[Sonic Defender]

Hi all, I thought I would give a bit of an update. I found that the Pass ACA amp was a bit rolled off and soft by itself. I have been using the GSX mini as a pre-amp. So I built the second ACA amp and now have them set up as monoblocks. It is sounding really great. Really tightened up the sound. Working really well with the 1266 TCs and the Utopias.

Here is a pic

So how does adding a second of the same amplifier change the sound signature? Gorgeous setup by the way, but I question that adding more of the same results in a change, unless I'm missing something.

 

[Nimzerz]

So how does adding a second of the same amplifier change the sound signature? Gorgeous setup by the way, but I question that adding more of the same results in a change, unless I'm missing something.

It is pretty documented that those ACA amps perform noticeably better as monoblocks

 

[Sonic Defender]

It is pretty documented that those ACA amps perform noticeably better as monoblocks

Documented how? You mean with people who spend the money adding a second one reporting that they hear a difference? That really isn't evidence that documents anything. It doesn't make sense from a technical standpoint at all. What would the technical reason for this "perceived" improvement be. That just isn't how it works. You just have two amplifiers with the same sonic characteristics working together, but it will still sound the same. Why wouldn't it?

This is what I would suggest is being implied. You have an amp run standalone that somehow suffers a performance degradation when being asked to run two channels, even though clearly it was designed to run two channels. Not only is it proposed that it degrades the sound, the effect is audible. Already if it were anything but an assumption people are making because they read what others are assuming (nobody is actually using equipment to measure and document these assumptions) you would have a very flawed amp. Right? An amp that can't drive two speakers without the sound being compromised.

So people are then proposing that by adding a second of the same amp you get this great sonic improvement, again, I imagine nobody is measuring anything, just "trusting their ears". Does this make any sense? The only thing that could explain this would have to be that the amp was so flawed that it couldn't transparently drive a pair of speakers and that when a second amp relieves the other amp, the circuits are now allowed to run more transparently, so much so that the frequency response of the speakers audibly shifts for the better.

That seems extremely unlikely and certainly something that some measurements would be needed to substantiate the claim. If you can hear this noticeable improvement, you can bet that it can be measured. You could just buy an amp that can transparently handle the load of two speakers. Monoblocks make perfect sense in some circumstances, needing more power, being used in a home theatre setup for example, so it isn't that I am questioning they can be useful. I am however saying that as people were discussing the use of above, even from a technical, theoretical perspective it just doesn't add up. IMO. I have no doubt others will not agree with me which is fine.

 

[Happy Camper]

Hi all, I thought I would give a bit of an update. I found that the Pass ACA amp was a bit rolled off and soft by itself. I have been using the GSX mini as a pre-amp. So I built the second ACA amp and now have them set up as monoblocks. It is sounding really great. Really tightened up the sound. Working really well with the 1266 TCs and the Utopias.

Here is a pic

Isn't it cool to discover a "wow" moment? Mono's are a best kept secret. The spacious sound makes capable headphones sound like speakers.

 

[Scarydog]

So how does adding a second of the same amplifier change the sound signature? Gorgeous setup by the way, but I question that adding more of the same results in a change, unless I'm missing something.

Thanks. The biggest change is that each monoblock is now working as a fully balanced amp (as I understand it). The change is super noticable, they sounded nice but a bit soft before. But now they have more definition and still retain lots of the character. With one I liked it but preferred the GSX mini, with both I prefer them over the GSX mini but they dont work well for the Utopia's or MM500. But definitely for the 1266 TC the difference is very apparent and really works well with them.

I'm not very good with the words about how things are different, sorry!

For the price, I highly reccommend building two of them . It was a fun project too.

 

[Scarydog]

It is pretty documented that those ACA amps perform noticeably better as monoblocks

I see you have a sit-3. That is a cool amp! Do you use it with headphones?

 

[Nimzerz]

I see you have a sit-3. That is a cool amp! Do you use it with headphones?

I do, I use it with my HE-500 and HE-6 and love it.

 

[A Jedi]

Documented how? You mean with people who spend the money adding a second one reporting that they hear a difference? That really isn't evidence that documents anything. It doesn't make sense from a technical standpoint at all. What would the technical reason for this "perceived" improvement be. That just isn't how it works. You just have two amplifiers with the same sonic characteristics working together, but it will still sound the same. Why wouldn't it?

This is what I would suggest is being implied. You have an amp run standalone that somehow suffers a performance degradation when being asked to run two channels, even though clearly it was designed to run two channels. Not only is it proposed that it degrades the sound, the effect is audible. Already if it were anything but an assumption people are making because they read what others are assuming (nobody is actually using equipment to measure and document these assumptions) you would have a very flawed amp. Right? An amp that can't drive two speakers without the sound being compromised.

So people are then proposing that by adding a second of the same amp you get this great sonic improvement, again, I imagine nobody is measuring anything, just "trusting their ears". Does this make any sense? The only thing that could explain this would have to be that the amp was so flawed that it couldn't transparently drive a pair of speakers and that when a second amp relieves the other amp, the circuits are now allowed to run more transparently, so much so that the frequency response of the speakers audibly shifts for the better.

That seems extremely unlikely and certainly something that some measurements would be needed to substantiate the claim. If you can hear this noticeable improvement, you can bet that it can be measured. You could just buy an amp that can transparently handle the load of two speakers. Monoblocks make perfect sense in some circumstances, needing more power, being used in a home theatre setup for example, so it isn't that I am questioning they can be useful. I am however saying that as people were discussing the use of above, even from a technical, theoretical perspective it just doesn't add up. IMO. I have no doubt others will not agree with me which is fine.

Perhaps research what happens to an amp when it's bridged?

 

[Sonic Defender]

Perhaps research what happens to an amp when it's bridged?

I know what happens. Not much in reality, unless the amplifier being used standalone was extremely poorly suited to the task, and that isn't what people are talking about here. This is classic confirmation bias. People read unsubstantiated (in terms of lack of measurements instead relying on subjective accounts) claims about the really huge differences from bridging. And this happens even though the theoretical benefits are known and are certainly not transformative, and definitely do not shift frequency response characteristics, but because of the buildup of expectation and hope, coupled with spending money, bam, they hear the same difference they were told to expect. Now they are posting online about the big difference, and we now have another pseudo data point being put out there as more evidence, but it actually isn't.

The only time the frequency response of a load may audibly be improved was if there was a significant impedance mismatch in the first place and the lone amplification circuit was truly inadequate, which is of course possible, but really should not be that common. Again, I am not saying there is not a use to bridging, that use is more power, and when it is truly needed, great it is needed, but consider this about bridged amplifiers, and I'm quoting:

"This equation also shows that bridging quadruples the theoretical power in an amplifier, however this is true only for low enough loads. For example, for loads where the amplifier reaches its full potential in single-ended mode, there is no gain to be made with bridging."

So, if you have already enough power for the load, if you just make all kinds of extra power available, past what is needed, it doesn't have some magical power in its unused state, that is audiophile mythology. If the power is unused, it has no influence on what you hear, it remains as stored energy potential. That really shouldn't be a controversial point. I get that with separate power supplies and amplifiers, even with higher resistive loads you get power doubling, but that is all you get, more power, not improved sonic capability. Which circles back to where these claims fall down, I would bet that the vast majority of people had enough power anyway, they were just doing what all audiophiles do, hope and dream about a way t0 unlock the magic they worry they are missing, so they buy more power than they will use, erroneously thinking that even though the extra power sits there as stored energy, it somehow shifts the frequency response of the load.

That may happen sometimes, absolutely, I'm not fool enough to think that there aren't sometimes underpowered amplifiers and once more power that is used is added, great, positive change can happen, but the power must be used. If you have an amplifier that swings 5 watts and that is enough to handle the dynamic peaks in the music at the SPL you listen at, it doesn't matter at all if you add 300 extra watts, if the load and your SPL doesn't demand the power, it is unused. If it is unused, you cannot hear it, if you cannot hear it, how can we write about how it changes the sound?

 

[Nimzerz]

I am not sure how you wrote that long paragraph without ever mentioning crosstalk, a big reason people claim to do it

 

[Sonic Defender]

I am not sure how you wrote that long paragraph without ever mentioning crosstalk, a big reason people claim to do it

People think they are hearing crosstalk now? At the level of fidelity typically found in todays equipment? I don't think crosstalk has been an audible concern for quite some time now. I have never in my life heard of a single person complaining about the crosstalk in their system. Be honest, have you had a problem with crosstalk, something you actually heard?

 

[Nimzerz]

People think they are hearing crosstalk now? At the level of fidelity typically found in todays equipment? I don't think crosstalk has been an audible concern for quite some time now. I have never in my life heard of a single person complaining about the crosstalk in their system. Be honest, have you had a problem with crosstalk, something you actually heard?

So now you are disregarding theory and measurements just because you claim you cannot hear the difference? Did you try it?

Just a second ago you were claiming that just because someone was hearing it that it didn’t mean anything because it wasn’t based on science.

 

[goldwerger]

Guys, get a room

 

[Sonic Defender]

Guys, get a room

Now that's funny.

 

[Gazza]

I guess this counts but I run a pre/power set up for both speakers and headphones. I use a Densen B-150 amplifier (an integrated but you can bypass the preamp which is how I use it) that my Stax Sr-009 taps into via the Woo Audio WEE energiser. Densen state that the B-150 operates in Class A for the first 20-or-so watts. For those not familiar with the Danish brand, they take inspiration from Naim both sonically and philosophically in that power supplies are king and you can upgrade many of their products with an external PSU. Personally, while they have much of the PRAT of Naim, I find them superior in the bass, capable of digging out the most natural and bombastic bass reproduction that frankly gear costing x3-5 times more struggle to match. Hence why I'm loathe to upgrade my B-150 as its only weakness is the rather dry sounding pre-stage which I don't use in place of my Manley.

Specs:

Power output in 8 ohm: 2x100W (I believe a review found the actual rating to be closer to 135W RMS into 8 from memory)
Power output in 4 ohm: 2x200W
Power supply size:750VA
Storage capacity:130.000uF
Weight/shipping weight:14/16 Kg
Product dimensions (WxDxH):444x310x64mm

Hi-Fi Choice review excerpt:

The analytical nature of some electronics is not always, to all people, deserving of unequivocal praise. Can Hi-Fi equipment sound both analytical and musical? Densen makes a good case for the answer being "yes". Too often in the past, there was an uncomfortable tradeoff where analyses came to mean dry, soulless separation of music into its constituent parts. That tendency has become rare with the passing of time and in this case is simple not applicable. What the B-150 achieves instead is a full scale representation of the sound where the details are perfectly apparent if you choose to listen out for them, but where they are still very much part of the overall picture. All the same, this is very capable amplifier that does things integrated models very seldom do. An excellent combination of analysis and musical integrity coupled with infectious rhythmic properties. Particularly wonderful at dealing with deep bass sounds in a rich, yet tuneful manner.

Conclusion: Truly gorgeous sounds in the lower octaves are a joy; very light treble dryness detracts only a little. Good sense of scale and rock-steady rhythms appeal too! This is one of the few integrated amps that can show up pre/power combos.
http://hififreaks.dk/Densen NEW Site/b-150 uk.pdf

Not sure how modern Densen fares (my amp released in 2005/2006) but I imagine it's still top class.