I recently was given a broken ReVox stereo amp from the early 90s. When I get it fixed this amp will draw 600 watts. Do I understand correctly that it will be burning 600W whether I’m listening on headphones or blowing apart a speaker on each of the four outputs?
The 600w is probably the MAX power output for all channels. With distortion.
Your real power output with decent sound and low distortion is considerably less than that.
Your headphones draw WAY less than the rating of the amp.
But I have been told that, regardless of the draw of the speakers or headphones, the rating of an amp was what it was drawing whenever it was turned on with the unused power turning into heat. Was I misinformed?
Depends on the amplifier’s “class” - a description of the circuitry and how the output transistors are “biased” - a Class A amp will consume pretty close to its rated power at all times, even when playing silence into speakers or headphones. Some audiophiles claim this kind of amp sounds better. <shrug> Most audio amps are Class AB or B, and draw little power at idle. Yours is most likely one of these.
Actual AC power draw from the outlet while driving headphones is probably going to be closer to 30-50 watts, with only about half a watt reaching your ears.
Is 600 W the maximum input or output power?
This thing is so rare and weird I can’t find specs online, even in German. All I know is that on the back it says “600 Watts” in the place where the overall power consumption is shown. As it is a high end amp I’m tempted to assume it’s a Class A, though I wonder if perhaps it is Class AB or B as I can’t imagine any Europeans in the past ten or fifteen years being that profligate with electricity. 
Also, when I have turned it on it doesn’t get particularly hot, which probably is telling me something–it may be broken but it sorta works which would mean the power supply is doing more or less what it’s supposed to do.
Crud. That means I don’t have the “it raises my electric bill too high” reason to fix it and put the pile of stuff he gave me, most of which works fine, on eBay. I’ll be stuck with a fabulous $10,000 system that is too good for my speakers.
My life is too hard sometimes. 
How many power tubes are there and what type? Could you post the labeling on each tube?
All solid state, which also probably argues for it being efficient.
Uh, perhaps I should have elaborated on that.
I doubt that a 600W (peak or RMS) amp will be a type A, since type A amps are inefficient by design. In any case, having the quantity and model of power tube should help me or someone else make a reasonable guess at what the supply voltages are in the output stage, and from there guess what type of amp you have.
Amplifier class has nothing whatever to do with quality and everything to do with the biasing of the active amplifying elements. Rather than try to go through each class myself, I’ll let this excellent page do it for me.
My 120 Watts into 8Ohms output Electrocompaniet class A power amp draws 230 Watts from the supply. Solid State, as your Revox. Any help? [the preamp draws 15W for bugger all output, Class A tube-output CD player (Shanling) draws 100 W, again, bugger-all output but by god it gets hot. You can practically toast muffins on it. How inneficient is that?
Try giving us the model number of the thing. I found some sites on the Net that gave some info on Revox.
I’d be surprised if it’s class A. It seems to me that there would have to be a cooling fan for the power output stage in that case. A class B amplifier with negative feedback will be pretty free of crossover distortion and will sound pretty damned good.
I agree. But it can’t be denied most audiophiles believe (all else being equal) that Class A amps are “better” than Class AB amps in terms of sound quality. This is because Class A amps are more linear, and thus introduce less distortion when compared to Class AB amps.
I’m not saying I can hear the difference. I’m also not claming the difference is all that significant. I’m just saying that there seems to be a correlation between “amplifier class” and “sound quality” amongst audiophiles.
Oh. Well, being solid state, it probably is a class AB/B. It’s power consumption should be directly related to the number of windows broken. 
I wonder if this has ever been put to a double-blind test.
I know that many audiophiles used to claim that you need a bandwidth of 200 kHz because of a mysterious quality called, at that time, “presence.” This they said was true even though your speakers won’t reproduce over 20 kHz.
Actually, if you have an amplifiier with an open loop bandwidth of 20 kHz and add a lot of negative feedback the bandwith will turn out to be in the neighborhood of 200 kHz. But you have full feedback, with it’s ability to linearize and improve performance, only over the 20 kHz of open loop bandwidth. The wide, closed-loop bandwidth is just an artifact of the feedback.
Well, if you found much on it I will give you my Top Googler trophy!
ReVox H5 stereo amplifier. I also have the H2 CD player (sounds fabulous) and the H7 tuner (or is it an H6–it’s at home) which works well but is a pain in the ass to set up. And the remote, the use of which is non-intuitive.
“You want to buy that junk I piled back in the warehouse? Gee, I paid ten grand for it but I think it’s broken. Just take it but don’t let anybody see you.”
I love working for a near-billionaire!
The easiest way to tell power draw is to hook the thing up to a watt meter and read it off.
Now you may say “but I don’t have a watt meter”! But you do. It’s generally on the back of your house, or in the basement or utility closet of your apartment building. It’s more commonly called an “electricity meter”, but what it is measuring is watts.
Time the wheel through one revolution at 3 different settings: receiver off, receiver on no volume, receiver on and cranked. Compare your results.
It is easier to see the differences if you turn off most loads, and make sure you turn off any load that can turn on and off or otherwise change the load by itself (air conditioner, furnace fan, oven, dryer, washing machine, computer, etc).
If you want to figure out actual usage, you’ll need the values for Rr and Kh off the meter face, then watts consumed is:
3600000 / (Rr * Kh * seconds per revolution)
Usually (but not always - check your meter!) Rr * Kh is 100, so the formula is simply:
36000 / seconds per revolution
You can double-check the formula by trying a simple resistive load, like an ordinary light bulb. Calculate watts with the light off, then with the light on. The difference between these two calculations should be pretty close (say, within 10%) of the watt rating of the bulb.
I was thinking of trying that, without the math part since I didn’t have the formulae. Thanks!
If you find that it is class A, and you intend to use this receiver a lot, you might want to factor in cost to keep this pig powered up.
A back-of-the-napkin number for electricity cost is $1 per watt per year in continuous use. This assumes a cost of about $0.12/kWh, which is typical in the US. If you check your electricity bill for kWh cost, be careful - some bills just break out generation costs, which is about half the total.
So anyway, back to cost. If this receiver consumes 600 watts, and you have it on all day, every day, and only turn it off when you sleep, it will be in use 2/3 of the time, which means $400 annual operating costs. Stretches the meaning of free, right?
I got an “almost free” network switch a few years ago. Very high performance, $8500 when new in the mid '90s, but it didn’t have enough ports and took too much space in the rack so it was sold off. I ran it for a few years at home, but one day it dawned on me that this switch might be a real pig. The meter reported 240 watts (!) consumption. I guess that’s why it had 3 fans inside the case :smack:. Brand new switches of comparable (or better) performance and features cost $250 to $500 and consume 30 watts.
Same goes for monitors. CRTs (even little 15" ones) consume 200 to 300 watts, LCDs consume 30 to 60 watts. Depending on how you use it, the added cost (at purchase) of an LCD can be worth it.