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Discussion Starter · #1 ·
Hi all,


For a month and a half, I'm playing with the idea to construct a full home multimedia system, consisting of both audio and video distribution.


To start with, I'm planning to develop my own audio distribution system with 7 input sources and 6 outputs (7 passive, 1 active). To keep costs as low as possible, I would go for custom programming under Linux to be able to build my own multiplexing system.


The only audio hardware I would need would be 6 audio cards (with all the old ones I have I would only need to buy one new 5.1 & DTS capable card), the different speakers (two old pairs, three pairs of cheap ones like the Teac LS-8mkII and a full set of cinema speakers) and last but not least... the amplifiers (since I would be using passive speakers).


Since the amplifiers are my real missing link (I don't have any old ones), initially I looked for a multi-zone distribution amplifier like the Sherbourn 12/900. However, these neat things are awfully expensive. Certainly when you consider I would use it in most rooms just for playing radio !


That's why I wondered if any of you encountered the same problem and thus my question : is there any cheap solution to my problem ?


The only fancy feature I required was some kind of triggering of the signals to automatically switch the amplifiers on and off. Except for my home cinema speakers (where I foresee a decent amplifier in the future) the rest would be not too power hungry, so I don't need a top of the shelf amplifying system.


I had several solutions already in mind :

1) find some kind of USB device that would serve as soundcard and amplifier in one (this would eliminate the problem of so much soundcards in one computer and facilitate programming)

2) use old external amplifiers and do the triggering using a RS-232 controllable power supply (I don't know if these things exist...)

3) buy very very cheap amplifiers and do the same triggering as above.


Does anyone have any comments on all my ideas ?


Ciaos,


Kristof Pelckmans
 

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Discussion Starter · #2 ·
My math is soo bad in the morning ;-)


with 7 input sources and 6 outputs (5 passive , 1 active)


since I found it a rather confusing post, a summary :


inputs :

1. mp3

2. cd

3. radio

4. cassette

5. dvideo

6. video

7. tv


outputs :

1. living room (cinema) (old speakers to start with)

2. dining room (cheap wall-mount speakers)

3. kitchen (cheap wall-mount speakers)

4. study (existing active computer speakers)

5. bedroom (old speakers)

6. bathroom (cheap wall-mount speakers)


Hope this makes things clear !


Kristof
 

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I'm looking into this also. I have decided to build my own amplifiers for each room, sounds scary but actually very easy and cheap as there are a number of single chip stereo amplifiers you can buy for $10 or so. I have chosen the LM4765 from National Semiconductor which does 35 Wpc with mute & standby modes. Add a power supply, a couple of capacitors & resistors and you are in business. You can even request up to 5 sample chips from their web site which will do 5 rooms for $0 cost. Can't beat that for cheap. There are other chips you can use but I like this one because its cheap, 35Wpc is heaps for a room amplifier, its simple to use, performance is good and allows me to control its standby mode (conserving power when not in use). As I'm building a house at the same time, I can prewire the line audio connections, centralise a +- 28v power supply and plan to build the amplifier into a wall plate so its conceiled. I'm controlling the amp volume via a touchpad in each room (based on the 3COM audrey) but that adds another level of complication and the topic of conversation for a different thread - you could just use a stereo potentiometer between the line signal and the chip input.


See this site for more technical info on the chip.

http://www.national.com/ads-cgi/view.../LM/LM4765.pdf


For the sound source, I recommend you use the Delta 410 card, it has 8 analog outputs, very high quality for the price.


The tough bit is the switching matrix, I have designed my own switch matrix that is controlled via the PC serial port, and allows me to matrix 4 stereo outputs to 15 rooms I will have connected. Its also pretty cheap (but harder to build than the single chip amp).


Not sure if this is the approach you are after - it works for me without having to shell out the big $$$ (and an equivalent commercial system will cost me upwards of $10K).


Regards,

Dean
 

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I've always gone to the local stores and checked what they had as far as straight amps go. They usually have a good name brand straight amp that is pretty cheap since it doesn't have the DSP sound effects, DD or DTS decoding. It's just a straight 2 channel amp with volume control. That's how I use my HT setup now. I adjust the main volume for the loudest I would ever want it, then use the computer to control the sound level.



-- just an idea --


Part of the product line that I sell are commercial matrix switching systems like you described, and your right, they are very expensive and bulky. With everything included that you need they run from 10k+ for equipment only to 60k+ installed, programmed and training.


For schools, who are the biggest customers, they are very strict with budgets as everyone knows.


If you could develop such a system that works good, user-friendly enough that secretaries could use, then you could have a good product line. Right now, on the commercial systems, there are so many adjustments and components that it makes their heads spin. Tweakers & installers love it, but not the typical user.
 

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I'm also doing some research on inexpensive amplification solutions and am leaning toward the DIY route.


Here's some useful websites:

http://www.diyaudio.com

http://www.printedelectronics.com/pe/gomain.htm

http://www.chipcenter.com/analog/images/c056.pdf

http://www.interlog.com/~cfraser/Gainclonehome.htm

http://www.sealelectronics.com/index.html

(so far the most useful of all of the sites -- check out his books on amplifier design)

http://sound.westhost.com/articles.htm

http://www.cadaudio.dk/pwmaudio.htm


Please let me know if anyone comes up with more (better) resources.
 
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