Alexander B Larsson wrote on Tue, 05 February 2008 11:11 |
I am still searching for that "big amp" for the bass boxes, but the more I read, the more contradictory the information seems... |
Scott Smith wrote on Tue, 05 February 2008 09:46 |
While I know the PL6.0 has a much beefier power supply, no one has ever been able to technically explain why this amp has a damping factor of 2000. All people will say is that this figure is just "marketing hype" and means nothing. Is it possible the figure is the result of the beefier power supply? |
Chuck Fry wrote on Tue, 05 February 2008 13:09 |
...My limited understanding is that the damping factor is more a result of a high feedback factor, and minimal impedance between the output stage and the terminals, than it is a function of the power supply... |
Scott Smith wrote on Tue, 05 February 2008 13:23 | ||
Ah yes... but isn't the job of the amplifier to ultimately get the power (from the power supply) to the speakers with the least amount of resistance and loss? |
Alexander B Larsson wrote on Tue, 05 February 2008 12:46 |
Thanks for all the replies! Don't you find it frustrating that we in this case not can quantify what we hear? And that amps that on paper are indistinguishable still do not sound the same, even within their linear operation (as in no clipping/current limiting). Or do we fool ourselves - how big are the differences? A few years ago I had the opportunity to pick up either of two Labgruppen amps for my bass guitar rig. One Lab 1000 or one Lab 1300. They are VERY close in spec, with most of the design the same, except the power supply. (The 1000 is a conventional and the 1300 is switched.) The price was the same, making the 1300 a bargain, as it is normally more expensive. However, there was no doubt the two bottom octaves where better with the Lab 1000. And I have to carry the 20 or so extra pounds every time I move the thing... /Alexander |
Ryan Lantzy wrote on Tue, 05 February 2008 12:27 |
I hate to even acknowledge this with a reply... but here goes. FOR THE LAST TIME, THE DAMPING FACTOR OF AN AMP CAN DO NOTHING TO IMPROVE THE DAMAGE THE COPPER IN BETWEEN DOES TO THE DAMPING FACTOR! It's VERY simple math. Look into it. |
Alexander B Larsson wrote on Tue, 05 February 2008 16:11 |
Considering our ear's limited sensitivity to detect distorsion in the bass range, what IS it that we hear? /Alexander |
Scott Smith wrote on Tue, 05 February 2008 16:11 |
Is the mention of "slew rates" a thing of the past as well? |
Bennett Prescott wrote on Tue, 05 February 2008 13:43 | ||
Yes. No modern amp should have any issue with slew rate limiting within the audible bandwidth. |
Richard Rajchel wrote on Tue, 05 February 2008 13:11 |
Arguing which amp sounds better and why is like arguing what shade of blue the sky is at 6pm just after a rain storm. It's so subjective, that there is no answer. |
Richard Rajchel wrote on Tue, 05 February 2008 13:11 |
The differences in amplifiers is probably much much less than that even....simply because there's only so much to an amplifier. A mixer is much more complicated and more components can have an effect on the sound. I would bet $1000 that if you took 100 engineers and setup an A/B blind comparison between a low end QSC amp and a Crown iTech and matched the voltage output of them both that the results would be 99% random. S |
Richard Rajchel wrote on Tue, 05 February 2008 13:11 |
Name brand equipment is for people who have to fill riders, and to compare another subjective thing like customer service and reliability. The only people who know how reliable products actually are is the manufacturer that keeps track of repairs, and I'm guessing they don't share that information readily. I can find someone who's had 10 Behringer amps for the last 6 years running 5 nights a week without one failure, or someone with a Midas board that has to go in for repair at least 3-5 times a year. |
Richard Rajchel wrote on Tue, 05 February 2008 13:11 |
One last thing about "punchy" bass. What the heck does that mean in reality? Most people, including a lot of engineers think to get a great kick drum sound you need subs that go to 20Hz flat(OK I'm exaggerating a little), but that "kick in the chest" feeling is usually in the 60-80Hz range, and in all actuallity the first harmonic of 120-160Hz is where most of that feel comes from. you can EQ the crap out of a kick to get it to feel where ever you want I suppose, and kick drums obviously get tuned different and can be as big as a house or smaller than most floor toms, but this dream that you need to go super low to feel the kick in a live sound application is just flat out a lie. Compressed recordings are a completely different animal, so if you're a DJ don't listen to me...heh. |
Richard Rajchel wrote on Tue, 05 February 2008 16:11 |
One last thing about "punchy" bass. What the heck does that mean in reality? Most people, including a lot of engineers think to get a great kick drum sound you need subs that go to 20Hz flat(OK I'm exaggerating a little), but that "kick in the chest" feeling is usually in the 60-80Hz range, and in all actuallity the first harmonic of 120-160Hz is where most of that feel comes from. you can EQ the crap out of a kick to get it to feel where ever you want I suppose, and kick drums obviously get tuned different and can be as big as a house or smaller than most floor toms, but this dream that you need to go super low to feel the kick in a live sound application is just flat out a lie. Compressed recordings are a completely different animal, so if you're a DJ don't listen to me...heh. |
Scott Smith wrote on Tue, 05 February 2008 15:11 |
In no way did I intend to start a DF discussion. Is the mention of "slew rates" a thing of the past as well? |
Richard Rajchel wrote on Tue, 05 February 2008 14:11 |
One last thing about "punchy" bass. What the heck does that mean in reality? Most people, including a lot of engineers think to get a great kick drum sound you need subs that go to 20Hz flat(OK I'm exaggerating a little), but that "kick in the chest" feeling is usually in the 60-80Hz range, and in all actuallity the first harmonic of 120-160Hz is where most of that feel comes from. |
Bob Leonard wrote on Tue, 05 February 2008 17:16 | ||
To this I agree. For me QSC 3602s dont get it for low frequency use below 100hz. Mine shut down under low voltage conditions, generate tremendous amounts of heat and my subs don't respond as well as they do using QSC 4050HDs. I'm not going to perform any analysis to prove my point to myself or anyone else. The 4050 has more in reserve than the 3602 and runs better under less than perfect conditions even though the specs are almost identical. However, if I roll the specs up and put the specs for the 4050 in one ear and the the specs for the 3602 in the other I don't hear any difference. But, when I pull that paper out of my ears and listen to them side by side the difference is night and day. To be kind though, the 3602 is a perfect amp (IMO) for a JBL SRX725 (with that extra 15" speaker helping to reproduce the in the 100-160hz range.) I read the statement linear in a response. By default power amplifiers are all linear. The job of a power amplifier used for radio, sound, etc. is to faithfully reproduce the input signal at an amplified (larger) level, be it 10, 100, 1000 times larger or more. I tend to think that class of service is what the post was meant to state, examples below as applied to ham radio. The same applies to audio; The class A amplifiers are very inefficient, they can never have an efficiency better than 50%. The semiconductor or valve conducts throughout the entire RF cycle. The mean anode current for a valve should be set to the middle of the linear section of the curve of the anode current vs grid bias potential. Class B amplifiers are more efficient, they can be 60 to 65% efficient. The semiconductor or vacuum tube conducts through half the RF cycle. Class AB1 is where the grid is more negatively biased than it is in class A. Class AB2 is where the grid is often more negatively biased than in AB1, also the size of the input signal is often larger. When the drive is able to make the grid become positive the grid current will increase. In a class B amplifier the grid current drawn will be large, and a large drive power will be required. Class C amplifiers are still more efficient, they can be about 75% efficient with a conduction range of about 120o but they are very non linear. They can only be used for FM or CW use only. The semiconductor or valve conducts through less than half the RF cycle. The increase in efficiency can allow a given valve to deliver more RF power than it could do so in class A or AB. For instance two 4CX250B tetrodes operating at 144 MHz can deliver 400 watts in class A, but when biased into class C they can deliver 1000 watts without fear of overheating. Even more grid current will be needed. A side effect of improving the efficiency is that the current drawn from the high voltage supply will vary more as a function of the power input into the amplifier, this can result in unwanted effects such as the output of the HT pack being modulated by the audio modulated RF driven into the amplifier. |
Bob Leonard wrote on Tue, 05 February 2008 15:16 | ||
To this I agree. For me QSC 3602s dont get it for low frequency use below 100hz. Mine shut down under low voltage conditions, generate tremendous amounts of heat and my subs don't respond as well as they do using QSC 4050HDs. I'm not going to perform any analysis to prove my point to myself or anyone else. The 4050 has more in reserve than the 3602 and runs better under less than perfect conditions even though the specs are almost identical. However, if I roll the specs up and put the specs for the 4050 in one ear and the the specs for the 3602 in the other I don't hear any difference. But, when I pull that paper out of my ears and listen to them side by side the difference is night and day. To be kind though, the 3602 is a perfect amp (IMO) for a JBL SRX725 (with that extra 15" speaker helping to reproduce the in the 100-160hz range.) I read the statement linear in a response. By default power amplifiers are all linear. The job of a power amplifier used for radio, sound, etc. is to faithfully reproduce the input signal at an amplified (larger) level, be it 10, 100, 1000 times larger or more. I tend to think that class of service is what the post was meant to state, examples below as applied to ham radio. The same applies to audio; The class A amplifiers are very inefficient, they can never have an efficiency better than 50%. The semiconductor or valve conducts throughout the entire RF cycle. The mean anode current for a valve should be set to the middle of the linear section of the curve of the anode current vs grid bias potential. Class B amplifiers are more efficient, they can be 60 to 65% efficient. The semiconductor or vacuum tube conducts through half the RF cycle. Class AB1 is where the grid is more negatively biased than it is in class A. Class AB2 is where the grid is often more negatively biased than in AB1, also the size of the input signal is often larger. When the drive is able to make the grid become positive the grid current will increase. In a class B amplifier the grid current drawn will be large, and a large drive power will be required. Class C amplifiers are still more efficient, they can be about 75% efficient with a conduction range of about 120o but they are very non linear. They can only be used for FM or CW use only. The semiconductor or valve conducts through less than half the RF cycle. The increase in efficiency can allow a given valve to deliver more RF power than it could do so in class A or AB. For instance two 4CX250B tetrodes operating at 144 MHz can deliver 400 watts in class A, but when biased into class C they can deliver 1000 watts without fear of overheating. Even more grid current will be needed. A side effect of improving the efficiency is that the current drawn from the high voltage supply will vary more as a function of the power input into the amplifier, this can result in unwanted effects such as the output of the HT pack being modulated by the audio modulated RF driven into the amplifier. |
Chuck Fry wrote on Tue, 05 February 2008 18:04 |
Hmmm... resonant circuits... could a Class C power amp be useful for those "one-note" car audio subs you hear booming down the road? |
Alexander B Larsson wrote on Tue, 05 February 2008 10:11 |
I am still searching for that "big amp" for the bass boxes, but the more I read, the more contradictory the information seems... I currently run a number of older "conventional PSU" Labgruppen amps, but having one bridged amp per driver is HEAVY! (Finding amps for listening tests is somewhat hard in Sweden, as many of the MI shops carry only entry level stuff, like Phonic, Alesis etc.) Normally one can find some general trends in opininons/reviews of stuff, but amps seem different? Strange, since they should actually have the smallest impact on overall fidelity of the rig, from a distorsion point of view. Some praise the QSC RMX 4050 and 5050 for subs, while some claim their upgrade from RMX to some "switched" Crown, Lab or similar made a world of difference. Listening test (shootout) says the differences are small, but that test only included few speakers, etc... Considering our ear's limited sensitivity to detect distorsion in the bass range, what IS it that we hear? A guy I talked to described the lightweight Lab amps as "punchy" in the bass, but are we talking about that amp adding something that was not originally there? Or are many other amps missing the "punch", whatever that would be? Power is clearly important, but amps that run below their clipping point should not colour sound at all, at least not detectable... /Alexander |
Richard Rajchel wrote on Tue, 05 February 2008 17:28 |
I'm not sure how well informed I might be, but the biggest impact on live sound is the talent of the musicians. The second biggest is probably the talent of the person mixing the band. As long as there's enough power to get the vocals over the sound of the band anyone should be able to get a listen-to-able mix...... |
Scott Smith wrote on Tue, 05 February 2008 18:19 |
has anybody offered any technical reasons why amps sound different |
Bob Leonard wrote on Wed, 06 February 2008 09:02 |
Yes Tim, I am aware those are all tube circuits, and; A class C amplifier is biased beyond cutoff. The class C amplifier like the class B amplifier will draw no current with no signal input but a class B will start to draw current as soon as a signal is applied and a class C will only start to draw current when the signal strength is sufficient to go beyond the bias level. The class C amplifier is not linear but is the highest in efficiency. In all classes of amplifier the linearity of the amplifier is determined by it's class. The APS-20 radar on an EC-121 Willy Victor used a class "C" amplifier. RTTY, CW are often used with class "C" amplifiers, but they can not be used with SSB. I posted these as classic examples, and being as basic as these classes of amplifier are I would think it may be good reading material for people who may want to understand amplifiers and how they operate. Guitar players may find interest in class A/B amplifier circuits especially if they use a Fender amplifier. |
Bob Leonard wrote on Wed, 06 February 2008 08:02 |
Yes Tim, I am aware those are all tube circuits, and; A class C amplifier is biased beyond cutoff. The class C amplifier like the class B amplifier will draw no current with no signal input but a class B will start to draw current as soon as a signal is applied and a class C will only start to draw current when the signal strength is sufficient to go beyond the bias level. The class C amplifier is not linear but is the highest in efficiency. In all classes of amplifier the linearity of the amplifier is determined by it's class. The APS-20 radar on an EC-121 Willy Victor used a class "C" amplifier. RTTY, CW are often used with class "C" amplifiers, but they can not be used with SSB. |
Quote: |
I posted these as classic examples, and being as basic as these classes of amplifier are I would think it may be good reading material for people who may want to understand amplifiers and how they operate. Guitar players may find interest in class A/B amplifier circuits especially if they use a Fender amplifier. |
Silas Pradetto wrote on Wed, 06 February 2008 13:35 |
Damping factor is the load impedance divided by the output impedance of the amplifier. This means, with an 8 ohm load and a .01 ohm output impedance of the amplifier, you would have a damping factor of 800. Damping factor has quite a bit to do with bass quality. It is related to cone control such that a higher damping factor is more control. If there is more control, the woofer flaps around less and relies less on it's own suspension to return it to the "zero" point in it's travel, making everything sound "punchier." I hope that kind of made sense. |
Andy Peters wrote on Wed, 06 February 2008 13:08 | ||||
As The Good Tim says, flat view, anyone? USE THE QUOTE BUTTON. And how is this relevant to the topic at hand? Other than to get into another mudwrestle with Duffin?
And the design goals of a guitar amplifier are at cross purposes with one designed for sound reproduction. One is a tone generator, one is not. So the discussion is rather pointless. -a |
Silas Pradetto wrote on Wed, 06 February 2008 14:35 |
." I hope that kind of made sense. |
Quote: |
I think the way that amps are used today they do have a "sound". It is typical to see amps driven into the non linear mode. In fact I think it has become commonplace. That makes a smaller system sound "louder". |
Ted Olausson wrote on Wed, 06 February 2008 22:27 | ||
http://www.moultonlabs.com/more/power_amps_revisited/ |
Duncan McLennan wrote on Tue, 05 February 2008 08:22 |
linear power supplies. |
Chuck Fry wrote on Thu, 07 February 2008 12:43 |
I found this "smackdown" thread via a link from a DIYaudio.com thread: http://srforums.prosoundweb.com/index.php/m/229083/19784/ Now what would explain the lower power output at low frequencies of 3 of the 4 amps tested? The PLX 3402 puts out literally twice the power at 20 KHz that it does at 20 Hz. Even the Crest 9001 has a dip in the power curve at 50 and 200 Hz - in the heart of subwoofer country. The burst test should be pulling the same energy from the power supply irrespective of frequency, shouldn't it? Answer that question and maybe we'll have a clue what we're really hearing from amps on sub duty. (BTW this is not intended as bashing any particular amp maker - I happen to own a PLX 3402 and have been happy with it as part of a bass guitar rig.) |
John Roberts {JR} wrote on Thu, 07 February 2008 11:08 |
While I am not familiar with than particular amp, the general mechanism that explains why an amplifier has lower power output at 20 Hz than 20kHz has been well described here several times. The PS capacitors in conventional PS are charged at a rep rate of 2x mains frequency (100 or 120Hz). Pure tones much higher than that charging rep rate pull roughly half the time from the + supply and half the time from the - supply. Pure tones that are much lower than the charging rep rate appear to alternately pull from one supply for several charging cycles, then from the other. This results in an effective 2:1 difference in short term PS draw. |
Alexander B Larsson wrote on Tue, 05 February 2008 10:46 |
And that amps that on paper are indistinguishable still do not sound the same, even within their linear operation (as in no clipping/current limiting). |
Bob Lee (QSC) wrote on Thu, 07 February 2008 12:35 |
Among the biggest problems are that when we compare amps …
|
Pascal Pincosy wrote on Thu, 07 February 2008 16:05 | ||
I did an amp shootout a few months ago where we did all of the above properly. The results? Entirely inconclusive. Buy amps based on price, feature-set, weight, and brand rep. Don't bother trying to find the best-sounding amp. Your results will change based on the source material used, the speakers used, and the phase of the moon. http://srforums.prosoundweb.com/index.php/t/27380/9721/ |
SteveKirby wrote on Thu, 07 February 2008 14:10 |
That shootout did notice a subtle different when used for subs. That actually helped me make my choice to get a Crest Pro9200, which has worked very well for me. In spite of it being one of those new fangled switchers. If we weren't on opposite coasts, it might be fun to compare it to Bob's big iron. |
Richard Rajchel wrote on Thu, 07 February 2008 15:32 |
I couldn't agree more. Everyone likes to believe they have somewhat golden ears. When we all hear as much with our eyes and preconceived notions is closer to the truth. In blind tests with output matched and no "voltage" shutdowns etc... I doubt anyone could tell you which amp was a Lab and which one was an RMX. The results would be completely random. Aren't volts volts and amps just amps? There are most certainly nuances, and maybe one amp has a sag at a certain frequency, but with just about any two amps behind a curtain driving identical speakers with the identical program material at the identical voltage I can't imagine anyone could tell. Reliability, weight, and how an amp handles overloads or under powering would be far better criteria than how you think an amp might sound better than another. |
Andy Peters wrote on Thu, 07 February 2008 07:24 | ||||
Well, he's driving easier loads at lower SPLs than typical for SR use and it's obvious that driving the amps to the edge all night is not a requirement. But, really, it just sounds like the guy who built the amps conservatively rated them lower than what they can really do. Which is fine, and even laudable, especially considering that he leaves some "marketing watts" on the table. Note how they measure SPL, but not amplifier output power, which would be the better test. |
Bob Leonard wrote on Wed, 06 February 2008 12:52 | ||||||
Andy, I don't care about Duffin. He asked for an answer and got it. And since when are class A/B amplifiers not a part of sound reproduction. I seem to remember working with many prior to the use of transistors in amplifier output stages. I don't remember saying anything about preamplifier circuits at all. Maybe that's where your confused. Besides that the above were used as examples of amplifier class in response to someone who doesn't understand the meaning of the word linear. Ever read an RCA tube manual? Regardless of the class most amplifiers can trace their roots back to those simplistic amplifiers of days gone by in some way or another. |
Tim Duffin wrote on Thu, 07 February 2008 18:09 |
Anyways, the correct answer for my question you did not get. |
Tim Duffin wrote on Thu, 07 February 2008 18:19 |
I wouldn't have said anything if the info was correct in the first place. |
Tim Duffin wrote on Thu, 07 February 2008 20:09 |
Fine, Ill use the quote button. Anyways, the correct answer for my question you did not get. The circuit which is class C is called a "gyrator" and it is not used in audio as per JR's comment. The reason why is because it conducts only for positive values of input-- so use your imagination as to what that looks like on a scope. I can tell that whomever wrote your quote has very little grasp of what the circuit does-- or it is very outdated information. "Biased beyond cutoff"---lol! thats the funniest thing I have read all week. T |
Andy Peters wrote on Wed, 06 February 2008 15:40 | ||
You forget the salient point: overall damping factor is severely degraded by the cable between the amp and the driver, as that cable's resistance adds to the amp output impedance. In fact, the cable resistance essentially sets the damping factor, making amplifier damping factor irrelevant except maybe as a marketing bullet point. This horse is dead. Please stop beating it. -a |
Jeff Hague wrote on Thu, 07 February 2008 22:08 | ||||
So, why wouldn't a higher damping factor be desirable anyway? If the copper between the amp and the speaker degrades it, wouldn't a higher damping factor to begin with cause less degradation? Is the effect that overwhelming (ie non-linear)? It seems to me that the effect of copper wire on damping factor is linear, as is the effect of speaker impedance. An amp with a damping factor of 200 into an 8 ohm load will have a damping factor of 100 into a 4 ohm load, right? In that light, the higher the damping factor of the amp to begin with (prior to the speaker cable), the better... Ive never beat a dead horse that I didn't like... |
Andy Peters wrote on Fri, 08 February 2008 01:52 | ||||||
See the charts at the end of this paper (pdf). Notice that the largest contribution to damping factor is indeed the cable resistance. -a |
Andy Peters wrote on Tue, 05 February 2008 16:39 | ||
Agreed. And furthermore, from which cabinet do you get that 160 Hz? Answer: not the sub! -a |
Tim Duffin wrote on Thu, 07 February 2008 21:33 |
I don't agree. How can you educate somebody without saying anything? |
Jeff Hague wrote on Thu, 07 February 2008 23:08 |
So, why wouldn't a higher damping factor be desirable anyway? If the copper between the amp and the speaker degrades it, wouldn't a higher damping factor to begin with cause less degradation? Is the effect that overwhelming (ie non-linear)? It seems to me that the effect of copper wire on damping factor is linear, as is the effect of speaker impedance. An amp with a damping factor of 200 into an 8 ohm load will have a damping factor of 100 into a 4 ohm load, right? In that light, the higher the damping factor of the amp to begin with (prior to the speaker cable), the better... Ive never beat a dead horse that I didn't like... |
Richard Rajchel wrote on Thu, 07 February 2008 19:00 |
Just the simple fact that anyone is using the word "better" makes it subjective in the first place. In the case where the RMX improved on some top cabinet sound over the Labs, what was it that made the RMXs "better". It had to be SPL in a "pleasing to the ear" range. For example at the level you were testing at the RMX/top cabinet combination had a slight rise in SPL for the frequency range from 2k-5k or something? Just an example, but if it's audible and repeatable you should be able to measure it. Like different microphones have different response curves, as well as speakers etc... More expensive mics might be closer to flat response, and more accurate, but that doesn't make them sound better to our ear. That slight rise in response in the 1.5k-10k range of frequencies(even if it's only a dB or 2) tends to sound clearer, or cleaner, or more presence, or any other number of descriptions for that particular sound quality. So maybe the RMX is just not quite as accurate as the Lab with those speakers, but the result is still pleasing to the ear. Change speakers and you get a different result perhaps as well. The question is who's going to spend the rest of their lives and millions of dollars documenting which amps work the best with each speaker in every situation? |
Dave Rickard wrote on Fri, 08 February 2008 08:48 | ||||
Yes you do, from the subs, in the form of distortion. At least in front loaded cabinets. I was skeptical about this concept, and/or at least, how much harmonic content a driver adds. When I got my horn subs back from the builder and was checking them out before finishing the raw wood. I needed to seal and check for leaks around the doors, handles, yada. While playing 40, 50, 60 Hz test sine waves with the access door open and closed, I could clearly hear harmonics which were not present in those sine waves. Taking the door on and off clearly demonstrated this. When the doors were on the folds in the horn filtered those overtones out. I believe that's why some folks don't like the "horn sound", the lack of distortion, and prefer gobs of double 18's. I don't recall what you use for subs at your club, but f you can get horn subs sometime you can verify this. |
Andy Peters wrote on Fri, 08 February 2008 01:52 | ||||||
See the charts at the end of this paper (pdf). Notice that the largest contribution to damping factor is indeed the cable resistance. -a |
Richard Rajchel wrote on Fri, 08 February 2008 15:59 |
I think the distortion of front loaded subs in particular is the actual cone/box acting just like an instrument. I'm not a scientist, but I'm taking a good guess that yes, 160hz can be heard from a sub even if it's crossed at 100hz. The cone of the speeaker might be like the string on a piano, and the box that it's in would obviously be like the piano. Even though all the movement of the cone forwards and backwards is controlled by electrical signals from the amplifier, the actual cone itself has it's own "harmonics". If you pluck an e string on a guitar you can still hear an octave above that, perhaps another 5th above that, and them some really high harmonics that tend to give it a bit of a ring...the newer the strings the more pronounced the harmonics are because it's not all deadened by string degradation and oils from the skin of the fingers playing the guitar. This "cone/box" distortion or harmonics is more pronounced with an 18" driver simply because it's much bigger and not as rigid. You won't hear nearly as much harmonic content from the high E string on a guitar as you might from the low E string. Just like you won't hear as much harmonics/distortion from a 10" speaker as you would from a 18", or God forbid a 21" speaker. That's my attempt at describing the distortion factor of front loaded 18" subs. Horn loaded subs don't have nearly as much of that distortion because of design. All the shorter length sound waves don't make it around all those corners inside a folded horn, and in addition most horns use smaller drivers than 18" so there's less cone area and the cone is more rigid to not enhance these harmonics/distortion. |
Bob Leonard wrote on Fri, 08 February 2008 15:40 |
This is not a very good analogy. First, if I were able to hear the second octave note, or any note, that I am not playing on any of my guitars not plugged into an amplifier I would be very concerned that the instrument were defective. |
Quote: |
Speakers that are used for sound reinforcement are designed to be void of these problems. Good speakers do not distort at their rated power, because if they did, the power rating would have to be lowered. Good speakers, regardless of size, have distortion ratings well below what is audible to the human ear while listening to the program content. Is it there? Maybe but I would doubt you'll hear it. Here's a link to my favorite 18" speaker. Note the distortion characteristics for the speaker within it's usable frequency range vs. the output. That should answer the question. http://www.jblpro.com/pages/pub/components/2242.pdf |
Bob Leonard wrote on Fri, 08 February 2008 14:40 |
This is not a very good analogy. First, if I were able to hear the second octave note, or any note, that I am not playing on any of my guitars not plugged into an amplifier I would be very concerned that the instrument were defective. And I know my doctor and close friend would dump both his baby grands if that were the case as well. IBBY, Bob L. |
Richard Rajchel wrote on Fri, 08 February 2008 13:59 |
I'm not a scientist, but I'm taking a good guess that yes, 160hz can be heard from a sub even if it's crossed at 100hz. |
Richard Rajchel wrote on Fri, 08 February 2008 12:59 |
I'm not a scientist, but I'm taking a good guess that yes, 160hz can be heard from a sub even if it's crossed at 100hz. |
Tony "T" Tissot wrote on Fri, 08 February 2008 17:33 |
No truly pure tones exist from any instrument. |
John Roberts {JR} wrote on Fri, 08 February 2008 17:01 | ||
The flute played pianissimo is pretty damn close from a real instrument, if we ignore synths that could but typically don't put out pure tones. Most musical instruments generate their notes using what I would call a one path resonator, and will generate harmonics that are simple multiples of that path, i.e. string length, for plucked, struck, or bowed instruments, or acoustic path length for wind instruments. In contrast there are instruments who generate overtones that are not simple multiples (harmonics) because of using different length paths for fundamental and overtone resonances (like them round drumheads). To contrast the contrast we have instruments like tympani that are engineered to sound tonal, but the note you perceive is not even the note that is being voiced in a little psychoacoustic manipulation of our perception (we hear a lower frequency "phantom" fundamental that is the difference between the resonances). Never say never, nature loves exceptions to any rule. JR |
Richard Rajchel wrote on Sat, 09 February 2008 02:13 |
One question I would have for someone more knowledgeable than me is would a straitened out LAB horn have the same distortion reduction as the folded version? My guess would be no, but of that I'm not sure. |
Duncan McLennan wrote on Fri, 08 February 2008 02:20 |
Home stereo or PA? I can easily tell the difference between both hi-fi amps and pro audio amps in my home system, even under blind test conditions. I've done it many times. |
Quote: |
In a PA application, I don't consider it a serious issue. If an amplifier will get through the night without thermaling, sound pretty good, not blow up my speakers, I'm a happy guy. Lighting weight, and low current draw are nice bonuses. |
Quote: |
Nobody said that you should change a winning concept. I only said that you should be aware of the fact that there still is a long way of technical development left to achieve the perfect sound. |
Tony "T" Tissot wrote on Fri, 08 February 2008 19:14 |
"Close" does not an exception make The search for exception has been fruitless. Even electronic instruments (although not in my consideration for the above mentioned "instrument") suffer when voiced through transducers. No truly pure tones exist from any instrument. |
Richard Rajchel wrote on Fri, 08 February 2008 20:19 |
Like I said in that thread you are referring to, it may very well add to the experience, but it's not sound if it's infrasonics. Below 30hz is different than what you originally described, and yes there may be audible stuff below 30hz, but that's a bit different that what you originally described. My question then, is if the lowest sound producing instrument on a stage is a 4 string bass with a low E at 41hz, where is the material below that coming from? Is it like the reverse of harmonics? |
Tony "T" Tissot wrote on Fri, 08 February 2008 18:33 | ||
As "fundamental" a law as inverse square. No truly pure tones exist from any instrument. Pianos and other stringed instruments really exhibit this (whatever the correct terminology is). From http://www.vibrationdata.com/piano.htm The beginning key on the left end is an A0 note with a fundamental frequency of 27.5 Hz. A piano key has harmonic overtones at integer multiples of its fundamental frequency. Thus, the A0 key also produces a tone at 55.0 Hz, which is one octave higher than the fundamental frequency. The second overtone is at 82.5 Hz. add reference. |
Andy Peters wrote on Fri, 08 February 2008 10:33 |
We have two double-18" front-loaded subs at the stage front and center. Each box is powered by a channel of a Crest 8001 (and in over seven years I have NEVER seen the clip light blink). We feed both amp channels from the processor's mono sub out (simple split). Ya know, if I had seen this post last night (or if you'd posted it last night!) while waiting for the band, I would have swept tones through the subs and measured it to see. So what causes the distortion? Is it as simple as "overloading the box" in the sense that the output is clean up until some SPL level which essentially puts the system into saturation? Or is the distortion present at all levels? I am the first to admit that my knowledge of loudspeaker physics details is limited. -a |
Richard Rajchel wrote on Fri, 08 February 2008 18:19 |
Like I said in that thread you are referring to, it may very well add to the experience, but it's not sound if it's infrasonics. Below 30hz is different than what you originally described, and yes there may be audible stuff below 30hz, but that's a bit different that what you originally described. My question then, is if the lowest sound producing instrument on a stage is a 4 string bass with a low E at 41hz, where is the material below that coming from? Is it like the reverse of harmonics? |
Andy Peters wrote on Fri, 08 February 2008 22:46 | ||
A beat frequency? -a |
Jeff Hague wrote on Fri, 08 February 2008 20:25 |
Reverse harmonics? They go both ways dont they? |
Quote: |
So what causes the distortion? Is it as simple as "overloading the box" in the sense that the output is clean up until some SPL level which essentially puts the system into saturation? Or is the distortion present at all levels? I am the first to admit that my knowledge of loudspeaker physics details is limited. -a |
Dave Rickard wrote on Fri, 08 February 2008 15:48 |
I believe that's why some folks don't like the "horn sound", the lack of distortion, and prefer gobs of double 18's. |
Richard Rajchel wrote on Sat, 09 February 2008 10:41 |
I disagree. Distortion by over powering a subwoofer is not what we are discussing here I don't think. That would be what we do to guitar cabinets on purpose to get "that sound". I would guess that all speakers have distortion at all power levels. The amount of distortion likely increases as the power increases. It should also be mentioned that the sound of a front loaded double 18" subwoofer may have a more pleasing sound to some BECAUSE of the distortion. It's what many people are used to hearing. I'm guessing that it can be reduced by running well below the power maximum, but not eliminated. Certainly not in front loaded designs or any design for that matter. Folded horn subs have much less distortion, but it's still there. |
Richard Rajchel wrote on Sat, 09 February 2008 02:52 | ||
And that's not achievable because the perfect sound is different for everyone. |
Richard Rajchel wrote on Sat, 09 February 2008 11:23 |
Once again I disagree. There is ALWAYS distortion present....not just when you over power a speaker. In addition many horn loaded subs including the ones you mentioned will go pretty flat into the 30s. |
Quote: |
You do need multiples to do it, but with the added efficiency of the horn you need less of them to reach a certain SPL that similar front loaded cabinets. |
Quote: |
It's not really trivial either. I highly efficient front loaded design may push 100 dB 1w/1 meter, but a highly efficient horn loaded design will be more like 106+ dB 1w/1 meter. Doubling power gains you 3dB so double once again to reach a 6dB increase. |
Quote: |
You need 4 X the amount of front loaded enclosures to reach the output of 1 horn loaded design...of course these are just estimates. 4 LABs would probably crush 8 or 10 front loaded 18s at 1/2 the power or less...and in a group of 4 would go well into the 30s relatively flat. |
Quote: |
I'm not sure where you see horn loaded subs that roll off 10dB by 40Hz...i'd like to see those, or at least know what they are so I can avoid them when looking to upgrade my rig. |
Elliot Thompson wrote on Sat, 09 February 2008 11:31 |
All speakers are subjected to distortion if/when they are pushed beyond their limits. |
Richard Rajchel wrote on Sat, 09 February 2008 12:07 |
OK, enough is enough. You keep claiming that at -20dB or what ever power level you choose that there is no distortion. Well I went to Turbosounds website and procured Turbosound's own SPL Chart for the TSW-718. It's a front loaded double 18" subwoofer of pretty decent quality. As you can see the 2nd harmonic and 3rd harmonic distortion are quite present at only 10% power. Where are your magical no distortion subwoofers? |
Ted Olausson wrote on Sat, 09 February 2008 13:02 | ||
No, speakers does SOFTLIMIT not HARDLIMIT (Unless you slam the coil in the bottom ofcourse). |
Elliot Thompson wrote on Sat, 09 February 2008 14:26 | ||||
The average user doesn't know anything about power compression in speakers. They just push it until it either rips to shreds or ketch on fire. Best Regards, |
Elliot Thompson wrote on Sat, 09 February 2008 03:31 | ||
Your assumptions about overloading the driver and/or amplifier is correct. |
Elliot Thompson wrote on Sat, 09 February 2008 07:24 |
I don't think I said there was no distortion. |
Elliot Thompson wrote on Sat, 09 February 2008 05:49 |
you shouldn't have any distortion from a reflex cabinet unless the distortion is coming the source. |
Richard Rajchel wrote on Sat, 09 February 2008 14:40 |
Just the simple fact that harmonic distortion is present in all speakers....even at 10% power. I could care less where that Turbosound dropped off -4dB it had measured distortion throughout the range of it's intended use. It was only used for illustration purposes because Turbosound is one of the only Pro Audio companies to publish that information on their equipment. I do, however, understand what you are saying about horns, and them unloading at a certain frequency. Why is that any different that an actual front loaded design if kept within a reasonable power limit? |
Elliot Thompson wrote on Sat, 09 February 2008 03:31 | ||
Your assumptions about overloading the driver and/or amplifier is correct. Notice those that carry ample amount of subs/amplifiers never complain about distortion? (snip) All speakers are subjected to distortion if/when they are pushed beyond their limits. Whether you choose Horn-Loads or Reflex cabinets. |
Richard Rajchel wrote on Fri, 08 February 2008 18:06 |
How do you think you can hear a low E on a bass guitar(41hz) on speakers that might be able to only go down to 100hz? It's harmonics that you hear. In my experience the lower the note the more prevalent the harmonics are. It's much easier to hear them with a low E on a bass than a high E on a guitar. That's just personal experience. I'm sure someone has a scientific explanation for that. . |
Alexander B Larsson wrote on Sun, 10 February 2008 14:01 |
Back on topic... I have now realized we are actually comparing apples vs oranges if we compare many PA amps. I looked at the specs from a number of the the major brands, and I was actually quite surprised to see they are not using the same spec at all! LAB and QSC clearly display all (?) relevant data, with the output power figures according to FTC (and even S/N ratio, that some manufacurers "forget"). EV shows the nice distorsion vs power graph of their P 3000, but no FTC power here (and I can not find any separate S/N figure)? Crown XLS and MA also sports some "home brew" specs, with very little information. "1 kHz power"? The Peavey figures ("hidden" deep in the owners manual of the amps) are also unclear - some kind of power "snapshot". Rated power at 1 kHz at < 0,1% THD - but for what duty cycle? I also checked the Digam 5000, which is only intended for 1 kHz? It has no power bandwidth, no CMRR, no channel separation and distorsion figures that are mediocre at best... Some other (MI stuff) brands display even more interesting concepts of "music power", "peak output" etc, but that is not surprising to me. However, with "big boys" like Harman Kardon, Peavey and EVI group not being very straightforward about power measurements, I don't know. To me, the openness about data is a very strong guide. I think I will focus on the LABs and some QSCs for my upcoming (small) purchase. /Alexander from Sweden |
Scott Smith wrote on Sun, 10 February 2008 17:33 |
I still smile when I see my big stack of Peavey CS1200's and my CS800S, knowing I don't have to lug them anymore. Despite their lower power ratings compared to today's amp, they sure had a nice punchy sound...if amps have a sound. |
John Roberts {JR} wrote on Sun, 10 February 2008 17:45 | ||
The FTC power spec you cite was a reaction to the wild west days of hifi consumer amps when power specs were indeed fast and loose, and wildly inaccurate. While I certainly supported the standardization of what "watts" means (more or less), the 1/3rd power preconditioning requirement was actually overly strict for class AB hifi amps. That said, making consumers buy a little more aluminum than they need was a fair price to pay for standardized power ratings. For professional power amps the 1/3rd power preconditioning is archaic and maybe even counter productive. Any engineer using class G/H topology will just dial in the mid power supply rail to run cool at 1/3rd power. Maybe optimal for real music, maybe not, it is surely optimal for passing FTC preconditioning. We can all look longingly back at the good old days when 800W power amps put out 800 watts 24x7 but now that same 800W platform is pushing 1200W with the same heatsink and power transformer so you do the duty cycle math. |
Alexander B Larsson wrote on Sun, 10 February 2008 12:01 |
I also checked the Digam 5000, which is only intended for 1 kHz? It has no power bandwidth, no CMRR, no channel separation and distorsion figures that are mediocre at best... |
Duncan McLennan wrote on Thu, 07 February 2008 17:20 |
I can easily tell the difference between both hi-fi amps and pro audio amps in my home system, even under blind test conditions. I've done it many times. |
Bob Lee (QSC) wrote on Tue, 12 February 2008 19:14 | ||
It may be that the pro amps are more hi-fi than the "hi-fi" amps. |
Ivan Beaver wrote on Sun, 10 February 2008 19:11 |
My standard test of day gone by was to put a sine wave in and look at the voltage at clip into both 8 and 4 ohms. That was the power rating, in my opinion. |
Rob Spence wrote on Tue, 12 February 2008 20:41 |
My DC300s don't have fans |
John Roberts {JR} wrote on Wed, 13 February 2008 02:28 |
I find, even in double blind listening tests, I can always pick out the one with a fan... at least on quiet passages. |
Ted Olausson wrote on Wed, 13 February 2008 11:24 | ||
Run a speaker fullrange and you will be able to tell the difference with ease just by comparing the final bandwith. -Unless you have trouble to hear the difference between 50Hz-400Hz compared to 16Hz-10KHz or 1Khz-12Khz compared to 200Hz-16Khz ofcourse... |
Elliot Thompson wrote on Wed, 13 February 2008 12:47 | ||||
Amplifiers are not the limiting factor. The loudspeaker is. What home audio woofers are you using capable in delivering 16 Hertz flat, without the aid of an eq? Please post the TS Parameters so I can run it through one of my programs and see the results. For the record all top of the line (In terms of series) pro amplifiers will go down into single digits as far as frequency bandwidth is concerned without shutting down. However, finding a Home Amplifier to do the same thing is a task in itself. Best Regards, |
Ted Olausson wrote on Wed, 13 February 2008 12:27 | ||||||
No home device can deliver that low what i know of.(Atleast my clockradio cant do that and that is the only homedevice i have seen in 20 years...) -If you wanna see it you have to come to my warehouse and listen for yourself, unless you try it yourself first. BTW: How did you intend to simulate different amps in a simulationprogram????? -Thats the running point, it is clearly audible but how does it work???? |
Elliot Thompson wrote on Wed, 13 February 2008 14:35 |
I wasn't planning on simulating different amps with a program. You mentioned 16 Hertz and, I was commenting on what speaker you've found that can reproduce 16 Hertz flat without the aid of an Equalizer. Many tend to state these lower than average response and don't take into account the processing (Eq, Bandpass filters, coupling with the walls in the room) to achieve such a fete. All of that changes when your only boundary is the ground it sits on when doing outside events. It is very easy for me to simulate the frequency response of the driver using a loudspeaker design program and see if indeed the woofer can deliver 16 Hertz, 0 dB Normalized gain. This is why, I requested the TS paramaters of the driver. |
Quote: |
As for the amplifiers, all you need is the documentation from the manufacter to see what is the lowest frequency the amplifier will produce before it: 1. Begins to rolloff or 2. Activates it's protection cicuitry. |
Quote: |
Rob Spence mentioned the DC 300 which, frequency bandwidth is flat down to 1 Hertz. So, it will have no issues delivering 16 Hertz. However, finding a woofer that can withstand 16 Hertz with a sizable amount of output (Considering the human hearing is very insensitive in terms of low frequency) so we can enjoy it, is not as easy as one may assume. |
Ted Olausson wrote on Wed, 13 February 2008 14:44 |
If you werent planning to simulare the SAME speaker with different amps then the simulation is useless.... I can get get different response from DIFFERENT speakers too and there is nothing strange with that... |
Quote: |
I also said in the message that is was best to focus on the change in midrange. AND that those 16Hz was a result of roomboundaries in the testenviroment. |
Quote: |
The only differnce is the amp, same room/placement, same speakers, same tonegenerator. (For measuring 16Hz a microphone+smaart were used) Even the same cables were used... |
Quote: |
So, what specifications from the amplifiermanual can explain a hicutoff at 400Hz versus 10Khz or the locut at 200Hz versus 1Khz???? Since both amps clearly can deliver those frequencies. |
Elliot Thompson wrote on Wed, 13 February 2008 16:25 |
Why not test it outdoors so you can eliminate the room and see if the conclusions are the same? |
Quote: |
You'll need to get your hands on the Service Manual to find out what you are searching for. The user Manual won't go into great detail for the average user doesn't need that type of information. |
Ted Olausson wrote on Thu, 14 February 2008 07:34 |
BTW how can an amp that is stated to have 1000w/8ohm and 1100w/4ohm at 0% distortion hade a DF above 1000!? It should be 1000/2000/4000 watt at 8/4/2 ohm... |
Ted Olausson wrote on Thu, 14 February 2008 09:34 |
BTW how can an amp that is stated to have 1000w/8ohm and 1100w/4ohm at 0% distortion hade a DF above 1000!? It should be 1000/2000/4000 watt at 8/4/2 ohm... |
Tim Duffin wrote on Fri, 15 February 2008 20:22 |
That is not what I was talking about. A class C "Amplifier" in the sense I am familar is used for unidirectional excitation of particles in water. I think about gyrators for ultrasonic cleaning while you are thinking of gyrators for RF... I never even knew that they had a circuit called a 'gyrator' in RF. I remember having to assemble a class-c amp in college and look at its output on a scope-- looked like a bunch of humps with some overshoot at zero crossing. T |
Tim Duffin wrote on Thu, 07 February 2008 20:09 |
Fine, Ill use the quote button. Anyways, the correct answer for my question you did not get. The circuit which is class C is called a "gyrator" and it is not used in audio as per JR's comment. |
John Roberts {JR} wrote on Thu, 14 February 2008 18:15 |
I understand the logic behind your misunderstanding but it assumes unlimited current capability in the amplifier. Amplifier DF is related to output impedance which is strictly a matter of device characteristics, internal wiring, and negative feedback, or more specifically loop gain margin. An amplifier's maximum power at lower load impedances, is dominated by current capability and only in the margin to source impedance related output stage losses. An amplifier's close but not perfect doubling, suggest source impedance effects. Wider divergence from 2x per halving is caused by PS or protection circuitry current limiting output stage. In an ideal world, there would be a strict doubling of power with halving of load impedance but in practice this requires delivering 4x the amp at 2 ohms as for 8 ohms. Customers have routinely voted with their purchases to support a lesser capability, The marketplace provides what customers are willing to pay for. |
Ted Olausson wrote on Sat, 16 February 2008 08:53 |
Sorry, i was tired. OPAMPS has the same behaviour. But what other (Known or suspected) factors except DF has a great impact on the relationship between speaker and amp? |
John Roberts {JR} wrote on Sat, 16 February 2008 16:06 |
I am very much a proponent of amplifiers sounding quite similar to each other as long as operated linearly. Besides voltage clipping which is more common than many operators suspect, there is running out of current. Especially for an amplifier that doesn't follow the approximate doubling of power with halving the load impedance. That amplifier will current clip before it voltage clips at low impedance loads. |
Quote: |
Another poorly understood factor is how loudspeakers, especially when using passive crossovers vary their impedance with frequency. Impedance dips with paralleled speakers could drop quite low at spot frequencies. |
Quote: |
The most audible differences are frequency response errors, and added signals (distortion). The tiny differences between amplifiers operating linearly are IMO insignificant in the context of the loudspeakers they are connected too, and room modes, and sources like microphones. |
Ted Olausson wrote on Sun, 17 February 2008 06:50 |
(One of the amps is also very close to "2xpower" from DC to 80MHz and has perfect stepresponse, the other is a normal amp) |
Duncan McLennan wrote on Tue, 05 February 2008 11:22 |
I've personally always like amplifiers with real toroidal transformers and linear power supplies. Switching amps, although convenient for weight purposes, have never sounded as good to my ear. That might be just me. So is weight worth sacrificing sound quality? I don't know. |
Alexander B Larsson wrote on Mon, 18 February 2008 05:01 |
Ted Olausson said: "There is also a numbergame with distortion, THD% is very inaudible but IM% is almost never stated but highly audible." Well, Labgruppen and QSC certainly displays figures for IM distorsion, at least for the amp models I checked. Coincidence? I DO find it interesting that many of the posters really liked the sound and reliability of the "old, continous power, 24/7" amps. Many of you have also clearly said that you ARE willing to compromise on the bass accuracy to get more power and lighter racks. And I think nobody argues that the D class technology is still in need of more development, since the IM and load matching issues are still not really solved... /Alexander |
Alexander B Larsson wrote on Mon, 18 February 2008 10:17 |
Well John, I mean exactly what I wrote... Apart from THD figures, Labgruppen and QSC also displays separate Intermodulation distorsion measurement figures, be it SMPTE or DIM 30. Regarding the class D, was I mostly thinking of the inherent "coloration" in the higher frequencies, and the problems to get rid of that kind of topology related issues. But the amps sure are light and use the supplied outlet power in a very efficient way - just what many here ask for! /Alexander |
Andy Peters wrote on Sun, 17 February 2008 13:57 | ||
80 MEGAHERTZ? Why does it need bandwidth out that far, if it's an audio amplifier? -a |
Bob Leonard wrote on Mon, 18 February 2008 17:01 | ||||
It won't and it can't. Well maybe, but it would be one hell of a circuit. Think of the possabilities. Audio through the RF spectrum with one amplifier. 80mhz is above most military radio frequencies. Look up BPL and tell me what you find. |
John Roberts {JR} wrote on Mon, 18 February 2008 18:32 |
The name of the company escapes me now, but there was an amp company back in the late '70s or early '80s whose claim to fame was strip line (?) technology and Mhz bandwidth, I doubt even they were pushing 80 Mhz power bandwidth but they were faster than your average Fender... Needless to say there was no "there" there and they faded into oblivion. Something about "you can't fool all the people all the time..." (without a huge marketing budget). |
Tim McCulloch wrote on Mon, 18 February 2008 18:42 |
Can we stick a fork in this thread? It's done.... Tim Mc |
Mac Kerr wrote on Mon, 18 February 2008 17:43 | ||
Mac |
Mac Kerr wrote on Mon, 18 February 2008 17:41 |
I don't know if it's what you were thinking of, but that was a claim to fame of Spectrasonics amps. The Spectrasonics 700 was a 70W amp on a card. You could load up to 8 of them in the card cage. they were very sensitive to wiring issues, I smoked a cage full of them when they went into ultrasonic oscillation because there was a grounding issue. Mac |
Andy Peters wrote on Sun, 17 February 2008 19:57 | ||
80 MEGAHERTZ? Why does it need bandwidth out that far, if it's an audio amplifier? -a |
Ted Olausson wrote on Mon, 18 February 2008 17:37 | ||||
No, typo, 80 KILO hertz is it bandlimited to. |
Andy Peters wrote on Tue, 19 February 2008 01:52 |
And this is EXACTLY why I'm a pedantic asshole. There is a significant difference between 80 MHz and kHz. (And if anyone writes mHz, that's a very small bandwidth.) So, at least proofread before posting. (And yes, I expect to be called on my typos, and I always admit to making mistakes.) Anyways -- I'm not significantly impressed by 80 kHz bandwidth. -a |
Ted Olausson wrote on Mon, 18 February 2008 18:11 | ||
It is easy to remove the 80KHzfilter, its just a cap and a resistor on the input but i dont expect it to do any difference. |
Andy Peters wrote on Mon, 18 February 2008 20:14 |
PS: it's kHz, not KHz. K is absolute temperature in Kelvin. Kower-case k is kilo-. |
Andy Peters wrote on Tue, 19 February 2008 02:14 |
OK, smart guy, why not try it -- remove the filter and see how long the amp lasts before ultrasonic oscillation destroys the output stage. |
Ted Olausson wrote on Mon, 18 February 2008 18:37 |
No, typo, 80 KILO hertz is it bandlimited to. It can only handle 300KHz at full power, but the risetime is 0,5uS and slewrate is 180v/uS. Should i mention the brand!? Naah |
John Roberts {JR} wrote on Mon, 18 February 2008 17:32 |
The name of the company escapes me now, but there was an amp company back in the late '70s or early '80s whose claim to fame was strip line (?) technology and Mhz bandwidth, I doubt even they were pushing 80 Mhz power bandwidth but they were faster than your average Fender... Needless to say there was no "there" there and they faded into oblivion. Something about "you can't fool all the people all the time..." (without a huge marketing budget). JR |
Ted Olausson wrote on Mon, 18 February 2008 19:20 |
What does inputcap have to do with oscilliation!? it is a inputbuffer after the cap... -If so, it would oscilliate when there wasnt any connector in the amp.... |
SteveKirby wrote on Mon, 18 February 2008 19:40 |
Are you thinking of Spectral? I think they were based in SF and founded on the premise that bandlimiting to 20kHz created slew limiting bluring time base information that provided directional cues. There was an arm of the company that made records, Reference Recordings. I have one record of theirs with Stephen Gordon playing Chopin. Lots of ambience that sounds like the rear third of the hall. |
Ted Olausson wrote on Mon, 18 February 2008 18:20 | ||
What does inputcap have to do with oscilliation!? it is a inputbuffer after the cap... -If so, it would oscilliate when there wasnt any connector in the amp.... |
Tim McCulloch wrote on Mon, 18 February 2008 18:47 | ||||
Hmmmm... Let's carve it up and serve it... lots of tofu; most of the real meat went unnoticed. Tim Mc |