Ok, I know some might think its pointless but others are using the 360 as a media center so obtaining better sound has it worth. Read on....
I recently got a dead xbox 360 and did some goolgling to see if I could fix it. I found out about the overheating issues and the dreaded 'Red Ring of Death' which apparently cost MS over a Billion to sort out....
So I came across a site called 'Xbox Scene' forums, found a fix and got the thing working. (Loving 'Race Driver GRID ', amazing graphics! )
While snooping around inside I found the chip responsible for the 360's analogue output. A WOLFSON WM8517HCGED. I couldnt find the datasheet for this i/c so I emailed Wolfson and spoke to a lovely lady who was very helpful. Turns out this chip was made for Microsoft only but is "very simmilar" to the WM8521 (identical piout) exept: "WM8521 outputs 2Vrms - the WM8517 is 1.7Vrms"
This is a DAC with built in output stage and derives its clock signal from the 360's master clock, the only one of the mother board.
The output has small SMD Ceramic's presumably for DC blocking. The local decoupling on the Digital and Analogue supply pins and 'CAP' pin (reference) are also small Ceramic SMD's. Output traces are very very thin. Voltage regs are miles away and have other components deriving power from the same rail's, which also has really thin traces.
This looks to me to be far from ideal for good audio, and looking at the Wolfson data sheet guideline's seems to confirm this.
We all know Computers put loads of crap on the power supply and the 360 is basically a PC. That troubles me knowing the audio stage is getting its juice from the same supply as all those noisy processors.....
So I decided I'll be adding chassis mount RCA's so I can use a decent set of cables. Figured I might as well use a pair of decent film caps and tack the leads directly to the chips output pins. I'm also thinking of tacking in better decoupling caps on the power rails using the same values as specified by the datasheet: 10uF with 0.1uF (film) bypass. Same for the 'CAP' pin. Im not going for any 'boutique' components here, just cheap wimas for the film bypass and reasonable Lytics for the 10uF.
Not knowing that much about digital audio, I have a few questions:
If I were to lift the supply pins and take them to an external PSU of my own creation, would that be beneficial? Something with separate regs for Digital and Analogue rails, good caps and diodes and a small trafo? Maybe with a chassis mount IEC filter also.
Can I take all the the chips ground connections to this new PSU, or do they need to reference to the mother board for any reason?
What about a decent clock just for the chip leaving the master clock to handle all the 'computery' bits? (Nothing megabucks, just something that isn't connected to the processors, running off the new 'audio only' external PSU? If I cant do this are there any other ways to reduce Jitter?
Let me know what you think people.
You're also limited by the fact that most 360s I've seen sound like vacuum cleaners when they're running. It might not be that bad for you if you're streaming off the network because that DVD player isn't running, but your noise floor with this setup will still be quite high. If you have have the extra room, you might want to consider building a silent media center PC, the performance from it should be much better than the 360.
Love that video!
The reason most stock 360's are so noisy is due to the crap heat sink on the graphics processor. The fans are temp controlled and the excessive heat causes the fans to go full tilt. I fitted an extra 5v fan helping the air flow over the heat sink so I now have a cool xbox that runs much quieter. See the link above and find out about 'RROD'.
Im not thinking of using this as a media center I just play games on it. With that in mind I suppose its pretty pointless to mod it. I know using an external DAC would be better but I dont have one and I dont think I'll be getting one any time soon. My 360 is one of the second gen ones and dosent suffer from a noisy DVD drive. Anyway, I'll probably add RCA's on the back so I can use a proper cable.
The reason most stock 360's are so noisy is due to the crap heat sink on the graphics processor. The fans are temp controlled and the excessive heat causes the fans to go full tilt. I fitted an extra 5v fan helping the air flow over the heat sink so I now have a cool xbox that runs much quieter. See the link above and find out about 'RROD'.
Im not thinking of using this as a media center I just play games on it. With that in mind I suppose its pretty pointless to mod it. I know using an external DAC would be better but I dont have one and I dont think I'll be getting one any time soon. My 360 is one of the second gen ones and dosent suffer from a noisy DVD drive. Anyway, I'll probably add RCA's on the back so I can use a proper cable.
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