Hi Folks,
For my own part, I like to listen to music on two channel equipment of my own design. However, in the future I would like to undertake building a home theater set-up for a friend of mine. My objective is to create a Dolby Digital (AC-3) preamp which uses 6sn7 tubes in the voltage amplification stages as I love their sound in my homebrew preamp. My problem: how to get an analogue signal to feed the 6sn7s.
My Questions:
1. Does there exist a circuit board (or just a chip) which will allow me to apply the digital signal from a dvd player and some B+ and get an analoge signal?
2. If so, where does one purchase said item?
For my own part, I like to listen to music on two channel equipment of my own design. However, in the future I would like to undertake building a home theater set-up for a friend of mine. My objective is to create a Dolby Digital (AC-3) preamp which uses 6sn7 tubes in the voltage amplification stages as I love their sound in my homebrew preamp. My problem: how to get an analogue signal to feed the 6sn7s.
My Questions:
1. Does there exist a circuit board (or just a chip) which will allow me to apply the digital signal from a dvd player and some B+ and get an analoge signal?
2. If so, where does one purchase said item?
Well, there are two problems to overcome here:
1. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.
2. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.
While technically this is only one problem, it's such a big one that I thought I would mention it twice. A work around would be to find a stand-alone decoder (I found one on e-bay two years ago for about $100), take it apart, trace out the analog signal runs to where they originate, and take the signal from there into your pre-amp, bypassing the probably low quality analog output sections. I did something similar with an older Sony integrated amp that didn't have pre-outs. I just traced the lines and added RCA jacks on the back to work with a friend's power amp.
1. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.
2. Dolby only licences the decoding algorythm to major manufacturers who pay a royalty for each unit produced. Of course, these go in products like DVD players, decoders, and integrated amps. The DIY market is so tiny that nobody makes a licenced stand alone board. The start-up costs and licence fees would make it financially unfeasable. Since the algorythms are patented, there's no "home-brew" solution.
While technically this is only one problem, it's such a big one that I thought I would mention it twice. A work around would be to find a stand-alone decoder (I found one on e-bay two years ago for about $100), take it apart, trace out the analog signal runs to where they originate, and take the signal from there into your pre-amp, bypassing the probably low quality analog output sections. I did something similar with an older Sony integrated amp that didn't have pre-outs. I just traced the lines and added RCA jacks on the back to work with a friend's power amp.
Note that free software libraries exist for both AC-3 and DTS decoding. While selling a commercial product based on them might get you in trouble, the software is suitable for personal use. So if you really wanted you could build a digital preamp arround a small passively cooled (Via C3 out to 1GHz) single board Linux computer with software on compact flash.
PC104+ boards are available for pretty much every purpose; you can get things like S/PDIF in for your DVD player. S/PDIF in+out to USB adapters are available too.
Boot times on the order of single-digit seconds are possible with the right system, which beats my Lexicon from a hard power cycle.
Use the DACs, current to voltage conversion (resistor with tube buffer), etc. of your choice. Or just use a mainboard with 5.1 analog outputs.
PC104+ boards are available for pretty much every purpose; you can get things like S/PDIF in for your DVD player. S/PDIF in+out to USB adapters are available too.
Boot times on the order of single-digit seconds are possible with the right system, which beats my Lexicon from a hard power cycle.
Use the DACs, current to voltage conversion (resistor with tube buffer), etc. of your choice. Or just use a mainboard with 5.1 analog outputs.
Get it while it's hot! Only 5 hours to go.
http://cgi.ebay.com/Klipsch-ProMedi...ryZ32861QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
You could easily add your tube output in place of the solid state.
I have a few DSP boards from some motorola HT receivers that have CS493263 decoder chips. The chips could be removed and used for a new project, but it would be a heck of a lot of work. Definitely more complicated than just spdif in, 5.1 channel out.
Here is a pic of the DSP board. If you want them their yours.
http://i13.tinypic.com/2cdaf6b.jpg
http://cgi.ebay.com/Klipsch-ProMedi...ryZ32861QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
You could easily add your tube output in place of the solid state.
I have a few DSP boards from some motorola HT receivers that have CS493263 decoder chips. The chips could be removed and used for a new project, but it would be a heck of a lot of work. Definitely more complicated than just spdif in, 5.1 channel out.
Here is a pic of the DSP board. If you want them their yours.
http://i13.tinypic.com/2cdaf6b.jpg
Anonymous1,
The board you have pictured seems like it would do the trick depending on the actual output level at the terminals. If it is not too high, I could probably do a direct-coupled 6sn7 gain stage/cathode follower. One question: would the input be the terminal labeled "AR"? Would this connect to the single digital audio output on the back of the DVD plaver?
6f6
The board you have pictured seems like it would do the trick depending on the actual output level at the terminals. If it is not too high, I could probably do a direct-coupled 6sn7 gain stage/cathode follower. One question: would the input be the terminal labeled "AR"? Would this connect to the single digital audio output on the back of the DVD plaver?
6f6
The price for that Klipsch box seems a little steep. You can buy a complete receiver for that money.
The Technics SH-AC300 and SH-AC500D aren't bad, and don't fetch as much on eBay. But, there's no EQ, the sub crossover frequency is fixed, only the 500D does DTS, and in DTS mode there's no "bass management" or phantom center support.
There's a Pioneer receiver that inexplicably has preamp outputs, the VSX816-K. It can be had for well under $300 US. http://reviews.digitaltrends.com/review3629.html
The Technics SH-AC300 and SH-AC500D aren't bad, and don't fetch as much on eBay. But, there's no EQ, the sub crossover frequency is fixed, only the 500D does DTS, and in DTS mode there's no "bass management" or phantom center support.
There's a Pioneer receiver that inexplicably has preamp outputs, the VSX816-K. It can be had for well under $300 US. http://reviews.digitaltrends.com/review3629.html
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