joessportster Posted January 25, 2015 Share Posted January 25, 2015 It was once explained to me that an amp (any amp rated at any WPC) rated at 40 WPC was putting out 40 WPC all the time, If thats the case how do we raise or lower the volume ?? In my limited understanding I assume that the lower the volume knob the lower the output, so it follows the higher the knob the higher the output so a 40 wpc amp would only put out 40 wpc at max volume........... can someone explain this please, I see conflicting statements about some things, IE it takes 2 wpc for My HE500 to reach full potential, but a 3/4 wpc amp I use I cannot turn the volume past 1/2 or the level gets so high hearing damage will occur. Quote Link to comment Share on other sites More sharing options...
russ69 Posted January 25, 2015 Share Posted January 25, 2015 No, no, no. Electronic devices run on smoke. As long as you keep the smoke in the amp everything will work fine. As soon as there is a leak and some smoke is let out, the amp will quit working. I thought everybody knew that? 5 Quote Link to comment Share on other sites More sharing options...
juniper Posted January 25, 2015 Share Posted January 25, 2015 Hey Joe, Maybe this will help. Amplifiers take small voltage signals and make them bigger and more powerful by automatically multiplying the input signal voltage and current. Different amp designs have different amounts of multiplication - which is called gain. They also have a factor called sensitivity, which is a measure of how much voltage it takes at the input to make them go to full power at the output. A sensitivity of 2V means that a 2V input signal will cause the amp to put out full rated power. There are no real standards for this. Some amps have a 0.5V sensitivity, some are 3V, most are around 2V for power amps. Integrated amps, which have a preamp built in, will have lower sensitivity. The knob at the input panel is there to limit the input voltage. Suppose your CDP puts out a 2V signal, and your amp has a 2V sensitivity. It would mean that the CDP would always drive the amp to full power. You don't want that. So, the knob is connected to a voltage divider, called a potentiometer. It divides the input voltage so that some of it is wasted into ground, and some is passed on to the amplifier. When the knob is very low, let's say 1.8V goes to ground and 0.2V goes to the amp and produces 5W of output. When the knob is turned higher, 1V goes to ground and 1V goes to the amp, and now you have 30W of power. When the knob is all the way up, 0V goes to ground and 2V goes to the amp producing full power - however much that is. By dividing up the input voltage, you can control how much power the amp puts out. Usually, that knob is located on the preamp. So, the preamp determines how much power the amp puts out. But, that knob can also be put on the amp too. A point about the knobs. The potentiometers behind those knobs are not usually linear. Linear would mean half a turn creates half the power. These pots are usually shaped so that it takes about 90% of the turn to create 50% of the power. It's called log taper. It allows much finer control of the lower power levels where most listening is done and people want to be very precise. Now, if you combine the taper of the pot, with the gain of the amp, and the sensitivity of the amp, you can see why 50% rotation on one amp might blast you, while 75% on some other amp, might not. You have three variables, and each designer may implement them differently. There's no standard. Mdeneen, that is the most lucid explanation I have ever read, you should be writing books........... 2 Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 (edited) It was once explained to me that an amp (any amp rated at any WPC) rated at 40 WPC was putting out 40 WPC all the time, If thats the case how do we raise or lower the volume ?? That's not how it works; see Mark's explanation. Another thing to consider about amplifier ratings, to mean much of anything they must have qualifiers (bandwidth, distortion levels, and into which loads). Some manufacturers will rate power using 1khz @ 1% THD into unspecifiied loads, where others will specify rms power into specific loads and across the entire audible band. (Let's keep it in the realm of clean, linear amps; no distortion/clipping allowed, for the sake of this discussion.) so a 40 wpc amp would only put out 40 wpc at max volume.......... Whichever method they choose to rate power by, the amps will be able to deliver more power than that, dependent on the limits of the hardware, albeit with much higher (and unlistenable) amounts of distortion. This is why it's imperative to be aware of one's power needs, and choose an amp capable of delivering what is required without clipping. Even using speakers like Klipsch, the leading edge transients of notes can demand quite a bit of power. Even your hypothetical 40 watt amp may be clipping transient peaks. ...it takes 2 wpc for My HE500 to reach full potential, but a 3/4 wpc amp I use I cannot turn the volume past 1/2 or the level gets so high hearing damage will occur. Shifting gears into the low power realm, where I think running ampsslightly overdriven (but not obnoxiously so) is kind of the whole point, and distortion profiles (low order) are more tolerated/preferred/disregarded, I think that pushing the 3/4 watt amp into heavy clipping will be ear-shredding simply due to excessive distortion. SETs in full clip are harsh sounding. The same amount of clean power would probably not sound as harsh (but the flea watter would probably be much more stimulating to listen to when not pushed so hard). If you can reduce the amp's input sensitivity as Mark suggested, you'll get more useful range from the volume knob (and better s/n on the input signal, woo hoo!) Edited January 25, 2015 by Ski Bum Quote Link to comment Share on other sites More sharing options...
Fjd Posted January 25, 2015 Share Posted January 25, 2015 Here is a post I remembered reading where Mark provided a very lucid description of various common characteristics of amplifers. Scott-- In electrical terms, not HiFi terms, an "amplifier" has a broad meaning that encompasses any method of increasing voltage or current in an AC signal. An audio preamplifier is an "amplifier", and an audio power amplifier is an "amplifier" and there are amplifiers in your FM tuner, and there are amplifiers in your CD player, and in your DVD player and so on. "Amplifiers" - - are everywhere. And, when that definition is applied, they all have some common characteristics: -They have distortion -They have noise -They have a transfer function (each interacts with its inputs and outputs in a unique way) -They don't have infinite gain, infinite, bandwidth or infinite power - i.e. they are are LIMITED from the ideal This holds true for ANY AND ALL kinds of amplifiers from audio preamps to 50kW FM transmitters. Therefore, the design of any specific amplifier will yield specific characteristics of noise, distortion, bandwidth, transfer function, power, gain, and so on. These entirely TOGETHER will form a kind of signature. When the amplifier is an audio type (meaning in the audio sound spectrum) this signature can often be heard, and distinguished from other signatures. To use a common example, a Dynaco MKIII Tubed Power amp, will have a distinguishably different sonic signature than a Dynaco ST120 Power Amplifier. Each is a power amplifier, each designer would probably sayhis amp is both "accurate" and "neutral," and yet the sonic results are clear. Two amplifiers with very close and similar designs, and sharing very similar specifications, might also sound extremely similar. As the design methods and specs diverge, so usually does the sound. When it comes to audio power amplifiers the case is exacerbated by the speaker itself which is a non-linear load being applied, while a randomly changing signal (music) is applied to the input. Since "frequency" is a circuit variable throughout the entire amplifier including it's output, the non-linear speaker load means each design of amplifier will interact slightly differently with this load (depending on the input source) and thus make different sounds. This effect of non-linear load is much, much less in preamplifiers, tuners, CD players. Believe your ears. Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 (edited) I can't speak for anyone else, but I have never heard of running a low powered amp "slightly over driven" on purpose. Is that what you meant? I know we bicker about wires, but on this I think we are in full agreement on the essence, if not the semantics, of flea watt single ended amps. Some of the most fun audio toys I've played with. More fun than the Aphex and BBE Sonic Maximizer, even. It seems to me that any flea power amp is going to clip, just based on speaker sensitivity, listening levels, distance to speakers, etc, but it's the nature of the clipping that separates these little beasts from sand amps and more powerful amps that avoid clipping. As a SET amp clips, a low order, monotonic THD pattern results. If pushed too far, higher order harmonics are excited and good sound goes out the window. But before that, a slightly clipped SET amp acts almost like an ideal compressor: the amp's electrical output plateaus, but the increasing harmonic content within that envelope is perceived as increased loudness, at least to the point of being grossly overdriven. Or did you mean they don't know it is slightly over driven? I think you would agree that there are different degrees to which amps can be overdriven before sounding objectionable. The high, odd order of clipped ss amps is intolerable at levels as low as 1%. PP tube amps cancel even harmonics in their output stage, so their profile is different than SET, but tolerated in higher amounts than that of SS. SETs have a lot of wiggle room, where 5% or more THD often slips right by the ear unrecognized as obvious distortion. Now, if the user recognizes audible differences as such is another story, but that's what I was getting at. Edited January 25, 2015 by Ski Bum Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 25, 2015 Author Share Posted January 25, 2015 Great information, Thanks Mark and all So let me ask this, At times on more complicated passages of music I will get some grain / poor sound, and at the same volume on slower say acoustic passages it will sound sublime. Now I dont think the amount of music in a passage can affect how the amp performs but I am by no means a professional so why not ask one (No such thing as a dumb ?, or so I have been told) So one of the important parameters to KNOW about my amp would be the Sensitivity and then match that with say my Pre-amp In other words if my amp is 2 V, Try and find a pre that has an output of 2V............Correct ?? Now I must assume my integrated was designed in a way that the pre section matches (or closely matches) my amp section, what about source materials into an integrated, does it follow the same basic principle, IE... have source output closely match integrated input sensitivity ??? Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 At times on more complicated passages of music I will get some grain / poor sound, and at the same volume on slower say acoustic passages it will sound sublime. Using the 3/4 watt SE amp? If so, you could be hearing modulation of that copious but low order harmonic distortion. Chris has explained this in numerous posts, and it is one of the weak points of flea watt single ended amps. I'm not quite sure myself, as I've listened to the most demanding and complex works in my collection via set amps and find the main limit is the overall power, not any congestion within it's power limits. Quote Link to comment Share on other sites More sharing options...
eth2 Posted January 25, 2015 Share Posted January 25, 2015 (edited) Great information, Thanks Mark and all So let me ask this, At times on more complicated passages of music I will get some grain / poor sound, and at the same volume on slower say acoustic passages it will sound sublime. Now I dont think the amount of music in a passage can affect how the amp performs but I am by no means a professional so why not ask one (No such thing as a dumb ?, or so I have been told) Most likely what is happening is that if you adjust your volume for average musical signal a big dynamic peak will drive your amp into clipping. You must be aware that the dynamics in music can make huge demands on the amp. If you have a 50W amp, and you are playing it at 10W for average musical passages, it will be clipping during even modestly dynamic passages. So one of the important parameters to KNOW about my amp would be the Sensitivity and then match that with say my Pre-amp In other words if my amp is 2 V, Try and find a pre that has an output of 2V............Correct ?? The preamp should be AT LEAST 2V. Yes. More is no problem. Now I must assume my integrated was designed in a way that the pre section matches (or closely matches) my amp section, what about source materials into an integrated, does it follow the same basic principle, IE... have source output closely match integrated input sensitivity ??? It rarely matters what the source output is. Your preamp will have enough gain to make the signal big enough. The exception is "passive preamps" (an oxymoron, actually) which have zero gain. When I setup my preamp, I have two gain decisions to make. First is the individual channel settings. Second is the master volume setting. What do you recommend as the best setting for the individual channel setting to avoid clipping? Edited January 25, 2015 by eth2 Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 (edited) When it comes to audio power amplifiers the case is exacerbated by the speaker itself which is a non-linear load being applied, while a randomly changing signal (music) is applied to the input. Since "frequency" is a circuit variable throughout the entire amplifier including it's output, the non-linear speaker load means each design of amplifier will interact slightly differently with this load (depending on the input source) and thus make different sounds. Loved the old quote, still on the money. Regarding this part, I would add that these load dependent freq response variations are forms of linear distortion, and typically on the order of a db or two even for high output impedance SETs paired with widely varying impedance speakers. Sure, it's audible, wide band changes generally are that way, but it's not objectionable non-linear distortion, and could even be compensated via eq upstream. Edited January 25, 2015 by Ski Bum Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 (edited) What's not true here is that all listeners of small amps are over driving them. I think that's just a derogatory claim. Not intended in any way to be derogatory, so please don't take it that way. It was simply based on real life speaker sensitivities, listening distances, that's all, not a criticism or derogatory. I'm in too good a mood to fight with you today, so let's play nice, ok? Edited January 25, 2015 by Ski Bum Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 25, 2015 Author Share Posted January 25, 2015 Great information, Thanks Mark and all So let me ask this, At times on more complicated passages of music I will get some grain / poor sound, and at the same volume on slower say acoustic passages it will sound sublime. Now I dont think the amount of music in a passage can affect how the amp performs but I am by no means a professional so why not ask one (No such thing as a dumb ?, or so I have been told) Most likely what is happening is that if you adjust your volume for average musical signal a big dynamic peak will drive your amp into clipping. You must be aware that the dynamics in music can make huge demands on the amp. If you have a 50W amp, and you are playing it at 10W for average musical passages, it will be clipping during even modestly dynamic passages. So one of the important parameters to KNOW about my amp would be the Sensitivity and then match that with say my Pre-amp In other words if my amp is 2 V, Try and find a pre that has an output of 2V............Correct ?? The preamp should be AT LEAST 2V. Yes. More is no problem. Now I must assume my integrated was designed in a way that the pre section matches (or closely matches) my amp section, what about source materials into an integrated, does it follow the same basic principle, IE... have source output closely match integrated input sensitivity ??? It rarely matters what the source output is. Your preamp will have enough gain to make the signal big enough. The exception is "passive preamps" (an oxymoron, actually) which have zero gain. Thank you very much, can the efficiency of your speakers be an issue with complicated passages causing the amp to clip ?? I am guessing yes Learning alot here thank you all very much Quote Link to comment Share on other sites More sharing options...
Fjd Posted January 25, 2015 Share Posted January 25, 2015 (edited) When I setup my preamp, I have two gain decisions to make. First is the individual channel settings. Second is the master volume setting. What do you recommend as the best setting for the individual channel setting to avoid clipping? Let's see if the post below still applies. What does the gain knobs do ? "BBX/Peach/Merlin Gain Controls" The gain controls are ganged to the volume control. This allows you to set the line stage gain to properly match your power amplifier, and provides L/R channel balance. It is also a method of setting the sensitivity and range of your volume control. If you have ever had a preamp where 9:00 is loud, and 9:05 is EXCRUCIATINGLY LOUD, then you will understand the value of these controls! To properly set the BBX/Peach/Merlin gain controls, do this: Turn all three controls OFF Turn the Volume Control all the way UP (full on) Play a CD source Slowwwwly turn the L/R gain controls up until the music is as loud as you will ever want it to be. Stop the CD source Turn the L/R gain controls up a "smidgin" Turn the Volume Control all the way DOWN (full off) You are now properly configured to have maximum use of the Volume Control for fine adjustment of volume This process gives you full use of the volume control to make it easy to find any volume you want. It is important to note that the sonics do NOT change character based on the setting of these three controls. The sound quality is consistent at any setting. Edited January 25, 2015 by Fjd 1 Quote Link to comment Share on other sites More sharing options...
Ski Bum Posted January 25, 2015 Share Posted January 25, 2015 (edited) Let's see if the post below still applies. It does. Assuming the amp gain is not so low as to make the pre-amp output clip (addressed in step 6), that method seems about perfect. an the efficiency of your speakers be an issue with complicated passages causing the amp to clip ?? Higher sensitivity actually gives you more latitude with power, as you simply need less of it. This is one of the reasons us Klipsch folks play with such toys, simply because we can. On the other side, such speakers reveal every flaw they're fed, which is why this gain staging stuff is so critical. GIGO. As for the complicated passages causing the amp to clip, not sure, but my guess is that the amp is clipping in any event, and the complex music exposes the interaction of the clipping distortion products. (Chris explains this one so much better than I do, where is that guy?) It could simply be that the complex music demands more power than the amp can deliver, pushing it further into the obnoxious end of clipping. Either way, you don't want ss to clip, ever, so the "too much is just enough" maxim seems to apply. But that's easy. With low power tubes it's certainly not about power, at least not primarily, and particularly if you use it as a processor for pleasant effect. Keep expectations realistic as to what they can do in the dynamics and spl department. Edited January 25, 2015 by Ski Bum Quote Link to comment Share on other sites More sharing options...
eth2 Posted January 25, 2015 Share Posted January 25, 2015 Thank you. It was a peach I wanted to adjust. Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 25, 2015 Author Share Posted January 25, 2015 Can I assume that if I play the offending passages at lower volume and I dont hear the same grain / distortion that it then becomes an issue somewhere else in the chain. and if I do still hear the grain / distortion it becomes part of the recording ?? Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 25, 2015 Author Share Posted January 25, 2015 "Higher sensitivity actually gives you more latitude with power, as you simply need less of it. This is one of the reasons us Klipsch folks play with such toys, simply because we can. On the other side, such speakers reveal every flaw they're fed, which is why this gain staging stuff is so critical. GIGO." All my questions are currently in regards to headphones moe pparticularly the HiFiMan HE500 ortho's which are somewhat considered harder to drive, The same principle applies though Quote Link to comment Share on other sites More sharing options...
joessportster Posted January 25, 2015 Author Share Posted January 25, 2015 I love this place, Have a ? and the base of knowledge here always seems to come through..............Thank you all Quote Link to comment Share on other sites More sharing options...
TJIann Posted January 25, 2015 Share Posted January 25, 2015 Awesome thread! Thanks guys. I'm pouring myself a bourbon and then going down to my lounge and re-adjust the gain knobs on my McIntosh 2105 properly. Quote Link to comment Share on other sites More sharing options...
Fjd Posted January 25, 2015 Share Posted January 25, 2015 (edited) Mark, now that Joe seems to be satified with the intial questions he had, do you have time to provide a layman's type of description to the "transfer function" of an amplifier? I've been thinking recently about the Bob Carver challenges of the mid-1980s where he did the "null difference testing" to modify the transfer function of his amplifiers to duplicate the transfer function of the "unknown amplifiers" in the challenge to duplicate the 'sound.' The Mark Levinson ML-2 (unknown to Bob at the time of the challenge) "sound clone" became the commercial Carver M1.5t amplifier. The Conrad-Johnson Premier Five (unknown to Bob at the time of the challenge) "sound clone" became the commercial Carver M1.0t amplifier. Here is a post I remembered reading where Mark provided a very lucid description of various common characteristics of amplifers. -They have a transfer function (each interacts with its inputs and outputs in a unique way) WOW - 2008? Sometimes I am scared about what I might have written in the past. But for that one, I wouldn't change much! Edited January 25, 2015 by Fjd Quote Link to comment Share on other sites More sharing options...
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