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bezeek 26th December 2006 06:05 PM

Looking for a surround processor.
Hi, I didn't know where to put this, so sorry if it's in the wrong section.

I've been curious to know, is there such a surround processor that can take 2-ch input from a 600w/ch amp @ 4-ohms and distribute the power amongst 2x110w (front), 2x100w (rear), and a center channel?

(I also need one with line-level output for a powered sub.)

As an alternative, would it be practical to re-route the circuitry on such a processor to bypass the internal amp and pass through mine instead?

Brian Ziemek

Pano 28th December 2006 06:26 AM

Hi Brian,
You may not have gotten any answers yet because you question is rather confusing. :scratch:

What do you want to do?

You want to have left-center-right + 2 rear?
Normally that is done at line level in a processor of some sort. Generaly built into AV receivers these days.

Then you will need 5 channels of amplification. Again, built into receivers. But you can use a separate processor and separate power amps if you like. Just remember that the processor is upstream of the power amps.

bezeek 28th December 2006 01:58 PM

Yeah, I see how impractical and confusing the question was now. At the time of writing I really had no idea of what sorts of equipment were available on the market, or in what order the average A/V receiver handled the signal from start to finish.

I was hoping to find a standalone processor (with absolutely no other functions) that assumed the amplification had already been done, but from what I hear such a thing is really not cost-effective on the consumer level, or common to find anyway.

I'd be glad if a mod can delete this thread. Thanks.

- Brian

taloyd 28th December 2006 09:01 PM

Actually, what you're looking for certainly exists, and only fell out of popularity due to surround receivers becoming mainstream.

It's a passive high-level (post amplifier) surround decoder circuit, based on the Hafler circuit back in the 60's and 70's...

Here's a schematic and some data:

and as an actual implemented box here:

I actually purchased one (a later model QD-1) that has much nicer binding posts for use in my home setup. It worked very well, and I later retired it due to purchasing an actual Dolby Digital/Pro-Logic receiver.

If you have a high-power stereo amplifier, this circuit will definitely work. The only important thing, is to try to have matched speakers all round...

If you're interested in the unit, I can sell it to you for $20 and $10 shipping (it's actually pretty heavy)... if so, email me at:
taloyd AT gmail DOT com

hope this helps,


bezeek 28th December 2006 11:02 PM

Wow! Thanks for that reply, I've been told everywhere else that either no such thing can be purchased by itself, or I'll never find one at a worthwhile price.

At this point, I'm looking at full-on receivers, but for the time I may just buy one of those until I can better afford a high-end receiver.

I'm going to visit family for a few days, but I might just drop you a line when I get back.

Thanks again!

- Brian

Pano 29th December 2006 03:29 AM

Hey Tal,
If Brian doesn't want it, I do! I love the analog decoders. Just like the old Dolby jobs in the cinemas.

Aloha and Happy New Year!

bezeek 29th December 2006 04:18 AM

Woah, hold up there man, I was first in line. ;)

I'm returning at night on the 1st, so I'll update the thread to let you know if I sent Tal that email or not, if that sounds fair enough.

Pano 29th December 2006 08:34 AM

No worries. :) I just want to be second in line.

I had another look at the one on Ebay. I didn't realize at first that it's a speaker level decoder, exactly what you were looiking for. Never seen one of those before.

bezeek 29th December 2006 01:20 PM

There's actually quite a few on eBay, most of which use line-level use with their own pre-outs.

When I first looked around I made the mistake of searching for retail products, and eBay slipped my mind completely. :p

Vidgamer 1st January 2007 06:29 PM

That box looks like a clean solution. But, if you want to try out the Hafler circuit (or part of it), you can wire up a simple Hafler circuit with just speaker wires (assuming that your amp can handle low ohms, but then, that's probably still and issue with that box -- I'd be afraid to do this circuit on a typical receiver).

I just connected 3 speakers (L/C/R) to a beefy 2ch amp. I'm still trying to decide what to make of it. Instead of having a distinct separation, it kinda blurs the channels together, creating a more seamless presentation. But it definitely gives you sound which images convincingly. Interesting.

Caution: if you wire this yourself, you need to not only take care to wire it correctly, but if your amp does not have a common-ground, I'm pretty sure that the wiring is different than if it does have common-ground. So, that's something to watch out for when looking at these diagrams.

Prolly the reason it's so hard to find information on stuff like this is that you can basically do it for free. :smash: I don't mind promoting it and sharing the fun, though. :D

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