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TX-NR709 impedance switch

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Post  FeelTheThunder Thu May 10, 2012 10:43 am

I finally upgraded from my trusty TX-DS747 to a new TX-NR709. The 747 has served me very well over the years but too many blue-rays that my son was watching did not have 5.1 and only had DTS. All the HDMI inputs are great also.

I have a question about 4-6 ohm impedance. I am using PSB Stratus Mini monitor front speakers (4 ohm). I have them connected BI-Amped (connectors removed). When I play it loud, up to about 0-DB and maybe a little more form a good CD source in 4 ohm mode it breaks up. When I switch it to 6 ohm mode it sounds much better up high and then it seems to switch down in quality just like the 4 ohm mode and breaks up again. Is that the built in protection circuit? Are my PSB speakers just too much for the AMP? I have tried it without bi-amping and the same thing happens. This did not happen with my 747 which was only rated for 6 ohms. My 747 also played my cerwin vega VS-120's (4 ohm) for years with no issues. I have not yet tried the cerwin vegas on the 709.

I do not quite understand impedance even after all the reading I have done about it. Back when my 747 was new Onkyo said "Beware of rear-panel speaker impedance switches. When set to the low impedance position, the switch reduces internal supply voltages and available output power." I am guessing this is what the 709 is doing.

This is an amazing receiver, I cannot believe all the functionality I was missing out on. I have so many analog audio cables left over after using HDMI for most of my audio sources. I purchased the "7" class 709 thinking it would be similar in performance to my 747 but maybe my thinking was a little off. My 747 was third to the 939 and the 838 in the day. the 709 is fifth down from the top now. I don't play it at max very much anymore so the 709 will do fine, I just want to make sure it is the protection circuit that is doing this and not something else wrong and is my 747 a higher class amp?

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Join date : 2012-05-08

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Post  OnkyoUSA Thu May 10, 2012 4:11 pm

Hi FeelTheThunder,

In so many words it is the protection circuit doing this.
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Post  FeelTheThunder Fri May 11, 2012 8:54 am

Since this receiver is Certified 4ohms performance and it sounds terrible at higher volumes with the 4 ohm switch on, which receiver would I have to move up to to get the same performance as my 6 ohm certified TX-DS747? Do I need an 809 or 1009? I expected this TX-NR709 to be equal to or better then my 747 due to the 4 ohm certification, not worse. Rolling Eyes Rolling Eyes

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Post  OnkyoUSA Fri May 11, 2012 2:09 pm

Hi FeelTheThunder,

It has more to do not with the power but with the older technology used on your speakers so one of our newer more powerful models will not resolve your issue.
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