radrobgray Posted September 26, 2007 Report Share Posted September 26, 2007 i hear this term used alot with tube amps. is it "voodoo-tone" marketing hype? im not sure exactly how this pertains to tone in a real world situation. for example when i bought my VHT 2902 poweramp the guys at the store said it had lots of headroom, i would assume because of the KT88s? Quote Link to comment Share on other sites More sharing options...
GregP Posted September 26, 2007 Report Share Posted September 26, 2007 Nothing at all to do with voodoo, and yes something to do with your tubes-- though I don't actually know the KT88 specs and performance. Tubes will eventually go into overdrive, with one side-effect being that the signal becomes compressed. You can push them harder, and you'll get more clipping, but you won't get much more volume. Amps with a lot of headroom will be able to achieve higher volume without clipping. In general, people will specify that they mean "clean headroom," but if not, you can assume that they're talking about the amp's ability to push the power section hard without clipping. If your distortion is generated in the preamp, you can still talk about 'headroom' in the power section. Ie. it's not a simple "distortion vs. clean" equation-- unless your amp specifically generates its usable distortion in the power section, at which time there's a more direct correlation. That's just layman-speak... someone who actually knows amps better might be able to refine or clarify that information. I'm no textbook authority on amps. Greg Quote Link to comment Share on other sites More sharing options...
westhemann Posted September 26, 2007 Report Share Posted September 26, 2007 Greg has it right,but I think of it in slightly simpler terms of how loud you can get without the power amp section getting mushy...after a certain volume amps can lose clarity... I play through a 100 watt engl so trhat I can get pretty loud without any power amp clipping...I absolutely hate power amp clipping in metal Quote Link to comment Share on other sites More sharing options...
radrobgray Posted September 26, 2007 Author Report Share Posted September 26, 2007 i know what preamp distortion sounds like. whats power amp distorion sound like? i would assume something similar to AC/DC or no? Quote Link to comment Share on other sites More sharing options...
fryovanni Posted September 26, 2007 Report Share Posted September 26, 2007 What Greg and Wes said. Different power sources will sound a bit different when they saturate or clip. Digital or solid state clipping can be really nasty sounding. Simply put your power source can't give you any more output in the range that is effected. This "clips" any more output and instead of hearing the peak of the wave it is clipped off at the saturation point. The net effect is that frequencies that are supposed to be lower in magnitude around the area being clipped become artificially closer to the level of the frequencies being cut off or clipped. When you have a wide band that is being clipped you hear a wide band of frequencies at the same level(this sounds like a block of un-dististingushed sound* as Wes puts it "mushy"). Frequencies that are normally lower in amplitude are going to be driven closer to this limit, and may be easier to hear, as long as the block of equal level sound is not too annoying. As your signal drops the level will not change until you reach the level of saturation or clipping and fall below it. This is where all that sustain comes from when you use heavy distortion or saturation. Using distortion in this way you can in a sense attenuate frequencies that are less audible, by making them sound louder than the frequecies that are actually higher in level (because they are being stopped at a certain level). The down side is if you over do it you get a big fat flat line of equal level frequencies that are not what is really being played, and nasty sounding. Really good control of distortion is not an easy thing to do, but when it is done by someone who knows what they are doing it is amazing, when sloppy or just cranked without knowing what you are doing it sounds like a big fat mushy wall off dung. If you look at a curve of how people hear frequencies in relation to level, you can start to see where this could work. link You can see that we can hear high mids and low mids easier than lower or higher frequencies. The higher mids are a good target for saturation. If you limit the level by clipping those frequencies, you are able to bring up the level of the lower and higher frequencies in relation to the clipped high mids(effectively making them less dominant). One thing that can be problematic is that you bring up the relative level of lower mids(which are also pretty easy to hear), and this can create that mushy sound. If you want to be able to hear what you are actually playing, you need to try to keep your levels below this the threshhold where clipping starts. This allows you to hear the dynamics of the actual levels, as they actually sound. The same rules apply to how you hear though(and everyone actually has a different curve that can change over time because of damage to your hearing), and this is where a little equalization can make things sound a little better. Limiters, and compressors work to achive a similar effect with a little better control, however you don't get the exact same curves and responce you would get from a given amp, speakers etc... Peace,Rich Quote Link to comment Share on other sites More sharing options...
mikhailgtrski Posted September 26, 2007 Report Share Posted September 26, 2007 i know what preamp distortion sounds like. whats power amp distorion sound like? i would assume something similar to AC/DC or no? Depends on the amp and tubes, but to my ears tube power amp distortion is fatter, with more pleasing harmonics. It's also an important factor contributing to the "feel" of an amp... usually when you drive the output section hard the amp becomes much more responsive to picking dynamics and varying guitar volume levels. An amp with lower headroom might start to feel overly compressed or "squishy" when cranked, whereas one with good headroom (ahem... HIWATT ) will be very responsive while retaining the "punch". But it depends on the sound you're going for. My Lexicon (low-wattage single-ended Class A EL84 amp) is good for some things, but it doesn't have the oomph and clarity of my HIWATT (100 watt EL34). Mike Quote Link to comment Share on other sites More sharing options...
ibanezlover Posted September 26, 2007 Report Share Posted September 26, 2007 What power amp distortion sounds like depends on the type of power amp. If it is a SS amp or tube with NFB (most high-power amps) you get a harsh, trebly distortion (like Marshall). A tube amp with no NFB (like a Vox) gives you a tube-ish overdrive sound. Quote Link to comment Share on other sites More sharing options...
westhemann Posted September 27, 2007 Report Share Posted September 27, 2007 alot of the usefulness or lack thereof of power amp clipping depends on the style of music as well...most metal guys don't like power amp clipping,while alot of blues guys do... Quote Link to comment Share on other sites More sharing options...
Digideus Posted October 1, 2007 Report Share Posted October 1, 2007 http://en.wikipedia.org/wiki/Headroom Try that Quote Link to comment Share on other sites More sharing options...
brewu22 Posted January 10, 2008 Report Share Posted January 10, 2008 alot of the usefulness or lack thereof of power amp clipping depends on the style of music as well...most metal guys don't like power amp clipping,while alot of blues guys do... Mesa 50/50 power amp on 6 when playin live, no clipping, sounds sweet Quote Link to comment Share on other sites More sharing options...
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