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alexclaber

Gain, power and volume - a confusing ménage à trois...

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Anyway, to jump back to the earlier part of the thread (I haven't quite worked out how to do "quotes" yet on here!)...

A better word to use instead of "gain" would be "attenuation", wouldn't it? In other words, zero attenuation equals letting the maximum signal through rather than restricting it in any way...?

Or maybe I'm wrong? :)

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[quote name='Oxblood' post='39703' date='Jul 31 2007, 07:26 PM']In a typical instrument amp, the first "Volume Control" you find is simply a pot placed in the signal path - just like the one we find in a passive guitar or bass, between the pickups and the jack socket. All it does is act as a [i]potential divider[/i]: a variable resistance that bleeds some of the signal away to earth and allows the rest through to the next amplifying stage. Turn it up full, and all (or nearly all) of the signal gets through. Like a water tap, it's a purely passive device. It can't give out more than is being fed in. In some amps this first pot is positioned directly after the jack input itself, but more commonly these days it is placed after an initial amplifying or buffer stage. Either way, the effect is the same.

Likewise, the "Master Volume" or "Output Level" control is another passive pot, placed at the point where the signal leaves the pre-amp/EQ circuitry and is being fed to the input of the Power Amp.[/quote]

I understand what your saying about the input volume control but if i was to turn that volume pot up all the way on my ashdown amp the needle on the vu meter would go right up in to the red and distort to hell so in that instance i dont believe you are correct in your comment unless ofcourse ashdown have put that there for no reason other than for it to look good/bad dependant on your taste and my amp is not a valve amp so i dont entirely understand why turning it up all the way isnt possible on my amp going by what you say above.

Markus

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[quote name='alexclaber' post='639729' date='Oct 29 2009, 09:01 AM']Almost 100% wrong. (500W into a 10W speaker will blow it up pretty easily, so that's the fraction that is correct). Not a good analogy at all.

Alex[/quote]

I have to say i agree you could get an amaizing result from a 10w amp even if you were running 500w cab if the speakers in the cab were highly efficient if they were very sensitive and not in any way power hungry they could sound fantastic and then you could put a different set of speakers in the same cab that were very power hungry there for not being eficient at all the amp would probably have trouble powering it at all.

its vvery important to know how your speakers perfom always check your db rating the higher the better and make sure your speakers are made of something lightweight Ie paper and so on as this will help massively with thier effciiency levels and as previously stated more speakers equalls greater SPL sound preasure levels.

Markus Edited by elliswasp

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I'm pretty stupid, and even though I got B's in both mathes and physics, I have no idea what anything on here means.

What if your amp has let's say, an input, gain, volume, master volume, what's the difference between the three, what I understand as, voltage attenuators?

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I have used trace gear for years and unless I have missed something(its like and idiots guide for me) the red knob to the left is labeled input gain,I suppose its what I have been conditioned to look for.With a flashing light or a thumbs up to tell you when its about right,go above that and the output signal distorts no matter how low my volume control is or whatever speaker cab is connected so I would have thought it is gaining the input stage.Also playing through 4x10s they sound better when being pushed a bit,if really low volumes they are a little thinner,or is that just me? I do understand about sensitivity etc but played through some new neo cab and even though the output seemed higher at lower output settings they came to life more when pushed.Sort of fuller.Thats my ears telling me I know its not really science. Edited by mikhay77

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Layman's guide to the Speaker power v Amplifier power myth exploded with no maths or numbers (or techie terms?)

Generally people mistake loudness for noise and the untrained ear will ignore distortion. Distortion is your enemy. Even comparatively small amounts of distortion, using effects or over-driving pre-amps can be bad if you don't know what you are doing.

Once an amplifier starts distorting the speakers are not going to get any louder no matter how far you turn up the volume knob. Everything will just get noisier and less intelligible, defeating the object!

Published amplifier power is fairly meaningless as it is given as a power with a small amount of distortion. A lot of amps can give out huge amounts of power at huge levels of distortion!

Large amp -> small speakers. The danger is that the user will turn the amp up beyond what the speakers can handle. This will cause distortion in the speakers. The speaker will either overheat or mechanically destroy itself.

Small amp -> large speakers. Again the amp can get turned up beyond the point at which it produces nice clean sound. At this point the amp is distorting and producing much more than the rated power of the amp. Most of the power will be dissapated as heat in the coil and can literally melt the speaker.

So neither is the correct solution:

1. Use your ears not the spec sheets or labels. If you hear distortion - stop and turn down!
2. When buying an amp and cab try before you buy and don't believe the hype. Edited by TimR

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[quote name='TimR' post='843446' date='May 20 2010, 07:27 PM']Layman's guide to the Speaker power v Amplifier power myth exploded with no maths or numbers (or techie terms?)

Generally people mistake loudness for noise and the untrained ear will ignore distortion. Distortion is your enemy. Even comparatively small amounts of distortion, using effects or over-driving pre-amps can be bad if you don't know what you are doing.

Once an amplifier starts distorting the speakers are not going to get any louder no matter how far you turn up the volume knob. Everything will just get noisier and less intelligible, defeating the object!

Published amplifier power is fairly meaningless as it is given as a power with a small amount of distortion. A lot of amps can give out huge amounts of power at huge levels of distortion!

Large amp -> small speakers. The danger is that the user will turn the amp up beyond what the speakers can handle. This will cause distortion in the speakers. The speaker will either overheat or mechanically destroy itself.

Small amp -> large speakers. Again the amp can get turned up beyond the point at which it produces nice clean sound. At this point the amp is distorting and producing much more than the rated power of the amp. The power will be dissapated as heat in the coil and literally melt the speaker.

So neither is the correct solution:

1. Use your ears not the spec sheets or labels. If you hear distortion - stop and turn down!
2. Getting huge speakers is genearally a waste of money if you don't have the amp to drive them.
3. Getting a huge amp is generally a waste of money if you don't have (or plan on getting) speakers that it can drive.[/quote]

Still trying to disagree with the rest of the thread then?

1 is fine.

2 is wrong. Huge speakers are awesome for sensitivity, so you get plenty of volume from not much power

3 is also wrong. A huge amp can drive any speakers.

Also, a distorting amp will only melt speaker coils if it is outputting enough power to do so, even fully distorted, it might not be.

And noisy and unintelligible is awesome. Distorting power amps are awesome. This is why we have power brakes and low powered valve amps. Or really really loud high powered valves amps of Doom.

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[quote name='Conan' post='688775' date='Dec 18 2009, 11:52 PM']Anyway, to jump back to the earlier part of the thread (I haven't quite worked out how to do "quotes" yet on here!)...

A better word to use instead of "gain" would be "attenuation", wouldn't it? In other words, zero attenuation equals letting the maximum signal through rather than restricting it in any way...?

Or maybe I'm wrong? :)[/quote]

gain is voltage gain.

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[quote name='Mr. Foxen' post='843459' date='May 20 2010, 07:43 PM']Still trying to disagree with the rest of the thread then?

1 is fine.

2 is wrong. Huge speakers are awesome for sensitivity, so you get plenty of volume from not much power

3 is also wrong. A huge amp can drive any speakers.

Also, a distorting amp will only melt speaker coils if it is outputting enough power to do so, even fully distorted, it might not be.

And noisy and unintelligible is awesome. Distorting power amps are awesome. This is why we have power brakes and low powered valve amps. Or really really loud high powered valves amps of Doom.[/quote]

You've basically just agreed with everything I wrote, while saying you disagree? Weird, I'm lost.

To recap:

Power ratings mean nothing.

When you go into a shop and the salesman says you must have speakers bigger than amp, or amp bigger than speakers you will know he is talking rubbish.

I said that distortion is bad if you don't know what you are doing. Using low powered valve amps, power brakes etc sounds like you probably do.

It was intended as straightforward advice for the newbies who are always asking the question. "I've got a 100W power amp what speakers do I need?" and "Why did I fry my 400w speakers with my 150W amp?" Edited by TimR

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[quote name='TimR' post='843515' date='May 20 2010, 08:24 PM']You've basically just agreed with everything I wrote, while saying you disagree? Weird, I'm lost.

To recap:

Power ratings mean nothing.

When you go into a shop and the salesman says you must have speakers bigger than amp, or amp bigger than speakers you will know he is talking rubbish.

I said that distortion is bad if you don't know what you are doing. Using low powered valve amps, power brakes etc sounds like you probably do.

It was intended as straightforward advice for the newbies who are always asking the question. "I've got a 100W power amp what speakers do I need?" and "Why did I fry my 400w speakers with my 150W amp?"[/quote]

Any speakers can go with any amp. There is no relationship between the "wattage" rating of them that needs to be adhered to, or even a guideline. Your points 2 and 3 are what I disagree with.

If you have a 100w power amp you need big speakers if you want to gig.

[quote]At this point the amp is distorting and producing much more than the rated power of the amp. The power will be dissapated as heat in the coil and literally melt the speaker.[/quote]

Is also not true. People distort their power sections really often without understanding what is happening, they just know it sounds awesome. They are often called guitarists.

Don't make generalisations for the benefit of people who don't understand, they are the reason why they don't understand. Because they are wrong.

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OK I've taken points 2 and 3 out and condensed them into one point as they were basically saying the same thing, but re-reading them I can see how they could be confusing. Edited by TimR

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[url="http://www.steamingaudio.myzen.co.uk/finnbass/clipping_and_you.pdf"]http://www.steamingaudio.myzen.co.uk/finnb...ing_and_you.pdf[/url]

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[quote name='Mr. Foxen' post='843520' date='May 20 2010, 08:32 PM']Don't make generalisations for the benefit of people who don't understand, they are the reason why they don't understand. Because they are wrong.[/quote]

Indeed but most of us would rather buy some gear that works as sold than do a degree in electronics and wade through the tons of opinion and misdirection on the web.

After reading that attachment written by an engineer in an attempt to clarify things. We get to the crunch....
[quote]clipping is acceptable provided that the average power over time is lower than the speaker’s limits[/quote]

The big question is "How do we know what the average power over time is and what the speakers limits are?" If anyone knows a quick easy way to calculate that from the smoke and mirrors leaflet that comes attached to your nice shiny things let me know.
Go careful when running your amp to distortion. Edited by TimR

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[quote name='TimR' post='843631' date='May 20 2010, 10:42 PM']Indeed but most of us would rather buy some gear that works as sold than do a degree in electronics and wade through the tons of opinion and misdirection on the web.[/quote]

This thread is pretty good for it, which is why anything even vague get's pounced on. I think Claber's degree is engineering, but I'd guess electronics figured highly.

[quote name='TimR' post='843631' date='May 20 2010, 10:42 PM']After reading that attachment written by an engineer in an attempt to clarify things. We get to the crunch....

The big question is "How do we know what the average power over time is and what the speakers limits are?" If anyone knows a quick easy way to calculate that from the smoke and mirrors leaflet that comes attached to your nice shiny things let me know.
Go careful when running your amp to distortion.[/quote]

That is kind of why that isn't so helpful. The main thing is to remember speakers sound bad before they break. They also get quieter when the heat up, due to their impedance increasing, its called power compression. With bass guitar, its not an issue unless you play full on drone, due to the quieter bits in the dynamic range giving cooling time. Over excursion at the volume peaks is the killer.

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Alex's was Mechanical. Speaker and cabinet design is all mechanical. Crossovers and thermal limits are fairly simple electronic concepts to grasp if you are bright. Mine's Electronics with an Acoustics module but that was in '94. Things have changed a lot since then. The way that engineers resort to numbers, formulas and long words to explain things hasn't and I still get the salesmen giving conflicting advice in shops.

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[quote name='TimR' post='843664' date='May 20 2010, 11:07 PM']....I still get the salesmen giving conflicting advice in shops....[/quote]
Surely you don't believe salesmen!!

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Great thread, but a question i have in respect to the whole premp and power amp sections of a combined all in one amp, is as follows :

I understand that the preamp takes a signal and boosts and shapes it accordingly. If you then, crank the preamp section and various boost and gain pedals, will the power amp section reach full power sooner? Or is there a cap that the preamp maxes the signal out at before it flows to the power amp?

Ive been thinking about this lately and cant find the info i want. When i crank the pre amp at home, a click or two on the power amp has a hell of a lot of gusto. Back off the gain and i then push the power amp harder to achieve the same levels. It makes sense.

I just wanted to clarify whether the amp reached full power well before its designed to if the preamp is cranked. Sorry if this seems rather dense, thought it was the thread to post in though!

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Putting more into the preamp section will get more out, it is a multiplier, as is the power amp stage. but both have limits, it is possible to clip the preamp section by putting too much power into it, just as it is possible to clip the power section by trying to get more out of it that it can give. Ideally there is a limiter somewhere along the line, but it is usually left to discretion.

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One of my favorite combos of all time, and one I use on half of my gigs is the Roland DB 700, which has Gain, Volume, and a Master. I typically run the Gain and Volume as hot as I can, and set the Master at noon. But, I never really understood why that Volume knob is there.

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There's a big difference between Pre-Amp - distortion and power-amp - distortion aka clipping.

If You drive Your power-amp into clipping You will destroy Your speaker.

This is why it is dangerous using a small amp (let's say 100 watt) into a big cab (let's say 500 watt).
If YAou have Your preamp maxed out, it will start clipping. If You don't hear this, the speaker will
get killed by thermal issues.

Pre-amp - distortion, carefully amplified with the power-amp, will add harmonics to Your sound,
compress it a bit and makes it richer.

This is why preamps with tubes (like Ampeg SVP Pro or the preamp-stage in my Peavex T-Max)
sound the way they sound when pushing the tube.

The T-Max, for example, has a pre-gain knob for pushing the tube, a post-gain for the tube-sound-
volume, and a master volume for the poweramp. ith pre- and post-gain You choose the sound and
the power of the tube-stage of the preamp. Master will dial the ammount of power sent to Your cabs.

It is not confusing at all.

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[quote name='Kong' post='1372737' date='Sep 14 2011, 04:03 AM']There's a big difference between Pre-Amp - distortion and power-amp - distortion aka clipping.

[b]If You drive Your power-amp into clipping You will destroy Your speaker.

This is why it is dangerous using a small amp (let's say 100 watt) into a big cab (let's say 500 watt).
If YAou have Your preamp maxed out, it will start clipping. If You don't hear this, the speaker will
get killed by thermal issues. [/b]

Pre-amp - distortion, carefully amplified with the power-amp, will add harmonics to Your sound,
compress it a bit and makes it richer.

This is why preamps with tubes (like Ampeg SVP Pro or the preamp-stage in my Peavex T-Max)
sound the way they sound when pushing the tube.

The T-Max, for example, has a pre-gain knob for pushing the tube, a post-gain for the tube-sound-
volume, and a master volume for the poweramp. ith pre- and post-gain You choose the sound and
the power of the tube-stage of the preamp. Master will dial the ammount of power sent to Your cabs.

It is not confusing at all.[/quote]


With all due respect, thats not actually true. It is not that simple.

If you have a driver that can handle 1000w (ie thats its thermal limit) and you clip the bejesus out of a 50w amp into it it will run all day and never ever have problem.

Clipping is clipping is clipping, pretty much every album released in the last 10 years has some form of clipping (or brickwall limiting, the two are almost identical in terms of waveform) on it, you didnt see your hifi go up in smoke now did you? No. It doesnt sound nice but the transducers can cope because its just not about clipping, its about how much power you are pushing into the transducer. You can push a tube into clipping, it could be a power amp tube or a preamp tube, the result on the wave form is the same.

A simple rule of thumb is if it sounds like its straining/clipping/distorting in a bad way, then it is, back it off. A speaker straining does sound different from an amp clipping, but if you dont know the difference then back off the amp until everything sounds happy, if thats too quiet for your situation you need more power, or more speakers. Its deciding which that can be an issue.

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iv got a laney dp 150 head going through a 115 and 118, if i turn up the gain,with the bass on the eq high it distorts even speakers of these size and the red light comes on,altho laney say this has to flicker,my gears on rickenfaker page,but dont seem loud,also the volume on the right seem not to do alot,also talk of volume 2 bassist i admire play heavy rawkus bass,first being lemmy,it suprised me hes sposed to be the loudest bassest yet he running a 100 watt head with 2 412s dont seem to powerfull to me,the other being alan davey he seems to use a mixture of stuff when gigging,but he uses 2 fender bassman 50 heads with a ashdown 115 and a 2112,but they seem to drive these and get some volume outta these!!,i wanna play loud!!

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[quote name='thunderider' timestamp='1318188872' post='1399055']
iv got a laney dp 150 head going through a 115 and 118, if i turn up the gain,with the bass on the eq high it distorts even speakers of these size and the red light comes on,altho laney say this has to flicker,my gears on rickenfaker page,but dont seem loud,also the volume on the right seem not to do alot,also talk of volume 2 bassist i admire play heavy rawkus bass,first being lemmy,it suprised me hes sposed to be the loudest bassest yet he running a 100 watt head with 2 412s dont seem to powerfull to me,the other being alan davey he seems to use a mixture of stuff when gigging,but he uses 2 fender bassman 50 heads with a ashdown 115 and a 2112,but they seem to drive these and get some volume outta these!!,i wanna play loud!!
[/quote]


Speaker size is not relevant to them distorting, the XMAX is. Typically those older speakers had pretty dismal XMAX compared to todays drivers. Certainly it is very easy to cause them to fart out with excessive bass boost and lowish apparent volumes.

I had a Laney G300 (the big daddy to the series that came after the dp150) back in the day (had HH power amps in it in fact - was pretty well build for the period too). Certainly capable of producing enough oomph in the low end to fart out two 410s.

As for Lemmy, you have noticed he has a massive PA behind him havent you? His onstage volume is probably not so loud in fact, and his tone was never massively bassy, plus he now runs nice shiny new kit, with nice modern drivers in. Edited by 51m0n

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