McIntosh Amp

[Stockinv]

I'm looking at a McIntosh MC-501 amp. It's rated at 500 watts continous power at 2, 4, and 8 ohms. I've read that the mark of a good amp is that power doubles as the amperage halves. That means 500 watts at 8 ohms, 1000 watts at 4 ohms and 2000 watts at 2 ohms. My question is, which one is preferable, or are they comparable? Thanks.

[Snap]

That is just the "Rule of Thumb" It does not actually "Double" More like 2/3 The Amp should let you know what it is rated at per the load.

Like my Denon 3805
Rated Output= 120 + 120 at 8 ohms, 160 + 160 @ 6 ohms.

Dynamic Power is: 140 x2 @8 ohms, 210 x2 @4, and finally 240 x2 @ 2 ohms.

So you got an aditional 70 watts for cutting your load in half.

As for the amp never heard it so I can not help you with that.

[Stockinv]

Mc207

I am considering the MC207 for my center and rears, along with the MC501 monos for my mains. Does anyone have this combination? Thoughts?

[Patt]

Hi Stock,

I dont have any McIntosh equipment but it sure seems to be a well known/respected brand. A few times I have auditioned McIntosh monoblocks powering B&W #800 series speakers and it made quite an impression on me, (WOW).

Maybe an owner of McIntosh will chime in and be of more help.

[autio]

You are correct a good amp will "double down " meaning doubling watts as resistance(ohms) is halved. I think it is kind of intuitivly understandable as resistance drops in half it "lets" more power flow from the amp (twice as much should) but from what I understand If the power supply can not handle it (it sags) than some amount less than double will be made but it will be more 4 ohms than at 8 and more at 2 than 4 unless the amp is not up to the task than all current will stop flowing (meltdown). lol
This does not happen with the 501's and has you wondering about the quality of the expensive mac

BUT this is info is for amps that do not have output transformers and the mac does not fall into this category !!!

Macs have the autoformers (one of the reasons they are so heavy). They
cause the amp to 'see' the impedance load from the speaker as being an ideal load. Autoformers multiply impedance and allow a user to use the tap that will multiply the speaker impedance load for the amplifier. Impedance matching for speakers and amp.
I hope this explains it (and I hope I got it right ) By the way this is one of the reasons the amps are as expensive as they are!!

[Snap]

You are correct a good amp will "double down " meaning doubling watts as resistance(ohms) is halved. I think it is kind of intuitivly understandable as resistance drops in half it "lets" more power flow from the amp (twice as much should)
I hope this explains it (and I hope I got it right ) By the way this is one of the reasons the amps are as expensive as they are!!

Autio- Like I mentioned in the above post. You are sort of correct. I have yet to see in both Pro and Home style Amps an amp that did "Double" just cause you went from 8 ohms to 4 ohms. It is really a myth that can really mislead people into thinking they have enough power to drive speakers when they do not. In the HT application it is less than common. But I have seen several Pro Installs were the installer was counting on "Double" power and left the speakers under powered because of his inpropper calculations. Like I said this plays a huge part when you are hanging line arays and you are talking thousands of watts of power.

The other thing to take into account is the amp itself. The closer you get to a short the "hotter" the amp will run. The more heat the amp has the more likely that there will be damage to the amp. I have seen some amps that had less that a 2 ohm load on it! 8O One of the Churches that I am fixing there system has to have new QSC amps placed in the rack cause they put 5 speakers on 1 CHANNEL! It is amazing that the amp has lasted this long!

The 2 math formulas that one must use is ohm's law.
Volts=Current x Resistance. And to get the watts.....

W = V x I or W = I2 x R or W = V2 / R. \

Hope this helps out with the Watts thing.

[autio]

snap,

Audio power amplifiers can be seen as voltage sources, putting out a certain amount of voltage at the output that is a multiple (gain)of an input voltage. Looking at it this way and using a ohms law formula that you gave above "W = V2 / R" I guess you can readily see that a well designed amp is supposed to "double down" . Amps from ayre and classe among many others do just that!

I do know that there are many tradeoffs whan optimizing an amp while designing it to meet certain goals, like making a profit. Many ht recievers will not double down because of undersized and sharred power supplies. This is to make a product that people can afford while mantaining a profit. I do understand that alot of amps cannot do a 2 ohm load but some well designed ones can.

But the main pupose of my post was to answer the original posters question of why an expense mac monoblock did not increase output at all when driving different loads (autoformers). I was hoping to point him in the direction of researching output transformers and their purpose(to optimize and match speaker impedence and amplifier output )

[Snap]

CA-5200 - POWER AMPLIFIER

click image to enlarge view
The CA-5200 is a 5 x 200W model, based on the same channels used in the CA-2200. Power supply components considerably large enough to allow for the greater power demands of five channels without sacrificing performance. Design features include balanced circuitry, overbuilt power supplies and oversized output stages to ensure the highest performance at every output level, with any loudspeaker.
models
(balanced inputs) CA-5200
voltage gain 29.1dB
bandwidth 155kHz (-3dB)
22kHz (-0.1dB)
phase < -10° (22kHz)
sensitivity 1.4Vrms
power/channel (continuous)
(120VAC line, 1kHz signal regulated to 1% THD + noise into resistive load, all channels driven)
load (resistive)
8O 200W
4O 370W
THD + noise (unweighted, 10Hz - 500kHz bandwidth, 1Vrms/1kHz input)
load (resistive)
none 0.002%
8O 0.003%
4O 0.005%
noise FFT noise floor peaks all below –95dBV
(with terminated inputs)
S/N ratio (relative to 1kHz sine wave full level output into 8O)
108dB

height
depth
(excluding
connectors)
width gross
weight net
weight
8.75” (222 mm) 21.0” (533 mm) 17.5” (445 mm) 133 lbs (60 kg) 121 lbs (55 kg)
rated power consumption 1056W

The above Info can be found on the Link below.

http://www.classeaudio.com/delta/specs/ca5200.htm

You are correct about a well designed amp being able to handle a 2 ohm load. I also am not trying to sound like I am attacking you about this issue. But what I am wanting to point out is several things.

1. People try and save money and get a lower powered amp, and try and use the "double" theory to make it put out the watts that they really needed. The trade off for the most part is not worth it. Definatly if you are talking HT. People are running speakers that will definatly show the increase in THD distortion, and ultimatly be unsatsified with the results.Then they blame the AMP for being poor quaility. Not to mention the life of the amp is reduced because of the strain on the amp at higher power settings.

2. Classe being on of the amps that you mentioned is by all means one of the cleanest and best sounding amps made. But even at that, it does not double. Now granted the distortion from this HIGH quality amp is only .002 more than the 8 ohm load, most amps are NOT going to be that clean going from 8 to 4 ohm load. And it only gets worse as you go down.

3. I guess to be honest it is a touchy subject for me, cause so many sound guys try and fight the amp selection that the church really needs insisting that the Double Watts theory will save them a couple hundred bucks. Then in a few months they call me back and raise cain about the sound system not sounding as good as I promised them it would sound. :cry:

4. The best advice that I can say about this. Is get the amp that has the power that you want at the highest ohm rating. This will allow the amp to run cooler, cleaner, and last longer. It also gives you the room to grow, should you need to cut the ohms to 4 and grab the extra watts that the amp is able to produce.

5. If you are not able to buy the amp with the right rating I would wait a few more months to save the money to buy the right amp in the first place. Definatly in the case of high doller stuff that you are wanting to keep for a while. How many times in this forum have we seen people saying they are going to upgrade this Rotel for a bigger one. Or upgrade there Bryston for a bigger one?

Once again please do not take any of these post in an attacking mannor. I am not attacking any one.

Hope this helps.

[autio]

jeez, I thought maybe you thought I was on attack It seems that we are looking at 2 different things here. You are talking ht amps with many channels and I was addressing mostly 2 channel, like the following amp from classe, an amp that the ht amp that you referred to is based on
model cA-2200
(balanced inputs)
voltage gain 29.1dB
bandwidth 155kHz (-3dB)
22kHz (-0.1dB)
phase < -10° (22kHz)
sensitivity 1.4Vrms
power/channel (continuous)
(120VAC line, 1kHz signal regulated to 1% THD + noise into resistive load, all channels driven)
load (resistive)
8Ω 200W
4Ω 400W
I can see where you are coming from. The only reason I presisted in this disscussion is thatthe original poster was asking about a audiophile grade monoblock amp, questioning why it seemed to put out the same power into different loads. For the 8200 dollars mac is asking for the 2 monoblocks, I hope, they are "better" designed and cut less corners, less tradeoffs than a 1200 "pro amp"! I think you are correct that many amps cut corners and cannot handle some of the loads they are asked to. And I definitatly see the value in your postings

[Snap]

Autio Yeh man in no way I was trying to attack you. :T
And WOW 8O the CA-2200 is the first amp that I have seen that does that. The best is the other amp that I put in the other post! I learned something new.

I am going to email them and ask them about that.

[Snap]

Autio-I got several emails and a phone call in to Classe. I am very interested in the CA-2200. If it really does that I might be upgrading! I will keep you posted.

[eddiem67]

That is just the "Rule of Thumb" It does not actually "Double" More like 2/3 The Amp should let you know what it is rated at per the load.

Like my Denon 3805
Rated Output= 120 + 120 at 8 ohms, 160 + 160 @ 6 ohms.

Dynamic Power is: 140 x2 @8 ohms, 210 x2 @4, and finally 240 x2 @ 2 ohms.

So you got an aditional 70 watts for cutting your load in half.

As for the amp never heard it so I can not help you with that.

I have to disagree with you on this one, there are many high end amps that will double in power when the resistance is cut in half, not only home audio but in car audio as well. Take a look at earthquake amps they have huge power supplies that can support the resistance when it lower than 8 ohms.

[Snap]

Having learned some new stuff from Auito. I still do not think that any one of us actually answered the FIRST post. He was asking and I was jumping the gun.... But he asked why the watts did not double in the MAC that he was looking at?

Well I think I might have the answer. SOME key word SOME new amps are being built with "autoformers" Crown has them. What they do is change the load to a predetermined ammount all the time. Regardless of the speaker. 8 ohm, 4 ohm etc. That way the amp is always ????? what ever watts they say it is.

MY GUESS. KEY WORD GUESS for fear of a barage of bullets flying.... :rofl:

The Mac that you are talking about has something like that in it. But that is just a guess.

[autio]

snap,
I thought my first two posts on this thread answered the the question (Autoformers). BUT then again maybe my answers were not clear enough If you would like to know a little more about autoformers check out http://www.enjoythemusic.com/magazin...autoformer.htm

[Snap]

snap,
I thought my first two posts on this thread answered the the question (Autoformers). BUT then again maybe my answers were not clear enough If you would like to know a little more about autoformers check out http://www.enjoythemusic.com/magazin...autoformer.htm

Yeah Autio you did mention it in the second post. We just got off track. I had forgotten that you had mentioned that in the second post when Eddie jumped back in on the double down thing. Heck I must have skimmed over that second post all together.

Sorry about that Bro you be RIGHT.

;x(;x(;x(;x(;x(;x(

[Snap]

I wonder if Classe has autoformers in some of their stuff?

[Snap]

snap,
url]http://www.enjoythemusic.com/magazine/equipment/0603/midmonth/zeroautoformer.htm[/url]

Good Read autio. It has some of the stuff that I was thinking about when I was making my "Custer Stand"

"The situation may even be worse, in terms of current demand, when the effect of complex crossover networks is considered. The impedance will dip even further, possibly as low as 1 ohm, around the crossover region due to the effect of shunt capacitance in the woofer's low-pass network. " from that link.

People need to be careful when they are dropping there speaker loads down to low ohm settings. Cause you might not be at 4 ohms all the time.

Autio may be we should start a new thread, but what are your thoughts on how the industry as a whole does thier ratings? is it fair to run a sine wave through and make your watt specs? Or would it be better for the consumer to list it at 300watts or what ever at this sine wave????

With "ALL the variables" Speakers, x-overs, power supply of the amp, power from the house, control circuits, THD, and the whole spectrum of freqs that we use for music, which causes different loads on the amp at times. Is the way we do things accurate? (not that it really matters. I mean I am splitting hairs here)

But remember back in the late 90's the industry had the big "watt" bust cause companies were out right lieing about there outputs?

I guess I still don't trust them to be honest.