Volunteer sir sanders zingmore Posted January 23, 2020 Volunteer Share Posted January 23, 2020 I'm sure this question has been asked before, possibly even by me, but I can't find anything that is easy for me to understand. Can someone please explain the relationship between gain and power - if indeed there is one. For example, lets say you have two amps of the same power but one has a gain of 26dB and another of 30dB, what does this mean in practice? Will one play louder than the other ? Conversely, what if they have different power but the same gain? Will they both play at the same volume an if so, where does power come in? 1 Link to comment Share on other sites More sharing options...
Super Mustud Posted January 23, 2020 Share Posted January 23, 2020 4 minutes ago, sir sanders zingmore said: I'm sure this question has been asked before, possibly even by me, but I can't find anything that is easy for me to understand. Can someone please explain the relationship between gain and power - if indeed there is one. For example, lets say you have two amps of the same power but one has a gain of 26dB and another of 30dB, what does this mean in practice? Will one play louder than the other ? Conversely, what if they have different power but the same gain? Will they both play at the same volume an if so, where does power come in? Well, Sir Sanders (Monarch of Oz in waiting), look at it this way, say you had a hammer. And you banged it up and down. Then someone said you should bang it up and down faster. That is gain. But your arm was weak and you couldn't bang faster. That is insufficient power. Of course, as a Monarch, you would never have insufficient power. Link to comment Share on other sites More sharing options...
Assisi Posted January 23, 2020 Share Posted January 23, 2020 If you have 30minutes Trevor watch this John 1 Link to comment Share on other sites More sharing options...
Addicted to music Posted January 23, 2020 Share Posted January 23, 2020 (edited) @sir sanders zingmore im not going to explain what power is, you should know this as it’s rated at 8ohms usually and what it is across the speaker. Gain is defined Vout divided by Vin.... let’s say you have an amplifer circuit that has a gain of 10. What that means is that amplifier circuit will output 10V if input voltage is 1V... it’s a multiplier of what that amplifier is capable with voltage.... 1 hour ago, sir sanders zingmore said: .For example, lets say you have two amps of the same power but one has a gain of 26dB and another of 30dB, what does this mean in practice? Will one play louder than the other ? In this case the one with 30db will be louder as it will make the amplitude larger with the same input voltage. 1 hour ago, sir sanders zingmore said: Conversely, what if they have different power but the same gain? Will they both play at the same volume an if so, where does power come in? That will depend on the figure of each power rating of each amplifer. Edited January 23, 2020 by Addicted to music Link to comment Share on other sites More sharing options...
Ittaku Posted January 23, 2020 Share Posted January 23, 2020 I've got a different answer that most people will disagree with, but what the heck. They're supposed to be the same thing, only one of them is easier to fudge and make look better. Link to comment Share on other sites More sharing options...
Addicted to music Posted January 23, 2020 Share Posted January 23, 2020 25 minutes ago, Ittaku said: I've got a different answer that most people will disagree with, but what the heck. They're supposed to be the same thing, only one of them is easier to fudge and make look better. Why it’s not the same thing is because most or all audio amplifiers are considered what’s known as voltage source, they amplify voltage.... Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted January 23, 2020 Author Volunteer Share Posted January 23, 2020 1 hour ago, Assisi said: If you have 30minutes Trevor watch this John John, for some reason I can't see whatever it is you linked? Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted January 23, 2020 Author Volunteer Share Posted January 23, 2020 58 minutes ago, Addicted to music said: In this case the one with 30db will be louder as it will make the amplitude larger with the same input voltage. Ok so lets look at an extreme example: what if the amp with 30dB of gain is a 5w amp and the one with 26dB of gain is a 500w amp? Link to comment Share on other sites More sharing options...
Guest Muon N' Posted January 23, 2020 Share Posted January 23, 2020 (edited) 40 minutes ago, sir sanders zingmore said: Ok so lets look at an extreme example: what if the amp with 30dB of gain is a 5w amp and the one with 26dB of gain is a 500w amp? Gain is voltage as has been said, now read what a watt is, It's derived from voltage and current. https://en.wikipedia.org/wiki/Watt Edited January 23, 2020 by Muon N' Link to comment Share on other sites More sharing options...
aechmea Posted January 23, 2020 Share Posted January 23, 2020 Gain is the ratio of Vout to Vin normally expressed as dB (20 log vout/vin) that is max achievable. No problems with that. But ... The complication is that Voltage is only part of the power equations W = I x I x R = V x V / R So it depends upon the impedance of the load and thus in turn is limited by the current capability of the amp's power supply bits (current = I). So it doesn't matter what the gain is, its limited by the power of the amp. Conceivably there is a set of numbers where your baby amp can get to its max gain but R would have to be very high and/or current very low. Also depends upon what Vin is, compared to the input sensitivity of the amp. If Vin is lower than the sensitivity, then the amp regardless of its gain will never achieve full power. That is what happens with my set-up. The PS Audio only outputs 1V (or something like that) but the Magtech's input sensitivity is 2V so even though the Magtech gain is 26dB I can never push it to its theoretical 500W (900W into 4ohm) limit - just not enough V at its input. Link to comment Share on other sites More sharing options...
Ihearmusic Posted January 23, 2020 Share Posted January 23, 2020 Power = work performed expressed in Watts. ( A 500W amplifier will likely never put that much work out) Gain is dependent on the amplification factor of the combined stages of an amplifier. Low amplification factor = low gain and visa versa. with equal imput a 30dB gain is still a touch louder then a 26dB gain Link to comment Share on other sites More sharing options...
Volunteer sir sanders zingmore Posted January 23, 2020 Author Volunteer Share Posted January 23, 2020 13 minutes ago, aechmea said: So it doesn't matter what the gain is, its limited by the power of the amp. So does that mean if there isn’t enough power (say if R is very low), the amp can’t achieve its stated gain? Link to comment Share on other sites More sharing options...
Soundscape Posted January 23, 2020 Share Posted January 23, 2020 1 hour ago, sir sanders zingmore said: John, for some reason I can't see whatever it is you linked? Such a small load is practically invisible to Class A watts Link to comment Share on other sites More sharing options...
Assisi Posted January 23, 2020 Share Posted January 23, 2020 1 hour ago, sir sanders zingmore said: John, for some reason I can't see whatever it is you linked? Trevor, Try this https://darko.audio/2019/12/what-is-the-difference-between-power-and-gain/ John Link to comment Share on other sites More sharing options...
aussievintage Posted January 23, 2020 Share Posted January 23, 2020 Why do we make it so complicated? 3 hours ago, sir sanders zingmore said: For example, lets say you have two amps of the same power but one has a gain of 26dB and another of 30dB, what does this mean in practice? Will one play louder than the other ? Gain means nothing, directly, about the loudness. Gain tells you how much the input signal is increased (amplified) by the amp. Amps with the same power, should make the same amount of noise through the same speakers, if rated fairly against each other. Assuming you want to run the amps at the rated power out, gain can be used to tell you how tiny a signal you can feed in to get that desired loudness (power). 3 hours ago, sir sanders zingmore said: Conversely, what if they have different power but the same gain? Will they both play at the same volume an if so, where does power come in? Different power, different loudness, all else being equal. You should not try to equate gain and power. They are different things. 1 Link to comment Share on other sites More sharing options...
Guest Muon N' Posted January 23, 2020 Share Posted January 23, 2020 22 minutes ago, aussievintage said: You should not try to equate gain and power. They are different things. Link to comment Share on other sites More sharing options...
Addicted to music Posted January 23, 2020 Share Posted January 23, 2020 2 hours ago, sir sanders zingmore said: Ok so lets look at an extreme example: what if the amp with 30dB of gain is a 5w amp and the one with 26dB of gain is a 500w amp? The formula for voltage gain in dB is 20log (Vout/Vin) So you have to know what what Vout is measured compared to the input voltage.... Form here you can do the maths..... Link to comment Share on other sites More sharing options...
Addicted to music Posted January 23, 2020 Share Posted January 23, 2020 1 hour ago, sir sanders zingmore said: So does that mean if there isn’t enough power (say if R is very low), the amp can’t achieve its stated gain? If R is low, this will forced the circuit to increase current, so in this scenario your low power amp will reach its max power rating quicker, however this doesn’t mean the amp can’t achieve its “gain” Just remember that with any amplifier, what you are doing in a typical amplifier circuit is that the power supply is being controlled by your input signal: small signal to large signal.... most will have what’s referred as the VAS ( voltage amplification stage): gain.... This is usually the front end circuit. This is used to controlled a buffer stage that’s usually consists of output devices that is connected to the load ( loudspeaker) at this final stage is where current of the power supply is being controlled. 1 Link to comment Share on other sites More sharing options...
PositivelyMusicallyGeared Posted January 23, 2020 Share Posted January 23, 2020 (edited) So in practical and simple terms, as I understand it, as long as the Vin is high enough to meet the requirement of the power amp, which is specified by the power amp's input sensitivity, the specified constant gain is guaranteed. With this full gain, the maximum amount of the current the power amp can output determines the amp's maximum output power. Edited January 23, 2020 by PositivelyMusicallyGeared Link to comment Share on other sites More sharing options...
andyr Posted January 23, 2020 Share Posted January 23, 2020 1 hour ago, PositivelyMusicallyGeared said: So in practical and simple terms, as I understand it, as long as the Vin is high enough to meet the requirement of the power amp, which is specified by the power amp's input sensitivity, the specified constant gain is guaranteed. Yes. 1 hour ago, PositivelyMusicallyGeared said: With this full gain, the maximum amount of the current the power amp can output determines the amp's maximum output power. Not exackly! The amp's maximum output power is determined by the +/- DC rail voltage. Andy Link to comment Share on other sites More sharing options...
Addicted to music Posted January 23, 2020 Share Posted January 23, 2020 18 minutes ago, andyr said: Yes. Not exackly! The amp's maximum output power is determined by the +/- DC rail voltage. Andy Not really Andy..... its the output stages that determined max power...... you can have a spot welding PSU that’s 1000A capacity. but if you only have one pair of output devices that’s only 8A considering it’s configured within SOA, that’s all that amp can give you. that’s why some power amplifiers are rated at 100s of watts use multiple pairs, an example is where a Magtech uses 10 pairs of transistors in parallel configuration to give you multiple current capability. 1 Link to comment Share on other sites More sharing options...
aechmea Posted January 23, 2020 Share Posted January 23, 2020 13 hours ago, sir sanders zingmore said: So does that mean if there isn’t enough power (say if R is very low), the amp can’t achieve its stated gain? This is how I understand it, Trevor. Conceptual diagram ... (A mathematician's version, not the engineer's one. Haha.) The 26dB block is fixed in size The 26dB block moves up and down the voltage column depending on volume knob. A low powered amp has its "voltage,current,power line" further down and runs the risk of being lower than where the actual output voltage would want to be. Full gain is not achieved before something goes bang. More powerful amps have more room in the voltage column for them to achieve full gain I suspect bad things happen when the output voltage hits/exceeds the power max. Link to comment Share on other sites More sharing options...
jessandkerry Posted January 24, 2020 Share Posted January 24, 2020 (edited) Lets put it this way, it all about the current, mainly power supply and output stage. Two amps below one 3000w !!!! the other only 20w Here is your 3000watter https://www.storedj.com.au/behringer-nx3000-ultra-lightweight-3000w-class-d-power-amplifier And here is your 20watter http://www.hifido.co.jp/photo/05/504/50446/c.jpg yes 20w!!! Which is going to sound better to a given level into the very evil load of the Wilson Alexia's that have an EPDR of .9ohm as seen by the amp. Jess Edited January 24, 2020 by jessandkerry Link to comment Share on other sites More sharing options...
Ratbob Posted February 3, 2020 Share Posted February 3, 2020 On 24/01/2020 at 11:00 AM, jessandkerry said: Lets put it this way, it all about the current, mainly power supply and output stage. Two amps below one 3000w !!!! the other only 20w Here is your 3000watter https://www.storedj.com.au/behringer-nx3000-ultra-lightweight-3000w-class-d-power-amplifier And here is your 20watter http://www.hifido.co.jp/photo/05/504/50446/c.jpg yes 20w!!! Which is going to sound better to a given level into the very evil load of the Wilson Alexia's that have an EPDR of .9ohm as seen by the amp. Jess Hi. I've neither seen nor heard a Class D amplifier and I've been waiting for someone to answer your question. Can someone put me out of my misery, (well on this subject anyway) I assume the 20 watter with the type of build pictured will be 100% stable and supply somewhere around 160watts into the .9 ohm load. But which will sound better? Link to comment Share on other sites More sharing options...
andyr Posted February 3, 2020 Share Posted February 3, 2020 On 24/01/2020 at 11:30 AM, jessandkerry said: Which is going to sound better to a given level into the very evil load of the Wilson Alexia's that have an EPDR of .9ohm as seen by the amp. Jess 8 hours ago, Ratbob said: Can someone put me out of my misery, (well on this subject anyway) I assume the 20 watter with the type of build pictured will be 100% stable and supply somewhere around 160watts into the .9 ohm load. But which will sound better? An excellent Qu, RB - hopefully, some knowledgable person can give you a definitive answer! On the one hand, those 20w monoblocs with a huge chassis and OTT heatsinking point towards an amp having a huge PS and, as you suggest, the ability to drive a 0.9 ohm load. But then again ... it's only a 20w amp and I suspect the Alexias are rather inefficient - so I suspect it would sound constricted with orchestral music (even though it wouldn't blow up). If you had the same amp but built larger so that, at 8 ohms it outputted 100w into 8 ohms (it would need a lot more output devices plus a lot more uFs in the PS), then that would make the Alexias sing! On the other hand, the Class D which can deliver 1500w per channel into 2 ohms (900w into 4ohms ... and no specification for 8 ohms) doesn't have such a robust PS - otherwise, at 900w into 4 ohms, it should be able to deliver 1800w into 2 ohms. In addition: it is described as 'lightweight' and has a SMPS ... so I suggest it's performance into 0.9 ohms is suspect. Andy Link to comment Share on other sites More sharing options...
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