Strabo Posted March 4, 2004 Share Posted March 4, 2004 What are, or where can I find, the advantages/disadvantages to having high powered tube amps? Specifically, what would be the difference in sound between two KT-88 amps where they each use two output tubes per channel but one amp is rated at 60wpc, and the other 100wpc? How do the amps differ in design to produce such a different amount of output? Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 Thank you mdeneen. That was exactly what I was looking for. Man, 90 years of tube amps has yielded lots of variety. I've got some catching up to do. Quote Link to comment Share on other sites More sharing options...
Klipsch RF7 Posted March 4, 2004 Share Posted March 4, 2004 It depends also on what you listen to. If you listen to alot of rock and blast your speakers loud, then you want good mono block push pull amps, if you listen to mainly classical and Jazz and more intimate music at lower volumes the SET will be more appropriate and since you have cornwalls it will sound great and still have plenty of power for higher volumes. Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 I'm not looking to rock the neighborhood, rather trying to learn what amps are available, and what they are doing to differentiate themselves. I am trying to look at all options to learn what the differences are in designs rather than read a company's sales pitch. It would be nice to have the knowledge to translate the sales pitch into technical terms. Which mdeneen's reply really helped with. My shopping involves looking at everything I can find. Narrowing it down by deciding how much I want to spend. Narrowing the list down again based on what I can listen to, and reviews by ears I trust. Finally bang for the buck out of the remaining list. I'm still at the first stage, and for example, I was reading through the info on some fairly pricy amps and was wondering what they are doing differenly to claim so much output. Output that I wouldn't necessarily need anyway but still want to know. One of their amps, push pull kt-88, claims 105wpc out of two output tubes per channel. They really don't explain how they do this. From the explination above I can summize that they are running them in class AB or B but probably not in class A. I still don't know what that means to me, but thanks to the knowledge here I'm hoping to find out. Keep it coming guys, because the more I learn the more questions I'll probably have. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 4, 2004 Share Posted March 4, 2004 Mark did a fine job of explaining everything to you ! I think he left one part that plays a huge roll in the output of a amplifier the transformer ! It also dictates how much clean output can be achieved. Craig Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 ---------------- On 3/4/2004 2:33:40 PM NOSValves wrote: Mark did a fine job of explaining everything to you ! I think he left one part that plays a huge roll in the output of a amplifier the transformer ! It also dictates how much clean output can be achieved. Craig ---------------- Oh great. How does one with no knowledge about this determine that? What are the most common types of transformers used? Which is the better? I've seen some refer to buying amps by the pound. Should a 100 watt amp weigh 100lbs, or is 60lbs enough? 40? Quote Link to comment Share on other sites More sharing options...
mike stehr Posted March 4, 2004 Share Posted March 4, 2004 "I've seen some refer to buying amps by the pound. Should a 100 watt amp weigh 100lbs, or is 60lbs enough? 40?" I don't really think that matters. For instance, my stereo SET amp weighs in at a good forty pounds. My stereo PP 6BQ5 amp weighs in at about 10, 11 pounds. Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 McIntosh amps are sort of Class B. Does that make them bad? No, because they did all manner of electronic compensation to make Class B sound like AB. A damn good job of it too. So there can be a difference in sound between class A, AB, and B but what you may get from a premium manufacturer is class B with class AB sound. Or AB with A sound, in which case, the fact that the amp is class AB doesn't really matter because to the ear it's a class A. Could someone explain to me the difference in sound that these different classes may have? Remember, we are talking generalizations here, not specific amps. Point taken on the transformer. It's a matter of the design. Quote Link to comment Share on other sites More sharing options...
3dzapper Posted March 4, 2004 Share Posted March 4, 2004 Oh my God, am I actually going to do this????? Mark, Mark, Mark, How do I tell you this? you of all people? An audio tube is on all the time there is conduction from the cathode to the plate. Unlike SS devices which actually turn on and off, a vacuum tube is on for the duration no matter the class of operation. The differences in operation are: Class A the entire signal is carried by a single or parrallel wired tube(s) the current to the plate increases as the signal drives the grid more positive and decreases as the signal is driven more negative. The net average is whatever bias current is set at. The output power is limited to the plate dissapation of that one tube. In classAB operation with 2 or more tubes in Push/Pull operation the input signals sent to the 2 sets of tubes are "split" into complementary waveforms. one set of tubes recieves the waveform as a positive voltage increasing plate dissapation. the complementary pair recieves the same waveform as a negative wave decreasing current flow. These signals as amplified are fed to the output tranny. As long as the negative going signal voltage does not impede the plate current to the point of cutting off the bottom of the waveform all the tubes in a complementary PP amp are operating in class A mode. The total net current is the combined bias current of the set of tubes. When the input signal increases to the point that the negative portion of the signal drives the grid so low that a portion of it is distorted and at the same time the positive going signal increases to complete the waveform through the output tranny more of the power dissapation ability of each given tube is used on the positive swing adding together and causing a larger voltage swing across the output tranny. The net current remains the originally set bias current. Since a tranny does not react to current only(some of it is dissapated as heat due to the internal resistance) but rather to changes in voltage, the availiable power across the output tranny is additive and the voltage swing is opposite, more energy can be delivered to the speaker. In all cases the current remains the same. Determined by the designer, the average amount of current through the tubes remains constant and the heat and energy disipated by the plate remains equal or nearly so. I still can't believe that! i took issue with the guy who will determine my sonic bliss or disgust in the near future. But, if I were an a$$ kisser I would have gotten along a lot further in life. Rick Quote Link to comment Share on other sites More sharing options...
sheltie dave Posted March 4, 2004 Share Posted March 4, 2004 Rick, Mark takes corrections in stride. He told me he has you lined up for thegooseberry, however! Strabo, a good colollary I use is to come close to duplicating what you already are satisfied with on the solid state side. If you have a fifty watt SS and listen to it below 50% almost all the time, then a fourty to fifty watt tube amp should suffice. Your listening patterns and behaviours aren't likely to change too much! Money is the first big divider. Less money generally = vintage, and you know the beasts that stalk this boneyard. More money can drive you toward Quicks and a few other solid tube designs. The key after money, I think, is deciding what type of output sound you want. Bass happy would equate with EL34 or KT88, mid = 6BQ5, clarity = Williamson, involved and open = 2A3, 300B, 45. Read through some of the postings of newbies who are rolling into their second tube amp purchases. It is a fun field to enter Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 4, 2004 Share Posted March 4, 2004 All I can say is Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 This has been a very helpful thread. One that I will probably have to read a few time to digest. My thanks to all! Quote Link to comment Share on other sites More sharing options...
3dzapper Posted March 4, 2004 Share Posted March 4, 2004 Well, see if I had agreed with you 100% I would never have learned about the Macs using true class B in their designs. I didn't think that anyone would use pure B because of the inherent problems you described. Elsewhere we said the same thing with different words. My use of the distortion of the lower wave is your shut off voltage. My point rather was that (I won't say all again) most amps using complementary circuitry run a good portion of their output in class A except when power demands exceed the bias voltage. Now my next question: the effiency you remarked about, are they talking about the same tube designation or differences in those normally used in pure A or pure B? Craig quick explain class D operation. Rick Edit: Oh yea, this is Strabo's thread. Another reason that amps containing multiple output tubes is thermonic noise. The more high heat high power output tubes in the circuit the more likely that there would be noise at low power where high effeciency speakers operate. Quote Link to comment Share on other sites More sharing options...
D-MAN Posted March 4, 2004 Share Posted March 4, 2004 ---------------- On 3/4/2004 11:02:00 AM mdeneen wrote: Keep in mind, there is very little discernable sound pressure level difference between a 50W amp and a 100W amp. ---------------- Absolutely correct. Since wattage ratings are logorythmic in order for an amp to be ONLY TWICE as loud as 50 watts takes +3db which would be in the vicinity of 10x's or 500 watts or so. Technically the 100 watt amp would be only 20% louder than the 50 watter at full blast. So what you could possibly gain by this is that the IM distortion rating of let's say 3% at 50 watts RMS compared to 3% at 100 watts RMS on the other amp? The 100 watter would expectedly have somewhat less IM distortion at half volume (or 10 watts) than the 50 watter at 10 watts volume which is above its half volume level (5 watts), all other things being equal. DM Quote Link to comment Share on other sites More sharing options...
ben. Posted March 4, 2004 Share Posted March 4, 2004 Actually, watts are a linear measurement, while SPL is generally expressed logarthymically. Right? Quote Link to comment Share on other sites More sharing options...
NOSValves Posted March 4, 2004 Share Posted March 4, 2004 Craig quick explain class D operation. Why should I explain anything ? I don't profess to be a audio engineer never have and never will ! Heck I don;t even want to be one ! Craig Quote Link to comment Share on other sites More sharing options...
3dzapper Posted March 4, 2004 Share Posted March 4, 2004 Can't say as I blame you. You would measure everything and your work wouldn't sound as good!! There is nothing wrong with engineering mods the way you did. Practical experiments are for the techs. Design is for the eng. I am not an engineer. Rick Edit: Mark I hope you don't get upset with me picking your brain from time to time. It's been almost thirty years since I graduated from electronics school and, you know more than I've forgotten. Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 ---------------- On 3/4/2004 8:08:48 PM 3dzapper wrote: Edit: Oh yea, this is Strabo's thread. ---------------- Don't worry, this is great stuff. Keep it going even if I don't understand it yet. How else can we learn? Quote Link to comment Share on other sites More sharing options...
Griffinator Posted March 4, 2004 Share Posted March 4, 2004 ---------------- On 3/4/2004 8:10:22 PM D-MAN wrote: Absolutely correct. Since wattage ratings are logorythmic in order for an amp to be ONLY TWICE as loud as 50 watts takes +3db which would be in the vicinity of 10x's or 500 watts or so. Technically the 100 watt amp would be only 20% louder than the 50 watter at full blast. So what you could possibly gain by this is that the IM distortion rating of let's say 3% at 50 watts RMS compared to 3% at 100 watts RMS on the other amp? The 100 watter would expectedly have somewhat less IM distortion at half volume (or 10 watts) than the 50 watter at 10 watts volume which is above its half volume level (5 watts), all other things being equal. DM ---------------- Help me out here, because this is diametrically opposed to everything I understand about SPL. I was led to believe that, in order to increase volume by +3dB, power had to be doubled. What you're saying is that a +3dB volume increase must be affected by a 10x increase in power. I'm confused... Quote Link to comment Share on other sites More sharing options...
Strabo Posted March 4, 2004 Author Share Posted March 4, 2004 ---------------- On 3/4/2004 10:22:04 PM Griffinator wrote: Help me out here, because this is diametrically opposed to everything I understand about SPL. I was led to believe that, in order to increase volume by +3dB, power had to be doubled . What you're saying is that a +3dB volume increase must be affected by a 10x increase in power. I'm confused... ---------------- "twice as loud"=10x increase. The difference is the definition. Twice as loud is usually 10dbs, still 2x power for +3dbs. Quote Link to comment Share on other sites More sharing options...
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