Relating to thread regarding a DIY 5.1 decoder. Posts there indicate licensing problems point to buying a used decoder.
So, if that route is taken, does anyone know of a DIY 5.1 preamp, either kit or plans?
Barring that solution any reccomendations as to model or source of moderately priced prefab 5.1 preamps would be appreciated.
Thanks
So, if that route is taken, does anyone know of a DIY 5.1 preamp, either kit or plans?
Barring that solution any reccomendations as to model or source of moderately priced prefab 5.1 preamps would be appreciated.
Thanks
Off-the-shelf, the Sony P9000ES runs about $500 or so. It's designed as an adjunct to the TA-9000ES to allow 5.1 switching/volume control, but it functions just fine as a 5.1 preamp. This is probably your only commercial option. Performance is supposedly relatively good.
DACT makes a nice-looking 6 channel stepped attenuator. Not cheap (~350 or so, I think). Great if you don't need input source switching. www.aloha-audio.com is a US source. DACT should (?) handle europe directly, I think.
The CS3310 volume control chip is used in a bunch of high-end pre-pros (Sonic Frontiers, TAG-McLaren, Rowland preamps). It's basically an analog-domain stepped attenuator implemented on a chip. The only theoretical drawback is that it does have an integrated op-amp stage to provide gain if needed. Properly implemented, these should be very, very good. Needs a microcontroller, but the serial protocol is really simple - can probably get away with a PIC, or a simple 68HC12 board. These use a cool shift in/shift out approach, which allows daisy-chaining an arbitrary number of units. Available as DIP or SOIC package.
Burr Brown has released/announced an equivalent which might be even better and handler higher voltages, but I think is only available in SOIC.
DACT makes a nice-looking 6 channel stepped attenuator. Not cheap (~350 or so, I think). Great if you don't need input source switching. www.aloha-audio.com is a US source. DACT should (?) handle europe directly, I think.
The CS3310 volume control chip is used in a bunch of high-end pre-pros (Sonic Frontiers, TAG-McLaren, Rowland preamps). It's basically an analog-domain stepped attenuator implemented on a chip. The only theoretical drawback is that it does have an integrated op-amp stage to provide gain if needed. Properly implemented, these should be very, very good. Needs a microcontroller, but the serial protocol is really simple - can probably get away with a PIC, or a simple 68HC12 board. These use a cool shift in/shift out approach, which allows daisy-chaining an arbitrary number of units. Available as DIP or SOIC package.
Burr Brown has released/announced an equivalent which might be even better and handler higher voltages, but I think is only available in SOIC.
I'm currently working on a roll-my-own 6.1 preamp. However, I'm still designing/prototyping. It really isn't that complicated, but the route I'm taking may not interest you. Let me know if you want more info.
Definitely still interested. Don't know yet about the decoder aspect but maybe something will surface there also as it seems there are more new/used decoders than decoder/preamps available at the present. When I started the quest I wasn't planning on an overnight solution.
In the interim I've been acquiring the bits and pieces for the power amps. As I plan to build the amps as monoblocks they can always be used in pairs for some friends' stereo systems if the home theater component DIY doesn't work out.
In the interim I've been acquiring the bits and pieces for the power amps. As I plan to build the amps as monoblocks they can always be used in pairs for some friends' stereo systems if the home theater component DIY doesn't work out.
My idea is basically to piggyback off of an existing AC-3 decoder. I'm using a Technics SH-AC300 decoder (cheap-see ebay) but I believe virtually any outboard decoder could be used, with varying degrees of success perhaps. However, instead of simply taking the analog outputs I pull the digital L/R/C/LS/RS/Sub signals out where they interface from the DSP to the AC300's internal DAC (a CS4226).
This digital signal is then routed through a ASRC (AD1896) to the output DACs (AD1853). Volume control is done with hybrid digital/analog attenuator; AD1853 allows analog attenuation via its current reference, so by using a uC to switch relays and set the digital volume one can achieve something like 30dB of cut (1dB steps) without much loss of S/N ratio, or more than 5 relays/channel. If you design this output stage specifically for your amps you can really maximize your system S/N, especially compared to commercial offerings that are forced to be compatible with a wide range of hardware.
I'm also planning on adding a selectable active matrix decoder for the center rear channel, because I'm curious about its value.\
This kind of setup is attractive to me, because it is a basically a high quality DAC/volume control, so it can be used with most any decoder that comes along...if it becomes possible to make my own decoder (or upgrade) in the future I can simply add that to the box. Also, using a differential output DAC means a balanced signal can be routed to the amps, eliminating ground loops and a good deal of common-mode noise. Better (and cheaper) than those $$$ cables.
This digital signal is then routed through a ASRC (AD1896) to the output DACs (AD1853). Volume control is done with hybrid digital/analog attenuator; AD1853 allows analog attenuation via its current reference, so by using a uC to switch relays and set the digital volume one can achieve something like 30dB of cut (1dB steps) without much loss of S/N ratio, or more than 5 relays/channel. If you design this output stage specifically for your amps you can really maximize your system S/N, especially compared to commercial offerings that are forced to be compatible with a wide range of hardware.
I'm also planning on adding a selectable active matrix decoder for the center rear channel, because I'm curious about its value.\
This kind of setup is attractive to me, because it is a basically a high quality DAC/volume control, so it can be used with most any decoder that comes along...if it becomes possible to make my own decoder (or upgrade) in the future I can simply add that to the box. Also, using a differential output DAC means a balanced signal can be routed to the amps, eliminating ground loops and a good deal of common-mode noise. Better (and cheaper) than those $$$ cables.
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