# Bridge 4 channel to 2 channels for components: Y-splitter or not?



## buzwork (Jun 24, 2009)

*Bridge Boston GT40 4 channel to 2 channels for components: Y-splitter or not?*

I have a 4 channel amplifier that I would like to bridge to 2 channels, but I'm unsure how to correctly feed the amp proper left and right signals.

I think I'll need to use Y-adapters and feed the left + and - on the amp the left Y-adapter input from the HU and feed the right + and - on the amp the right Y-adapter input from the HU. I've attached a quick drawing to elaborate.

The amp is a Boston Acoustics GT-40. I've read through the manual but the only reference to bridging is for a subwoofer, which I'm guessing sums the L+R to derive a mono signal.


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## ealvar (Mar 9, 2007)

I too have a GT40 but I'm currently running it in 4 channel mode.

Seems like using the adapters should work, but I've also seen where amps you would run the HU Front Right to the Left + on the amp and the HU Front Left to the Right +. So, only 2 RCA connections to the amp. The elemental designs nINE.4 is like that.

Also, on the GT40 you'll want to make sure that the Front & Rear input switches are set to Stereo.

If you could post your results, that would be great  I'm interested to see what works best.


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## 60ampfuse (May 18, 2008)

I may be wrong but i believe using the y adapters will just devide the H/U output in half anyways which would be the same as just connecting 1 rca to the front and 1 rca to the rear.


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## ealvar (Mar 9, 2007)

60ampfuse said:


> I may be wrong but i believe using the y adapters will just devide the H/U output in half anyways which would be the same as just connecting 1 rca to the front and 1 rca to the rear.


I think you're talking about the amp summing the inputs? I believe on the GT-40 that's only the case on the rear channels when the input is set to mono. Otherwise it will not sum stereo inputs.

Feeding the Front amp input with two Left signals from the head unit and feeding the Rear amp input with two Right signals should give stereo separation to the 2 bridged channels.

Buzwork, I'll try it on my GT-40 tomorrow and let you know what I come up with.

I also sent Boston Acoustics a quick inquiry on RCA inputs for stereo bridging. I'll post results if/when I get them.


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## NOTORIOUS97200 (Dec 11, 2008)

ealvar said:


> I think you're talking about the amp summing the inputs? I believe on the GT-40 that's only the case on the rear channels when the input is set to mono. Otherwise it will not sum stereo inputs.
> 
> Feeding the Front amp input with two Left signals from the head unit and feeding the Rear amp input with two Right signals should give stereo separation to the 2 bridged channels.
> 
> ...


I'm waiting for this too.
I would like to bridge my GT42 to my front components only! 
We all will have to be careful with the gain settings!!! These amps are very powerful for small comps!


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## buzwork (Jun 24, 2009)

Thanks for looking into it!

I was reading the manuals for some other amps (in particular the Directed 200 & 400 4 channels amps) and they also show connecting the HU Front R to the Amp Front inputs with a Y-adapter and connecting the HU Front L to the Amp Rear inputs with a Y-adapter.


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## ealvar (Mar 9, 2007)

Ok... so I emailed Boston Acoustics and got a reply back from Andres H.

He asked me to give him a call to clarify what I was trying to do.

Ultimately his recommendation was to use a Y-splitter from the Front R of the HU to the Front L & R of the amp and a Y-splitter from the Front L to the Rear L & R of the amp.


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