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#48467 - 03/25/02 07:36 PM Re: anybody know the transformer size?
JasonA Offline
Gunslinger

Registered: 01/17/02
Posts: 84
Loc: Marion, Iowa
Quote:
Originally posted by charlie:
The FTC regulates this. Here is the newest set of amendments I could find. The federal government has this rule for a good reason.

http://www.ftc.gov/os/2000/12/amplifierrulefrn.pdf

Charlie


I emailed Dennis Murphy, who's name appears in this document. Here is his reply:

Quote:

I do enforce the FTC rule, and I also am
the happy owner of an Outlaw 1050. It would not seem to me that the new Outlaw
could produce 7 channels of 300-watt power at 4 ohms continuously in the home.
(That's a personal opinion, not a legal ruling, and it's subject to rebuttal.)
But you should know that the Rule does not really apply unambiguously to
multichannel amplifiers of this type. The Rule requires that all "associated"
channels be driven to full power simultaneously during the FTC rating test.
That part was written in 1974 when the only real "multichannel" amps were
stereo. For those, "associated" channels clearly meant left and right. But
which of the 7 Outlaw channels are "associated"? The Rule doesn't give a clear
answer, and we are not insisting at present that home theater amps be rated with
all channels driven simultaneously. The industry just announced a voluntary
standard, which we are studying. So--it's possible that Outlaw's 4-ohm spec
is a little misleading, but at the same time they would not be violating the
rule just because the unit could not put out all that power simultaneously.


Just thought some of you might be interested. I believe a standard for rating multi-channel amps would work something like running the front 2 or 3 channels at full power, and the remaining channels at 1/8th or 1/3rd power. This presents more of a real world scenario than a "continuous, all channels driven" spec.

Jason

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#48468 - 03/25/02 08:25 PM Re: anybody know the transformer size?
morphsci Offline
Gunslinger

Registered: 02/15/02
Posts: 243
Loc: Charleston, IL, USA
Quote:
I tried that one once too - "But dad, everyones doing it...."


Sorry Charlie. I think you misunderstood. My statement was that the rule, as is now clear, is probably a little more complex and outdated. My point, was that it is very unlikely that numerous companies would use this terminology and not get called on it if it really was illegal. Now deceptive .... thats a 'hole 'nuther kettle of fish. (another tuna reference).

[This message has been edited by morphsci (edited March 25, 2002).]

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#48469 - 03/25/02 10:50 PM Re: anybody know the transformer size?
charlie Offline
Desperado

Registered: 01/14/02
Posts: 1176
I'm curious if Jason made it clear to Mr. Murphy that the 770 spec clearly states 'all channels driven'. As for the rest - yes, the FTC discussion was pretty clear that they were still getting up to speed on the new multi-channel stuff.

The doc I cited seems pretty clear that 'associated channels' would be any that are driven within the same frequency range, but I'm sure the FTC is probably still pondering.


Charlie
_________________________
Charlie

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#48470 - 03/25/02 11:02 PM Re: anybody know the transformer size?
charlie Offline
Desperado

Registered: 01/14/02
Posts: 1176
Quote:
Originally posted by steves:

I'm sorry, but this I don't understand.


It's hard to explain without pictures, but they are different shapes. If you go here:

http://www.hubbell-wiring.com/new/hub9811.pdf

You can see on page 2 a 15 amp receptacle on the left, a 20 amp on the right. The 20 amp is designed to accept either a 15 or 20 amp plug.

I could be wrong, but I suspect a device with a 15 amp plug shouldn't draw more than 15 amps over the long haul, discounting surges and so forth.


Charlie
_________________________
Charlie

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#48471 - 03/25/02 11:28 PM Re: anybody know the transformer size?
rcaudio Offline
Gunslinger

Registered: 11/19/01
Posts: 81
Quote:
Originally posted by charlie:
[QUOTE]Originally posted by rcaudio:
[b]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 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[/B]


How else would you calculate RMS power. It's simple Ohm's law.
Learn to design your own amps. You can start here;
http://www.diyaudio.com/

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#48472 - 03/26/02 12:55 PM Re: anybody know the transformer size?
charlie Offline
Desperado

Registered: 01/14/02
Posts: 1176
I suppose it depends on what you mean by 'peak'.

Take music out of it for a moment and lets talk power distribution. In a DC circuit watts is simply voltage multiplied by amperage. It gets more complex in AC due to phase angles and so forth which can make VA not equal watts, but in a resistive circuit (like a test load) RMS is computed the same as DC IIRC. So RMS volts times RMS amps would result in RMS watts, or AC watts that heat the same as DC watts would, not the AC watts as measured instantaniously at the peak of the AC waveform.

If you are talking about 'peak' as in musical peak then that's a whole different thing and isn't really germane to my point.

In any case the line input and speaker output are BOTH AC and both obey the same laws. You can't put in 1800 watts and get out 2100, that is the crux of the issue.


Charlie
_________________________
Charlie

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#48473 - 03/26/02 02:32 PM Re: anybody know the transformer size?
rcaudio Offline
Gunslinger

Registered: 11/19/01
Posts: 81
Peak means peak. Any EE would know what peak means. RMS only applies to sinusoidal waveforms. RMS Voltage is computed by Vpeak
times square root of 2, RMS current is calculated by Amps(I peak) times the square root of 2. The rest is simple Ohm's law. Check your EE textbooks.
No one can use program material to spec a power amp. Sinusoidal waveforms are always used therefor any reference to program
material is completely irrelevant in this discussion.
Peak power may very well be applicable since transformers are rated with Volt Amps. Also, my calculation seemed to match what Outlaw
indicated in their post. As a telecom engineer I've never speced parts for a commercial audio amp and don't know what standard practices are used in the process.
As a DIY audio designer I've always went for overkill since I'm not designing to a price point. In my 450 Watt sub amp I used peak power and a 80% derating, the transformer is a 550 VA unit. This is a bit small but I've never had a problem (you can't be that picky with surplus parts). What do you use in your designs Charlie, I'd really like to know.

I did notice that Pass Labs 125W 5 channel amp has a maximum power spec of 600 W. The Pass amp is much more expensive and
conservative design than an Outlaw amp (or any of the other cheap amps, Rotel, ATI, B&K ect) and appears to be rated in the same manner as far as power dissipation is concerned.

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#48474 - 03/26/02 02:41 PM Re: anybody know the transformer size?
charlie Offline
Desperado

Registered: 01/14/02
Posts: 1176
RC,

That's all really cool. In interests of keeping it simple, do you agree or disagree that any device that draws 1 watt max average over time cannot output 2 watts average over time?

This is, in a nutshell, my point. Anything beyond that is needless complication.

The 770 is spec'd to draw AT MOST 1800 watts, yet is also spec'd to put out 2100 watts in some cases.

This might be of interest:
http://www1.tpgi.com.au/users/tps-seti/baloney.html


Charlie

PS - RMS can apply to any waveform - sine is easier to compute and most commonly used. To compute RMS (1) square the waveform function (2) average over time (3) take the square root.

[This message has been edited by charlie (edited March 26, 2002).]
_________________________
Charlie

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#48475 - 03/26/02 04:48 PM Re: anybody know the transformer size?
charlie Offline
Desperado

Registered: 01/14/02
Posts: 1176
Here's an interesting thought experiment:

(1) Build a 2100 watt monoblock amp that draws 1800 watts.
(2) Drive it to max output with a 60hz sine wave. A voltage reduced version of the power line is ideal.
(3) Use a transformer to bring the output RMS voltage to 120 volts.
(4) Sell the excess 300 watts to the power company, repeat 1-4, plugging each new amp into the output of the last one.
(5) Retire, move to Tahiti.


Charlie
_________________________
Charlie

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#48476 - 03/26/02 10:13 PM Re: anybody know the transformer size?
rcaudio Offline
Gunslinger

Registered: 11/19/01
Posts: 81
QUOTE]Originally posted by Charlie:
RC,

The 770 is spec'd to draw AT MOST 1800 watts, yet is also spec'd to put out 2100 watts in some cases.
PS - ROMS can apply to any waveform - sine is easier to compute and most commonly used. To compute ROMS (1) square the waveform function (2) average over time (3) take the square root.

[This message has been edited by Charlie (edited March 26, 2002).]
[/QUOTE]

Yes, that is the true definition of RMS. This proves you knew exactly what I meant by peak. But I like being corrected in this manner.
I can't disagree with the figures we have here but I don't think they apply directly. This is what bugs me;
Pass Labs designs and manufacture ultra high end amps. I just don't see any reason for them to fudge on the specs, they doesn't advertise so there is no point. Since the amp is rated at 125W per channel all channels driven and yet dissipates only 600 watts something isn't right, just as you point out about the model 770. I think, and I'm speculating, that the 600 watts refers to the power the amp itself dissipates and not the total power which would be at least 1200 watts for the Pass amp.
In any case the Outlaw amp looks like a very good product. The heat sinks are big and judging from the weight the transformers are plenty big enough. It's not going to have the head room of an amp like the Pass Labs unit, but the Outlaw costs much less.
What got me to post is when someone on that other forum wrote that they weren't going to buy the 950/770 if Outlaw didn't come clean and release proprietary information. I hope that individual passes on the 950 so someone else can move up on the list.

BTW my dog is a perpetual motion machine and I don't expect I'll make a cent from him.

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