DIY 5.1 amplifier and decoder

[martin88]

I am new to DIY audio and was wondering has anyone crated a 5.1 amplifier and decoder

[martin88]

i dont know if this would even be possible would it anyone

[slackerbob]

this has been dicussed before.

http://diyaudio.com/forums/showthrea...threadid=32021

I believe it was determined that the best thing would be to steal the decoder chips from a cheap player, and then them as part of another project.

[martin88]

thanks

[Cameron]

If someone with the appropriate skills (not me) gets up the courage to do a complete 1394 digital audio receiver implementation for us...

With 1394 digital audio, the decoding is done at the DVD player. So the 5.1 channels are readily available. No worrying about dolby algorithms or hard coded hardware.

The only player I am currently aware of with a 1394 digital audio output is the Denon DVD-5900. But there should be a cheaper DVD-3910 coming shortly. I believe DCS using 1394 too, but with a proprietary protocol. Come to think about it, the Denon also uses a proprietary protocol, but can also do the standard one too.

[samsagaz]

so if i want to design and sell some amps with DD decored i need to pay a lot to dolby right?


that sux :S

[thomas997]

Originally posted by samsagaz
so if i want to design and sell some amps with DD decored i need to pay a lot to dolby right?


that sux :S

yes a lot

[Learnincurve]

Cant help with building from scratch, but what about modding an existing decoder?....:

Just got hold of a Klipsch DD-5.1 decoder/preamp. These babies are supposed to do a pretty good job of the decoding, but the analog circuitry and power supply are basic, and the bass channel crossover frequency of 120 Hz. is too high.


Have no schematic yet, but took off the lid and found among other things 3 SB61L256bs-8 chips inside. These look like the most likely candidates for analog op amps but have as yet not found any datasheets on the net.

Was wondering among other things whether upgrading the analog amps to higher quality chips, and replacing the wall plug power supply (12v. 1 A) with something more robust and closer to the actual unit would help the sound quality.

The crossover frequency is probably set digitally so will be difficult to modify. Theres a programmable ROM in there, probably containing Dolby activation codes and settings such as the bass crossover, but Im guessing re-programming it would be beyond the scope of the amateur (is there a source out there for modded ROMS)?


Any ideas/suggestions/experience on modding?

[Schaef]

Originally posted by Learnincurve
Cant help with building from scratch, but what about modding an existing decoder?....:

Just got hold of a Klipsch DD-5.1 decoder/preamp. These babies are supposed to do a pretty good job of the decoding, but the analog circuitry and power supply are basic, and the bass channel crossover frequency of 120 Hz. is too high.


Have no schematic yet, but took off the lid and found among other things 3 SB61L256bs-8 chips inside. These look like the most likely candidates for analog op amps but have as yet not found any datasheets on the net.

Was wondering among other things whether upgrading the analog amps to higher quality chips, and replacing the wall plug power supply (12v. 1 A) with something more robust and closer to the actual unit would help the sound quality.

The crossover frequency is probably set digitally so will be difficult to modify. Theres a programmable ROM in there, probably containing Dolby activation codes and settings such as the bass crossover, but Im guessing re-programming it would be beyond the scope of the amateur (is there a source out there for modded ROMS)?


Any ideas/suggestions/experience on modding?

Well, it looks like you have a better idea than others I've read, but I'd be willing to bet the chips you've identified as op-amps are actually ram chips. A lot of older decoders (and even some modern ones) needed external ram to help with the processing.

As to the power supply, it certainly won't hurt to replace it, and I'd probably do the same.

What you also want to do is, identify the decoder itself and see what you can find out about it, then you can figure out what can be done with it. Chances are, there is an external rom containing the dolby code like you said, or it may be internal to the chip. You may also find that the decoder and the controller are two separate chips and the controller is setting the crossover frequency in the chip. But, again, you'd need to know the decoder chip to figure all of that out.

[emuman100]

Sorry guys, my multichannel decoder project has been on hold. The STA310 is available without a license in small quantities from AVNET electronics for $18 a piece. I ordered 4. It's controled by I^2C ir a parallel interface. All you need is the input and 3 DACs and you have yourself a decoder that will decode AC3, multichannel PCM, multichannel MPEG and MP3. Problem is, trying to code asm is very time consuming for me for an IC I haven't worked with yet. It will get done, one of these days. Any help on the 8051 asm and help with the design would be greatly appreciated.