neo33 Posted July 14, 2004 Author Share Posted July 14, 2004 Talking about the devil! Link to comment Share on other sites More sharing options...
ben. Posted July 14, 2004 Share Posted July 14, 2004 I'm not sure what the ad has to do with the supposed demo he did. The 5W thing seems like a coincidence to me. Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 In alphabetical order the amps involved in the test were: Adcom GFA-535II Dynaco MkIV (restored, lightly modded) RCA P.A. Amp SA-101-B (somewhat restored.. this uses the 7868 tube in a single ended configuration) Transcendent Sound SE-OTL 3 tube amps, one SS. All use negative feedback. The Dynaco and RCA were both driven off their 8ohm taps. The Adcom is rated to 60w/ch. The Dynaco is rated to 40w/ch, though it is probably a little lower then that depending upon how much distortion you want to consider as being the indicator of max power. I don't really know what the RCA is rated to and haven't measured it. Probably only a couple of watts though. The SE-OTL is rated to 1.5w,though it is probably a little lower then that depending upon how much distortion you want to consider as being the indicator of max power. Knowing the above anyone want to match these up with the distortion pictures? There are two SE amps and two PP. This should be easy as according to some the PP amps will be nothing but third order distortion. Shawn P.S. And before someone pops up and says... "Well *MY* amp doesn't distort like that!" ask yourself if you are really sure of that.... IOW have you tested it or had it tested? Or are you just assuming that is the case? Link to comment Share on other sites More sharing options...
Parrot Posted July 14, 2004 Share Posted July 14, 2004 ---------------- On 7/14/2004 2:08:31 PM bclarke421 wrote: I'm not sure what the ad has to do with the supposed demo he did. The 5W thing seems like a coincidence to me. ---------------- Hartley talks about a demo of a symphony orchestra recording. No one in his right mind would think a 5 watt amp would be a good way to attain high fidelity with such a source. The ad, written by PWK, talks about a symphony orchestra and 5 watts. But not a nominal 5 watts, but 5 acoustic watts. To achieve 5 acoustic watts in the room PWK is talking about, he has 2 Klipschorns and a Belle Klipsch, each channel connected to 20 watt amps. It's pretty obvious what happened. Hartley dropped the word "acoustic." Link to comment Share on other sites More sharing options...
NOSValves Posted July 14, 2004 Share Posted July 14, 2004 sfogg, You have me sitting on the egde of my chair waiting to hear which is which. I myself will not touch guessing with a ten foot pole ! I'm not familar with what the graphed actually represent so I'm lost on this one. What are you using to create them and what does this all represent would be helpfull to many I'm sure. Craig Link to comment Share on other sites More sharing options...
neo33 Posted July 14, 2004 Author Share Posted July 14, 2004 "But not a nominal 5 watts, but 5 acoustic watts." I hate to admit it, but Paul may be right. "A 1 db increase would just be audible. A 10dB increase will be judged to be twice as loud, (ten fold increase in power). Acoustic power must not be confused with electrical power, the power forms must be converted by something like a loudspeaker, but a standard cone/coil loudspeaker can be as inefficient as 3%, so as an example a 100W amplifier at full output would only give approximately 3W acoustic power. 1 acoustic Watt measured at 0.282m, (A sphere radius 0.282m has a surface area of 1m), (4 * pi * r^2) gives: Acoustic power = 1W Power level = 120 dB-SPL Acoustic intensity = 1W/m sq Acoustic pressure = 20 Pa or 20ubar" Of course, the KHorns are much more efficient then standard cone/coil loudspeakers, so they may need less nominal watts. Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 Craig, " I'm not familar with what the graphed actually represent so I'm lost on this one. What are you using to create them and what does this all represent would be helpfull to many I'm sure." These are FFTs of the audio range of 0 to 500hz. Each vertical division is 50hz. This are produced by a Spectral Dynamics SD-380 spectrum analyzer. What I'm doing is feeding each amp a 50hz sine wave (from a H/P 3325A function generator) and the amp is driving an 8 ohm dummy load. The level from the H/P function generator is adjusted so that each amp is putting out one watt into the dummy load. The SD380 is measuring the output. What the SD380 basically does is break the audio down into its component frequencies and charts them sort of like a bar graph on the display... frequency along the horizontal, amplitude on the vertical. It also measures the voltage/frequency of wherever you put the marker. That is what the little square is at the top of the highest peak on each picture. The markers readout is on the bottom left side of the display it is showing 50hz and 2.83v (or 2.84 I think on one) RMS for each amp. If the amps had no harmonic distortion at all then all you would see on this test is the line at 50hz and nothing else. None of these amps do this though. They all have additional output that is not what was put into the amplifiers.... IOW distortions. In amp one you can see a harmonic at 100hz. 100hz/50hz = 2. IOW this is the second order harmonic distortion of the fundamental frequency. In some of the others you can see second order as well as third, fourth, fifth...etc...etc... In two of the amps you also see a 60hz component which is powerline noise. One is also showing the second harmonic (120hz) of the AC line as well. That may have just been picked up in the test leads though, I'm not positive that was coming from the amps under test. So these pictures are basically a simple display showing the amplifiers harmonic distortion of this test frequency at this tested power level. BTW, if I have time I'll probably retest #3 or #4 tonight just to be sure nothing was screwing up the results shown above. If I do I'll also test them at a lower power level to see what they look like. Shawn Link to comment Share on other sites More sharing options...
ben. Posted July 14, 2004 Share Posted July 14, 2004 His amplifier power was 5 watts. Whatever. I'm not going down this road again. I'm sure lots of people in their right minds think lots of things. He very well may have been mistaken. I just didn't see the correlation between the two. And for what I'm sure is not the last time, an increase of 10dBSPL is not a doubling. 6dBSPL is. I could give a rat's arse what perceptual research has "discovered". We're talking about concrete, measurable, physical facts. Sound pressure levels are not opinion. Green "looks like" gray to a lot of people. That doesn't make my lawn gray. A 10dBSPL increase may "sound like" a doubling of sound pressure to many people; that's because they apparently don't know how to properly judge sound pressure differences. Link to comment Share on other sites More sharing options...
ben. Posted July 14, 2004 Share Posted July 14, 2004 BTW, Sean (Shawn?, sorry, I forget...) you make a great point about assuming what kind of distortion or other anomalies one's equipment may exhibit without knowing what to measure and then doing so accurately. Link to comment Share on other sites More sharing options...
NOSValves Posted July 14, 2004 Share Posted July 14, 2004 Okay now I get it. But if I understand this correctly then amp 1 - 2 - 3 have the 60hz and 120hz line noise at varying levels. Amp 4 has zero. Rick is under the impression the amp 3-4 is in clipping is this true ? I would think not they just have 2,3,4... order distortion. When the lines keep continuing in the ladder effect like in amp 4 is this 2nd and 3rd ect. order distortion repeating itself on the existing distortion or is it 4th, 5th and so on? Craig Link to comment Share on other sites More sharing options...
neo33 Posted July 14, 2004 Author Share Posted July 14, 2004 "Adcom GFA-535II Dynaco MkIV RCA P.A. Amp SA-101-B Transcendent Sound SE-OTL" None of the listed amps is SET. Link to comment Share on other sites More sharing options...
NOSValves Posted July 14, 2004 Share Posted July 14, 2004 Neo, That is because the screen would be completely white with SET Link to comment Share on other sites More sharing options...
neo33 Posted July 14, 2004 Author Share Posted July 14, 2004 Lots of forum background noises lately! Link to comment Share on other sites More sharing options...
NOSValves Posted July 14, 2004 Share Posted July 14, 2004 ---------------- On 7/14/2004 10:59:11 AM sfogg wrote: Mark, "Very good and interesting analyser photos." Thanks, when I get some time I'll try and do some more. This was obviously only testing at one frequency. It is certainly possible that the levels and distribution could be different elsewhere. It would also be interesting to see if/how they vary depending upon if the amp is seeing a nice simple 8ohm load vs. a more reactive load. And of course the output level will alter these as well. I will post the identities after Neo gets a chance to see them. Shawn ---------------- Well surely Neo has seen the photo's ! So let the cat out of the bag here. Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 "None of the listed amps is SET." Guess again. Every tube in the SE-OTL is a triode, and it is run single ended. So tell me how that isn't a SET amp? Besides, you were the one that said PP was all third order. Why can't you identify them based on this then? Shawn Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 Craig, "When the lines keep continuing in the ladder effect like in amp 4 is this 2nd and 3rd ect. order distortion repeating itself on the existing distortion or is it 4th, 5th and so on?" It is 4th fifth and so on. Take the frequency of the distortion and divide it by the fundamental. That will tell you the order of the distortion. Shawn Link to comment Share on other sites More sharing options...
neo33 Posted July 14, 2004 Author Share Posted July 14, 2004 "I will post the identities after Neo gets a chance to see them." You have alternate handles on the forums? And I thought Trey and Amy HAVE already taken care of that. . Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 Here is another amp.. this time at 0.1w. Second order harmonic is at 0.000434v. Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 Same amp 5 at 1w. Shawn Link to comment Share on other sites More sharing options...
sfogg Posted July 14, 2004 Share Posted July 14, 2004 Amp5 at 10w.. second order is at 0.00438v. In the 1w above second order was at 0.00104v. Link to comment Share on other sites More sharing options...
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