Legitimate example of an amp that "colors" sound?

[Symphoniac]

I know that there are several threads on "whether all amps sound the same" and although some of the technical discussions go over my head, the impression I'm getting is an amplifier should not color the sound provided that it has flat frequency response. In other words, if you're comparing amp A to amp B at the same power wattage, and both are flat in the audible range, there should not be any coloration to the frequency response such as less bass or more treble, etc.

I was recently looking at Amir's review of the Buckeye NC252PM and saw the following graph. My naive question is... is this an example of where an amp will in fact color the sound? Or is increasing distortion not related to audible sound quality? Another related question is... if max power at 20hz is 122 watts, and if you happen to listen to a lot of music that plays that low at loud enough volumes to require 122 watts (probably not a common scenario, but let's just assume this for the sake of argument), then for all intents and purposes, shouldn't this be rated 122 W at 4ohm, as opposed to the 250 W at 4ohm spec?

 

[staticV3]

I was recently looking at Amir's review of the Buckeye NC252PM and saw the following graph. My naive question is... is this an example of where an amp will in fact color the sound? Or is increasing distortion not related to audible sound quality?

Considering the distortion amplitude and spectral nature of music, you can expect the Amp shown here to be fully transparent.

 

[Doodski]

For audible distortion view this 4:17 video that shows in the most obvious way what distortion sounds like at varying levels of distortion. Basically unless distortion is pretty high you won't hear it usually. (most of the time.)

 

[mhardy6647]

Any amplifier with a "low damping factor" (high output impedance) will "color" sound from any real-world loudspeaker as the load and the source interact with each other. Whether the effect will be audible probably depends on the actual output impedance of the amp and (in particular) upon the frequency-dependent impedance and phase behavior of the loudspeaker.

Amplifiers with a single ended output will have a quantifiably different harmonic distortion spectrum than amps with push-pull output (even if all else were equal ). This might or might not be audible.

Both of the "effects" I mention above are, I think responsible for many of the audiophile tropes surrounding, e.g., vacuum tube amplifiers, particularly so-called SET (single-ended triode) amps, and also much of the "synergy" experienced by ahem audiophiles.

Full disclosure - I am a SET kind of guy, but I am also a realist.

 

[restorer-john]

then for all intents and purposes, shouldn't this be rated 122 W at 4ohm, as opposed to the 250 W at 4ohm spec?

Hypex's ratings are somewhat flexible.

Here is their own datasheet:

The rated continuous power output is supposedly just 50W. But at what impedance and at what frequency or range of frequencies?

They can deliver a lot of power on a peak basis. A a reasonable amount of power on a continuous basis. But, the numbers used by themselves and every other box-stuffer out there are just inflated to get attention and sales.

If the module trips into protection at 122W at 4R@20Hz, it cannot be rated as a full bandwidth amplifier (20Hz-20kHz) with a continuous rating above that. But Hypex doesn't care about genuine continuous ratings. They just sell modules to assemblers and those assemblers blindly reprint the datasheet numbers as their "own" specs.

As for the potential for sonic coloration with the NC-252MP- I doubt you would hear any, unless you had particularly challenging loudspeakers attached.

 

[GXAlan]

Record breaker: Raphaelite CS30-MKII tube amplifier review and measurements

Raphaelite CS30-MKII 300B integrated tube amplifier review: A New Performance Record This is a review and detailed measurements of Raphaelite CS30-MKK 300B single ended tube amplifier. It is available on eBay for $1449 + $310 shipping to California + tax. There are some better deals from...

www.audiosciencereview.com

This is a 300B set which you can see colors the sound through distortion. It’s much easier to measure and hear this because the distortion is much higher but conceptually this does suggest that high distortion in real loads can color the sound.

 

[Doodski]

I know that there are several threads on "whether all amps sound the same" and although some of the technical discussions go over my head, the impression I'm getting is an amplifier should not color the sound provided that it has flat frequency response. In other words, if you're comparing amp A to amp B at the same power wattage, and both are flat in the audible range, there should not be any coloration to the frequency response such as less bass or more treble, etc.

I have heard and owned one amp out of the thousands of amps that I have experience with and one sounded colored. It was a expensive exotic amp with linear power output and a huge power supply and some design differences that made it sound different. So generally speaking colored amps is usually not a issue. There are also some cheaper designs that will sound a bit dead and not with very good transient power output.

 

[sam_adams]

The speakers will be the limiting factor with their distortions that are at least 2 - 3 orders of magnitude greater than that of the amplifier. You will not hear the amp distorting until it clips—severely.

 

[Dunring]

For headphones, I think a lot of people make the mistake of plugging in headphones with less than 8 times the output impedance of their amplifier (easy to do with some like the original Topping DX7 Pro which I have). Then they blame the amplifier for changing the sound because their 10 ohm IEMs sound weird/different.

 

[kemmler3D]

I'm going to disagree a bit with some of the statements in this thread so far - if you are really asking the amp for >120w at 20hz, it may not deliver and the bass will be clipped, you can hear a shortfall in low bass that way because the amplitude is limited.

What is often missed in these discussions is the clipping (despite the look of the graph) is it's relatively soft clipping, so you don't hear a big crunch coming out of the speakers. The speakers are probably contributing more THD than the amp even when it's starting to clip. So you don't hear the amp distorting, you just hear a vague weakness in the bass.

So it would be fair to say the amp is "colored" in the case that you're trying to play a ton of bass with it. This is not an amp you want to drive a subwoofer with.

 

[DVDdoug]

whether all amps sound the same

I usually say all GOOD amps sound the same, except that some have more noise than others and sometimes the noise is audible. The audibility of the noise also depends on the sensitivity of the speakers, how close you are are to the speakers, and other ambient room noise, etc.

Of course an amp can be defective or poorly designed, or there may be more gain in one channel than the other, etc. Not ALL amps sound the same.

I've NEVER heard distortion from ANYTHING unless it was broken or overdriven.

With modern solid state electronics it's cheap & easy to get distortion and frequency response that are better than human hearing.

In the 1970s when I was in high school somebody gave me two tube amps. One was a mono McIntosh amp and it sounded perfect. The other (unknown or un-remembered manufacturer) was stereo but it had rolled-off highs. I made some random-experimental modifications to improve the highs but I didn't have any equipment to measure the frequency response.

Poor sound was pretty common back in the "tube days", but generally the speakers weren't very good either, and all we had was records (with questionable phono cartridges) so I can't blame the tubes for EVERYTHING. In tube power amps, the output transformer is a big part of the problem. It's not hard to make a good tube preamp. It's just more expensive than solid state.

 

[Prana Ferox]

Part of the advantage of class D is that you can use a much smaller (usually switch-mode) power supply. However, as frequency drops and gets closer to DC, you end up becoming power supply limited. That is greatly exaggerated when applying test tones (like Amir's testing).

A simple close-enough way to think of it is that instead of trying to throttle the voltage to the speaker, the class D amp just slams open the throttle, then slams it shut, then opens it, over and over again (usually hundreds of thousands of times a second) so the average over a more meaningful period of time looks just like a class A/B's throttling. But with very low frequency and high output, that class D amp is spending relatively a lot of its time wide open where it behaves more like that class A/B, and it ends up needing the full-size current supply of the A/B, or having to soft clip / go into protection.

Amplifiers are going to have three main power limiting factors:

• Peak voltage, this is primarily a function of the power supply
• Long-term thermal dissipation (i.e. cooling), a class D amp's generally greater efficiency generally makes this easier but also generally they have smaller heatsinks to match, any amp can overheat if you abuse it
• Short term current supply, this is again a function of the power supply, and is affected by the duty cycle of the amp. For a testing sine wave, duty cycle is 1, i.e. 100% of the signal is at peak amplitude. For normal music that is not just a blast of test tones that duty cycle is usually more like 1/8 to 1/15 which is much much easier on an amp

Early class D amps had trouble with very low bass / deep subwoofer duty but modern amps have much better setup to handle it. Also, actual music is pretty different from test tones and doesn't draw high current at low frequencies for extended periods of time (movie LFX, your mileage may vary.)

To the OP's question, for an amp to 'color' sound it either needs to have a noticeably screwed up frequency response, or an audible distortion spray (which results in a screwed up frequency response, but in different conditions.) Both are most prevalent with valve/tube amps. Tube amp power supplies also often run out of current during low frequency output, producing a soft clip / distortion into the low midrange which many people find pleasing, but isn't particularly hi-fi. If you wanted to get colored sound out of an nCore amp you'd want to eq it in upstream.

 

[Matias]

@existingbrain FAQ number 7.

Class D FAQ

This topic is dedicated to Frequently Asked Questions about class D amplifiers. If you have been directed here the reason is that it is easier to concentrate the frequent answers here instead of repeating them in several topics. Q1: Class D power ratings cannot be true. How can these small and...

www.audiosciencereview.com

 

[MarkBee123]

Not suggesting I know anything. I guess in my recent continuation into audiophilia (I periodically go down the upgrade rabbit hole)my thought is that current delivery and slew rate can impact the tonality of an amp, as I thought my adcom 535mk2 amp sounded muscular and defined versus an old Marantz 2270 just using the amp inputs with the same preamp, but now Amir has messed with my brain and has enlightened me that it's actually not him who is doing the messing.. it is me.

 

[Doodski]

my thought is that current delivery and slew rate can impact the tonality of an amp

Current delivery and a shortage of that current delivery is caused by the power supply as @Prana Ferox mentioned being overloaded or underbuilt.
Slew rate is calculated by using the slope of a waveform and that is the upper frequency limit of an amp.
Modern amps generally have no issues to be concerned about regarding slew rate.
Pretty much all modern class A/AB/ABH etc have immense bandwidth so they can amplify up into the hundreds of kiloHertz. Far above what you can hear.

 

[MarkBee123]

Current delivery and a shortage of that current delivery is caused by the power supply as @Prana Ferox mentioned being overloaded or underbuilt.
Slew rate is calculated by using the slope of a waveform and that is the upper frequency limit of an amp.
Modern amps generally have no issues to be concerned about regarding slew rate.
Pretty much all modern class A/AB/ABH etc have immense bandwidth so they can amplify up into the hundreds of kiloHertz. Far above what you can hear.

thanks, I am forgetting that slew rate is a frequency term... doh. I am conflating voltage transitions and current transitions. (again.. I think). But that aside, I did think I was hearing real differences between the power amp section of the old 2270 and the more modern 535mk2. I didn't really have an expectation when I did the A/B and the amps did seem to have a different sound. It could have been that the Marantz had some aging components and as such not performing "ideally".

 

[Doodski]

thanks, I am forgetting that slew rate is a frequency term... doh. I am conflating voltage transitions and current transitions. (again.. I think). But that aside, I did think I was hearing real differences between the power amp section of the old 2270 and the more modern 535mk2. I didn't really have an expectation when I did the A/B and the amps did seem to have a different sound. It could have been that the Marantz had some aging components and as such not performing "ideally".

I owned a Marantz 2270 and used it as a head unit at my repair bench for years. It sounded good. The much much older Marantz models do sound a bit flatter but that's because they use a quasi complimentary amplifier design and run the output through a big fat capacitor. The Marantz 2270 on the other hand uses a class AB complementary pair for amplification and that powers the speakers without a big fat capacitor in the amplifier signal path and those sound good. So if your Marantz 2270 was in good operating condition it should sound the same as the Adcom 535 MKII.

 

[MaxwellsEq]

the impression I'm getting is an amplifier should not color the sound provided that it has flat frequency response

Unfortunately, that is an incomplete summary.

Yes, you do need a flat frequency response. But measurements are often given into a resistive load of 8 or 4 Ohms. Real world speakers are generally not a pure resistance, but a combination of resistance, inductance and capacitance. These create a much tougher load on the amplifier and its power supply.

To not create a coloured sound, then, an amplifier needs a flat frequency response, low noise and low distortion. It also needs a low output impedance, sufficient current drive (and heat extraction) to handle speaker low impedance frequencies, sufficient voltage swing to handle speaker high impedance frequencies, the ability to sustain voltage AND current drive out of phase for frequencies where the speaker is significantly reactive, sufficient power supply delivery to maintain bursts without sagging and excellent recover from these bursts.

 

[DSJR]

I can think of some British made amps in the past with a very definite sonic signature - Naim's 'CB and Olive' cosmetic model ranges for a start (it's all in what are today mediocre to poor higher odd-order distortion measurements coupled with basic band limiting an dhard clipping in many of those designs, coupled with a veiled 'sounding' preamp which began to improve with expensive supply additions). RIAA eq on various phono inputs used to be all over the place on too many amps back then, even some far eastern made ones, and bearing in mind over here that vinyl was the main source right up until the late 80's for most 'HiFi' buyers, I can understand these differences compared to today, where a line input is the usual connection method.

To be fair to Naim, after the c2000 model range changes, the performance of their products seemed to improve quite dramatically, adding 10 - 15dB estimated to their distortion figures if Stereophile figures can be trusted, the circuit layouts were changed again and more modern component choices made. The 'sound character' of old has thankfully now seemingly all but disappeared to all intents and purposes. Just my vibes here shared by others with less tribal aspirations as regards amp makers, but obviously subjective here.

Reviewer Martin Colloms (who was 'everywhere in the UK press at this time) also helped perpetrate the view that we could 'hear' things we cannot measure in at least one HiFi Choice review book in the mid 80's (I have them here and read this yesterday in one of the introduction articles). Interesting how so many well performing far eastern amps reportedly sounded 'lean and spatially flat' where the favourite pr@t laden valve amps he loved so much measured terribly (distortions in the -40 - 50dB region). Earlier HiFi Choice tests with different test engineers used to have swept intermod graphs and these results could tell their own story as every one was different from make to make.

So glad much of this doesn't apply today, where most good amps are appliances to do the job and can be chosen on power available for the task, facilities and looks (i have to add price tags too with many high end brands) rather than 'how they sound.'

 

[ferrellms]

I know that there are several threads on "whether all amps sound the same" and although some of the technical discussions go over my head, the impression I'm getting is an amplifier should not color the sound provided that it has flat frequency response. In other words, if you're comparing amp A to amp B at the same power wattage, and both are flat in the audible range, there should not be any coloration to the frequency response such as less bass or more treble, etc.

I was recently looking at Amir's review of the Buckeye NC252PM and saw the following graph. My naive question is... is this an example of where an amp will in fact color the sound? Or is increasing distortion not related to audible sound quality? Another related question is... if max power at 20hz is 122 watts, and if you happen to listen to a lot of music that plays that low at loud enough volumes to require 122 watts (probably not a common scenario, but let's just assume this for the sake of argument), then for all intents and purposes, shouldn't this be rated 122 W at 4ohm, as opposed to the 250 W at 4ohm spec?

View attachment 376237

A story from Stereophile magazine relates how their listeners were able to distinguish blindly between one of Bob Carver's amps (solid state) and a Cary(?) tube amp. (Bob Carver is a famous amp designer who cooked up the first amps with 200W and more). So Carver came in with his soldering iron, etc, and used audible nulling and changed the Carver with light amp tweaking (slight distortion) to remove any audible difference between the amps. Stereophile was impressed and declare the sound identical. So, not all amps sound the same! But which sounded BETTER??