Stupid Power amp question

[Lerxst]

Hi,

I have an 80 watt power amp. The household name varieties start at 500 watt. Ish.

Power (watts), in this context, is not linear as I understand it, so a 100 watt system with be 2x as loud as a 10 watt system - outside.

Indoors, there are other factors, like resonance and reflections which will, I assume highten the difference in volume.

500 watt would at first sight seem like overkill for me. I am told a higher power amp will be able to deliver dynamic music faster (ie it can draw on more reserves quickly). That sounds logical and desireable.

I have never owned a 500 watt power amp but I suspect some of you may have. So, if I were to buy a 500 watt amp and hook it up to the same pre-amp I am interested to hear from members what happens in practice.

With the 80 watt amp a nice listening level is at about 10 o'clock on the volume dial on my preamp. 75dB ish. No audible distortion.

What happens with the 500 watt amp? Is the 10 o'clock setting still the same volume level?

It is louder? Or is it the "reserves" that are important? If were much louder the volume control would become less adjustable/useable. That sounds like a rubbish idea

I guess it would be able to drive higher resistance speakers, or more speakers.

And why isn't 80 watt enough anymore? Mine is fine.

So, any experience on that front? I haven't got a few grand lying around to test it, so it will not happen in practice. Just interested. I feel I should know the answer, but I don't.

Over to you. Thanks in advance.

[walpurgis]

You do realise that 500 watts will only give something like 8db increase in maximum loudness over 80 watts?

[Lerxst]

Hi Geoff,

Yes, I get that. Let's say for argument's sake that it is twice as loud (+10dB). Would my volume control be half as sensitive?

[jandl100]

The volume knob will stay in the same position (assuming amp sensitivity is the same, which is totally unrelated to power).
As you say, it's all in the reserves which are available for peaks.

I've had 300 - 500wpc amps - some of which I liked and some of which I didn't, just on sound quality grounds.

So if you love your 80wpc job, then it's a sound quality lottery as to whether you would prefer a 500wpc amp. It will sound different, but that will not be very strongly related to the power available.

Some speakers, though, present difficult loads and would welcome the extra power (or, more likely, would welcome extra current delivery) and you would hear that as an improvement in sq, but by the sound of it you have a good amp/speaker match already.
As ever, it all depends ... :)

[Jazid]

The volume knob will stay in the same position (assuming amp sensitivity is the same, which is totally unrelated to power).
As you say, it's all in the reserves which are available for peaks.

I've had 300 - 500wpc amps - some of which I liked and some of which I didn't, just on sound quality grounds.

So if you love your 80wpc job, then it's a sound quality lottery as to whether you would prefer a 500wpc amp. It will sound different, but that will not be very strongly related to the power available.

Some speakers present difficult loads and would welcome the extra power (or, more likely, would welcome extra current delivery) and you would hear that as an improvement in sq, but by the sound of it you have a good amp/speaker match already.
As ever, it all depends ... :)Assuming like for like amps (of course they won't be but...) along with the 10dB increase in power output you will get a 10dB increase in noise floor which may make a more significant difference as this is independent of listening level so may be audible when listening at low levels.
I do not see the need for extra power, although I had a 250wpc amp once and liked it very much. I have a 25wpc amp in the home system and occasionally the 5w LED flickers if the music is very very loud. Speakers are average efficiency. 6wpc amp in the main system with the AN-Es and its more than I need.

Sent from my GT-I9195 using Tapatalk

[Haselsh1]

I currently (geddit) use a 40 Watt valve amplifier but have in the past used a 300 Watt per channel studio power amp. The difference was quite simple really. The valve amp has a more explicit treble whereas the transistor amp had an effortless bass which never seemed to run out of sheer grunt. The valve amp is, I guess, a whole lot more refined though. Do I prefer it ? No. I liked both of them.

[walpurgis]

I used to drive my low 84db sensitivity Celestion SL600Si speakers with a pair of 15 watt valve monoblocks with no difficulty and I've driven 102db sensitivity horns with a 220 watt mosfet power amp, so really, anything can work, but of course common sense applies.

50 watts will be more than enough in most situations. Buy active speakers and then the power of the amp is already decided for you! :)

[Haselsh1]

I used to drive my low 84db sensitivity Celestion SL600Si speakers with a pair of 15 watt valve monoblocks with no difficulty and I've driven 102db sensitivity horns with a 220 watt mosfet power amp, so really, anything can work, but of course common sense applies.

Of course Geoff and your experience here proves it. Common sense always. I seriously loved the first Celestion SL6's though but not with valve amps. I didn't discover valves myself until many years later but I remember hearing a track by Joan Armatrading at a dealers place on SL6's and it sounded sublime. That would've been around 1981/82. Those vocal sounds were stunning.

[Pharos]

My take.

Firstly are you happy with your current speakers? Speakers are the most variable component IMO, and they should be chosen after careful auditioning.

Then choose an amp which will best suit the speakers, the speaker variables being; sensitivity, ease of drive, some speakers end up presenting negative impedances at some frequencies, and this demands very high current capability from an amp. (Current capability was a much discussed issue in the late 90s, and is needed for difficult loads), and how loud you want the system to be, (IME we can listen too loudly when we actually want is clarity).

Of course you may have a preference for valves over SS, or vice versa, my personal view is that SS have it nailed, and that the lack of maintenance is a real bonus, but I am not decrying the love of valves.

The position of a volume pot is not really much of an indicator of anything because sensitivities are not standardised, but a useful range of sweep is of course desirable.

I would not recommend listening at more than 80dB for extended periods, and even that can do ear damage, and the range of speaker sensitivities is from about 83 to 105dB/W. Even at the low end of 83dB sensitivity, your 80W will give you about 100dB.

[RothwellAudio]

Let's say for argument's sake that it is twice as loud (+10dB). Would my volume control be half as sensitive?
No, not necessarily.


The volume knob will stay in the same position (assuming amp sensitivity is the same, which is totally unrelated to power).
Amp sensitivity is usually/often specified as the input voltage required to deliver full power. In that case, a 100W amp with the same sensitivity rating as a 10W amp will actually have more voltage gain and be more sensitive, ie louder for a given position of the volume control.
But yes, sensitivity doesn't have to have any relation to total power.


Assuming like for like amps (of course they won't be but...) along with the 10dB increase in power output you will get a 10dB increase in noise floor which may make a more significant difference as this is independent of listening level so may be audible when listening at low levels.
Yes, maybe. Or maybe not.


It's actually more useful to consider power amps as voltage amplifiers - in fact, that's what they are. The power rating is really only a measure of the maximum voltage swing they're capable of into a specified load. The gain of a voltage amplifier could be anything, and power amps have gains covering quite a range. About 30dB is typical, but it could be more or it could be less, and it has nothing to do with the maximum power available. It's quite common for valve amps with only a few watts available to have a higher than average voltage gain and be very sensitive. But that isn't always the case.

It's also unwise to assume that more power equals a better amp. It's quite possible to design a low power amp that performs beautifully, and equally possible to design a high power amp that sound horrible.
50W should be enough in a domestic setting - unless you like it really loud - and if it sounds good there's no need to worry. I suspect the trend towards higher powers is driven by the idea that customers are more likely to buy a 100W amp than a 50W amp, and modern semiconductor technology has introduced more transistors that will cope with higher powers.

[Yomanze]

Just to make things a bit more complicated, watts for amps are measured as a continuous sine wave rating, which does not reflect the dynamic nature of music and what happens during musical peaks.

For example, there might be a 250W amp that measures well for THD in the traditional way, but has low instantaneous current delivery. A lower wattage amp, say 90W, could be able to deliver short peaks of 900W or more. A lot of people seem to mention how Colin Wonfor's amps, whilst only 10W or 20W, seem to have extreme grip of the speakers, more so than 100W+ on paper amps. This will be due to the amp having high instantaneous current delivery i.e. the amp can quickly dump current into the speakers during musical peaks.

[Haselsh1]

Just to make things a bit more complicated, watts for amps are measured as a continuous sine wave rating, which does not reflect the dynamic nature of music and what happens during musical peaks.

For example, there might be a 250W amp that measures well for THD in the traditional way, but has low instantaneous current delivery. A lower wattage amp, say 90W, could be able to deliver short peaks of 900W or more. A lot of people seem to mention how Colin Wonfor's amps, whilst only 10W or 20W, seem to have extreme grip of the speakers, more so than 100W+ on paper amps. This will be due to the amp having high instantaneous current delivery i.e. the amp can quickly dump current into the speakers during musical peaks.

Yep, I have found the same from experience over the decades but surely this ability has a lot to do with the amplifiers power supply ? I am certainly no expert but the power supply must be able to deliver huge chunks of power in an instant ?
I don't understand it but I sure as hell love the sound it gives.

[Yomanze]

Yep, I have found the same from experience over the decades but surely this ability has a lot to do with the amplifiers power supply ? I am certainly no expert but the power supply must be able to deliver huge chunks of power in an instant ?
I don't understand it but I sure as hell love the sound it gives.

I’m not expert either but yes it is pretty much all down to how quickly current can get delivered, and how stiff the power supply is I.e. doesn’t drop voltage or clip during peaks.

[bobvfr]

Another non expert here.

Firstly 500w is meaningless by itself, for a start off a lot of amps are now shown as 500w, if that is into 4 ohm and that would be pretty dammed close to another amp for sale at 250w into 8 ohm.

If my understanding is correct, if everything is about equal (Same input and same speakers etc) to double the volume you would need to go from say a 100w amp to a 200w amp and this would give you about a 3db increase in sound intensity, to double it again you would need a 400w amp to get to about a 6db gain over the 100w amp but I would guess there is a lot more to this especially the way a lot of "Hi-Fi" is both measured and marketed.


Someone mentioned "Only gaining 10db", again not claiming to be an expert but a 10db gain on a logarithmic scale is massive increase in sound levels as, at the higher end of the scale it would be the difference between putting your hands over your ears in pain or "too late you have burst eardrums", by going up 3db you have doubled the sound intensity, so by going up 10db you have doubled, doubled again, and then doubled again with a bit more thrown in for good measure.

I have an 80w Pioneer receiver (I only use stereo) that 80w is into 6 ohm so probably only about 55/60w into 8 ohm speakers, but even then you have speakers with massive differences in sensitivity, I have a pair of Tannoy Cheviots, these were considered a reasonably sensitive speaker, and they can easily take the full power of the Pioneer, given I live in a flat, I would be asked to move out pretty quickly if I ever put it on full blast.

I also have a 40w Aiwa and Quad 33 pre amp with a Quad 405 power amp that is 100w into 8ohm and is a lot more powerful than the Pioneer but luckily it has a volume control dial on the pre amp so I can turn it down, but given the sensitivity of the Tannoy's all three amps could get me thrown out of my flat with ease, but the Quad's are capable of causing long term hearing loss.

As someone else mentioned if the sound you get from your gear is fine then don't get hung up on the figures and only worry about the power of you amp if you are needing the volume dial up at 9 or 10 (Out of 10) to get it to sound normal, if your speakers need a bit more poke then buy a bigger amp so you can produce the same sound with a lower volume setting as most amps would be designed to work somewhere in the middle ranges of volume.

[Haselsh1]

If my understanding is correct, if everything is about equal (Same input and same speakers etc) to double the volume you would need to go from say a 100w amp to a 200w amp and this would give you about a 3db increase in sound intensity, to double it again you would need a 400w amp to get to about a 6db gain over the 100w amp but I would guess there is a lot more to this especially the way a lot of "Hi-Fi" is both measured and marketed.


Yep, inverse square law methinks the same as light.

[paulf-2007]

Doesn't make much sense and it doesn't seem that anyone has explained it. A 500w amp in a hifi set up can only mean the speakers are dogs, too much old crap between the binding posts and drivers. I know scanspeak drivers are very inefficient.
Not completely off topic, I used to play in bands and in pubs I used a 20w valve Marshall with plenty of spare power on tap, obviously no crossover as all drivers, whether one, two or four were ran full range of whatever came from the amp. In my home set up I have used 4w PX25 into Zu omen but now use a Sony receiver, solid state of course and more horses, controls the bass much better. I would have to say of the set ups I've heard with huge bel canto and other big ss amps they sounded very ordinary, probably due to the inefficient speakers.

[RothwellAudio]

I used to play in bands and in pubs I used a 20w valve Marshall with plenty of spare power on tap...
Guitar amps are a different kettle of fish because they're hardly ever played clean - at least not by people looking for the classic rock sound. A hi-fi played with the same amount of distortion as a typical guitar amp would sound awful.
But I agree, if you want it loud it makes sense to go for efficient speakers rather than trying to push ever more power into inefficient speakers.

[paulf-2007]

Guitar amps are a different kettle of fish because they're hardly ever played clean - at least not by people looking for the classic rock sound. A hi-fi played with the same amount of distortion as a typical guitar amp would sound awful.
But I agree, if you want it loud it makes sense to go for efficient speakers rather than trying to push ever more power into inefficient speakers.yes Andrew, I was aware of the distortion from guitar amps and it being what was wanted, strangely, the solid state guitar amps in the '70s sounded dreadful and I avoided them for decades.

[Colin Wonfor]

The problem has and always has been how manufacture specifies Watts.

I rate my designs in RMS or if you like the equivalent to DC power.:eyebrows:

Others spec there's in Peak Music Power or even Peak - Peak music power. This type of spec IMO is crap and meaning less, so beware of the Techno Babble ask for real Watts in RMS.

Also some will spec in RMS but it is for a short time I spec mine at RMS all day not just 10 or even 20mS, dissipation is the problem and over heating can occur.:stalks:

Also the PSU design is normally the last thought in a standard audio designer head, and in my designs I design them to be big enough plus a horrid load bit added and using my favourite saying give us a KISS. :D

I also allow for 0.5V2C = J or W/S energy stored in my Bulk Caps and to have reserves available. For horrid loads.

Sorry about the grammer and spelling but I am not a writer. Thank god. :lol:

[Yomanze]

I couldn’t give a monkeys about your grammar, some of the brightest people I have met are dyslexic, and some of the least bright people I have met spend time correcting grammatical errors. You’d think such clever people would be able to read posts regardless. [emoji3]

[Lerxst]

Hmm, still a little bit confused. Begs the question why the likes of Arcam and NAD do not make any 40Watt or 80watt power amps anymore.

But plenty of manufacturers still do, so the future still seems normal (in this context at least...).

As usual, although I have my A-level in physics, the stuff of HiFi - logarithmic loudness scales, power, amplification, sound floors, sensitivity, sampling rates and bit depth etc etc - still kinda seem like a "black art" to me. And I failed Art!

I also tried to study music with much the same result.

I should really stop worry my pretty little head about it and enjoy the music shouldn't I?:lol:

[bobvfr]

I should really stop worry my pretty little head about it and enjoy the music shouldn't I?:lol:

I have spent the morning ripping the Cranberries "No need to argue", Neil Young and Crazy Horse "Every one knows this is Nowhere" and Fairport Convention's "Unhalfbricking" and now have a date with my Tannoy's, and Dolores O'Roirden and Sandy Denny, I am sure Neil can watch in the background.

Yes the tech stuff is OK but the music is the important bit.

[Haselsh1]

I couldn’t give a monkeys about your grammar, some of the brightest people I have met are dyslexic, and some of the least bright people I have met spend time correcting grammatical errors. You’d think such clever people would be able to read posts regardless. [emoji3]

:lol:

[337alant]

I couldn’t give a monkeys about your grammar, some of the brightest people I have met are dyslexic, and some of the least bright people I have met spend time correcting grammatical errors. You’d think such clever people would be able to read posts regardless. [emoji3]

Plus Colin has already proven to the world that he has the talent to design and deliver exceedingly good amplifiers :eyebrows:;)

Alan

[Colin Wonfor]

Plus Colin has already proven to the world that he has the talent to design and deliver exceedingly good amplifiers :eyebrows:;)

Alan

Pure luck, I think but not so lucky choosing the right people to work with, so failed again.

Beside it is fun I recall a Inca Tech Amp we did called MSB (Mono Stereo Bridge) it was a monster at 50W except it could provide over 200Amps all day.
A lovely dealer in London borrowed it for a while using it on Wharfdale Diamond these tiny speaker were great but to be honest had no balls.
On the MSB it sounded like a large speaker akin to Tannoy Buckinghams and he became the best dealer for sales of Diamonds in the UK.
I wish I could recall his name he played a Japanese Drum and Percussion recording I would love to have a copy of. Does anybody remember him?? and the recording , a stab in the gloom but always hopeful.

[wee tee cee]

Im lucky enough to have two of Colins amps and another winging its way to me in a few weeks.

I run 57s which can be tricky to run and turn most amps to shite-due to the evil impedance curves they present.

Aint no daft questions on here-lots of folk just looking to help!!!!

Colin is first and foremost a hi fi/music lover- just happens to be quite handy at building fabulous sounding equipment to let you enjoy music.

Forget the numbers and grammar-try to get help from members locally to hear different kit in your gaff/music genre!!!

[Colin Wonfor]

Oh great PM me I forgot what we in private was talking about, Mrs W was not to well so I got busy doing home things sorry mate.

[wee tee cee]

PM sent...