Can you hear a difference in Sound between Audio Amplifiers?

[M Code]

I just want and re-read the Audioholics article "The Sound of Audio Amplifiers: Can you hear a difference between Amps".
It is great. The biggest take away for me comparing good amsp operating within there limits was the impedance statements by Julian Hirsch.

I had to throw my shirt away after the torching I took from postulating that might be a reason for the differences that some HTM reviewer found between the Parasound A5 and Outlaw 7900 (ATI 3000 clone).

Here is the quote from Julian Hirsch concerning his measurements:




For what it is worth, I found the specs on these amps to be comparable:

Output Devices per channel: A5:8, ATI3000: 12
Power Supply per channel: A5:440va, ATI3000: 450va (gestimate)
Capacitance per channel: A5:32,800 uv, ATI3000: 36,000 uv

Both amps have very high slew and damping factors.

If these amps were to sound slightly different, then I think I will go with Julian on this one.
I wonder if .5 DB on the upper end is in fact "air".

- Rich

Regarding output devices..
The # is interesting but the pertinent spces are the voltage and current specs for each output device as to calculate their SOA....

Just my $0.02...

 

[ski2xblack]

I don't think you would look to spend what the I-Tech HD's cost. Five channels would set you back $13-20K

Hey, that's expensive enough to appeal to the boutique audiophile crowd!

 

[TLS Guy]

I believe that there is a subtle but audible difference between class A and class A/B under some conditions and I believe TSLGuy did hear that difference. I meant that in my post.

I really do believe there is a difference. If there is any validity to the tube craze this is the issue. I spoke with Peter Walker about this often and he was anything but an audiophool, maintaining "wire is wire." He had a good ear and played the flute to professional standards. He was always to be seen in the orchestra of the great Three Choirs Festivals, held in the Cotswolds every year. He was never happy with variable bias A/B amps and I have to agree. His solution was brilliant as standard solid state class A amps are a real pain in the you know what. His solution gave class A by elegant sleight of hand, delivering an efficient reliable design.

I have no real experience yet of class D, and that might be a solution, I don't know. However Peter's current dumpers have give me excellent service for just short of 40 years now.

 

[Irvrobinson]

Just as an interesting sidebar, here is a link to Stereophile's reviews of the Quad 405 amps: Quad 405 power amplifier | Stereophile.com. These are from 70s and 80s, which was prior to John Atkinson joining the staff, and bringing measurements to parity with subjective analysis in their product reviews. I'm not sure I buy a word of what's written here, but it makes for interesting reading nonetheless, as we ponder whether or not amps have character.

 

[TLS Guy]

Just as an interesting sidebar, here is a link to Stereophile's reviews of the Quad 405 amps: Quad 405 power amplifier | Stereophile.com. These are from 70s and 80s, which was prior to John Atkinson joining the staff, and bringing measurements to parity with subjective analysis in their product reviews. I'm not sure I buy a word of what's written here, but it makes for interesting reading nonetheless, as we ponder whether or not amps have character.

The 405 was a problem child, at least the initial ones. There was a significant circuit error (easily remedied) that made distortion higher than it should have been. There were also stability problems. There were 11 or twelve iterations of the 405 through the 405 II.

All boards are easily upgradeable to the second to last iteration. The final iteration of the 405 II had a custom IC in the driver stage, which is NLA.

Basically the 405 II is a huge improvement over the 405s in all its iterations. Any 405 that anyone purchases should be upgraded to the latest iteration of the 405 II possible.

Any version of the 606 or 909 should be a good amp, although there have been questions raised about some ground plane issues in some Chinese built 909s.

The 909 is now superseded by the Quad QSP.

 

[AcuDefTechGuy]

Are the Pass Labs amps fully balanced? I don't see them mentioning that. I see them saying "single-ended", but not "fully balanced dual differential". So I was just wondering.

 

[Irvrobinson]

Are the Pass Labs amps fully balanced? I don't see them mentioning that. I see them saying "single-ended", but not "fully balanced dual differential". So I was just wondering.

Yes, they are balanced, but he uses a different strategy than other designers do. Pass has described his amps as a balanced implementation built from two single-ended circuits. The idiosyncrasy of the design, if I may use that term, is that you don't get the value of common mode rejection unless you drive the amps with a balanced (XLR) input. Using the RCA input you have just single-ended operation. Pass claims his combination strategy of a low number of gain stages, single-ended gain stages, and differential operation at a more global level results in better performance. It's very interesting thinking. The question is, whether strategies like this, or even more innovative strategies like current dumping, really result in better sounding amplifiers than a classic, well-implemented Class AB design, or are all of these strategies merely so much high-tech showmanship?

 

[Irvrobinson]

The 405 was a problem child, at least the initial ones. There was a significant circuit error (easily remedied) that made distortion higher than it should have been. There were also stability problems. There were 11 or twelve iterations of the 405 through the 405 II.

I didn't realize this was the case, and it's amazing in a disturbing sort of way. Bob Carver has operated like that too, releasing products that are really still a work in progress. Interesting that Walker and Carver were (are in Carver's case) two of the most innovative engineers in audio. From a consumer's perspective twelve iterations of essentially the same product would be damned annoying.

 

[Goliath]

I've heard people saying that amplifiers are "fast". Some amplifiers have a faster sound than others. I'm assuming that's a load of bollocks?

 

[Steve81]

I've heard people saying that amplifiers are "fast". Some amplifiers have a faster sound than others. I'm assuming that's a load of bollocks?

My amp just sits there. Is that bad???

 

[AcuDefTechGuy]

My amp just sits there. Is that bad???

Well, my amps have moved a little bit, but that's because those big metal handles just beg to be pulled.

 

[3db]

I've heard people saying that amplifiers are "fast". Some amplifiers have a faster sound than others. I'm assuming that's a load of bollocks?

Audiophool speak........similar to a review I read in Home Theater Magazine stating a 12K pair of interconnects were danceable and perfect PRAT. It just doesn't get richer than that.

 

[Goliath]

Correct me if I'm wrong but there is nothing in an amplifier or in the design of an amplifier that can cause a faster signal or anything like that? It sounds a little preposterous just thinking about it but I'm no amplifier designer. I don't know why people think one amplifier can operate quicker than another amplifier. Aren't there electrical laws or something like that?

 

[3db]

Correct me if I'm wrong but there is nothing in an amplifier or in the design of an amplifier that can cause a faster signal or anything like that? It sounds preposterous just thinking about it but I'm no amplifier designer.

The only thing I can think off that may hold that characteristic is a thing called "slew rate" measured in volts/microsecond as its most common unit. The slew rate is a measure of an amps ability to handle rapid changes in a signals amplitude in a VERY short time frame. ie, an instantaneous or transient burst of loud music.... An amp whose slew rate is too low will smear the signal.......ie if you feed an amp a square wave, you should see a square wave on the output (ideally) The higher the slew rate the more square is the wave at the output. The lower the slew rate, the rounded and smeared the output looks.

Here's a good read.

Google Image Result for http://www.amplifier.cd/Tutorial/Slew_Rate/images/slew_rate_rising.jpg

 

[RichB]

Correct me if I'm wrong but there is nothing in an amplifier or in the design of an amplifier that can cause a faster signal or anything like that? It sounds preposterous just thinking about it but I'm no amplifier designer.

I have asked this before and came away with slew correlates with high frequency response and bandwidth.

I do wonder about my old Sunfire since it had to adjust the rails.
Could that process lead to a sag in the power that affected speed?

The Outlaw G rail switcher advertise a 2 microsecond transition after the first 70 watts.
Yet, some amps like the ATI produce 50 volts per microsecond.
It might be inaudible but it has to produce a lag.

I even asked an designer of a popular value oriented amps (in a private email) and he recommended their A/B amp over their rail switched for better linearity.

In my own comparissons, I found the Outlaw 7500 A/B amp sounded cleaner at volume than my Sunfire 7400.
I would have loved to see some of the detailed measurements for that amp that you can find now.
One thing I did notice, is the ATI and many other well designed amps produce less destortion (to a point) as they are driven.
Perhaps, the Sunfire went the other direction.

- Rich

 

[Steve81]

Here's the AH slew rate article FWIW:
Amplifier Slew Rate - What Does it Mean?

 

[Steve81]

I do wonder about my old Sunfire since it had to adjust the rails.
Could that process lead to a sag in the power that affected speed?

The Outlaw G rail switcher advertise a 2 microsecond transition after the first 70 watts.
Yet, some amps like the ATI produce 50 volts per microsecond.
It might be inaudible but it has to produce a lag.

Some "light" reading:
Class-G Amplifiers

Suffice it to say, there's not a lag to speak of.

 

[RichB]

Some "light" reading:
Class-G Amplifiers

Suffice it to say, there's not a lag to speak of.

I liked the Outlaw M2200 mono-blocks when I auditioned them at my house.
They could greatly reduce the weight and/or increase power.
I wonder why more manufactures don't implememnt them?

- Rich

 

[Steve81]

I wonder why more manufactures don't implememnt them?

The intro of the linked article addresses that:

One thing is quite clear - the added complexity is only of benefit for high powered amplifiers, having an output power of 200-300W or more. In addition, the use of Class-G is of dubious value for normal home listening, where the average power may only be a few Watts but instantaneous (peak or transient) power may reach far higher levels. Although there are modest gains in efficiency, they do not warrant the additional complexity.

At the modest power ratings generally needed for home use (generally below 200W per channel), a traditional Class-(A)B amplifier is perfectly capable of providing as much noise as you'll need, without raising a sweat. In addition, the lower complexity reduces the likelihood of distortion artefacts, which (it is claimed) may become audible in some (others may say all) Class-G designs.

 

[3db]

The intro of the linked article addresses that:

My Technics 5.1 receiver is a class H..... SA-DX940...still going strong and relegated now to my secondary system.