacitors and used a heat gun to go over the transistors near J8... J7 and J6. Seems to have done the trick hopefully. *phew*
Edit: nope... sigh not sure what's up now.
I've since used kapton to cover the resistors and capacitors and used a heat gun to go over the transistors near J8... J7 and J6. Seems to have done the trick hopefully. *phew*
Edit: nope... sigh not sure what's up now.
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Managed to pull the pad from J7 for one of the outputs
Problem is now the fpga sometimes goes to Rev. FF and won't detect inputs sometimes... any ideas on what I should be looking at Soren?
If it show fpga rev F.F, then the fpga is not programmed on power up for some reason....
Assuming it's a new board that have not been exposed to heat guns or other heavy modifications, then it could be a power issue, how are the board powered ?
Why bother with heat guns when removing components you will likely never use again? Just get some side-cutters and clip the leads of the op-amps and remove the remains with iron. Done and dusted, no damage.
With lead-free solder you are just asking for trouble reheating the entire board like that, kapton tape or not.
With lead-free solder you are just asking for trouble reheating the entire board like that, kapton tape or not.
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Adding capacitor to VDD
Seems the most critical supply of this and most any DAC is the reference voltage. I am thinking about adding capacitors to the +/- 4V output. One way to do this is to hang say a 100uF OSCON at the shift register VDD. Thus (one can add 16 of them, one per shift register). Comments?
Seems the most critical supply of this and most any DAC is the reference voltage. I am thinking about adding capacitors to the +/- 4V output. One way to do this is to hang say a 100uF OSCON at the shift register VDD. Thus (one can add 16 of them, one per shift register). Comments?
No doubt it is best to try this first. Yours is good advice.
Worked easily enough for the output opamps. I am a believer in creative destruction ...
Thanks for responding Soren! It is my second board so it has been modified per the first board to prep for your upcoming firmware. I know this ruins the warranty.
The +-5v is provided by PA's SSR03 (+5.022v and -5.032v if that makes a diff)... which is powering my first board and this second one. When significant time has passed the second board always powers up properly. After that it is a crap shoot and you're right the +-4v isn't coming up even though it gets the 5v. I can't seem to find out what's causing the intermittent failure on this board.
On this problem board, yes. I've since put two bleeder resistors. I tried it with just +5V which I thought was working. Now I'm trying both to see if it works.
Edit: I'm glad I'm not troubleshooting this issue alone. Hopefully you discover which capacitor is causing the issue. I can't seem to find which capacitor (and there are a lot!) is causing the problem.
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The +-5V need to come up quickly and together, and power down quickly and together, I could imagine a situation that if the +5V is not up when the negative reference is turned on then the reference inverting opamp, powered by +5V, could latch up....
Thanks for this info Soren. I tried with bleeder resistors (470R across the 100uF caps) and it still takes a long time (~2 mins) for consistent successful power on between power cycles.
Is it possible to let me know the location of the SMD (I'm assuming here?) capacitor powering up the negative reference? (I'm assuming it's the ones near J7?) I think having the bleeder resistor there would be more effective. Based on your post, I think my negative reference is taking too long to drop. You can PM me if you think this is making things go way too off-topic.
The strange thing is that I'm using the exact same power supply for both boards (the boards are stacked) and the board that's been the pilot is working perfectly fine. The power out of the SSR03 does come on and goes out very quickly.
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I just did a few more power cycles and the SSR03's negative rail does power-off just a tad of a split-second slower. Soren are you suggesting that for my second board it's that sensitive that this slight discrepancy has enough charge that it will cause the inverting opamp to latch up no matter what? (unless fully discharged)
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if this is a problem, then i would guess a shunt regulator would be best suitable for this, since if you build both regulators exactly the same way, with same current - then they will power-off pretty much exactly the same (since they always consume CCS-current). Would maybe be worth trying?
Wineds is using salas shunts (AFAIK) and he's having the same problems.
It helps that Soren has shared a situation as to why the +-4V supply can sometimes lock up like that. Evidently my second board stores charge more than my first board, I guess? I will try to remove the bleeder resistor on the positive rail next and hopefully that helps.
Don't think it's because of power off itself, although it probably have some influence if in latchup. And if something run at the edge there will be difference between boards
The important thing is that the +- 5V are up quickly, which the original power design do and the rest of the board then assume.... There is one second between power on and the uC turn on the reference, power need to be ready then.
But can't really say much as I don't know your regulators.
Thanks for this Soren... if the uC powers up quicker than the +- 5V can that possibly cause the same problem as well?
Hi All,
This weekend, I have tried the power inputs from 7.5v to 7v DC on J2, it seems the sound is better with more dynamic.
On the another hand, I searched on the net there is a power supply by Dexa, which can adjust the power input with very low noise level. Just wonder if someone already tried it for the DAM, or using R-core transformer with good regulator will be better....
could someone share suggestion or experience?
Thanks
This weekend, I have tried the power inputs from 7.5v to 7v DC on J2, it seems the sound is better with more dynamic.
On the another hand, I searched on the net there is a power supply by Dexa, which can adjust the power input with very low noise level. Just wonder if someone already tried it for the DAM, or using R-core transformer with good regulator will be better....
could someone share suggestion or experience?
Thanks