Members megadan Posted January 1, 2006 Members Share Posted January 1, 2006 Can a power amp be damaged in such a way that it will still produce output, but all of that output will be clipping/square waves, thus damaging every speaker it touches, so to speak? I ask because I want to make sure I can blame my {censored}ty old speakers instead of the amp, before I hook new, better speakers up to it. (long story short, see http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=968558&highlight=MOSFET+2000M ) There was a much longer thread about that amp (The general idea I got, I think, was that it was a decent amp, if a bit old and outdated), but the recent post-count killing purge seems to have wiped it out. Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 1, 2006 Members Share Posted January 1, 2006 If it goes DC,I believe it will kill anything connected to it. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 1, 2006 Members Share Posted January 1, 2006 An unfortunate possibility with any amp, but seemingly more common with MOS-FET technology amp is the occurance of oscillation, an unwanted high frequency signal that can destroy both speakers and power amps in a hurry. Have a qualified amp tech evaluate your problem to eliminate this possibility. Link to comment Share on other sites More sharing options...
Members megadan Posted January 1, 2006 Author Members Share Posted January 1, 2006 Will (in either case) the amp do this when it's not recieving an input signal? ie, if I just plug it in to to the speakers and turn it on, will it damage the speakers? I don't mind wrecking the old ones...Also, would a limiter/compressor do any good? or is is a frequency thing and not an amplitude thing (in the case of oscillation) Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by megadan Will (in either case) the amp do this when it's not recieving an input signal? ie, if I just plug it in to to the speakers and turn it on, will it damage the speakers? I don't mind wrecking the old ones...Also, would a limiter/compressor do any good? or is is a frequency thing and not an amplitude thing (in the case of oscillation) Don't take my word as absolute truth but common sense would tell me that it wouldn't matter if anything was plugged into the inputs on the amp and therefore it wouldn't matter if there was a comp/limiter in front of the amp. The problem seems to be inside the amp,therefore,beyond the amp's inputs. But I don't really have any knowledge,that's just what my common sense tells me. but take the words of the knowledgeable ones here over mine on this. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 2, 2006 Members Share Posted January 2, 2006 Amplifier oscillation problems are a fault (either design or component) within the inside of the amplifier. Nothing can help this as it's an equipment fault (if that is what's truely happening). Link to comment Share on other sites More sharing options...
Members JohnnyGraphic Posted January 2, 2006 Members Share Posted January 2, 2006 Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker? My guess is that it still will since the square wave is still hitting the amp regardless of input gain??? Thanks for your patience!!! Johnny Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by JohnnyGraphic Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker?My guess is that it still will since the square wave is still hitting the amp regardless of input gain???Thanks for your patience!!!Johnny I think you have been fed somewhat of an old wive's tale. Link to comment Share on other sites More sharing options...
Members bigmike216 Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by tlbonehead I think you been fed somewhat of an old wive's tail. Not quite. A cliped signal is a clipped signal, reguardless of where in the signal path it is created. An amplifier reproduces what you feed it, only at a higher level. If you feed it a clipped signal, it'll output a clipped signal. Link to comment Share on other sites More sharing options...
Members moody Posted January 2, 2006 Members Share Posted January 2, 2006 One of my first bad experiences in that respect was an amp going dc while practicing. I instantly plugged into another speaker to see if the amp was still working and lost that as well. You plug in the speaker and it sounds like a bit of a hum / buzz backgroundy noise.... that's your voice coil frying! Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by bigmike216 Not quite.A cliped signal is a clipped signal, reguardless of where in the signal path it is created. An amplifier reproduces what you feed it, only at a higher level. If you feed it a clipped signal, it'll output a clipped signal. Yes,obviously. However,speakers can usually handle a clipped signal if it isn't above their capability. It has been perpetuated that a clipped signal is a guaranty that you are going to fry VC's. Link to comment Share on other sites More sharing options...
Members gruvjack Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by tlbonehead I think you been fed somewhat of an old wive's tail. You meant TALE, did'nt ya? I'd hate to be force fed grandma's ass V. Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by gruvjack You meant TALE, did'nt ya? I'd hate to be force fed grandma's ass V. Oops! No,there was no MILF pun intended there. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by JohnnyGraphic Another question, hopefully not to derail this thread too much-But, if I have a clipped signal several units before the power amp, does it still have the ability to fry a speaker? In other words, if I clip the signal at the board, but the EQ and Comp (or anything else) is at unity gain, will it still fry the speaker?My guess is that it still will since the square wave is still hitting the amp regardless of input gain???Thanks for your patience!!!Johnny Absolutely correct... except as it's been pointed out, total power level of the pre-clipped signal does matter. The speaker's thermal rating must be "de-rated" appropriately in order to account for the additional heat in the squared off signal. On many drive units, mechanical issues may also come into play. With a conservatively (or accurately) rated driver, a 50% derating is customary. This IS in fact considered when calculating power ratings of electric guitar speakers that are used with distorted signals. For high frequency driversm another phenomona comes into play, the clipped signal contains a higher % of HF information due to harmonics. Additional derating is necessary... say ANOTHER 50% or so. Link to comment Share on other sites More sharing options...
Members megadan Posted January 2, 2006 Author Members Share Posted January 2, 2006 semi-related to this supposed wives tale is my pondering of, 'why don't all good PA's use all tube power amps?' - if indeed clipping causes speaker destruction, and since tube cliping doesn't seem to kill speakers, then it seems like a logical idea. The answer to my own question, is, of course, the massive size, weight, heat, cost, and reliability of all tube power amps (24, 36 6L6's! ) I will however attempt to sacrific one speaker and listen for the VC's frying Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by moody One of my first bad experiences in that respect was an amp going dc while practicing. I instantly plugged into another speaker to see if the amp was still working and lost that as well. You plug in the speaker and it sounds like a bit of a hum / buzz backgroundy noise.... that's your voice coil frying! The buzz/hum you hear is the sound of the power supply ripple in absense of any audio, at higher than designed power supply currents. It's not a pretty sound, and it's often followed by silence and a nasty smell. Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by agedhorse The buzz/hum you hear is the sound of the power supply ripple in absense of any audio, at higher than designed power supply currents. It's not a pretty sound, and it's often followed by silence and a nasty smell. But no smoke? What a letdown. Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by tlbonehead But no smoke? What a letdown. Naaah, no letdown... the nasty smell is because of the smoke:thu: Link to comment Share on other sites More sharing options...
Members tlbonehead Posted January 2, 2006 Members Share Posted January 2, 2006 Originally posted by agedhorse Naaah, no letdown... the nasty smell is because of the smoke:thu: Yaaaaaaaayyyyyyy!! Link to comment Share on other sites More sharing options...
Members megadan Posted January 5, 2006 Author Members Share Posted January 5, 2006 On a related note, is it possible that 1 channel of a stereo power amp could be damaged, but not the other? In a more general sense, is a stereo power amp really two whole amps in one (this one sure feels like!), or do they share parts? Stupid question, I know, but I gotta learn sometime Link to comment Share on other sites More sharing options...
Members ctardi Posted January 6, 2006 Members Share Posted January 6, 2006 Usually, the power is shared, but everything from when the signal enters on is seperate. Link to comment Share on other sites More sharing options...
Members JohnnyGraphic Posted January 15, 2006 Members Share Posted January 15, 2006 Originally posted by agedhorse Absolutely correct... except as it's been pointed out, total power level of the pre-clipped signal does matter. The speaker's thermal rating must be "de-rated" appropriately in order to account for the additional heat in the squared off signal. On many drive units, mechanical issues may also come into play. With a conservatively (or accurately) rated driver, a 50% derating is customary. This IS in fact considered when calculating power ratings of electric guitar speakers that are used with distorted signals. For high frequency driversm another phenomona comes into play, the clipped signal contains a higher % of HF information due to harmonics. Additional derating is necessary... say ANOTHER 50% or so. So, the answer is 'yes-sort of...'. Just when I think I've got some stuff figured out, you come along & make me know what little I know! Hahaha. Did I ever tell you that you make me sick with how much you know about this thing I think of as a hobby? Your patience in putting up with newbies like myself is amazing. Thank you! Johnny Link to comment Share on other sites More sharing options...
Members dboomer Posted January 16, 2006 Members Share Posted January 16, 2006 Originally posted by JohnnyGraphic Did I ever tell you that you make me sick with how much you know about this thing I think of as a hobby? Naaaw! He's making it ALL up! It's not clipping itself that does the damage ... it's the extra power that comes along when this happens. Link to comment Share on other sites More sharing options...
Members JohnnyGraphic Posted January 16, 2006 Members Share Posted January 16, 2006 O.K. I think it's starting to make sense. Thanks again! Johnny Link to comment Share on other sites More sharing options...
Members agedhorse Posted January 16, 2006 Members Share Posted January 16, 2006 Some folks work hard to make this a hobby for others. I sat downand played piano tonight for the first time in months. I am so immersed in music that I have no real desire to play music. When you work with really top notch players, it is discouraging to play at the level I play at, but with the engineering side of things it's no hobby and I can work with the best at their level. For example, because of the music turning from hobby into a real job, I have carefully avoided doing the same thing with my hobby which is horses. I do work with high level folks in that area too, but intentionally keep my involvement and commitment at a less demanding level or it will stop being fun. Link to comment Share on other sites More sharing options...
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