'Headroom' is a measure of the badness of an amplifier. The bigger the number, the worse the amplifier.

[Zaphod]

I am sorry, I do not follow.

1. A 100 Watt amplifier that employs a (say) 1kVA power transformer and 100,000uF of filter capacitance
2. A 100 Watt amplifier that employs a 400 VA power transformer and 10,000uF of filter capacitance

In the example you have given, all else being equal, which one has more "headroom" and why would it sound worse?

Maybe a better starting point : what do you mean by headroom?

If you read the review of the amplifier, you will note a reference to "headroom". That should explain all.

Then look at the review of the Ncore amplifier and note the headroom of that amplifier.

 

[Zaphod]

That's nonsense. No one designs a 100 watt amp and then put a 1 KVA power supply in it. Ignoring that, you have no idea of the level of headroom an amplifier has in those circumstances. Most likely amp #1 would have the same headroom as limited by the amplifier design as #2. And since amp 1 would cost a lot more, that is the bad option.

The right analogy is the same power supply with one having 10,000 uf filter cap and the other, 50,000. The latter would provide more headroom with some incremental cost that is cheaper than having same headroom but with more average power.

It's not nonsense. My secondary amplifier is rated to deliver 120 Watts @ 8 Ohms, employs a 2.5kVA power transformer + 245,000uF of filter capacitance. Output current is limited to 70 Amps. So, not only did someone design such an amplifier (Class A/B), but it was a wildly successful product here in Australia. Heavy? Yep. Expensive? You betcha, but way cheaper than the imported competition (AUS$5k vs. AUS$20k). Not cheaper than an NCore though. The NCore has changed the game.

Headroom is damned close to zero.

 

[amirm]

Headroom is damned close to zero.

Show the measurements.

 

[IAtaman]

If you read the review of the amplifier, you will note a reference to "headroom". That should explain all.

Then look at the review of the Ncore amplifier and note the headroom of that amplifier.

I understand what headroom is. What I do not understand is the logic of your claim.

Therefore, all other things being equal, an amplifier with a higher headroom figure will always sound worse than one with a lower headroom figure.

Are you trying to say what restorer john explained last week, that higher voltage but not strictly regulated power supplies are better at powering transients?

 

[sigbergaudio]

Damn. You really nailed me to wall with your carefully reasoned technical response.

NOT!

But you're only repeating "headroom is a measure of how bad an amplifier is" in every single post. Also not very technical or reasoned?

 

[Waxx]

If you bring such a strong claims to the table, that go against the general consensus about the subject, you better bring scientific proof also. What you do is just some ranting and some annecdotical impressions, nothing scientific at all. So we laugh at you.

Better bring the measurement and the science theory to the table if you want to make a point here. Now you just proved nothing to us.

 

[sergeauckland]

It is. Take two amps. One has 100 watts average power and burst power of 100 watts. The second also has average power of 100 watts but able to have peak power of 150 watts. Are you saying the second amplifier is worse than the first?

I wish I could remember the source, but tests were done in the 1970s or '80s with three amplifiers of identical circuit but different power supplies. They all provided 100 watts into 8 ohms continuous, but were configured as follows:-

A) Conventional Sagging Supply, providing 100 watts continuous, but 150 watts on 'short-term' peaks.
B) Stabilised supply providing 100 watts continuous, but no extra on peaks.
C) Stabilised supply providing 150 watts continuous but no extra on peaks.

Blind listening tests were carried on with a panel of 'experienced' listeners and amplifiers were rated as to preference. Volume was set to whatever the panel felt comfortable with, so not level matched. Output level was monitored, but there was no attempt to avoid clipping on peaks. This is in line with how people normally listen to music.

Not surprisingly, Amplifier C came out best, but amplifier A came out as clearly preferable to amplifier B thus indicating that peak power, i.e. headroom, was more important than continuous output power.

The testing was reported in either HiFi News or Wireless World (might even have been both) but I can't now find a reference.

Allowing headroom is ALWAYS a Good Thing, whether just for peaks or continuously, and I take a somewhat dim view of an amplifier with little headroom that may just be adequate but would fail if listening to high dynamic range music.

S.

 

[Golf]

It is. Take two amps. One has 100 watts average power and burst power of 100 watts. The second also has average power of 100 watts but able to have peak power of 150 watts. Are you saying the second amplifier is worse than the first?

All things being equal (which they usually not), yes.

»All things being equal« would mean that even those two amps themselves are equal. At least if »all things« means all things, that is.

 

[mhardy6647]

... and here I thought that this thread was about the Michael Jackson kind of Bad.

(the not-director's cut)

 

[Lambda]

@Zaphod​

One has 100 watts average power and burst power of 100 watts. The second also has average power of 100 watts but able to have peak power of 150 watts.

They will "sound" the same... but the one with more peak power can play louder deepening on the musical content.


You all seam to forget that an speaker is not a purely resistive load!
A class D amp can deliver mush more VA to a speaker then it consumes from the power-supply.

In Professional Amps this is normal to have 8kW (actually VA) on 16A barker that could only sustain ~sightly blow 4kW
This is why Professional Amps have Voltage and Current ratings.

X4L

www.powersoft.com

M-Drive

www.powersoft.com

All Equal Else Equal:
100 watts average power and burst power of 100 watts. > 80 watts average power and burst power of 100 watts.
100 watts average power and burst power of 100 watts. < 100 watts average power and burst power of 120 watts.

the only controversial question would be:
100 watts average power and burst power of 100 watts. Or 90 watts average power and burst power of 120 watts.
In this case it depends on your needs. your speakers and your music.

 

[solderdude]

That specific NAD was purposely designed that way (power envelope).

For other designs there is some truth in there about the difference between continuous and peak power and drop in max output voltage with lower load impedances.
This does not mean it is a poor design nor necesarilly that the power supply is underdimensioned.

Music is never a continuous signal, it is all transients and that should be handled well. This comes down to reservoir caps where the continous power is determined by the power supply and circuit itself.

 

[Deleted member 21219]

To cite you: "Nice bit of headroom."

You make that sound like a good thing. A large headroom figure is merely measure of how bad the power supply is.

Let's approach this logically.

First things first. If you come in here like gangbusters, having all the appearances of a troll, you're not going to get anywhere. This site is constantly under siege by trolls who gleefully take advantage of Amir's policy of tolerance, and many members here have long ago gotten sick and tired of them. Knock off the hyperbole and ask questions rather than adding fuel to flame, and this thread may turn into an interesting discussion.

A large headroom figure is not a measure of how BAD the power supply is, it is the measure of how uncontrolled the power supply is. Although many regard a loosely controlled power supply as "bad", that doesn't have to be true. Designers and manufacturers continually balance costs against characteristics under load, and make what they believe are the best decisions for their products in the real world.

You said:

Therefore, all other things being equal, an amplifier with a higher headroom figure will always sound worse than one with a lower headroom figure.

It is technically impossible for all things to be absolutely equal between two amplifiers that have different headroom characteristics. The differences will always be obvious on the bench. But that's not the problem with your statement (above). Your statement discussed the sound of the amplifiers being compared, and you used the adverb "always", but you didn't specify the exact conditions of "equality".

If your basis of equality is RMS measured power, then amp #1 would output (let's say) 100 watts continuous without any headroom. Amp #2 would output 100 watts continuous, but have 3dB headroom, for a short-term output of 200 watts. Under the condition that the 3dB of headroom would be necessary to trace the signal, amp #2 would actually sound better, not worse.

If your basis of equality is the total power envelope, then you would compare (let's say) amp #1 with 100 watts continuous and no headroom with amp #2, which would now necessarily be defined (becasue we've moved the goal posts) as an amp with 50 watts output continuous and 3 dB headroom for 100 watts total. So you would be comparing what would seem to be a 50-watt amp to a 100-watt amp. Under that circumstance, there could be an audible difference ... but in my experience it would be slight. IMO, it would favor the 100-watt amp.

This is assuming that both amps are designed to deliver their power into extremely difficult loads as seen in some hard-to-drive speakers such as electrostatics, or dynamic loads with low impedance combined with odd phase angles.

Unfortunately, that doesn't happen often. Manufacturers who favor high-headroom designs usually do so for reasons of economy. They want to offer their customers greater short-term capabilities while lowering the demands on the overall circuitry so as to cut costs. Such designs are not usually created to deal with the exceptionally demanding speaker loads that are the minority on the market. Instead, they are created to deal advantageously with common loads as seen in the vast majority of loudspeakers on the market.

I said, "unfortunately, that doesn't happen very often." In reality, I am not sure that it happens at all ... ever. I'm not sure that it CAN happen ... at least, not if the amps are both rated exactly the same and under the same loads.

Which brings up the last factor; advertising.

If the FTC rule (as originally implemented) were adhered to rigidly, differences in circuit design capability would be stated ( and obvious) in the specs. But almost no one does that anymore.
So comparing the power of two amps on an equal basis depends on the point at which an advertiser wishes to set the limit. 1% distortion? Beginning of the "knee"? 4 ohms at the expense of 8 ohms?

If the advertiser wanted to set the rating dependant on short-term headroom limits, then I'm sure that you are correct; there would be some circumstances under which that amp, like amp #2 above, would sound inferior to an amp, like amp #1, with a higher RMS figure.

Whether that would be encountered in the normal 1-watt-average-output scenario of the average home is up for grabs, so to speak. And the cost-cutting designers know that. They bet on it to work in their favor.

So your use of the word "always" is inaccurate and inappropriate. Your use of the word "sounds" as the basis for your comparison is, I believe, untenable. It may apply in a rare case, but the sound difference cannot be determined to be verifiable in each and every case.

As usual, I might be wrong.

Jim

 

[antcollinet]

Another sleeper troll account.

Why do they invest the time and energy - and sheer preparation - to do this?

 

[Mikig]

In my experience as a curious hobbyist and not as a technician, I think I understood from the web, magazines and operators in the sector these topics regarding amplifications. In fact, I'll take this opportunity to understand from you too if these are real topics. in summary 4 points, (obviously among many)

1) if you have an extra peak of power that can better handle transients, certainly the music you hear will be more dynamic.

2) Extra power and a good rise speed on transients therefore become important.

3) Good practice for amplifiers is the ability to adapt to the difference in speaker impedance. Therefore being able to manage impedances closer to "zero" with an if not double (theoretical) but at least adequate increase in output power.

4) the ideal amplifier is the one that does not suffer from the often difficult and "tormented" electro/mechanical characteristics of the speakers.

 

[Deleted member 21219]

Another sleeper troll account.

Why do they invest the time and energy - and sheer preparation - to do this?

They get their jollies from putting us to the task, so to speak. Kinda like throwing several dogs a Frisbee and watching what happens.

Jim

 

[mhardy6647]

Come to think of it -- ohm (volts per ampere) is the SI unit of measurement for resistance. The measure of conductance (the inverse of resistance) is (was ) commonly expressed in units of mhos ( which is, of course, ohms backwards).

So... if headroom measures amplifier badness, perhaps we should consider measuring amplifier goodness in units of moordaeh?
I mean, possibly not -- it sounds like one of those words that, if said thrice in succession, would summon demons.


OK, my work is done here.

 

[Vladimir Filevski]

A large headroom figure is merely measure of how bad the power supply is.

Before writing such ...(censored)... wrong sentence, please consult some basic electronic book for absolute beginners.

 

[Multicore]

Another sleeper troll account.

Why do they invest the time and energy - and sheer preparation - to do this?

Winning a fight feels good and winning an argument activates the same reward mechanisms more or less. Notice how Zaphod used a lot of sarcasm, exaggeration, and taunts, all standard ways (across cultures and history) to start arguments/fights. If Zaphod had wanted to learn something, the same technical issues could have been framed as questions. So that seems deliberate.

What's not so clear is if Zaphod believes the arguments or just knows that they are good enough to provoke responses. But if the main purpose (answering your "Why?" question) is to start a fight that it doesn't really matter.

 

[Mikig]

They get their jollies from putting us to the task, so to speak. Kinda like throwing several dogs a Frisbee and watching what happens.

Jim

Hi Jim,

OT!! you should make a collection of your metaphors, which I have noticed you often use as a response, always "funny and appropriate"!!!!

 

[Deleted member 48726]

Let's approach this logically.

First things first. If you come in here like gangbusters, having all the appearances of a troll, you're not going to get anywhere. This site is constantly under siege by trolls who gleefully take advantage of Amir's policy of tolerance, and many members here have long ago gotten sick and tired of them. Knock off the hyperbole and ask questions rather than adding fuel to flame, and this thread may turn into an interesting discussion.

A large headroom figure is not a measure of how BAD the power supply is, it is the measure of how uncontrolled the power supply is. Although many regard a loosely controlled power supply as "bad", that doesn't have to be true. Designers and manufacturers continually balance costs against characteristics under load, and make what they believe are the best decisions for their products in the real world.

You said:



It is technically impossible for all things to be absolutely equal between two amplifiers that have different headroom characteristics. The differences will always be obvious on the bench. But that's not the problem with your statement (above). Your statement discussed the sound of the amplifiers being compared, and you used the adverb "always", but you didn't specify the exact conditions of "equality".

If your basis of equality is RMS measured power, then amp #1 would output (let's say) 100 watts continuous without any headroom. Amp #2 would output 100 watts continuous, but have 3dB headroom, for a short-term output of 200 watts. Under the condition that the 3dB of headroom would be necessary to trace the signal, amp #2 would actually sound better, not worse.

If your basis of equality is the total power envelope, then you would compare (let's say) amp #1 with 100 watts continuous and no headroom with amp #2, which would now necessarily be defined (becasue we've moved the goal posts) as an amp with 50 watts output continuous and 3 dB headroom for 100 watts total. So you would be comparing what would seem to be a 50-watt amp to a 100-watt amp. Under that circumstance, there could be an audible difference ... but in my experience it would be slight. IMO, it would favor the 100-watt amp.

This is assuming that both amps are designed to deliver their power into extremely difficult loads as seen in some hard-to-drive speakers such as electrostatics, or dynamic loads with low impedance combined with odd phase angles.

Unfortunately, that doesn't happen often. Manufacturers who favor high-headroom designs usually do so for reasons of economy. They want to offer their customers greater short-term capabilities while lowering the demands on the overall circuitry so as to cut costs. Such designs are not usually created to deal with the exceptionally demanding speaker loads that are the minority on the market. Instead, they are created to deal advantageously with common loads as seen in the vast majority of loudspeakers on the market.

I said, "unfortunately, that doesn't happen very often." In reality, I am not sure that it happens at all ... ever. I'm not sure that it CAN happen ... at least, not if the amps are both rated exactly the same and under the same loads.

Which brings up the last factor; advertising.

If the FTC rule (as originally implemented) were adhered to rigidly, differences in circuit design capability would be stated ( and obvious) in the specs. But almost no one does that anymore.
So comparing the power of two amps on an equal basis depends on the point at which an advertiser wishes to set the limit. 1% distortion? Beginning of the "knee"? 4 ohms at the expense of 8 ohms?

If the advertiser wanted to set the rating dependant on short-term headroom limits, then I'm sure that you are correct; there would be some circumstances under which that amp, like amp #2 above, would sound inferior to an amp, like amp #1, with a higher RMS figure.

Whether that would be encountered in the normal 1-watt-average-output scenario of the average home is up for grabs, so to speak. And the cost-cutting designers know that. They bet on it to work in their favor.

So your use of the word "always" is inaccurate and inappropriate. Your use of the word "sounds" as the basis for your comparison is, I believe, untenable. It may apply in a rare case, but the sound difference cannot be determined to be verifiable in each and every case.

As usual, I might be wrong.

Jim

You are soo patient. -Damn!