OPPO DV-970HD modification

[ivodonchev]

I have OPPO DV970 which I have bought from ebay because of very positive review.

The first impression was very good. I have liked the fat and musical sound, the bottom and middle frequency seems to be fine but the top end was not so good. After one-two hour of listening the sound of the Oppo is tiring me.
I have spend many hours with oscilloscope to measure and many hours to listen my oppo to improve the sound. Because I have only one Oppo DV970 player I have use the other player for reference which is with the some DAC CS4360 inside but with tube out section. However here is what I have done mostly on the power supply section.

Here is schematic and board of the SMPS.

[ivodonchev]

Here is the power supply and current for the different line:
- 3.3v digital section for MediaTek take 0.75 A and are well regulated with very low noise.
- 5V digital and analog power supply of the DAC take 0.05A and is very bad regulated with a lot of noise. After checking what cause this noise I have noted that the motor drive servo control circuit is connected together with digital/analog DAC power supply.
- 5V power supply of the motor servo control take 0.5A
- (+9V and -9V) for opamp's take 0.01A and are very well regulated with low noise especially at -9V.

So my purpose was to separate the 5V DAC supply from BA5954 motor servo control.

The PCB is very well made with a lot of holes and jumpers so the work is easy.
I have try many way to made well controlled power supply line with low noise but the most proper manner is to force SMPS feedback circuit to control 5V line not 3.3V. This is done by removing jumper JP502 and place jumper at JP506 and change resistor R509 with 3.3K. Now the 3.3V line will be post regulated from 5V line via UZ1084-3.3 device. For this purpose TC505 and TC506 was increased to 1500uF (I have use Rubicon MBZ 1500uF/16V) and L507 was increased to 3A. For the diode D510 I have try MSR860, 1N5822, FR307, SF36, HER307, SR360 but the best working diode is SR580. For UZ1084 I have use 470uF/16V for input and output. D513, TC514, L506 and TC510 should be removed if you want to free the space. In every case D513 must be removed. Install UZ1084 in place of JP507 or JP514 (I cannot remember) because there is close +5V input, GND and 3.3V output. Now we have excellent 5V and 3.3V power supply.

[ivodonchev]

For the 5v analog/digital DAC power supply remove jumper JP501 which connect the two 5v line and place D507, TC515, L509 and TC508 to build separate 5V line. For D507 I have use SR580 again but the holes should be enlarged. Measure the new 5V line and If everything is fine you should read 5.45V on this line. If the line is below 5.45V change the R509 with 3.4k, 3.6k so that you have 5.45V. Now the 5V line will be post regulated from 5.45V line via LD29150 device. I have use LD29150 in DPAK package.
For the input pin put 470nF and for the output pin 33uF/10v. I have install it in place of JP520. Now 5v analog/digital DAC power supply is ok.

[ivodonchev]

Here is schematic of main board

[ivodonchev]

In the main pcb place capacitor TC231 and TC236 which are missing. I have use 47uf/25v Elna Silmic II. Remove all ceramic capacitor near opamp (C2138,........,C2143) and place two 47uF/25v Silmic II for +/-9V near TC220. Use the GND hole of TC220 for the Silmic's and the other legs of caps directly to the +9 and -9V trace (scratch the trace).