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

[sam_adams]

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

 

[Purité Audio]

Surely not the Zaphod, Zaphod Beeblebrox .
Keith

 

[MAB]

Surely not the Zaphod, Zaphod Beeblebrox .
Keith

'Headroom' is a measure of how many heads Zaphod has.
With three arms, even more handwaving arguments should ensue.

 

[rdenney]

People measure amplifier power in different ways. The only thing that matters is whether, at the desired listening level and into the desired load, the amplifier is able to fill the waveform without distortion. If the load has very low impedance, the amplifier may not be able to provide the necessary current, the voltage will sag, and the waveform will assume a different shape than the incoming signal. If the person turns it up too loud, the amplifier is asked to create voltage levels higher than the rail voltage being switched in by the amplifier devices, and the voltage sags, often abruptly. Both of these fall into my description: clipping.

Clipping is usually audible and must be avoided. If that's what the OP means by "demanding conditions", then the solution is a design that provides more power at the desired listening level and into the desired load so that it doesn't clip. The limitation may be the power supply, but it may also be the active amplification devices and surrounding circuits that become saturated.

If the power at which the desired listening level and load is supported without distortion is the same between two amplifiers, then the cheaper and more efficient design would normally get better engineering marks. They should report the same specifications, but of course they don't, because the standards for reporting power output just pick one condition, not all conditions. When I look at measurements, I ask what the power output is relative to load and frequency, and relative to distortion levels. Even with all the measurements we see these days, it's not always obvious.

The term "dynamic power" or "headroom" means little to me in practice. I suppose it usually means the ability of the amp to fill some rogue waveform at a higher power level than specified within some acceptable distortion, to provide sufficient current at the maximum rail voltage for some useful but not indefinite period of time.

Is the OP is asking for is a power supply that at the rail voltage can supply all the current necessary indefinitely? Regulated switching power supplies are designed to do that, and so don't have "headroom". And they do that without car-sized transformers and garbage-can-size filter caps. Unregulated linear power supplies can always do more for short periods of time. If the maximum continuous output is the same (which is a statement that carries a lot of freight), and if that continuous output is sufficient to achieve the desired listening level into the desire load without distortion, then what does it matter?

Rick "late hit, I'm sure" Denney

 

[MAB]

Turning radius is a measure of a car's handling.
Stopping distance is a measure of a car's lack of forward acceleration.
Glass half-full is a measure of emptiness.
Oversimplification is a measure of how complex a system is and how little we understand it.

 

[darrellc]

Surely not the Zaphod, Zaphod Beeblebrox .
Kei name of amirm’s engagement seeking alter ego

And assumed name of one of amirm’s engagement seeking alter egos?

 

[radix]

To try and clarify my understanding... switching power supplies cannot have large buffer capacitors, so they just don't have this type of short peak power headroom. I thought one of the main advantages of linear power supplies in A/B designs (e.g. Yamaha) is that they can have large buffers and deliver short peaks when operating near their max nominal power.

Personally, I build my desired headroom into the nominal amplifier power, not its peak power.

 

[Ordin Aryguy]

To try and clarify my understanding... switching power supplies cannot have large buffer capacitors, so they just don't have this type of short peak power headroom. I thought one of the main advantages of linear power supplies in A/B designs (e.g. Yamaha) is that they can have large buffers and deliver short peaks when operating near their max nominal power.

Personally, I build my desired headroom into the nominal amplifier power, not its peak power.

SMPS can certainly have larger bulk capacitance. They just don't need it. It's a function of the frequency at which the different supplies operate.

In a linear supply application operating with a 60Hz input and a full wave bridge rectifier, the "energy pulses" come around every 8.3mS. The time in between those pulses is when the bulk capacitance is expected to hold up the voltage, keep it from sagging.

In a SMPS the "energy pulses" are at a MUCH higher frequency (hundreds of kHz into MHz) meaning that the time during which the bulk capacitance is expected to prevent voltage sag is dramatically reduced. This allows for much smaller capacitors to be used.

 

[voodooless]

SMPS can certainly have larger bulk capacitance.

Most really can’t, not without special measures. Check the spec sheets, usually they do not allow more than a few thousand uF. More gives issues with inrush currents at startup. So it you want more, make sure to limit inrush current accordingly.

 

[radix]

Most really can’t, not without special measures. Check the spec sheets, usually they do not allow more than a few thousand uF. More gives issues with inrush currents at startup. So it you want more, make sure to limit inrush current accordingly.

Yes, that's what I had thought. For example, the Mornsun 450W SMPS (LOF450-20Bxx-C, [1]) tops out at a 6000 uF capacitive load. The Hypex SMPS1200A400 (just to pick one of theirs at random) has a max "external capacitance Vaux" of 1000 uF [2].

EDIT: I guess the Hypex already has buffer capacitors on the Vmain.

[1] https://www.mornsun-power.com/html/pdf/LOF450-20B15-C.html
[2] https://www.hypex.nl/media/8c/22/86/1646037796/SMPS1200Axx0_10xx.pdf, p. 5

 

[Deleted member 21219]

You are soo patient. -Damn!

There's no reason to lose control. If you do, your adversary has free rein to manipulate you. Not a good situation.

Jim "Been There, Done That" Taylor

 

[Ordin Aryguy]

Most really can’t, not without special measures. Check the spec sheets, usually they do not allow more than a few thousand uF. More gives issues with inrush currents at startup. So it you want more, make sure to limit inrush current accordingly.

An empty (discharged) capacitor looks very much like a short circuit at the instant of power on. That's the inrush current.

Many, many (dare I say most) SMPS regulators have built in soft start features to prevent the regulator from having issues at start up. The designers of the regulators take into account inrush.

In my previous post I didn't mean to imply that there is not some limit to the amount of bulk capacitance that can be hung on the output of a SMPS. I'm certain there likely is. What I did say, is that SMPS just don't need the tens of thousands of uF to prevent voltage sag.

We're literally talking about time periods changes on the order of 1000 times to 10,000 times smaller when comparing linear and SMPS. In a very simplistic view, the output capacitance can shrink by those same ratios and still provide the same voltage sag performance.

 

[voodooless]

An empty (discharged) capacitor looks very much like a short circuit at the instant of power on. That's the inrush current.

Many, many (dare I say most) SMPS regulators have built in soft start features to prevent the regulator from having issues at start up. The designers of the regulators take into account inrush.

Yet all of these SMPSes have datasheets that show a maximum capacitance load of a few thousand uF as a maximum. If inrush is covered, what else could be the reason to limit this? Obviously it’s not needed, but that is besides the point.

 

[krabapple]

Zaphod has posted all of 12 messages since January 2019, all on this thread.

So, he waited five years to drop this load on ASR?

The internet is a funny place.

 

[MAB]

Zaphod has all of 12 messages since 2019, all on this thread.

So, he waited five years to drop this load on ASR?

The internet is a funny place.

Yes, I think OP's point is amps have zero headroom when turned off, so likely sound the best then.
They certainly have the lowest noise and distortion when off.

 

[Ordin Aryguy]

Yet all of these SMPSes have datasheets that show a maximum capacitance load of a few thousand uF as a maximum. If inrush is covered, what else could be the reason to limit this? Obviously it’s not needed, but that is besides the point.

Two possibilities:
1) The control loop for voltage regulation will not function properly with that capacitance.
2) The soft start circuitry is time limited. At power on it will essentially ignore the short circuit sensing for a fixed period of time. After that time the short circuit sensors activate to protect the power supply in the event of an actual over-current situation. The larger the external capacitance the longer it will take to charge, and at some point in time this extends beyond the soft start period.

I highly suspect that reason number 2 above is the mostly likely factor for the capacitor size limit.

 

[Deleted member 48726]

Zaphod has posted all of 12 messages since January 2019, all on this thread.

So, he waited five years to drop this load on ASR?

The internet is a funny place.

Huh?
That's so weird..

 

[MAB]

Huh?
That's so weird..

It is consistent with his zero-headroom ethos.

 

[popej]

My secondary amplifier is rated to deliver 120 Watts @ 8 Ohms, employs a 2.5kVA power transformer + 245,000uF of filter

You were scammed. Yo should get 2x600W continuous.

 

[Deleted member 48726]

It is consistent with his zero-headroom ethos.

He can have that.

It's much stranger that the 70th member on ASR waits five years to post 19 times in two days guns blazing and then disappears.

I'll leave the internet for today..