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Old 21st October 2019, 04:56 PM   #5111
damiangt3 is offline damiangt3  United Kingdom
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Quote:
Originally Posted by Markw4 View Post
For LT1763, probably wise to follow the advice in the data sheet on choice of input, output, and noise suppression caps.

Whether LT1763 or LT304x would be better may depend more on layout rather than regulator data sheet specifications. It helps for regulators powering HF/RF circuits to be dedicated to particular loads, located very near the load, and be mounted on the same ground plane as the load (in order to minimize ground inductance and or noise effects).

What might be best for you may depend a lot on your experience/skill at fabrication using small parts.
Looking at the job in hand, it shouldn't be too difficult, I'm going to be using some small 100v Wima MKSs. For the clock, there's already a 106C (10uf) tantalum cap in place, should I leave this or replace with a better quality electrolytic?

Quote:
Originally Posted by Markw4

Regarding AK4137 board power, I used a Chinese LT3042 (with pass transistor) board as a +5v digital supply pre-regulator. AK4137 was powered by that since there are secondary 3.3v regulators on the board, just as there are on the dac board.
I have one of these, a useful board to have.

Quote:
Originally Posted by Markw4
One thing I did find when using one LT3042 board to power all digital board functions is that a ground loop was formed between the +5v ground returns from the dac board and the AK4137 combined with the I2S ground connections between the two boards. Some I2S RF was apparently flowing between the two boards through the +5v power grounds rather than the I2S connection grounds, and that caused some audible degradation of sound quality.

What I did to verify and correct the problem was add some cable clamp ferrites on one of the power supply ground returns to the 5v supply. Adjust the number and size of the ferrites for best sound quality.

As an alternative to that I probably could have used two transformer windings and two LT304x regulators to independently power the dac board and the AK4137 board. Then I2S ground currents might stay where they are wanted and not go where they are not wanted.
That's really interesting to know, it's been a while since I had the board connected up, I did have that powered separately (using the NewClassD at the time).

Quote:
Originally Posted by Markw4
However, since LT1083 regulators, and other good sounding analog stage regulators, tend not to be super high gain error-amp regulators they don't fully eliminate all power supply ripple in one stage. For that reason it can help to use two stage regulators and or one or two-stage RC filters before the regulators. LC filters don't usually sound as good. If using multiple regulator stages it can be helpful to use transformers with maybe 20v or 22v secondary windings. Then some voltage can be dropped across the primary regulator and a little more voltage dropped across the secondary regulator. It all depends on what lengths one is willing to go to in order to get the best sound quality.
This really interested me when you mentioned it earlier on the thread, this coupled with providing more voltage and not relying on the minimum needed for the LDO. For the LT3045s I have, they are powered by my Salas running at 7v, this has sufficient power for the LT1763s when I mount them.

Space-wise, I'm struggling, so using a R-Core with 2x15v and 2x6/9v might be worth considering.

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Last edited by damiangt3; 21st October 2019 at 05:05 PM.
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Old 21st October 2019, 11:16 PM   #5112
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by damiangt3 View Post
For the clock, there's already a 106C (10uf) tantalum cap in place, should I leave this or replace with a better quality electrolytic?
The caps and other components that come with the dac board (except for the ES9038Q2M chip) are all very cheap parts. I found that the ceramic caps were pretty piezoelectric (probably not X7R). Up to you what you want to do though. The compromised quality of components that come with the board is not as big a problem as the circuit design. That is to say, the dac really needs proper AVCC supplies and a 3-opamp output stage. If those things are being fixed, then it might make sense to fix other things too.
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Old Yesterday, 08:36 AM   #5113
Solve is online now Solve  Sweden
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I stumbled over Vivo Xplay 6 smartphone with ES9038Q2M inside.
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Old Yesterday, 06:45 PM   #5114
damiangt3 is offline damiangt3  United Kingdom
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Quote:
Originally Posted by Markw4 View Post
The caps and other components that come with the dac board (except for the ES9038Q2M chip) are all very cheap parts. I found that the ceramic caps were pretty piezoelectric (probably not X7R). Up to you what you want to do though. The compromised quality of components that come with the board is not as big a problem as the circuit design. That is to say, the dac really needs proper AVCC supplies and a 3-opamp output stage. If those things are being fixed, then it might make sense to fix other things too.
Thanks Mark, having 'dumped' the output stage in favour of the offboard Twisted Pair, implemented an op-amp AVCC and moved all of the other DAC power supplies to a mix of LT1763 (next stage) and LT3045 there really isn't much left. Once I start to use the IIS route in from the AK4137 and 'remove' the onboard inputs this leaves 11 SMDs surrounding the DAC and the crystal.

I must get the Arduino connected!
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Old Yesterday, 10:02 PM   #5115
damiangt3 is offline damiangt3  United Kingdom
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Have I made a mistake by removing the inductors whilst finding a point on the PCB for soldering the new power source?
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Old Yesterday, 10:11 PM   #5116
Markw4 is offline Markw4  United States
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Originally Posted by damiangt3 View Post
Have I made a mistake by removing the inductors whilst finding a point on the PCB for soldering the new power source?
The inductors are presumably there to minimize noise from loads from getting into the power supply rails and adversely affecting other loads, and or possibly affecting performance of the voltage regulator.

Once dedicated regulators are available for each load then its not clear if there would be reason for keeping the inductors. Might do more good to remove them. Hard to know for sure without trying it both ways.
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