View Full Version : Phase Inverter bridge and SDAs?
12-21-2004, 12:11 PM
Okay all you lurking EE's, what do you think the effect of this (http://www.avahifi.com/root/equipment/bridge/index.htm) might be on the SDA SRS? Probably a dumb question, but since the grounds of the two amps are not used, and the phase is inverted between the channels, would this allow bi-amping with the SRS?
12-21-2004, 12:42 PM
Good question that has been perkin in the back of my mind also.
I have an AA DTI which has a phase inverter built in. In my case I have a Modulus 3A preamp which I believe does not correct for phase prior to the output. That said, I should be able to use the DTI in the digital domain to invert the phase and get the SDA effect back.
I THINK but am not sure this would work(I have not tried it yet but will) and if it does the DTI could be had for less than $75.00.
I would think this would not work well with the SDA's. I have an amp that uses an inverted channel and the effect on the SDA is horrible. I assume that this inverted phase would work similar to the inverted channel and cause the SDA effect to be poor.
12-22-2004, 02:44 PM
Looks to me like this device goes between a preamp and and amp. It looks to be the same device as Soundcraftsmen used to bridge some of their amplifiers. Maybe you already know this and are talking about using it to bridge amps and then run the SDA-SRS. This certainly will not work. What happens is the "-" speaker outputs (physically one of the + outputs on the amp) are at a potential, not ground. This is the worst scenario for the SDA-SRS.
12-22-2004, 06:22 PM
Thanks for the thoughts.
What if the SDA IC wasn't used? Yes, I know the SDA drivers would be disabled. But if channel crosstalk was completely cancelled/eliminated by this type circuitry (prior to the crossovers) would the stereo drivers in the SDA produce the "true stereo" effect were used to?
12-22-2004, 06:43 PM
But crosstalk etc wouldn't be eliminated. From what I read it looks like all this device does is allows you to input L&R input from pre, it then has L&R out (normal phase, same as the input) and L&R out (180 degrees out of phase, same as swapping + and - leads). I'm not sure what you could do with that as far as SDA or crosstalk is concerned. Inside the speaker the SDA array is out of phase with respect to the mains but that is driven by the crossover. If you just drive the speaker with the out of phase outputs through an amp it would be the same as your normal amp setup with the + and - wires swapped. Sure, if you ripped out the crossover you could drive your mains with the normal phase out (and then through an amp) and drive your SDA array with the 180 degree out (through another amp) but I don't think it would buy you anything. As a matter of fact you would have to tweak the frequency response so as to not output much bass or treble. (the crossover currently does this to the SDA array). Could be I'm missing the intent here. If you are thinking the SDA cannot be hooked up with certain amps (as is a very common complaint) it is not because the amps are out of phase, it is because the "-" terminals have different voltages on them. Connect them together (through the IC) and it is like connecting the + and - side of a battery together.
12-22-2004, 07:07 PM
Originally posted by madmax
If you are thinking the SDA cannot be hooked up with certain amps (as is a very common complaint) it is not because the amps are out of phase, it is because the "-" terminals have different voltages on them. Connect them together (through the IC) and it is like connecting the + and - side of a battery together.
Thanks, that's the information I needed to "get it."
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