Little upgrade to shunt
After receiving the final version of DAC modules we have detected a very little oscillations on shunt regulators in high frequency range (about 150KHz).
Measurements and simulations made with the collaboration of CAAD allowed to find a simple solution to this problem.
To make this modifications are not necessarily required SMD components but if you want to use SMD and you have problems to find these components you can ask to Quang Hào.
1) Remove R9 on op-amp modules (as suggested before)
2) Remove R10 on op-amp modules (as suggested before)
The following modification must only be made only on +1.2V , +3,3V and +15V shunt regulators.
3) Add 100n X7R as described on attached pic -->All are X7R (better dialectric compared to U5r , Z5R etc)
4) Add 1uF X7R as described on attached pic -->All are X7R (better dialectric compared to U5r , Z5R etc)
These modifications also will reduce the temperature on the shunt of the op-amp module.
The modification as been applied on the last DAC modules sent.
See the image created by CAAD.
After receiving the final version of DAC modules we have detected a very little oscillations on shunt regulators in high frequency range (about 150KHz).
Measurements and simulations made with the collaboration of CAAD allowed to find a simple solution to this problem.
To make this modifications are not necessarily required SMD components but if you want to use SMD and you have problems to find these components you can ask to Quang Hào.
1) Remove R9 on op-amp modules (as suggested before)
2) Remove R10 on op-amp modules (as suggested before)
The following modification must only be made only on +1.2V , +3,3V and +15V shunt regulators.
3) Add 100n X7R as described on attached pic -->All are X7R (better dialectric compared to U5r , Z5R etc)
4) Add 1uF X7R as described on attached pic -->All are X7R (better dialectric compared to U5r , Z5R etc)
These modifications also will reduce the temperature on the shunt of the op-amp module.
The modification as been applied on the last DAC modules sent.
See the image created by CAAD.
Attachments
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Are there shunt regs on the main board that are not 1.2 or 3,3V?
Are the light blue indications your suggestions where to do the mod most easily?
Summary of all the modifications
The modifications necessary for the shunt are only these four.
The correction made in the post #1464 is solved with these last modifications.
If you have problem with spdif input because your source is not standard 75 ohm you can eliminate the 75 ohm resistor after input transformer and add a 1uF or 10uF capacitor on C35 and C36 (a little cut of pcb is necessary) [post #1547].
The modifications necessary for the shunt are only these four.
The correction made in the post #1464 is solved with these last modifications.
If you have problem with spdif input because your source is not standard 75 ohm you can eliminate the 75 ohm resistor after input transformer and add a 1uF or 10uF capacitor on C35 and C36 (a little cut of pcb is necessary) [post #1547].
No, the I/V jump covert the output to voltage mode
Could you explain better the other problems ?
Ok I want I out so I remove the "I/V" Jumpers thank you.
Other problems are solved. The plexi glass is Glued properly. Before that I sawed a little off it and the receiver could be placed properly and everything works perfect.
Really looking foreward to listen when I have finished my amps.
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Everything worked and I turned it off took out the I/V jumpers. The little Dc on output was gone but remote and buttons on front does not work anymore. Must be the moon ?
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