Amp that refuses to play L-R?

888 Views 7 Replies 4 Participants Last post by gijoe, Apr 22, 2009

Fast1one

Discussion Starter · Mar 20, 2009

This is a little odd... I am now using a cerwin vega 400.4 for my rear channels. I hacked up a splitter(or combiner, if you will) to make L-R and the amplifier refuses to, well, amplify it...?

It works on all three of my home rigs. I took it out twice to confirm that the amplifier is working and for some odd reason it just doesn't play L-R. Have any of you heard of an amplifier circuit that does this?

Thanks!

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capnxtreme

· #2 · Mar 21, 2009

Don't you need balanced inputs, to do the subtraction?

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Fast1one

Discussion Starter · #3 · Mar 21, 2009

capnxtreme said:
Don't you need balanced inputs, to do the subtraction?

I thought so, then I tried it with two splitters I had laying around and it worked for me in my home rig. Center information completely canceled...

Once I tried it in my car, no worky

I did a temporary fix. I already had the phase flipped on one of the mids (for R-L). So I added time alignment and compensated for my seating position. After playing with the TA difference, gains, and crossover points I got something fairly acceptable.

Of course this is an acoustic cancellation, I would love to figure out how to do it before the amplification

PS, I tried hard wiring with the speaker leads and it doesn't work that way either. The amplifier has a stereo and bridged setting, I tried both to no avail.

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capnxtreme

· #4 · Mar 21, 2009

I suspect your home rig might have balanced input circuitry, even if it's not in the specs.

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Fast1one

Discussion Starter · #5 · Mar 21, 2009

capnxtreme said:
I suspect your home rig might have balanced input circuitry, even if it's not in the specs.

Even my 1973 Pioneer SA-7100?

I can guarantee my DIY amp doesn't have balanced inputs, yet it works :surprised:

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14642

· #6 · Mar 21, 2009

If the inputs are balanced, then this is simple, you just invert the phase of one of the inputs. You can use a simple splitter to do that. If the amplifir doesn't have balanced inputs, you need to isolate the signal ground. A ground loop isolator will do. Invert the phase of one of the outputs (on the amplifier side of the ground loop isolator). You need one with transformers.

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Fast1one

Discussion Starter · #7 · Mar 21, 2009

Interesting. So essentially add the L-R splitter after the ground loop isolator and connect it to the amplifier.

Will something like this work? Does anyone have experience with this product? Ground Loop Isolator - RadioShack.com

Or does anyone have a better option? Thanks guys!

Andy Wehmeyer said:
If the inputs are balanced, then this is simple, you just invert the phase of one of the inputs. You can use a simple splitter to do that. If the amplifir doesn't have balanced inputs, you need to isolate the signal ground. A ground loop isolator will do. Invert the phase of one of the outputs (on the amplifier side of the ground loop isolator). You need one with transformers.

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gijoe

· #8 · Apr 22, 2009

I want to bump this up for a little more info on how to implement this without balanced inputs.

I've got an 880 prs and even when running a 2way front stage and sub, you can connect rear speakers. I was thinking about how I can take those speaker wires and wire an amp to get L-R and try to work out a proper rear fill situation.

I understand the concept of L-R, but I'm not sure how I can make it work. Does anyone know on the 880 (when in network mode and Internal amp on) whether the rear speaker wires are full range and if there is any delay programed already?

To summarize. If I don't have balanced inputs, what steps need to be taken to run a proper L-R, delayed rear fill? If you can guide me to links about this I would appreciate it, most of what I find is only applicable to balanced inputs.

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