alexclaber Posted January 11, 2011 Share Posted January 11, 2011 I'm taking advantage of my current condition to get on top of not only the thrilling paperwork I generally avoid but also some R&D I've been meaning to do, and writing some more articles to address this, that and t'other that I see getting discussed on forums but rarely getting resolved. The first one is here: [url="http://barefacedbass.com/technical-information/mythbusters1.htm"] Mythbusters #1 - Amplifiers[/url] Quote Link to comment Share on other sites More sharing options...
Merton Posted January 11, 2011 Share Posted January 11, 2011 What's your current condition? Doesn't sound good! Quote Link to comment Share on other sites More sharing options...
alexclaber Posted January 11, 2011 Author Share Posted January 11, 2011 [quote name='Merton' post='1085983' date='Jan 11 2011, 08:01 PM']What's your current condition? Doesn't sound good![/quote] Broken ankle: Was operated on last Friday (I have new titanium upgrades) so on a mission to get it back to normal asap! Quote Link to comment Share on other sites More sharing options...
clauster Posted January 11, 2011 Share Posted January 11, 2011 Ouch! Hope you make a speedy recovery Alex! Enjoyed the article: good work. Quote Link to comment Share on other sites More sharing options...
fatback Posted January 11, 2011 Share Posted January 11, 2011 Yeah, hugely informative. Thanks. A big get well from here too. Does titanium set off the scanners at airports? Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted January 12, 2011 Share Posted January 12, 2011 What is 'crest factor'? It is probably maths, that they tried to teach me in school, but did it without context. Quote Link to comment Share on other sites More sharing options...
mart Posted January 12, 2011 Share Posted January 12, 2011 [quote name='Mr. Foxen' post='1086331' date='Jan 12 2011, 02:13 AM']What is 'crest factor'? It is probably maths, that they tried to teach me in school, but did it without context.[/quote] [url="http://en.wikipedia.org/wiki/Crest_factor"]http://en.wikipedia.org/wiki/Crest_factor[/url] Quote Link to comment Share on other sites More sharing options...
Stylon Pilson Posted January 12, 2011 Share Posted January 12, 2011 [quote]Truth #3 - You will never blow woofers or mid-bass drivers, i.e. the 8"/10"/12"/15"/18" speakers found in a bass cab, because your amp isn't powerful enough.[/quote] Heh, I misread this initially as having meaning synonymous to "no amp is powerful enough to blow woofers or mid-bass drivers". Which is clearly nonsense, but that second comma does introduce a certain ambiguity. S.P. Quote Link to comment Share on other sites More sharing options...
Salt on your Bass? Posted January 12, 2011 Share Posted January 12, 2011 [quote name='Stylon Pilson' post='1086818' date='Jan 12 2011, 03:49 PM']Heh, I misread this initially as having meaning synonymous to "no amp is powerful enough to blow woofers or mid-bass drivers". Which is clearly nonsense, but that second comma does introduce a certain ambiguity. S.P.[/quote] +1, I had a double take on that! Nice piece though. Probably the most informative manufacturer website out there. I feel like I actually learn something every time I read it! Hope the ankle recovers soon Alex. Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted January 12, 2011 Share Posted January 12, 2011 [quote name='mart' post='1086803' date='Jan 12 2011, 03:36 PM'][url="http://en.wikipedia.org/wiki/Crest_factor"]http://en.wikipedia.org/wiki/Crest_factor[/url][/quote] This is why I mentioned being without context makes it unhelpful. Quote Link to comment Share on other sites More sharing options...
ShergoldSnickers Posted January 13, 2011 Share Posted January 13, 2011 This is how I understand Crest Factor. I may be utterly misguided. Imagine a drummer doing a constant roll on the snare drum. That establishes a sound level that is fairly constant. Now if he or she were to introduce rim shots every now and again, there will be a peak increase in sound level per rimshot. Make these rimshots louder and you are increasing the crest factor. The peak level in comparison with the 'average' level has increased. With crest factor, it's the rms level and peak levels that are compared in the form of a ratio. I guess a compressor/limiter reduces crest factor. Quote Link to comment Share on other sites More sharing options...
alexclaber Posted January 13, 2011 Author Share Posted January 13, 2011 Maybe I'll write something on crest factor with respect to bass guitar. There's quite a lot to cover. But on the Claber scale of quick and dirty crest factor then: Violently slapping a sparse bassline on my RIM with Q-Tuners (passive pickups with zero compression) through Avalon U5 (extremely high headroom preamp) = highest crest factor that's possible from a bass guitar (maybe 1000:1 or 30dB or more) Live bass playing, no compression = typical bass guitar crest factor (between 10:1 and 20:1, 10-20dB) Straight 8ths with the same bassist playing the same thing as below, but live instead of studio = lowest normal live crest factor (somewhere between 4:1 and 10:1, 6-10dB) Heavily produced recorded straight 8ths with lots of compression = lowest normal crest factor (somewhere between 2:1 and 4:1, 3-6dB) Playing constant notes, no rests or muting, through a Big Muff with all the controls cranked = lowest crest factor that's possible from bass guitar (probably almost 1:1 or 0dB) The snare roll example is a good one - just bear in mind that the extra rimshots not only raise the peak level but also the average level - so the less frequent but louder the rimshots, the greater the crest factor. Turning up your treble will increase the crest factor whilst turning up the bass will decrease the crest factor. Adding compression or limiting will decrease the crest factor. Adding distortion will decrease the crest factor. Plucking closer to the bridge will decrease the crest factor. Plucking harder will increase the crest factor. Quote Link to comment Share on other sites More sharing options...
dincz Posted January 13, 2011 Share Posted January 13, 2011 "Clipping only increases the power output at higher frequencies" But the RMS voltage of a sine wave is about 0.7 of its peak value, whereas the RMS voltage of a square wave is the same as its peak value. So a square wave of a given peak voltage has an RMS value 1.4 times that of a sine wave of the same peak value. Surely that results in a doubling of power (I^2 x R)? At least in an ideal world with an ideal power supply. OK, I'm talking pretty severe clipping here - bags of level into a sensitive input - and an amp running into a purely resistive load. I've only ever tested this into a dummy load as I've always had intolerant neighbours Quote Link to comment Share on other sites More sharing options...
alexclaber Posted January 13, 2011 Author Share Posted January 13, 2011 [quote name='dincz' post='1087906' date='Jan 13 2011, 01:06 PM']"Clipping only increases the power output at higher frequencies" But the RMS voltage of a sine wave is about 0.7 of its peak value, whereas the RMS voltage of a square wave is the same as its peak value. So a square wave of a given peak voltage has an RMS value 1.4 times that of a sine wave of the same peak value. Surely that results in a doubling of power (I^2 x R)? At least in an ideal world with an ideal power supply. OK, I'm talking pretty severe clipping here - bags of level into a sensitive input - and an amp running into a purely resistive load. I've only ever tested this into a dummy load as I've always had intolerant neighbours [/quote] But if you run a Fourier Transform on that square wave you'll see that the additional energy is entirely made up of higher frequency overtones. Quote Link to comment Share on other sites More sharing options...
dincz Posted January 13, 2011 Share Posted January 13, 2011 (edited) [quote name='alexclaber' post='1087959' date='Jan 13 2011, 02:42 PM']But if you run a Fourier Transform on that square wave you'll see that the additional energy is entirely made up of higher frequency overtones.[/quote] OK the fog is clearing. Of course it makes sense that there's nothing below the fundamental. It's just so tempting to see "alternating DC" in a square wave. But what about this: "Clipping does not cause square waves" Can't quite get my head around that. Edited January 13, 2011 by dincz Quote Link to comment Share on other sites More sharing options...
Mr. Foxen Posted January 13, 2011 Share Posted January 13, 2011 [quote name='dincz' post='1088224' date='Jan 13 2011, 04:05 PM']OK the fog is clearing. Of course it makes sense that there's nothing below the fundamental. It's just so tempting to see "alternating DC" in a square wave. But what about this: "Clipping does not cause square waves" Can't quite get my head around that.[/quote] I think that is the lack of vertical bit, like you need two lines to make a right angle, and it ain't a square without one. So it is just a flat topped wave, not a square one like you can do with synths. Quote Link to comment Share on other sites More sharing options...
Noisyjon Posted January 13, 2011 Share Posted January 13, 2011 Love it Alex, Keep 'em coming! Regards, Jon Quote Link to comment Share on other sites More sharing options...
dincz Posted January 13, 2011 Share Posted January 13, 2011 [quote name='Mr. Foxen' post='1088229' date='Jan 13 2011, 05:10 PM']I think that is the lack of vertical bit, like you need two lines to make a right angle, and it ain't a square without one. So it is just a flat topped wave, not a square one like you can do with synths.[/quote] OK, not perfect square waves with infinitely short risetimes, but definitely squarISH. A synth (or anything else) won't produce a perfect square wave either but an amp with good HF response and slew rate would surely produce as good an approximation as a synth, no? Quote Link to comment Share on other sites More sharing options...
alexclaber Posted January 15, 2011 Author Share Posted January 15, 2011 Another update - new Vd info added: [url="http://barefacedbass.com/technical-information/Volume-displacement.htm"]http://barefacedbass.com/technical-informa...isplacement.htm[/url] Quote Link to comment Share on other sites More sharing options...
LawrenceH Posted January 17, 2011 Share Posted January 17, 2011 Hi Alex these are very good articles, but going back to what I said to you before, I think they would be even better if it linked to (separate) graphs/figures illustrating some of the points! Teaching scientific/technical stuff I've found some people are very visual in their understanding and will find that easier no matter how clear the prose - it also gives a great solid point of reference for otherwise interminable internet discussions Quote Link to comment Share on other sites More sharing options...
alexclaber Posted January 20, 2011 Author Share Posted January 20, 2011 [quote name='LawrenceH' post='1092077' date='Jan 17 2011, 01:24 AM']Hi Alex these are very good articles, but going back to what I said to you before, I think they would be even better if it linked to (separate) graphs/figures illustrating some of the points! Teaching scientific/technical stuff I've found some people are very visual in their understanding and will find that easier no matter how clear the prose - it also gives a great solid point of reference for otherwise interminable internet discussions [/quote] You're quite right of course but it takes me ten times as long to do the illustrations as to write an article - so the visual learners will have to miss out for now! Quote Link to comment Share on other sites More sharing options...
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