McIntosh Labs MC601 Monoblock Amplifier Preview

[Irvrobinson]

Do you think the quality of those MAC are better than the AT3000 amps?

It depends how you define quality. If we compare an AT3002 to an MC302, which are very comparable 2-ch, 300w/ch amps, they are very different products. From a topology perspective I like the ATI better. McIntosh has taken to the same terminology balderdash I see at Emotiva, where some amps are described as differential and others as balanced. When these amplifier manufacturers refer to differential they seem to be referring just to the topology of the output stage, while balanced seems to be an all-stages term that is really quad-differential. Regardless, the ATI is fully balanced and the MC302 isn't, but more expensive McIntosh amps, like the MC601 this thread is actually about, are fully balanced.

The MC302 uses an output transformer, and I've posted several times that I don't like this feature. McIntosh sticks to output transformers for reasons of tradition, IMO, and they come up with, again IMO, unconvincing technical arguments for it.

For parts quality I'd have to give the nod to McIntosh. For example, their amps use custom (they're stamped with the McIntosh brand name) US-made power supply capacitors, which look like they're premium parts made by Cornell-Dubilier, but I'm guessing on the manufacturer. Every electronic part I see in a McIntosh product is always of premium quality. There aren't any cheap parts like flimsy switches or low-grade potentiometers. The amps use very little wiring; the physical designs use interlocking boards and buss bars. It's either overkill or built to last, depending on your point of view.

From a mechanical design perspective there's no comparison. The MC302 is an industrial work of art. Those watt meters (and they are real, circuitry-computed watt meters) are behind glass, not plastic. ATI amps look like my old Adcom from the 1980s.

So is the MC302 higher quality than the AT3002? It's a mixed bag. From a purely technical perspective I'd rather have the AT3002. It's balanced, the MC302 isn't, and into 4 ohm loads the AT3002 will put out at least 50% more power, while the MC302 is rated to stay at 300w/ch. For overall build quality and parts selection I think it's the McIntosh all the way. If money isn't a factor and pride of ownership is, the McIntosh wins, hands down. If money really isn't a factor then you can get a pair of MC601s and you get fully balanced topology and 600 watts per channel, beating the ATI by 3db. You also get huge, sexy power meters.

As an aside, "Macs" are only Apple products. The name is spelled differently. In the 1980s when Apple released the MacIntosh, McIntosh Labs sued Apple over the name similarity and won. For many years Apple had to acknowledge McIntosh Labs in their advertising.

 

[Grador]

It really amuses me how quickly this argument gets restarted.

 

[Irvrobinson]

It really amuses me how quickly this argument gets restarted.

+1 Or how long the echoes continue for. This thread is over two years old.

 

[AcuDefTechGuy]

You know regarding "fully balanced" topic, what's the advantage of having a fully balanced amp (like the McIntosh amp) when the pre-pro is NOT fully balanced (like the McIntosh pre-pro) ?

I'm thinking the phrase "you are as strong as your weakest link".

 

[Irvrobinson]

You know regarding "fully balanced" topic, what's the advantage of having a fully balanced amp (like the McIntosh amp) when the pre-pro is NOT fully balanced (like the McIntosh pre-pro) ?

I'm thinking the phrase "you are as strong as your weakest link".

How do you know the McIntosh pre-pros aren't balanced? Their web site doesn't say, and neither do the owner's manuals. The MX151, for example, has balanced inputs and outputs. Considering that the MX151 weighs 31lbs, dissipates 75W, and lists for $12K, I find it difficult to believe that McIntosh got cheap like that, when they sell stereo pre-amps for much less that are fully balanced.

As for the advantages of fully balanced topologies in consumer audio components... I'm of a mind that those advantages are mostly theoretical. By that I mean that common mode rejection ratios in differential circuits, and fully balanced designs too, are real and measurable. CMRR is not some minor factor either, it's measured in db. That's why high-gain output stages are always differential; they get a big benefit. But for fully balanced operation, where you're looking to get reductions in noise and distortion from end-to-end in an amp that already has differential output stages, I'm less convinced the advantage is audible.

Since you like ATI amps so much, let's compare my bottom of the line AT602, which has a differential output stage but does not have a fully balanced topology, to my top of the line AT3000, which is fully balanced. I've compared these two amps driving the Salon2s, and even in sighted comparisons I can't tell the slightest bit of difference between them, so long as I don't clip the AT602 (which is actually easy to do). Is there a measurable difference? I don't know, because I haven't seen test reports on these two amps, but there probably are measurable differences. But if I can't hear it I assume it's a "theoretical" advantage.

I normally run fully balanced from the DAC all the way through the AT3000, but I have to admit I'm probably doing the equivalent of wearing a belt and suspenders (and underwear).

 

[cpp]

You know regarding "fully balanced" topic, what's the advantage of having a fully balanced amp (like the McIntosh amp) when the pre-pro is NOT fully balanced (like the McIntosh pre-pro) ?

I'm thinking the phrase "you are as strong as your weakest link".

Really

 

[AcuDefTechGuy]

How do you know the McIntosh pre-pros aren't balanced? Their web site doesn't say, and neither do the owner's manuals. The MX151, for example, has balanced inputs and outputs. Considering that the MX151 weighs 31lbs, dissipates 75W, and lists for $12K, I find it difficult to believe that McIntosh got cheap like that, when they sell stereo pre-amps for much less that are fully balanced.

You're probably right. It's just that they brag about some of their amps being "Quad Balanced", but they don't even say a single word about anything fully balanced on their MX151 Pre-pro. I would have bragged about it. I can't believe they didn't mention anything.

For example, they clearly said that their C1000 preamp is fully balanced:

"The C1000 preamplifier utilizes fully balanced circuitry".

$12K pre-pro that weighs 31lbs? Don't most AVRs and pre-pros weigh about 30lbs? I know the Denon 5308 & AVP-A1 weigh about 60lbs each.

 

[AcuDefTechGuy]

...let's compare my bottom of the line AT602, which has a differential output stage but does not have a fully balanced topology, to my top of the line AT3000, which is fully balanced. I've compared these two amps driving the Salon2s, and even in sighted comparisons I can't tell the slightest bit of difference between them...

You're preaching to choir, man.

 

[Irvrobinson]

Don't most AVRs and pre-pros weigh about 30lbs? I know the Denon 5308 & AVP-A1 weigh about 60lbs each.

No, most processors weigh less, but I was just saying that in that 31lb weight and 75w of power, balanced circuitry wouldn't be a big factor.

That Denon is like buying a female connector store of your very own.

 

[cpp]

I guess it all depends on what your definition of balanced its, are you talking about just inputs and outputs or all circuits and is there really a noticeable difference in sound quality across the spectrum when using balanced connections where all components are connected via a balanced connection.

 

[moves]

What the hell does fully balanced, quad differential, differential blah blah mean?

 

[Irvrobinson]

What the hell does fully balanced, quad differential, differential blah blah mean?

I'll take a shot at this. I don't know how much you know about circuit theory, so this might not be all that understandable.

Differential audio circuits are those where two independent circuits operate on two versions of the same signal, one being 180 degrees out of phase with the other - the mirror images of the signal. The two versions of the signal are created by what's called phase splitter circuitry at the sender, and when the signal is finally ready to get sent to a non-differential device, like a speaker, the two signals are combined to form a single signal again. The advantage of using differential circuits is that during the combining process at the receiver, the common noise and distortion in both signals are cancelled out to large degree, resulting in a final reconstructed signal with much lower noise and distortion than if you used a single path.

The disadvantage is that you have two circuits doing the work of one.

So, for example, if you have a low voltage signal, like the output of a microphone, and you have a long cable, by using differential signaling you can reduce the amount of noise and distortion introduced by the transmission of the signal on the cable. The noise might be due to interaction with other cables, or perhaps electrical fields from transformers or whatever.

In the output stages of amplifiers this technique is used to reduce noise and distortion, because the output transistors (or tubes) will highly amplify any noise or distortion created by the output stage circuits. The advantage is so great, the common mode rejection, as it's called, is often in the range of 70-100 decibels.

So, when an amplifier is referred to as a differential amplifier, it means that the audio signal is split, sent to two amplifying circuits, and then recombined at the output. In the high-end audio industry it seems like when manufacturers describe an amplifier as "differential" they are really only referring to the output stage.

Technically, balanced and differential are synonyms, but the high-end audio amplifier guys seem to using the term "balanced" to refer to circuits that are differential in every stage, and the signals are not combined until the final output stage. In fact, if you have a source component like a balanced pre-amp or processor, and you use XLR (balanced interconnects between the components, the combined signal paths of the source and the amp can be fully differential, and the common mode noise and distortion from the entire signal path will be reduced by the common mode rejection ratio.

Quad balanced or quad differential refers to taking a differential circuit, and then making a differential pair with another circuit just like it. So you have four circuits doing the work of one. You have cancellation at two levels. This sort of circuit is used in situations where extremely high CMRRs are needed, like high-speed digital circuits, but if you create a balanced output stage of an audio amplifier you get the same thing, because the output stage is already going to be differential.

 

[AcuDefTechGuy]

We should start an amp company and make a Fully Dec-Differential design from Input to output.

It will sound 3 x better than the Quad design.

 

[cpp]

All I know with balanced comes increased cost over a unbalanced component be it a BR/CD, DAC, Pre-amp, AVR, or amp.

 

[moves]

Wow IvRobinson great explanation. I don't know anything about circuit design and I understood that. Good work! How do you know this stuff?

 

[Irvrobinson]

Wow IvRobinson great explanation. I don't know anything about circuit design and I understood that. Good work! How do you know this stuff?

You're welcome. Sometimes I get lucky.

 

[Irvrobinson]

I should mention that there is a segment of the audiophile community, and a very misguided segment IMHO, that believes differential output stages in amplifiers sound bad, and these folks advocate single-ended topologies. The most difficult to understand are the folks that like single-ended tube amplifiers, sometimes abbreviated SET amplifiers. SET amps are so weak they can only be used with the most efficient speakers that present a very benign load.

There's also a more sophisticated version of single-ended design, called balanced single-ended, which Nelson Pass advocates in his Pass Labs products. I think of it like a macro-differential design. I'm not sure that Pass's amps really sound any better than a more conventional differential output stage, but his "balanced single-ended" topology looks like a clever variation on achieving a similar result, and maybe it measures better. Gene certainly measured some incredibly low distortion at 1W from the Pass amp he tested.

Pass also gets into the fringe market for amps with a separate company he has, FIRST WATT, where he experiments with some really different topologies, both single-ended and otherwise. The web site makes for some interesting reading. Nelson may rub elbows with the fringe guys, but he seems to really know his stuff, and he's very open about what he does and how he does it. His FAQ is especially worth a giggle.

 

[cpp]

I should mention that there is a segment of the audiophile community, and a very misguided segment IMHO, that believes differential output stages in amplifiers sound bad, and these folks advocate single-ended topologies. The most difficult to understand are the folks that like single-ended tube amplifiers, sometimes abbreviated SET amplifiers. SET amps are so weak they can only be used with the most efficient speakers that present a very benign load.

There's also a more sophisticated version of single-ended design, called balanced single-ended, which Nelson Pass advocates in his Pass Labs products. I think of it like a macro-differential design. I'm not sure that Pass's amps really sound any better than a more conventional differential output stage, but his "balanced single-ended" topology looks like a clever variation on achieving a similar result, and maybe it measures better. Gene certainly measured some incredibly low distortion at 1W from the Pass amp he tested.

Pass also gets into the fringe market for amps with a separate company he has, FIRST WATT, where he experiments with some really different topologies, both single-ended and otherwise. The web site makes for some interesting reading. Nelson may rub elbows with the fringe guys, but he seems to really know his stuff, and he's very open about what he does and how he does it. His FAQ is especially worth a giggle.

Most of the SET's I have heard are usually feeding horns.

 

[ski2xblack]

Without the hoopla surrounding SETs, First Watt would probably have no market to sell to.

Irv, you need a time machine to go back and teach those Japanese audiophools in the '80's the error of their ways. The whole SET thing is all their fault!

 

[Miketuason]

Just want to chime in. Few weeks ago I purchased a pair of MC601 and have about 100 hours to date. All I can say is WOW! I am so glad I chose these amps over the Pass Labs X600.5 The 601s are so detail and just gets better and better as I add more hours to them. I agree, it may not be everyone's cup of tea as far as looks but for me, my primary reason for buying these amps is for their sound quality that they produce and the looks is just my secondary reason. Before I bought these amps I first auditioned the Pass Labs, Audio Research, Krell, Classe', Conrad Johnson, and the Canary Audio, by far at least to me an with my system, the Mc 601 are still the one of the best.