Question about the Classé CA-5300

[Iron Man]

I was just reading some specifications for the Classé CA-5300 and I have a couple of the questions for the more technically skilled.

Power consumption says: 1300W @ 1/8 th power into 8 ohm. How does that compare to for example an Anthem A5 which has a power consumption of 1800W?

In the datasheet it also states:

300W RMS into 8 ohm all channels driven*

*specifications for output into 4 ohms are omitted because the AC Mains power supply cannot support all channels driven simultaneously at this level,........

When soundandvision had the Classé CT-5300 in the test bench it showed 292,9W into 8 ohm but no measurement was made into 4 ohm because it shut down at about 190W.


I'm not quite sure what to read out of this?

[TomScrut]

Presuming soundandvision tested it with all channels, could will mean that it can't get enough power from the mains with all channels driven, and that the 4 ohm will be less efficient to drive (due to more current and therefore more heat) and so it can't output as much power compared to what it draws in.

[Iron Man]

Is the thing about the 4 ohm load something I have to consider when choosing the AMP over for example an Anthem or is it irrelevant?

When they tested the Anthem P5 i showed 5 * 485,7 watt into 8 ohm and 5 * 636,7 into 4 ohms.

Here is the article:

"Five channels driven continuously into 8-ohm loads:
0.1% distortion at 292.9 watts
1% distortion at 322.1 watts

To channels driven continuously into 8-ohm loads:
0.1% distortion at 390,2 watts
1% distortion at 434,1 watts

Into 4 ohms, the amplifier consistently engages protection at 190.0 watts and cannot be driven further."

http://www.soundandvision.com/content/classeacute-ct-ssp-surround-processor-and-ct-5300-amplifier-ht-labs-measures-classe-ct-5300-

[mjb]

A UK mains socket is 3KW (230v x 13 amp). The output power will be the input power less efficiency. 5 x 300 is 1500, assuming 50% efficiency, it does indeed get pretty close to the available input power. A problem with amps is building a power supply that can handle the power transients, and they're not all very good at driving low impedances - due to the high current. If speaker impedance changes significantly over its bandwidth, the amp may have problems keeping up. So, yes, you want to make sure it can happily drive into 4 ohms. Also, its really a good idea to run a dedicated circuit from the fuse panel for your amp(s).

[Lex]

A good general rule of thumb for any amplifier is. The very best amps, will double output wattage when the load is doubled, or is it the load is halved. I forget the proper terminology just now. But for example, my old workhorse Proceed HPA-2 amplifier is a 250 watt X 2 amp @ 8 ohms. At 4 ohms, the amp is rated at 500 watts per channel RMS. That means the power supply is beefy enough to handle the load for one thing. IF you don't have enough power supply to generate the doubled load, the amp cannot double the output when the load is halved. The VERY best amps, would double it again when going all the way down to 2 ohms. I would add that is a lot of load, and very few speakers would demand that load, though a great 4 ohm rated speaker "might" have a few peaks that get into the 2 to 3 ohm zone. Excellent designs with more than 2 channels will "loan" power to the channels that are demanding it. So, this is one way an amp can get around the lack of ability to double wattage when the load is double. Of course on a 2 channel amp, there's nowhere to borrow that power from. Generally, you wouldn't have a right channel only for example demanding something the left channel isn't demanding as well, though I guess it is possible.

I believe my Proceed AMP5 was constructed in such a mannor. But I cannot recall for sure on that. It may just flat out be able to halve the load from 8 to 4 ohms X 5. I'd have to look up some old specifications. Not that it matters here.

I am a little surprised Classe is not giving their product enough power supply to double output from 8 to 4 ohms, given this brand's stature. It may be a great amp under normal loads, but it would not classify (no pun intended) as the very best with this design without some kind of sharing topology for a 5 channel amp, capable of distributing load under heavy loads. That shutting down you mentioned past a certain load would mean it is not able to borrow for even short duration's possibly.

Levinson, the maker of Proceed formerly is known for doubling wattage from 8 to 4 ohms with ability to handle transient spikes even below 4 ohms. My Mark Levinson 333 is such an amp. according to Audio Review.com the Mark Levinson 333 is capable of 300w/ch @8 ohms; 600w/ch @4 ohms; 1,200w/ch @2 ohms. That's handling a load. My 4 ohm Sonus faber extremas are running at 600 watts per channel. The amp never strains.

[TomScrut]

Are all these amps you are talking about 5 channel? The 2300 more or less doubles its load into 4 ohm and it appears the issue is the amount of electricity you can get through the mains, not exactly Classé's fault. Mjb, we are lucky in the UK too, isn't the mains power worse in the states?

[TomScrut]

Sorry Lex I see what you are getting at, 2 channels busting out at 190 isn't very good...

[windshear]

I had this same question answered from Classe when they first came out. This is the response from Dave Nauber himself. I have cut and pasted only the relevant part.

The problem is that with a linear amplifier and power supply and a 120V AC supply, there is no way to pull enough power out of the wall to double its power output into 4 ohms. Assuming 60% efficiency, you would need (600W x 5)/0.6 = 5,000W! We are already at the limit of what is possible to get from the wall when testing for 300W/CH x 5 at 8 ohms. It takes twice as much current at 4 ohms to get the same amount of power output as at 8 ohms (you reach 300W at half the voltage and twice the current output), which is why the protection circuit cuts in at a lower power output at 4 ohms than at 8 ohms. In other words, for the amp to develop 5x300W at 4 ohms requires twice as much current as 5x300W at 8 ohms, so we run up against the limitations of power from the wall quite quickly in a multichannel amp driving lower impedance loads. The amp is perfectly stable at all loads and could deliver 600+ watts at four ohms if we disabled protection and tested one channel at a time so as to avoid the limitation of what we could get the out of the wall. It’s because of this confusing nature of the power rating that we decided not to rate the amp at four ohms. Sometimes good intentions backfire, but judging from the sales of the amps, people aren’t distracted by the lack of a 4 ohm spec.

So straight from the horses mouth. Maybe not 100% correct in its explanation, but im sure one can make out the intent. I was never able to get clarification if the protection circuit monitored things on a by channel basis or the total power supply demand, ie could 1 or more channels double power into 4ohms as long as it did not exceed a total power supply threshold.

[mjb]

It worth remembering that a 5 channel amp will never have all of its channels at full output, other than in the lab!

And yes Tom, its good to be in the UK/Europe with 230 volts in the wall. I wonder if anyone in the States uses two phases feeding a 230 volt amp for extra punch? Sound like a good idea after reading Dave Naubers explanation.

[Lex]

I may have mis-understood to some degree. I sure dodn't know about UK power sources Tom. That 190 bombing out didn't sound very good to me either. Of course, in reality, we probably place to much demands on our specifications to begin with. I don't really push my gear that hard, I am sure I could get by with less, and be "fine" But you know, I hope my amplifiers are for life, and I don't have to buy more!

I was speaking of several 2 channel amps, only my Proceed AMP5 is a 5 channel that does double from 8 to 4. I do not believe it will double from 4 to 2 like the Levinson big dog I have though. That isn't realistic expectations unless an amp costs about 4-5K per channel. The Amp5, cost ~ 5K for 5 channel, so about 1K per channel. I use my AMP5 to drive center, sides, and rear in my 7 channel configuration. The Levinson 333 drives my mains.

Absolutely Michael on 5 channels never drawing full current except in the labs. but a design has to be designed to share power supplies among channels if you get full benefit from the power supplies, because most 5 channels are a bit anemic in the power supply area. As I recall, John Curl (is that right?) Parasound engineered some of these designs that share power supply. Great idea, so you don't have to have 100% beef, but under a load, you can borrow power when needed where it's needed.

Doug

[mjb]

I believe a 5 channel amp will typically have two power supplies, one for the front pair, and another for the rear three, this way surround effects are not sapping resources from the main action. Think of a power supply (capacitors) as a swimming pool, constantly being filled and emptied - you never want it to run dry, so demand can't outstrip supply.

[TomScrut]

I have had my 5200 go into protection under two very similar circumstances, neither in normal listening.

When doing (loud) REW sweeps it has been known to cut out if I reduce the lower frequency to 15hz, and this happened with two sets of speakers, 803Ss and 802 Diamonds. I presume the low impedance involved with these speakers at these frequencies is what caused the cut out. In music and HT use it has never sounded like it was getting itself into trouble!

[Kal Rubinson]

I believe a 5 channel amp will typically have two power supplies, one for the front pair, and another for the rear three, this way surround effects are not sapping resources from the main action. Think of a power supply (capacitors) as a swimming pool, constantly being filled and emptied - you never want it to run dry, so demand can't outstrip supply.

I do not know what is typical as there are many possible permutations of PS number and channel number from one PS per channel to one PS per chassis. The argument for the former is that, given no limitation on wall outlet feed, activity in one channel will not affect any other. The argument for the latter is that, given the limitation on wall outlet feed, each channel can draw as much as it need as long as activity in the others permits.

[windshear]

I have had my 5200 go into protection under two very similar circumstances, neither in normal listening.

When doing (loud) REW sweeps it has been known to cut out if I reduce the lower frequency to 15hz, and this happened with two sets of speakers, 803Ss and 802 Diamonds. I presume the low impedance involved with these speakers at these frequencies is what caused the cut out. In music and HT use it has never sounded like it was getting itself into trouble!

When you say it has cut out, did the led turn red for the respective channel to show it had gone into protection. The other thing to be aware of when running REW from say 15 Hz is that when you run the Freq sweep it actually starts from lower than the selected Freq.

[TomScrut]

Yes the LED went red for protection. The results only show from 15hz? Not an issue as I don't really test from 15 I was just seeing how low they would go one day!

[Iron Man]

Thanks for the responses, it was very helpful