It might be useful to check out Pat's post on HTF this morning -- he asked the Outlaws about this very subject.

------------------
Gonk

I was going to post that here ... guess it's not necessary now.

------------------
pat----

email: pat@sklenar.info ---===--- home page: Grumpy's Lair

Pat,

Good job! I didn't get it either. Something else that I don't get was this post over at HTF:



Well, I've been looking, but can't find any manufacturer who offers a SEVEN channel amplifier rated at 200 WATTS per channel for $1800.00. What did I miss?

I don't know of many seven channel amps at all (B&K has the Reference 7270, but it retails for closer to $3000 -- and it is rated at 7x375W at 4ohms and 1830 watts max power consumption). There are some 5 channel amps that are competitive with the 755 in the sub-$1500 price range (not necessarily with 200W of power, but considered sonically competitive based on the 750), and I think that's what was being referred to at HTF.

------------------
Gonk

Steve,

What Gonk said.


Gonk,

Man, are you fast!


------------------
pat----

email: pat@sklenar.info ---===--- home page: Grumpy's Lair

Pat, Gonk'

Thanks for your reply. I looked at the spec's shown on their web site for the 7270 and it was interesting to note power ratings are listed as: at 8 ohms,200W @1 kHz and at 4 ohms it is 375W @ 1kHz. Seems the Outlaws were right-at least in this case (as indicated in your original post at HTF)! Thanks again.

CHARLIE FTC rules cont....for ever?

I think Outlaws response to this issue is accurate enough. What is the issue? Do you think the 750/755/770 will not actually deliver their rated power?
P=V^2/2R
Power is RMS, volts are peak and R is in ohms. Buy my hand the 750 delivers 51.3 volts peak into an 8 ohm load. Peak current is 6.4A. All 5 channels driven gives you 32A peak. Peak volts times peak amps give you peak power; 1644W. I believe that I read that the 750 has a 1650 VA transformer. Judging from the 4 ohm performance this is conservative.
The 750 delivers 44.7 volts peak, 11.2 Amps into 4 ohms; all channels driven for a total of 2500 W peak. If it can do this and not catch fire I think we're OK. I don't think fire has been a big issue, at least with the 750.
Hopefully the material you listen to has an average 50% duty cycle, DC just doesn't sound that interesting. If the amps are 50% efficient and considering 50% duty cycle the VA ratings make sense.
IMHO unless the amps don't deliver on their spec this is a moot issue. Wait for a test if you really doubt Outlaws ratings on the 755/770. I'm sure the 750 was tested; did it not deliver full power?

[QUOTE]Originally posted by rcaudio:
I think Outlaws response to this issue is accurate enough. What is the issue? Do you think the 750/755/770 will not actually deliver their rated power?
P=V^2/2R
Power is RMS, volts are peak and R is in ohms.

Um.... How can you compute root mean square watts from peak volts?

Basicly I think the issue is whether the 770 can really deliver 2100 watts to 7 speakers CONTINUOUSLY while drawing 1800 watts from the outlet. This would seem to be a neat trick.

I have little doubt it can do it (and probably more) for brief moments and I'm pretty sure it can more than deliver the goods on real program material. That's not at issue.

I can't think of any MUSICAL or HT application where I would have a source that required a symetrical high level sustained signal from all channels. But this (highly artificial) scenario seems to have made its way into the specs.


Charlie

The problem isn't that the amp won't sound good or won't be satisfactory, as 99.9999% of people will never experience a lack of power or clipping with this amp. Even 100 watts per channel into 4 ohms for 7 speakers is way more wattage than most people need. The problem is that the specifications say that the amp can produce a continuous 300 watts per channel for all 7 channels into 4 ohms. This simply is not possible based on an admitted limitation of 1800 watts through the transformers.

The issue is simply incorrect specifications. There should be an asterisk that says something to the effect of "* amplifier power is limited to input voltage and current. With a 120V and 15A circuit, this amp will produce X watts per channel into 4 ohms, all 7 channels driven 20-20kHz." Where X is less than 300 watts.

For me, when a company makes a statement that I know is not true, I lose some faith in the company. Is it a big deal? Not really, but it does make me wonder.