A little off balance

[slipperybidness]

This is incorrect. For those of us who run long interconnects, like me, balanced cables have proven advantages in noise rejection. Second, XLR connectors are far and away superior to RCA connectors in mechanical integrity and ease of use. This isn't at all comparable to passive biamping connections on speakers.

YES! The mechanical "click" of most XLRs is a huge advantage that should not be over-looked!

 

[Irvrobinson]

Bottom line, speakers have a lot more variables that affect the sound than amps.

I think that's correct, but that doesn't necessarily force a conclusion that amplifiers are immaterial to the perceived sound of an audio system.

 

[AcuDefTechGuy]

I think that's correct, but that doesn't necessarily force a conclusion that amplifiers are immaterial to the perceived sound of an audio system.

Not immaterial or irrelevant. Just not as significant as the speakers themselves and how they interact with the room.

 

[JohnnieB]

The real advantages of a true balanced design, balanced is better for:

Long runs
Noisy areas
Very small signals (i.e. microphones)

If you aren't dealing with one of these situations, then good quality single ended RCA will almost certainly be "good enough" and the benefit of XLR most likely won't be audible.

Still, I would prefer the XLR, but I know it's not necessary

A question for the OP: How do you know that the XPA-2 is only balanced at the input? It says "dual differential" on the spec sheet.

If you look on the Emo website, under the overview for the XPA-2 it reads "Inside, we've refined our classic differential input,"
In addition, several threads discussing the topic of which Emo amps are and aren't balanced show the XPA line as not being a fully differential amp.
I realise this is by no means definitive proof. I contacted Emo tech to find out point blank if the XPA are or aren't fully differential. Still waiting on the return correspondence.
So now we get into terms that sometomes get misused or, for myself, confuse the issue. This all brings me back around to believing I bought something I may not have.

UPDATE: Just got off the phone with Emo tech. The only amps they have that are fully balanced are the mono blocks, the rest are balanced on the input side only. Great marketing. Give people enough tidbits of truth, and then let them believe what they want. I'm only slightly dissapointed. As i've stated, I like the amp, and will still buy the XPA-3 to finish out my HT, but will definately be much more dilligant in researching gear from here on out.

 

[AcuDefTechGuy]

Just got off the phone with Emo tech. The only amps they have that are fully balanced are the mono blocks, the rest are balanced on the input side only. Great marketing. Give people enough tidbits of truth, and then let them believe what they want. I'm only slightly dissapointed. As i've stated, I like the amp, and will still buy the XPA-3 to finish out my HT, but will definately be much more dilligant in researching gear from here on out.

I consider that a lie then. It states clearly that the XPA-2 is discrete dual differential. That means fully balanced. But it is actually not.

 

[Irvrobinson]

UPDATE: Just got off the phone with Emo tech. The only amps they have that are fully balanced are the mono blocks, the rest are balanced on the input side only. Great marketing. Give people enough tidbits of truth, and then let them believe what they want. I'm only slightly disappointed. As I've stated, I like the amp, and will still buy the XPA-3 to finish out my HT, but will definitely be much more diligent in researching gear from here on out.

Or... you could buy another XPA-2 and run them both in bridged mode. Instant balanced monoblocks. I don't recommend it, but there's your solution.

 

[PENG]

I consider that a lie then. It states clearly that the XPA-2 is discrete dual differential. That means fully balanced. But it is actually not.

I wouldn't consider that a lie, just not enough details in their specs and description.

Following is taken from their website:

XPA-2

Topology: fully discrete, highly optimized dual differential, high current, short signal path Class A/B with premium components throughout

XPA-1

Topology: fully balanced, fully discrete, quad differential, ultra high current, short signal path selectable Class A/AB

So it should be quite clear, if not totally transparent, that the XPA-1 is fully balanced, fully can reasonable be assumed to mean all amp stages. As for the XPA-2, it just says fully discrete, i.e. as opposed to using IC's, and optimized dual differential simply describes the amp stage configuration, one can assume that applies to all amp stages but that would not be a reasonably assumption. Just my two cents, you may, and you did make different assumptions.

 

[AcuDefTechGuy]

I wouldn't consider that a lie, just not enough details in their specs and description.

Following is taken from their website:

XPA-2

Topology: fully discrete, highly optimized dual differential, high current, short signal path Class A/B with premium components throughout

XPA-1

Topology: fully balanced, fully discrete, quad differential, ultra high current, short signal path selectable Class A/AB

So it should be quite clear, if not totally transparent, that the XPA-1 is fully balanced, fully can reasonable be assumed to mean all amp stages. As for the XPA-2, it just says fully discrete, i.e. as opposed to using IC's, and optimized dual differential simply describes the amp stage configuration, one can assume that applies to all amp stages but that would not be a reasonably assumption. Just my two cents, you may, and you did make different assumptions.

Well I'm learning.

Yeah, I always thought "dual differential" means "fully balanced".

So what if they just said "quad differential" but did NOT say "fully balanced"? Is it possible to be quad differential and still not be fully balanced?

 

[AcuDefTechGuy]

Looking at the expensive McIntosh amps. The MC452 says:

"In MC452, the latest circuit components are deployed in the classic McIntosh Quad Balanced design for impeccable audio performance."

It doesn't say "Quad fully balanced". So is it possible that it is not fully balanced?

The MC601 also does not say "fully" balanced, just "Quad balanced".


The McIntosh MC303 300WPC amp doesn't even have the word "balanced" anywhere in the description.

 

[PENG]

Well I'm learning.

Yeah, I always thought "dual differential" means "fully balanced".

So what if they just said "quad differential" but did NOT say "fully balanced"? Is it possible to be quad differential and still not be fully balanced?

I'd say it is still possible. Does the ATI say fully balanced or something like differential from input through to output stages?

 

[Irvrobinson]

I'd say it is still possible. Does the ATI say fully balanced or something like differential from input through to output stages?

The ATI AT2000 and AT3000 series amps are fully balanced.

Edit: On the AT6000 series, see if you can decipher this quip from the ATI web site. I'm not sure I can:

As in Kessler’s previous top-of-the-line designs, these amplifiers are fully balanced, differential amps, but unlike his earlier balanced designs which were essentially balanced bridged amplifiers, the 6000 series uses only a single input stage with dual-differential output stages. The reason: the advantages of balanced designs are retained and noise is reduced by 50%.

 

[AcuDefTechGuy]

I'd say it is still possible. Does the ATI say fully balanced or something like differential from input through to output stages?

ATI’s “Pure Balance”® technology introduces a range of models that feature true differential design; balanced from input to output.

A fully differential amplifier is basically two separate amplification circuits per channel. One channel is inverted at the input and the output of each is summed allowing the speakers to be driven by a push/pull action. The benefits of this design are tremendous. It automatically rejects any noise coming in from external sources, such as radio-frequency and electromagnetic interference. It eliminates hum and reduces distortion. It also doubles the slew rate (speed) of the amplifier, for better reproduction of high frequencies and better transient performance. And. because of the push/pull output, we are able to reduce the power supply voltage (B+ and B-) to the output transistors enhancing amplifier longevity and reliability. We call this technology Pure Balance®, and we use it in the AT3000 and the AT2000 series.

But please don’t be confused by other competing designs. While many amplifiers have balanced, XLR-type input connectors, most simply convert the balanced input signal to unbalanced in the first amplification stage and discard most of the benefits of a balanced connection in the process. Not Pure Balance® amplifiers. ATI’s Pure Balance® amplifiers keep the signal balanced all the way from the XLR inputs to the speaker outputs.

 

[JohnnieB]

From what I can discern, most solid state amps are dual differential input. If it's dual-dual differential input, it is quad differential. Again this does not mean it's fully differential. I can't say with the Mac specifically. The more I dig into this the more confused I get.

 

[JohnnieB]

The real advantages of a true balanced design, balanced is better for:

Long runs
Noisy areas
Very small signals (i.e. microphones)

If you aren't dealing with one of these situations, then good quality single ended RCA will almost certainly be "good enough" and the benefit of XLR most likely won't be audible.

Still, I would prefer the XLR, but I know it's not necessary

A question for the OP: How do you know that the XPA-2 is only balanced at the input? It says "dual differential" on the spec sheet.

By noisy areas, do you mean electrically noisy? If so, this brings up the whole line conditioner debate. If electrical noise is the enemy, which I think most will agree it is, why not use a line conditioner? Furthermore, if balanced inputs already reject the "noise", would only those with unbalanced inputs, need line conditioners?

 

[RichB]

This is what I have been told about the ATI-6000:

</SPAN>In conventional differential balanced amplifiers, you have two </SPAN>
complete mirror imaged amps. You drive the conventional input on one
</SPAN>and the inverting output of the other. When the outputs are summed, </SPAN>
anything common to both sides is cancelled. This typically results in </SPAN>
1/2 the noise of a non-balanced amplifier. The common design has 4
</SPAN>transistors in the input of each half or 8 in all.</SPAN>
</SPAN>
In the newer design, Morris is able to use only 4 transistors to drive </SPAN>
two balanced output stages. This requires significant "sleight of </SPAN>
hand", current feedback and dual DC servos, but with half the input </SPAN>
devices we also cut the noise in half again. Signal to noise ratio of </SPAN>
these "current feedback designs" approaches 130 dB "A" weighed referenced to rated output.

I can't remember where I head this but the ATI6000 series uses a new package where the transistor and bias monitoring in the same package.

Were I in the market, I would definitely have a look at the 6000 series. It seems to redefine beast.
Ant the design is elegant.

Still, I would like to see 2 to 10 multi-tests. Of course, there is a possibility that such a test would not "look" as good as a the commonly performed tests and this could be controversial. If amps suddenly have very different performance, I suspect manufacturers might not be pleased.
It's debatable whether that is fair.

- Rich
</SPAN>

 

[Irvrobinson]

From what I can discern, most solid state amps are dual differential input. If it's dual-dual differential input, it is quad differential. Again this does not mean it's fully differential. I can't say with the Mac specifically. The more I dig into this the more confused I get.

No, most amps have differential output stages and single-ended input stages (there are usually two input stages).

The underlying problem is that some very specific circuit design issues have become marketing terms aimed at people who aren't circuit designers by training. As I've posted before, I can't hear any differences at all between my fully balanced AT3000 and my conventional, single-ended input / differential output stage AT602, within the 602's power limitations. I suspect the AT3000 measures better, but that appears to be more of a discussion point that a matter of practical listening quality.

 

[PENG]

From what I can discern, most solid state amps are dual differential input. If it's dual-dual differential input, it is quad differential. Again this does not mean it's fully differential. I can't say with the Mac specifically.

Exactly, it does not matter if they say dual, qual, hexa, poly differential, unless the word fully is there, we should not assume the amp is differential end to end. If they did say fully balanced, or fully differential, then we could reasonably though not necessarily legally hold them to the end to end differential understandin

The more I dig into this the more confused I get.

It isn't that confusing if we consider just one stage. Problem is most amps are multi-staged. The main benefits to have differential is the input stage for common mode noise rejection. After that, you are approaching the point of diminishing return. Again, I would stay away from the extra low cost fully balanced amps as I believe in most cases you get what you pay for. Fully balanced amps mean doubling the power transistors and they have to be well matched otherwise you end up solving one problem but creating new ones.

This whole mess is a little like the two channel driven and all channel driven thing that also confuses people. If the amp specs say 140W per channel, 7 channel equal power, or even 7X140W (now that's cutting it closer), we cannot accuse them of lying or false advertising. If they say 140WPCX7, 980W total then we could reasonably say they are at least misleading, perhaps intentionally. But still, unless they say 140WPC, all channel driven simultaneously, we should not assume the rated output is ACD rated.

 

[PENG]

No, most amps have differential output stages and single-ended input stages (there are usually two input stages).

Are you sure about that, preamp, or power amp? In we are to generalize, then I would think the reverse is true.

 

[PENG]

see if you can decipher this quip from the ATI web site. I'm not sure I can:

As in Kessler’s previous top-of-the-line designs, these amplifiers are fully balanced, differential amps, but unlike his earlier balanced designs which were essentially balanced bridged amplifiers, the 6000 series uses only a single input stage with dual-differential output stages. The reason: the advantages of balanced designs are retained and noise is reduced by 50%.

Me neither, perhaps they meant wheatstone bridge was used in the input differential stage?

 

[PENG]

If you want to see the real deal, don't forget this:

Denon AVP-A1HDCI Balanced Transmission Further Explored | Audioholics

Thanks to Gene, you can see a really good block diagram for that pair of fully balanced beasts.