Axiom Home Page Forums General Discussion Advice from Axiom Owners Help me understand amplifiers!!

Hi All,
Right now I am running a 7.1 system with 7 M3's and a EP350v3 powered by a Marantz 7500. The Marantz is rated at 105W per channel. Would I notice any sonic difference adding an amp? Secondly when one adds an external amp the receiver's amp is bypassed correct, or is it an additive thing? I have been thinking about a 7 channel amp but people say that is overkill for the rears. However I like to listen to cd's in multichannel stereo which I assume means all speakers are receiving the same single and would need the same amount of power in this instance, correct? Can anyone clear any of this up for me??
Thanks,
Mike
PS: I really like the system already. Upgradeitis is all!! That EP 350 ROCKS!!

If you are using either SACD/DVD-A or DPL IIx/NEO6 etc for your multichannel then it is actually sending different signals to the appropriate speakers to give the surround sound, so, no, they would require different amounts of power with the fronts still requiring the most (generally speaking).

Thanks for the quick reply. Unfortunately that didn't answer my question. I found the next article in Alan's tech talk a bit more helpful. The one about headroom. What I still don't understand is are separate amps power added to the amps in your receiver or do they supersede them? For instance, my Marantz is rated at 105 X 7. I was looking at the Outlaw 7125 which is 125 X 7. On the face of it it seems only 20 watts more per channel if the Outlaw's amps take the place of the Marantz or am I now getting 230 watts per channel? Can someone clarify this for me??
Thanks,
Mike

An outboard amp will supersede the inboard amp, they do not combine power.

What some do is to buy a two channel amp for the fronts to take some of the "burdon" off the receiver...allowing it to flex it's muscle a bit with the remaining channels...

I understand that part but I believe (according to my owners manual) that multichannel stereo is acomplished by feeding the left channel signal to both left front and left surround speaker and the right channel signal to both right front and right
surround speaker. Additionally, the center channel
reproduces a mix of the right and left channel. As well in 7.1 feeding the signals to my left and right rear surround.
What is my point?? Surely this must suck a lot more power then any of those other DSP??
Mike

It doesn't use amplifier power to do that, that's all in software and in the pre-amp stages.

Thank-you sir!!!!

Ok,I'm confused again. I understand that Multi Channel stereo is yet another DSP like Neo 6 or DPL. But when ALL speakers are playing something ALL the time (unlike some DSP's where a rear surround may be playing very little)surely this must be more taxing on the internal amps of the receiver no?? Sorry if my questions are simplistic!!
Mike

Possibly, but it's not something I would stress about. If you've got the volume almost all the way up and you're using multi channel stereo, then it might be a concern, but if you've got the volume almost all the way up and you're playing anything, you probably need the external amp.

Ok, so if one were to buy a stereo outboard amp that is only rated at 50 watts per channel (audiosource amp100) for the front L/R is this still better than the 105W (x7) from the Marantz?? KWIM?
Mike

I would say not. Either save your money or look for something in the 200 to 300 watt class.

So something like the Behringer A500 may be a better fit?? Thanks again for listening to my ramblings!!
Mike

Sure, you could run a pro amp with good results.

Why do you think you need more power, is your receiver showing signs of distress or clipping? How loud are you listening in dB's and how big is your room.

A second question I have which is a little off topic, is how do you like your new 350v3? Did it replace another sub? I just ordered 2 350v3's to go with my ep600, but my room is massive.

Mike, you shouldn't notice any difference(mainly because there wouldn't be any)if you added another amplifier unless the maximum power capacity of your 7500 is being exceeded(unlikely). As was already pointed out, another amplifier would use the pre-out of the 7500 to drive it and the internal amplifier channels of the 7500 wouldn't even be connected to those speakers, so the power would be the responsibility of the new amplifier alone.

As to the use of all channel stereo, this is sometimes suggested for a more uniform sound all over a room in party situations, etc., but it isn't realistic to have the same sound coming from all different directions. If you like it, of course, it's your money and your call, but I use modes such as DPLII, Neo:6 or Logic 7 to put the other speakers into more realistic use with 2-channel material.

As to the power used in all channel stereo, you're correct that the surrounds get the same sound and use the same power as the mains on that side. However, you may be overlooking the fact that when two speakers play the same sound the result is 3dB louder than before. For example, if the front left speaker is playing at a fairly loud 85dB level and using about 1 watt, and you then add the left surround at the same 85dB level, yes 1 more watt is used for that speaker, but the sound level from the two combined would be 88dB. If you kept the same 85dB combined level, each speaker would use 1/2 watt to play at 82dB and produce the combined 85dB sound level, and total power usage would be the same 1 watt as when just the front speaker was used. So, don't be concerned about extra power usage in that mode.

To answer your first question. No my receiver has never shown signs of distress. I don't get my SPL meter out alot, but when kids are down with me probably low 60's. When it is just me high 70's. Movies probably louder for small instances. Room is 28 by 28 by 7, so if my math is right roughly 5500 sq.ft. The only reason I ever thought about it is everyone seems to preach that seperates are the way to go and I guess I got caught up in that and upgradeititis.
To answer your second question, I LOVE the 350, it replaced a PDR10. I think I could probably use 2 in my room downstairs, but that is another whole thread!!
Mike

High 70s? You probably don't need an amp.

I agree with Ken. If you had larger speakers and liked to crank things up a bit, an extra amp may be helpful in that bigger room. The m3's are rated at 92dB from 1meter(3ft away) when only driven by 1 watt. Sounds like you could be a member of the Mojo 1/2 watt club.