Running yamaha's m70 amps/ for each channel

clayton h · 02-25-2004, 09:13 PM

Well frist off i would like to say hi to everybody iam new to this board, and to all this stereo stuff. Ok to the question, the stereo i have consist of c70 preamp, two m70 amplifers(all yamaha stuff) and a pair of klipsch klf 20 speakers. i would like to run each m70 on there own channel, the preamp has two set of preouts one normal the other inverted. In the yamahas book i would hook left normal to left input and left invert to right input on the left channel amp, then i would hook right normal to left input and right invert to right input on the right channel amp. Left channel speaker hook up from the left amp would be left + to left + and right + to left -, as for the right channel speaker hook up from the right amp it would be right + to right - and left + to right +. These amps are rated at 200 watts per channel into 8 ohms, and 250 watts per channel into 4 ohms. Is this called briding the amps into mono, what would the watts output be and would there be a possibility of hurting these amps. The speakers are rated at 200 watts continous, 800 watts peak into 8 ohms. Sorry for the long thread just want to make sure you all know what i talking about and trying to find out. Why iam doing this would like to have more power without spending more money.

thanks
clayton huff

Wayne A. Pflughaupt · 02-26-2004, 10:55 AM

Clayton, what is it you’re trying to do? Use two amps to drive one pair of speakers?

Regards,
Wayne A. Pflughaupt

clayton h · 02-26-2004, 04:26 PM

yes one amp for the left cahnnel and one for the right channel.

Wayne A. Pflughaupt · 02-26-2004, 05:55 PM

Clayton,

Yes, you are bridging the amps when you do this. Bridging an amp is accomplished by driving the inputs out of phase. Most amps have a switch on the back to accomplish the signal inversion but apparently Yamaha takes the unusual approach of accomplishing the inversion from the pre amp’s outputs

However, I have to wonder why you want to do this, especially since bridging will net you only a negligible 50 watts increase in power. Your Klipsch speakers are highly efficient. One of those amps is sufficient to drive them to earl-bleeding levels.

Regards,
Wayne A. Pflughaupt

clayton h · 02-26-2004, 09:26 PM

thanks wayne for the info, these amps where made back in the middle 80s. i guess that is why yamaha did it that way. one last thing you dont think that it would hurt the amps.

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Wayne A. Pflughaupt · 02-27-2004, 06:26 PM

Quote:

one last thing you don’t think that it would hurt the amps.

I expect not, since I assume both the pre-amp and amps were manufactured at the same time. And I assume the “book” you mentioned is the original amplifier manual? If it’s the manual telling you how to do it, then it’s fine. Just remember that you have to be more careful of the speaker’s impedance when you bridge. I wouldn’t use anything lower than 8-ohms.

Regards,
Wayne A. Pflughaupt

clayton h · 02-27-2004, 08:30 PM

yes both where made at about the same time, again thanks for the infomation. well i will give it a try, maybe i can blow something up.

clayton huff

KyleGS · 02-28-2004, 08:12 AM

I'm running an M70 and wasn't aware you could bridge the amp... Does it state the word "bridge" or "mono bridge" in the manual?

clayton h · 02-28-2004, 08:30 AM

well no it does not, in the c80 preamp manual it does show how to hook up the amps as i described in my first post. now i dont know if yamaha was talking about there amps or useing some that could be bridged, i did email yamaha a week ago but have had no repily. i just thought that if they show it in there preamp manual then it should be safe to do it. also this is why i posted this thread in the frist place, but being that these amps are almost twenty years old not much info would be out there and probly why yamaha has not email me back. like i said i will give it try and see what happens.