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Old 2nd May 2010, 06:19 AM   #1
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Default xbox 360 compatible diy DAC?

Hello, I have an xbox 360 and since it is my primary media center, I wanted to build a DAC that is compatible with its TOSlink output. I am going to use it with a tube surround sound decoder(circa JRB) so it will be driving high impedance (220k~500k). Budget is somewhat of an issue, but I don't mind spending more if I have to. Any suggestions?
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Old 9th May 2010, 01:24 PM   #2
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Default What is a tube surround sound decoder(circa JRB)

What is a tube surround sound decoder(circa JRB)
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Old 10th May 2010, 12:17 AM   #3
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The decoder that John Broskie outlined in the tubecad journal.
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Old 10th May 2010, 07:58 AM   #4
Joris is offline Joris  Netherlands
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Hi,

Do you want to build a surround DAC?
Or just two channel driving a surround amp?

I'm using my TDA1541A DAC, but I can only play games on the xbox, when I put in a movie, the sound will change from stereo to DTS or something like that. It's not possible to fix the digital output to stereo only?

Best regards,
Joris
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Old 11th May 2010, 06:37 AM   #5
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I believe that in the xbox settings you can choose digital stereo and it should pretty much stay that way. I plan just to use it for games though, I rarely watch movies and if I do I'm usually not at home, watching them on my setup. If I can find a DAC that outputs 6 surround channels that would be great, but any Diy DAC that will work with the 360 is cool, then I'll just build up a decoder, although I'd rather it be an all in one thing. I already have power amps and speakers, and from a space and practicality standpoint, just can't bring myself to buy a new surround sound amp and speakers setup just for the 360 when I could build a dac and use what amps I have.
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Old 11th May 2010, 07:20 AM   #6
Joris is offline Joris  Netherlands
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Quote:
Originally Posted by Lingwendil View Post
I believe that in the xbox settings you can choose digital stereo and it should pretty much stay that way. I plan just to use it for games though, I rarely watch movies and if I do I'm usually not at home, watching them on my setup. If I can find a DAC that outputs 6 surround channels that would be great, but any Diy DAC that will work with the 360 is cool, then I'll just build up a decoder, although I'd rather it be an all in one thing. I already have power amps and speakers, and from a space and practicality standpoint, just can't bring myself to buy a new surround sound amp and speakers setup just for the 360 when I could build a dac and use what amps I have.
Hi,

I know about the settings, but when you set it to stereo and put a DVD in the tray, it Will change to Dolby Digital, causing the DAC to produce any sounds but music...

I guess you'll be able to find some DAC at ebay, it is also possible to create the PCB for yourself though.

Xbox 360 AV Cable Modification to Add coax digital | Warnock Inc.
Doing that will save the money of buying an optic receiver, they're quite expensive.

You should be able to use something like this:
Hi-End CD DAC TDA1541A (CS8412 & SAA7220) Standard Kit - eBay (item 280411615600 end time May-15-10 23:25:38 PDT)

It is less expensive to create it yourself though...

Best regards,
Joris
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Old 10th January 2011, 01:32 AM   #7
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So, digging this thread out from way back when, I'm finally getting around to build this unit for my system. After some research, I'm going to go with DIR9001 w/ Toslink input, and run that into a PCM1794 with low impedance discrete I/v stages, and this will be sent through a differential amplifier using 6111WA sub-miniature triodes, from there I'll pull my signal from one anode for SE output, as well as using an XLR jack for each channel. Any ideas for a good passive I/V stage? So far I'm thinking, 47 ohms to ground, and then a 470 ohm resistor with a 10nF capacitor to ground for each input to the differential amplifiers' grids. This should put my low pass filter at about 33KhZ. Then I'll use a tube converter for the L-R and L+R for the rear and center channels. The Circuit I'm going to use for my rear and center channels is outlined in the TubeCad journal here.
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Old 10th January 2011, 04:51 AM   #8
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Ok, no interest? Oh well. Anyways, for my design, I'm using 47 ohms from each current output to ground, and then a 470 ohm, 10nF low pass filter, should this be good for the PCM1794? Voltage gain will be provided by a tube differential amplifier using 6111 subminiature triodes. The tail will be a BJT CCS. The 6111 has a gain of 20, so I should get a gain of 8 or so at each anode of the tube, taking into account the 7.8mA signal current, I should get .366v across the 47 ohm, and I should get 2.938v at each anode. Does this all seem reasonable?
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Old 10th January 2011, 04:08 PM   #9
qusp is offline qusp  Australia
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reasonable yes, worth the effort?... not sure. the dac you mention does not perform well with passive IV IMO.

also have you addressed this
Quote:
I know about the settings, but when you set it to stereo and put a DVD in the tray, it Will change to Dolby Digital, causing the DAC to produce any sounds but music...
this would seem quite an issue.

I always think visual gimmick whenever someone mentions subminiature tubes
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Old 10th January 2011, 05:38 PM   #10
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Quote:
Originally Posted by qusp View Post
reasonable yes, worth the effort?... not sure. the dac you mention does not perform well with passive IV IMO.

also have you addressed this


this would seem quite an issue.

I always think visual gimmick whenever someone mentions subminiature tubes
I mainly use my xbox for games, music and videos, rarely for DVD, so We'll see. Worst case scenario I'll just put the xbox RCA outputs into my amp and have them switched.


I know the submini's are a little novel, but I like them for their linearity, low plate resistance, and lower voltage requirements. If I had some 6GM8 or 6922 they could work here just as fine, but I have seven new JAN 6111 still in box,
so that's what I'll use.
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