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Old 8th July 2006, 10:57 PM   #1
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Default 5 channel amp with digital in (DIY)

I'm looking for a very simple amp with low part count to drive 50-100 watts into 8 ohms. Power supply +/- 60VDC from 1kVa XFMR. 5 channels inside one case with 5 heatsinks.

It's one purpose to drive home theatre with direct digital input for DVD player. RCA sub woofer out.

I see:

Master volume control
Front volume control
Rear volume control
Center volume control
Sub woofer volume control with frequency adjust

I don't know jack about setting up a digital decoder and I have not yet found an amp schematic that is smallish running with 60 volt rails. So I hand it over to you folks to help me out.

Cheers,

Shawn.
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Old 9th July 2006, 03:26 AM   #2
jaycee is offline jaycee  United Kingdom
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"Direct digital input" means you want to decode Dolby Digital/DTS. Forget about doing this in DIY stuff. If you could get the required DSP chip, you couldn't easily get the code to run on it. The nearest you will get is getting a DVD player with 6-channel output, and then making a 5 channel power amp with routing/control for the sub.

100W into 8 ohms would only require 50V rails. If you really want to use 60V rails, you would get nearer 250W into 8 ohms.

All those volume controls mean you'd be controlling your preamp stage digitally, using PGA2311 or similar chips, so I hope you can program a microcontroller
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Old 9th July 2006, 06:07 AM   #3
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There's a different approach to your solution that does what you propose.
Look around for a separate surround decoder. The digital version of the Lexicon decoder is now a pretty good buy. The DC-2 is a really good decoder and was available in THX. It functions as your pre amp with all the controls you desire. Make a separate amp for the subwoofer. Good plate amps are available from Parts Express at reasonable cost.
Then check out member Rob Cheng's web site showing how he made a five channel amp that makes 120 watts with a 1K+ trannie all in one box.

http://www.robcheng.com/

I've used the same approach for my home theatre system with success. Altho the amps are in separate boxes with their own power supplies and individual volume controls.

Regards
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Old 11th July 2006, 04:58 AM   #4
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Quote:
Originally posted by jaycee
The nearest you will get is getting a DVD player with 6-channel output, and then making a 5 channel power amp with routing/control for the sub.
I will look further at these DVD players. It looks like a $200-$300 purchase and it may solve half of the scenario. Thanks.

Quote:
Originally posted by acenovelty There's a different approach to your solution that does what you propose.
Look around for a separate surround decoder. The digital version of the Lexicon decoder is now a pretty good buy. The DC-2 is a really good decoder and was available in THX.
Nice but the DC-2 is obsolete and sells for $1000 used on eBay Lexicon do not seem to have any equivalent to their previous product. Very nice gear though. I like this approach but I want less whistles.

Nice Link! Great builder. Very inspiring for a 5 channel amp if I do say so myself.

I'm very surprised that there are not any DSP/decoder sub system boards out there? Hmmn what was Bryston stuffing their theatre preamp with a few years back? I recall seeing a sub assembly with Motorola at the core but I can not recall the details. It was designed and built in Europe, then tested and shipped to Canada.

I realize it could be a waste of time but I wonder if a DIY digital Decoder can happen at a reasonable cost? Does no one else find this project intriguing? I'm talking DIY baby? Have I inhaled too much solder fumes?

Shawn.
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Old 11th July 2006, 09:56 AM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
just like Ace, I would use amps dedicated to each speaker and save all that speaker cable by locating each amp beside the speaker. Then you only need interconnect from processor to amplifiers.
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Old 11th July 2006, 05:16 PM   #6
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Getting the required DSP or similar chip is near impossible for the DIY'er. Writing or getting the code to program it? Ummm, is there any other electronic secret more closely guarded by Dolby and others? Nope. Even the analogue route is closed since Panasonic stopped making the bucket brigade capacitor device (MN3004)along with the clock (MN3101) needed to produce delays. It's not the solder fumes clouding your judgment.

But, take a look at this solution;
http://www.holtek.com/english/docum/consumer/8970.htm
There's a pdf too big to post here showing application notes and schematic for the delay lines.

There are few (any?) makers of separate surround decoders left in the marketplace. The DC2 sold for something like $9,000 USD when it was introduced about 8-10 years ago. Lexicon owners generally take very good care of their gear. That's an expensive pizza box, but now quite a bargain.
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Old 12th July 2006, 06:35 AM   #7
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Default LYNIX 5.1 SURROUND DECODER

Quote:
Originally posted by acenovelty
Getting the required DSP or similar chip is near impossible for the DIY'er. Writing or getting the code to program it? Ummm, is there any other electronic secret more closely guarded by Dolby and others? Nope. Even the analogue route is closed since Panasonic stopped making the bucket brigade capacitor device (MN3004)along with the clock (MN3101) needed to produce delays. It's not the solder fumes clouding your judgment.
Listen to me, out there on the street, company's purchase license to decode Dolby and others. I have seen turn-key solutions with hidden code embedded in the DSP's on sub PCBs. The end user was given input and output parameters. No need to get into the taboo of what Dolby wants to hold so close to their pocket books. A few requests, a little back and forth and voila the board is suited to the OEM purchasing the turn key solution.

Am I talking like a fool here?

I guess each client of "such" a sub contracted builder must authenticate their clients through Dolby first? Then "these" licensed turn key sub platform PCB makers are allowed to produce the product for their "approved" client(s)? If licensed manufacturers of Dolby products are not allowed to sub license their ASIC's, programmed DSP boards and FPGAs(as they see fit) then the DIY community and the black market are held back? I don't believe in black markets but they exist for ancient social reasons.

I'm a little off but I feel I am on the right track? Please advise? So to me it would be time for an open source version of "their" product and it sounds to me like it is way over due? Again, is it the solder fumes? Why are we not hooking digital optical links to our own DIY gear? Do we not have the right?

I'm getting off the soap box. I need more information as I may have it all wrong?

Back out to the DIY, what is the deal on decoding digital?

BTW, I would love to pay a license fee to use "said" technology for home DIY use. If it is not accessible than I want to destroy the format. I need an open source LYNIX 5.1 SURROUND DECODER and want my source code for free. That way, I know, the DIY forum folks would make it better

Cheers,

Shawn.
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Old 12th July 2006, 11:10 PM   #8
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I looked at a Marantz SR4600 Surround receiver. If I ignored the speaker connections I can use just the front end of this thing as it has outputs for each speaker. $600

I also looked at Anthem's(Sonic Frontiers connection) AVM30/50 processors. $3500 and up.

Then Bryston's SP2 $4000 which is now using TI DSPs not Motorola.

Still no signs of DIY decoding for theatre formats, what a shame. Too many fumes.

Cheers,

Shawn.
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