Sound signature of amplifiers ..

[rkumarblr]

Though many a user and manufactures claim that their amplifiers are neutral sounding.
Assuming its the same set of Speakers, Streamer, DAC etc, also that the speaker is easy to drive say 90dd plus and if its resolving.
The very same set of branded high end components sound very different when paired with different amplifiers that all have adequate power and can easily drive the speakers. In my experience there is a distinct difference. A Rega sounds different from a Marantz which sounds different from a Audiolabs and a valve amp sounds very different from all of these.

Technically speaking even if we send an analogue signal to an amp, probably the pre-amp has an influence on what the designer has done with emphasizing any specific aspect, like rolled of highs for a warmer sound or accentuated bass etc.
I wonder if its the same with power amps, since all the decoding etc has already been done and it should be pure amplification at that stage.

So the questions is, in the case of a power amplifier all other components being the same and if its a high end set of resolving gear.
Will a calls D power amp sound different from a class AB from a Valve all of which are well suited to drive the speakers ?
Valves are high current and class A and seem to sound much warmer is great for Jazz and melody but can lack bass for music like hard rock and metal or fast dynamic unless its very high output and thereby equally at a much higher price.

What has been your experience ? and why this difference in sound characteristics.
Checking if this different will be apparent when using different power amps with similar specifications ?

 

[mbhangui]

1. Nothing in this world is perfect. No amp in the world can have a straight line as frequency response curve
2. Valve amps can never be near solid state amp in achieving neutral frequency response. They are always distorted with harmonics. You many actually like these even order harmonics. I for one prefer my class D amps over my valve amp any day, any time of the year.
3. Speakers are the most difficult animal in achieving neutral signature. They are electro mechanical devices and will have a frequency response extremely dependent on the driver, mounting of the driver, enclosure and the crossover
4. Even if you make a perfect amp and perfect speaker by some miracle, your room will have it's own signature.

If you try achieving a neutral signature, hoping to achieve nirvana, you will end up making the manufacturers rich. Ultimately it is your brain that needs to be happy. Audiophillia is like religion. It is upto you to put more emphasis on faith or science. Condition it properly (faith or science) and you will achieve peace.

EDIT: To compound things further, even if you achieve a neutral setup, the recording too is never neutral. It is left at the mercy of the recording setup, recording methodology, media and the sound engineer and marketing (if you know what MQA did). So if the recording itself is a lie what will you achieve by getting a neutral sounding setup. How do you determine what is neutral?

 

[availlyrics]

Checking if this different will be apparent when using different power amps with similar specification

All amps are tested on a resistive load, it is a standard practice for publishing specifications .
But when they are connected to loudspeakers thru cables & passive crossovers (real world loads have a varying combinations resistive, inductive and capacitive parameters), even an equally spec. amp based on similar topology will sound or react differently, resulting in one sounding different from another.
Speaker cables with higher capacitance may make an amp unstable or if it is having more inductance may result in an early high freq. roll off also affecting the damping factor for worse. Some amp may run out of juice when paired with difficult to handle speakers with big variations in their impedance curve graph.
Choices and compromises made by the designer in thermal management , protection circuits, PSU designs, active/passive components, etc will also have an impact on the amplifier's sound signature.

 

[sandeepmohan]

What has been your experience ? and why this difference in sound characteristics.
Checking if this different will be apparent when using different power amps with similar specifications ?

I have next to no experience with valve or Class D amplifiers so I won't comment on that.

More than sound signature changing with typical AB amplifiers, I have found that it is the drive to the speakers that makes a big difference. For me, that pretty much sums it up. I care less about the finer nuances. To be frank, its a bit hard to judge when you spend only 30 minutes with a component. When I go to buy something, I don't focus on one particular type of music. The amplifier needs to satisfy all genres. I don't have the luxury of running (...and accommodating) 2 or 3 amplifiers based on what I am listening to. I need one of those " do it all" amplifiers and there are many that achieve this. Critically, its how the loudspeaker responds to that power or amplifier. You can tell if all is well within those first few minutes and then you spend some more time to be sure you're not experiencing any ear fatigue. What you need to ensure though is that you have a good recording as well.

There are no standard specifications to follow. Each manufacturer rates their product different. A Denon with a claimed 100 watt output maybe equal to that of a NAD that puts out 50 watts of power. Does that make the NAD a weak amplifier? Absolutely not. You got to listen to the two though and then decide if the sound works for you. Or not.

An amplifier is not just about sound signature. Personally, I like to have a remote, decent aesthetics and some inbuilt equalization to compensate for recordings that are not perfect.

 

[reignofchaos]

1. Nothing in this world is perfect. No amp in the world can have a straight line as frequency response curve
2. Valve amps can never be near solid state amp in achieving neutral frequency response. They are always distorted with harmonics. You many actually like these even order harmonics. I for one prefer my class D amps over my valve amp any day, any time of the year.

To the contrary valves are much more neutral devices than solid state on their own. You can't stabilize a SS amplifier without some form of significant negative feedback either local or global while valves will work perfectly on their own without any feedback and the circuit will not oscillate.

See the response curve below of an 845 tube - it is perfectly linear. There is no transistor on the planet that can match the curves below.

What I personally find is that while SS on paper has perfect characteristics, due to feedback, it robs the sound of naturalness, accurate timbre and harmonic richness that I get from valves. Many SS amps on top of that have a volume control which uses ICs (OPAMPs) and these grey out the sound even more. Class D - as of now it is not fully mature. Yes it can sound good eg: Purify and Hypex ncore but they are nowhere near the best of Class AB let alone valves.

Have tried multiple amps of different types - SS Class A/AB/D, Valve PP/SET etc and I find SETs to be the most natural sounding of them all.

 

[mbhangui]

To the contrary valves are much more neutral devices than solid state on their own. You can't stabilize a SS amplifier without some form of significant negative feedback either local or global while valves will work perfectly on their own without any feedback and the circuit will not oscillate.

See the response curve below of an 845 tube - it is perfectly linear. There is no transistor on the planet that can match the curves below.

What I personally find is that while SS on paper has perfect characteristics, due to feedback, it robs the sound of naturalness, accurate timbre and harmonic richness that I get from valves. Have tried multiple amps of different types - SS Class A/AB/D, Valve PP/SET etc and I find SETs to be the most natural sounding of them all.

View attachment 87999

My valve amp is push pull. I have never tried a SET. Maybe one day I will experience it at some FM's house.

 

[Kannan]

@rkumarblr valve amps are voltage driven and not high current. Either you need very high voltage-based valve to achieve power or go to a push-pull design.
Overall unlike SS amps, each valve has its own sound signature and within the same amp that supports different valve options, the sound characterestic can change.
I prefer SS over valve for various reasons including overall sound, VFM, real estate and efficiency.
For me Class D from now on is the way to go.

 

[mbhangui]

For me Class D from now on is the way to go.

Ditto here. I first moved to Allo class D (allo volt plus amp). With an AB switch I could easily make out the better sound from the allo compared to my PP valve amp. The better High end was palpable. Just a month back I have moved to Fosi V3 monos.

My valve amp is now like a paper weight. It serves as a nice raised table top to hold my class D amps.

 

[reignofchaos]

Ditto here. I first moved to Allo class D (allo volt plus amp). With an AB switch I could easily make out the better sound from the allo compared to my PP valve amp. The better High end was palpable. Just a month back I have moved to Fosi V3 monos.

My valve amp is now like a paper weight. It serves as a nice raised table top to hold my class D amps.

View attachment 88000

Cadence VA-1 is a very poor amp. It has severe drive issues and will work with only the most sensitive of speakers. Never ever liked it to be honest.

 

[mbhangui]

Cadence VA-1 is a very poor amp. It has severe drive issues and will work with only the most sensitive of speakers. Never ever liked it to be honest.

Exactly. Like you, I have never found it to be good. I'm wondering if this could be converted to a SET and reuse the transformer and valves. It is in my mind. Maybe one day.

 

[prem]

95% of the tube amps out there sound bad. Unfortunately the few that sound good are expensive. Tube amps need very good power supply and output and interstage transformers. This increases cost.

For most of my life I have used SS amps. I don’t find anything wrong with them. It’s only in the last decade when I moved to high sensitive vintage drivers with paper cone, that I moved to low power tube amps. Modern SS amps don’t work well with high sensitive vintage drivers.

Just to put things in perspective, recording studios and mastering suites use SS amps.

 

[Kannan]

Cadence VA-1 is a very poor amp. It has severe drive issues and will work with only the most sensitive of speakers. Never ever liked it to be honest.

Cadense are among the worst designs. The Canasya is a ticking bomb, absolutely horrible under the hood. Would not pass a single safety parameter, especially when deploying such high voltages. My friend had to totally rewire and re-engineer it to his satiafaction.

 

[rkumarblr]

Thanks for the interesting feedback on your individual experiences.
Any SET valve amps that you found particularly good.
I use a PP Melody Dark, have not heard a SET.

Came across class D, Benchmark AHB2, has some excellent technical specs and reviews but is crazy expensive to get in India.
Again any specific class D that is highly rated or you found to be a great power amp ?

 

[alpha1]

To the contrary valves are much more neutral devices than solid state on their own. You can't stabilize a SS amplifier without some form of significant negative feedback either local or global while valves will work perfectly on their own without any feedback and the circuit will not oscillate.

See the response curve below of an 845 tube - it is perfectly linear. There is no transistor on the planet that can match the curves below.

What I personally find is that while SS on paper has perfect characteristics, due to feedback, it robs the sound of naturalness, accurate timbre and harmonic richness that I get from valves. Many SS amps on top of that have a volume control which uses ICs (OPAMPs) and these grey out the sound even more. Class D - as of now it is not fully mature. Yes it can sound good eg: Purify and Hypex ncore but they are nowhere near the best of Class AB let alone valves.

Have tried multiple amps of different types - SS Class A/AB/D, Valve PP/SET etc and I find SETs to be the most natural sounding of them all.

View attachment 87999

What is the significance & impact of the bottom section of the graph? Where the curves become curved

 

[rkumarblr]

I stand corrected. Looks like the Benchmark AHB2 is not a class D but a combination of AB and class H (whatever that is) with a unique feed forward system to get the lowest noise level and distortion. And though they do extensive technical testing they themselves state that impressive measurements do not necessary lead to transparency therefore a listening test is essential.

 

[mbhangui]

Cadense are among the worst designs. The Canasya is a ticking bomb, absolutely horrible under the hood. Would not pass a single safety parameter, especially when deploying such high voltages. My friend had to totally rewire and re-engineer it to his satiafaction.

I opened my VA1 amp. The wiring inside is horrible. The soldering horrible. I was eyeing the Canasya when I auditioned VA1, but the size of that beast and the cost detered me. My ears couldn't find much difference between the two. I was using the VA1 with Cadence electrostat Arista speakers. Currently I'm driving the same with V3 mono blocks.

 

[availlyrics]

To the contrary valves are much more neutral devices than solid state on their own

After seeing the graphs below, anybody will agree 100% with your statement "There is no transistor on the planet that can match the curves below."

Examples of harmonic distortion

If grid curves are wider on one side than another, gain is asymmetrical, creating even-order harmonic distortion:

If grid curves are wider in the center than at the extremes, this causes symmetrical odd-order harmonic distortion:

You can see in these examples that an equal change in grid voltage would not cause a proportionally equal change in anode voltage at all areas of the load line. When the gain is asymmetrical around the operating point, the output waveform will be misshapen, or distorted, on one side but not the other. This will cause a type of harmonic distortion that is even-order. If the non-linear effect is symmetrical on both sides of the waveform, then this causes odd-order harmonic distortion.
You might also consider what happens if the operating point were too far to the left or right on the load line, or if the input signal were too large relative to the span of grid curves—if the input voltage pushes into saturation (near or above 0 volts on the grid) or down to cutoff (deeply negative grid curves, with low or no current), then obviously the output signal will be extremely distorted and a sine wave would appear as flattened on top or bottom. This is what we would refer to as clipping. Guitar amplifiers operate closer to these conditions to achieve a desirable overdrive or distortion sound, but obviously in a hifi amplifier, this is undesirable.
Now, we’re finally ready to look at harmonic distortion another way to visualize these even and odd-order harmonics! I love this part, because the natural world, physics and math are sometimes like magic.
The sine wave that we input is at a frequency, let’s say 1000 Hz. We can call this the fundamental frequency (FF). Multiples of this frequency are the harmonics: the second harmonic is 2x the fundamental frequency, or 2000 Hz; the third harmonic is 3x the fundamental frequency, or 3000 Hz; and so on…fourth, fifth, etc.

https://www.analogethos.com/post/understanding-distortion

Tube amps have their very own unique sound signature due to its asymettrical "soft clipping" nature, some may tend to prefer it more over SS sterile sound with negative feedback resulting in a near perfect sinewave & THD figures well beyond 100dB range.

 

[availlyrics]

Many SS amps on top of that have a volume control which uses ICs (OPAMPs) and these grey out the sound even more

Majority of our music (before DDD) that we hear today has already passed thru hundreds such cheap jellybean opamp stages in the analog signal path, often thru cheap JRC 4558 , TL 072/082 opamps or the humble but best NE5532 costing few 10s of cents each. I always wonder how these very same recordings becomes "grey" after passing thru a couple more of such opamp ICs (instead of valves), when they are already well beyond 100 shades of grey.
BTW the very first opamp made during 1930's was also made from valves, horrible specs. In 1952, Philbrick Researches manufactured the first commercial op-amp, the K2-W, which was made up of two twin-triode tube

 

[reignofchaos]

Majority of our music (before DDD) that we hear today has already passed thru hundreds such cheap jellybean opamp stages in the analog signal path, often thru cheap JRC 4558 , TL 072/082 opamps or the humble but best NE5532 costing few 10s of cents each. I always wonder how these very same recordings becomes "grey" after passing thru a couple more of such opamp ICs (instead of valves), when they are already well beyond 100 shades of grey.
BTW the very first opamp made during 1930's was also made from valves, horrible specs. In 1952, Philbrick Researches manufactured the first commercial op-amp, the K2-W, which was made up of two twin-triode tube

So your point being? That the signal is already ruined, so let us ruin it even further?

 

[reignofchaos]

What is the significance & impact of the bottom section of the graph? Where the curves become curved

That is outside the typical operating point so it is immaterial. You will normally bias the active device in a way such that it never encounters that region.