What rectifier diodes are worth upgrading in the power supply? And what numbers would they be on the circuit board?
I've already replaced all the reccomended caps in there with blackgate std's. I'm just looking for the next jump in performance without spending the $300.00 for the linear supply.
I've already replaced all the reccomended caps in there with blackgate std's. I'm just looking for the next jump in performance without spending the $300.00 for the linear supply.
I stacked 3 1955 dac chips in total last night.
I can't say I like what it has done. There is more air and seperation between instruments and vocals, but the bass is too tight now.
Also when playing SACD there is a pop in between track changes and the noise floor seems elevated.
All of the eletrolytic caps in that area are still original. I've noticed that people have changed them for oscon and upped the values. I'm wondering if this is the problem. I don't know what caps or values to change?
I can't say I like what it has done. There is more air and seperation between instruments and vocals, but the bass is too tight now.
Also when playing SACD there is a pop in between track changes and the noise floor seems elevated.
All of the eletrolytic caps in that area are still original. I've noticed that people have changed them for oscon and upped the values. I'm wondering if this is the problem. I don't know what caps or values to change?
Hi,
When you stacked the DACs, did you adjust the bias voltage of the I/V converters to compensate ?
Regards,
Jon
When you stacked the DACs, did you adjust the bias voltage of the I/V converters to compensate ?
Regards,
Jon
Hi,
Have you checked the voltage at the output pins of IC7403 and 7404 (pin 1 and pin 7) ? It should be 2.4volts.
Regards,
Jon
Have you checked the voltage at the output pins of IC7403 and 7404 (pin 1 and pin 7) ? It should be 2.4volts.
Regards,
Jon
Hi,
Change resistors 3438, 3439, 3440 and 3441. Let me know what voltage you measure first though.
Regards,
Jon
Change resistors 3438, 3439, 3440 and 3441. Let me know what voltage you measure first though.
Regards,
Jon
They both now read 2.4 volts after I fixed 4 lifted pins on the stack of dacs.JonHarrison said:
However I noticed that pin 9 and pin 10 of the dacs are shorted together. I can't say I noticed before I fixed the pins if they were like that before. Pin 9 says analog ground and pin 10 says DSD Phase.
The player sounds great in SACD and regular CD. The musicality is back.
Hi,
Don't worry that is correct, the DSD_PHASE signal (phase modulation mode) is not used and thus the pins SHOULD be tied low.
Did you have to change the resistor values to get 2.4V ?
Cheers,
Jon
Don't worry that is correct, the DSD_PHASE signal (phase modulation mode) is not used and thus the pins SHOULD be tied low.
Did you have to change the resistor values to get 2.4V ?
Cheers,
Jon
Ah.. very good to hear that pin is tied to ground. I didn't have to change any of the resistors. 3 pins read 2.4 volts and one read 1.4 I checked all my joints with a meter and found 3 lifted pins on the 3rd dac chip. Once I reflowed those pins everything sounded great and all four power pins read 2.4 voltsJonHarrison said:
Thanks for all your help by the way. Do you think there is any improvement to be had by giving the output stage a linear psu?
Hi,
Yes, absolutely 😀 , the +/-8V regulators are nothing special and the SMPS is noisy - just look at the supplies under a variable load with a scope. Certainly improvement to be heard if you were to fit a seperate supply with (discrete) linear regulators having feedback bandwidth into the MHz and low output Z. A Jung style regulator would be good but even a simple Sulzer type or in fact any op-amp based discrete linear regulator fed by its own supply would be better than what is there at the moment. You may not even have to go to that extreme to get an improvement, just fit a seperate supply with a pair of standard pos and neg 3 pin regulators and listen to the difference.
Cheers,
Jon
Yes, absolutely 😀 , the +/-8V regulators are nothing special and the SMPS is noisy - just look at the supplies under a variable load with a scope. Certainly improvement to be heard if you were to fit a seperate supply with (discrete) linear regulators having feedback bandwidth into the MHz and low output Z. A Jung style regulator would be good but even a simple Sulzer type or in fact any op-amp based discrete linear regulator fed by its own supply would be better than what is there at the moment. You may not even have to go to that extreme to get an improvement, just fit a seperate supply with a pair of standard pos and neg 3 pin regulators and listen to the difference.
Cheers,
Jon
Hi,
Link 4604 isolates the -8VA supply from IC7602 (MC79M08). L4606 isolates the +8V_OpAmp supply from IC7601 (LF80C). The advice not to remove the caps 2612 and 2613 is correct although they are there as reservoirs - not for decoupling as stated.
+8V_OpAmp and -8VA feed the I/V opamps IC7403 / IC 7404 and the output buffer IC7405 as well as the analog switch (scart / surround) IC7400 and the LM833 opamps IC7401 / IC7402 and NE5532 IC7501 / IC7502 used for buffering the scart and surround sound channels.
If you're not worried about the surround channels you could remove R3501/3502 to isolate the new +8V supply and R3504 / R3505 for the new -8V supply then connect these with the same 10R back to the original +/-8V regulators.
R3659 is in the supply feeding IC7601. This in turn feeds IC7603 (LF50) which supplies +5VA. +5VA supplies the analog side of IC7300 (the Crystal CS4362 used for the surround sound DACs) and the analog side of IC7301 AD1955 (the main stereo DACs) so the comment that it improves the digital circuit power supply is incorrect, it is still the analog circuit.
The commonly used recipe for a linear supply here seems to be +/-9V (AC) 1A transformer , bridge , 0.25A fuses , 2 x 1000uF BG standard, NJM7808FA and NJM7908FA then 2 x 470uF BG standard. I wouldn't use the blackgates personally, Panasonic FC / Rubycon ZA,ZL or similar bypassed with polypropylene.
The size of the fuses give you a guide to the current but you could try and measure the volt drop across a low value resistor, you'll probably measure mV though. I'd guess at 10's of mA on each rail.
Regards,
Jon
Link 4604 isolates the -8VA supply from IC7602 (MC79M08). L4606 isolates the +8V_OpAmp supply from IC7601 (LF80C). The advice not to remove the caps 2612 and 2613 is correct although they are there as reservoirs - not for decoupling as stated.
+8V_OpAmp and -8VA feed the I/V opamps IC7403 / IC 7404 and the output buffer IC7405 as well as the analog switch (scart / surround) IC7400 and the LM833 opamps IC7401 / IC7402 and NE5532 IC7501 / IC7502 used for buffering the scart and surround sound channels.
If you're not worried about the surround channels you could remove R3501/3502 to isolate the new +8V supply and R3504 / R3505 for the new -8V supply then connect these with the same 10R back to the original +/-8V regulators.
R3659 is in the supply feeding IC7601. This in turn feeds IC7603 (LF50) which supplies +5VA. +5VA supplies the analog side of IC7300 (the Crystal CS4362 used for the surround sound DACs) and the analog side of IC7301 AD1955 (the main stereo DACs) so the comment that it improves the digital circuit power supply is incorrect, it is still the analog circuit.
The commonly used recipe for a linear supply here seems to be +/-9V (AC) 1A transformer , bridge , 0.25A fuses , 2 x 1000uF BG standard, NJM7808FA and NJM7908FA then 2 x 470uF BG standard. I wouldn't use the blackgates personally, Panasonic FC / Rubycon ZA,ZL or similar bypassed with polypropylene.
The size of the fuses give you a guide to the current but you could try and measure the volt drop across a low value resistor, you'll probably measure mV though. I'd guess at 10's of mA on each rail.
Regards,
Jon
I see, so it's fine to attach the new - and + 8V supply to the power pins on 7403 or 7404 once I remove 4604 and 4606?JonHarrison said:
I'm going to use a lm317 based design mainly because I have the parts already
I'm guessing 375 ma from each secondary of the transformer with a 0.250 amp fuse on the primary side will work fine.
I'm planning on just using a switch in the back to turn the supply on and off. Is there a better way?
Hi,
Yes, or something connected to the power pins.
You could use a relay from the +12V supply to switch it.
Jon
Yes, or something connected to the power pins.
You could use a relay from the +12V supply to switch it.
Jon
Hi,
Yes, when current from the +12V supply flows through the relay coil it attracts the armature and closes the relay contacts, the contacts are used to switch the linear supply on. Don't forget to fit a diode backwards across the relay coil to clamp the switch-off spike.
Jon
Yes, when current from the +12V supply flows through the relay coil it attracts the armature and closes the relay contacts, the contacts are used to switch the linear supply on. Don't forget to fit a diode backwards across the relay coil to clamp the switch-off spike.
Jon
Is anyone willing to share your copy of 963SA schematic with me? I'm modding mine according to the excellent recommendation posted here. Replaced some cap in SMPS with BG and I love the improvement. Now I'm proceeding to the components on AV board and a schematic would be very useful to learn and make sure what I'm going to do.
So could anyone of you kindly share your 963SA schematic with me? Thanks in advance
Wallace
So could anyone of you kindly share your 963SA schematic with me? Thanks in advance
Wallace