The real answer should be , no difference.
However, you don't need lot of power. So the higher wattage amp needs more parallel resources in case of transistors and tubes. Paralleling devices is a deviation from linearity. So the IDEAL amp should be just enough for your needs, and you are the best to know this.
You don't want to run off juice, also you don't want to have too much (unnecessary multiplication of devices).
So in a big room, yes the higher wattage is better.
In a small room, yes the lower wattage is better.
Can you have both, well it is like splitting a hair in 4.
Please audition both amps and see for yourself.
To me, with my room and speakers, I am happy with 40 to 100 watts, this gets me the edge, 150 watts makes no improvements, nor 200, I can live and be happy with 25.
So how big is your room? how loud do you listen?, do you go to your audiophile shop and talk, listen to system? if no, the answer doesn't lie in an INTERNET forum,
However, you don't need lot of power. So the higher wattage amp needs more parallel resources in case of transistors and tubes. Paralleling devices is a deviation from linearity. So the IDEAL amp should be just enough for your needs, and you are the best to know this.
You don't want to run off juice, also you don't want to have too much (unnecessary multiplication of devices).
So in a big room, yes the higher wattage is better.
In a small room, yes the lower wattage is better.
Can you have both, well it is like splitting a hair in 4.
Please audition both amps and see for yourself.
To me, with my room and speakers, I am happy with 40 to 100 watts, this gets me the edge, 150 watts makes no improvements, nor 200, I can live and be happy with 25.
So how big is your room? how loud do you listen?, do you go to your audiophile shop and talk, listen to system? if no, the answer doesn't lie in an INTERNET forum,
other answers here disagree.
You never need a lot of power? Ever?
If you're talking about playing them at a different volume, then you didn't understand the OP.
thx
I think it is hard to find a real world example for the comparison because to make an amp run at a lower (or higher) voltage than another design, more needs to change than just the wattage of the components.
Not sure if it is entirely correct (I'm no spice guru), but I have run 2 spice sims on an existing design that runs off a single sided supply. One is run at 24v rails, the other at 48v. The output is 2.8vpk for both and well within spec output (i.e no clipping for either).
The 48v sims at 0.027% thd.
The 24v sims at 0.17% thd.
The only way to get the distortion under control on the lower voltage version is to change the design component values to achieve performance and stability. But then you have a different design, a different amp.
I think in the real world, such a comparison is quite complex and difficult to achieve as a true apples=apples venture.
I wonder - is your question just a hypothetical or have you seen 2 amps you are trying to decide between?
--edit--
The more/less volts argument is essentially what you are asking though? Remember watts = voltage x current:
"The r.m.s. Power delivered to the load (Pac) is therefore given as:"
Not sure if it is entirely correct (I'm no spice guru), but I have run 2 spice sims on an existing design that runs off a single sided supply. One is run at 24v rails, the other at 48v. The output is 2.8vpk for both and well within spec output (i.e no clipping for either).
The 48v sims at 0.027% thd.
The 24v sims at 0.17% thd.
The only way to get the distortion under control on the lower voltage version is to change the design component values to achieve performance and stability. But then you have a different design, a different amp.
I think in the real world, such a comparison is quite complex and difficult to achieve as a true apples=apples venture.
I wonder - is your question just a hypothetical or have you seen 2 amps you are trying to decide between?
--edit--
The more/less volts argument is essentially what you are asking though? Remember watts = voltage x current:
"The r.m.s. Power delivered to the load (Pac) is therefore given as:"
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Thx gabdx and avtech23 for replies.
Re different supply V's, as mentioned in my OP, each amp is given its own optimum supply V. Not the same supply V as the other amp. But also same configuration. Meaning both single sided. Or both bipolar supply.
Resistors, PCB traces, etc are optimum size on each amp for it's power level-- not same size as the other one.
Yes, as mentioned above, it's a hypothetical. Not looking for real world examples.
Thx!
Re different supply V's, as mentioned in my OP, each amp is given its own optimum supply V. Not the same supply V as the other amp. But also same configuration. Meaning both single sided. Or both bipolar supply.
Resistors, PCB traces, etc are optimum size on each amp for it's power level-- not same size as the other one.
Yes, as mentioned above, it's a hypothetical. Not looking for real world examples.
Thx!
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You set the 30W to it's optimum volume
Makes no sense at all, most music plays at 1 watt anyways, unless your listening in an auditorium.
The answer to your question is no, should make no difference.
The amplifier THD and wattage specification is irrelevant in most settings or applications for home use. Home use = 1 watt max, 5 to 10 for big rooms. There are many posts about this.
IF you are talking about class D, then NO again. I listened to high power and low power class D, all sounding mellow and good. The highest wattage sounded maybe more detailed, but this is only my impression. Class D is a different animal than all other types of amplifiers, power alone is irrelevant of sound quality
Makes no sense at all, most music plays at 1 watt anyways, unless your listening in an auditorium.
The answer to your question is no, should make no difference.
The amplifier THD and wattage specification is irrelevant in most settings or applications for home use. Home use = 1 watt max, 5 to 10 for big rooms. There are many posts about this.
IF you are talking about class D, then NO again. I listened to high power and low power class D, all sounding mellow and good. The highest wattage sounded maybe more detailed, but this is only my impression. Class D is a different animal than all other types of amplifiers, power alone is irrelevant of sound quality
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Ok, set it to whatever volume is 1 watt. Why doesn't it make sense?
Why don't you consider that relevant?
that's allowed in my hypothetical, to accommodate different wattage or power supply. As long as same design.
trying to compare two hypothetical amps that are as similar as possible, but one is 30W and the other is 200W. So, design should be as similar as possible. Each amp should have optimum components for it's power level.
In fairness, the premise is somewhat flawed anyway.
If you look at a Firstwatt amp, typically the virtues are simplicity and minimal feedback. Start multiplying the output devices, raising the rails, and thus reducing the current through the parts will move those parts out of their sweet spots, and add more of them. Then as capacitances mount, you'll need to find a different solution to the front end, and on and on we go.
So, whilst yes, having greater headroom to call on can't hurt, from an engineering perspective there's compromises to get to that point...
If you look at a Firstwatt amp, typically the virtues are simplicity and minimal feedback. Start multiplying the output devices, raising the rails, and thus reducing the current through the parts will move those parts out of their sweet spots, and add more of them. Then as capacitances mount, you'll need to find a different solution to the front end, and on and on we go.
So, whilst yes, having greater headroom to call on can't hurt, from an engineering perspective there's compromises to get to that point...
i.e.: Instantaneous current = short term current available from the bigger power supply. Or better damping, or better distortion at lower power because of transistors experiencing optimum condition with higher voltage (Mosfets need higher voltage between Drain and Source)
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Class D have comparators, Triangular generators and Filters.
The only thing which could change physically in the bigger power unit is the capacity of current and voltage of the final inductor and capacitor.
Maybe I am wrong, but a decent class D with quality transistors is super efficient and there are no reason why it cannot achieve into hundred of watts without any paralleling of units.
The answer to your Q. is amplifier topology dependent.
The only thing which could change physically in the bigger power unit is the capacity of current and voltage of the final inductor and capacitor.
Maybe I am wrong, but a decent class D with quality transistors is super efficient and there are no reason why it cannot achieve into hundred of watts without any paralleling of units.
The answer to your Q. is amplifier topology dependent.
Sounds like you're saying, we can have a low watt and high watt class D with same topology. Correct? Therefore, we can compare them.
Not power dependent? So a 30W and 200W class D of same topology, at same volume, will have identical SQ?
Unclear what decibel volume is in chart on the right. I assume THD is volume dependent.
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So a 30W and 200W class D of same topology, at same volume, will have identical SQ?
=Yes
Amplifiers don't have any sound quality. The THD of an amplifier is not meaningful for perceived SQ.
Unclear what decibel volume is in chart on the right. I assume THD is volume dependent.
Decibels is a ratio of two numbers in logarithmic scale, Dbv is not decibel volume.
Dbv = decibel-volts.
THD has nothing to do with volume knob turned up and down, or volume which means nothing, it has no unit in electricity. Volume of milk OK volume of sound? no.
The volume is a variable divider of the INPUT signal to the amplifier. It has no relationship with the output power.
In a THD chart you won't find any decibel volume.
The chart is made by Internal Rectifier to explain THD vs output power of a single signal in a defined load by a class D amplifier.
My point was that at the listening power of home use you hear the amplifier perform at 1 watt and you see that the Class D has a raising THD under 1 Watt.
In class D your music is converted to a digital sample (square waves), amplified by transistors switching on and off (completely), and then the digital Square wave is filtered by a 2n order filter to remove the digital noise, restoring or letting pass the original signal without digital noise.
=Yes
Amplifiers don't have any sound quality. The THD of an amplifier is not meaningful for perceived SQ.
Unclear what decibel volume is in chart on the right. I assume THD is volume dependent.
Decibels is a ratio of two numbers in logarithmic scale, Dbv is not decibel volume.
Dbv = decibel-volts.
THD has nothing to do with volume knob turned up and down, or volume which means nothing, it has no unit in electricity. Volume of milk OK volume of sound? no.
The volume is a variable divider of the INPUT signal to the amplifier. It has no relationship with the output power.
In a THD chart you won't find any decibel volume.
The chart is made by Internal Rectifier to explain THD vs output power of a single signal in a defined load by a class D amplifier.
My point was that at the listening power of home use you hear the amplifier perform at 1 watt and you see that the Class D has a raising THD under 1 Watt.
In class D your music is converted to a digital sample (square waves), amplified by transistors switching on and off (completely), and then the digital Square wave is filtered by a 2n order filter to remove the digital noise, restoring or letting pass the original signal without digital noise.
There's no "decibel volume" as such. That is strictly dependent on the loudspeakers used. That's pretty much why drivers have, among many other specs, the sensitivity, expressed in dB (SPL) @ 1 watt 
THD is definitely very much volume-dependent in loudspeakers, given their electromechanical nature And i'm sure all are in agreement that loudspeakers have orders higher levels of distortion than just about any amplifiers.
The levels at which they're more apparent are different, of course, but numbers don't lie. Well, that might depend on how one chooses to interpret said numbers.
Has anyone mentioned yet, that <ahem> "sound quality" is a very vague and subjective term, in and of itself?
1) YouTube
2) YouTube
THD is definitely very much volume-dependent in loudspeakers, given their electromechanical nature
And i'm sure all are in agreement that loudspeakers have orders higher levels of distortion than just about any amplifiers. The levels at which they're more apparent are different, of course, but numbers don't lie. Well, that might depend on how one chooses to interpret said numbers.
Has anyone mentioned yet, that <ahem> "sound quality" is a very vague and subjective term, in and of itself?
1) YouTube
2) YouTube
but not in amplifiers? Why one and not the other?
If you agree with gabdx, that THD in amplifier has nothing to do with sound quality, then do you also agree that THD in loudspeakers has nothing to do with sound quality?
If i understand gabdx, THD is never acoustically apparent in amplifiers, at any level.
My question is: however you, listener, scientist, analyst, or hobbyist, define sound quality. If that includes lab tests, great. If not, fine. Could be perceived distortion, headroom, resolution, transient response, bass response, frequency response, and any other parameters of interest. Can also include non-acoustic factors, like efficient use of power supply (eg for battery considerations).
So you agree that two amplifiers of extremely similar design and configuration, any type (Class D, tube, or solid state), 200W and 30W, each optimized for their own respective power output, set to the same perceived loudness level (by adjusting input amplitude), will have the same SQ, same battery efficiency, and no other qualitative or quantitative, subjective or objective, benefit of one over the other?
Am i the only person here who questions those two statements?
Perhaps i should say "perceived loudness" or sound pressure. I'm not talking about the volume knob position, nor any voltage level in the system.
My OP is asking to compare the two amps at the same perceived loudness. I assume the power amp has a fixed gain, so changing the perceived loudness requires adjusting the source amplitude, or pre-amp output.
You also said THD is not meaningful for perceived SQ. Therefor, it would follow that changing the input amplitude to the amp will not affect perceived THD, which according to you, cannot be perceived.
Your chart says THD is "not good" under certain conditions. Seems your saying THD is irrelevant under any conditions.
So, you're saying that measured amplifier THD will not change, as input amplitude is changed?
-by different class D amps of difference wattage, no?
and a lowering THD under higher wattages. But, you say THD isn't perceivable, so who cares?
Understood. Unclear how that supports your statements.
thx
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Comparing amplifier distortion to speaker distortion now?
If you are interested in how and why speakers distort I suggest you go back to the very basics of how they work
So, top line (and I'll reference the pass articles to support as Pass is more articulate and considerably better informed!) and to use the F5 amp as an example...
The output 'fets see ~23V across them at a bias of over an amp, for a dissipation of say 30W. Thats kind of the practical upper limit for all day use (you can go father though). If you up the rails to accommodate greater output power, you have to drop the current through to maintain safe operation. so, you need to multiply the output devices to get sufficient current drive.
There's evidence to suggest that the higher current through the Fet = reduced distortion, so you're 'moving out of the sweet spot' as I characterized it earlier.
With multiple devices come multiples of input capacitance, meaning increased drive requirements, and ultimately a different front end to deliver that drive/deal with the higher rails, and lower bandwith.
If you're genuinely interested in learning more (and not just trolling us all here), bias and distortion should see you through the current component, and for the challenges on capacitance
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