KLUDGE@AGCB1.LARC.NASA.GOV (09/25/90)
Class A amplifiers are not ecologically unsound. They do not make energy disappear, they merely transform it into heat. For example, a 120 watt Citation II amplifier pulls 750W idling (and also 750W when in operation). This means when it's idling, it dissipates 750W as heat, and it is just as efficient in this as an electric space heater. Granted it is not as good a way of heating your house as possible, but it isn't bad. So think of your amplifier as taking a load off of your furnace in the winter. --scott (formerly kludge@pyr.gatech.edu... ask chen@debesys about my amplifier)
gt4586c@prism.gatech.edu (WILLETT,THOMAS CARTER) (09/26/90)
In article <6584@uwm.edu>, KLUDGE@AGCB1.LARC.NASA.GOV writes: > Class A amplifiers are not ecologically unsound. They do not make energy > disappear, they merely transform it into heat. For example, a 120 watt > Citation II amplifier pulls 750W idling (and also 750W when in operation). > This means when it's idling, it dissipates 750W as heat, and it is just as > efficient in this as an electric space heater. Granted it is not as > good a way of heating your house as possible, but it isn't bad. So think > of your amplifier as taking a load off of your furnace in the winter. > --scott > (formerly kludge@pyr.gatech.edu... ask chen@debesys about my amplifier) Of course, there's the opposite problem in summer, when you have to run your air conditioner harder to keep your room comfortable. And then there are those nice fall and spring days when you can just open your windows to get your house to a nice temperature - with your Class A heater you've reduced the number of days in which this is possible and increased the number of days when you have to run your AC. Of course from the Second Law of Thermodynamics we knew we couldn't win anyway. Judging from a couple of Email responses I received from my original post, some of you just see red when the word environmental is spoken. Let me reassure all of you that I was not about to go before Congress and recommend that Class A amplifiers be banned as ecologically unsound. Whether you care about the environment or not, it seems that idling a Class A amp all day and night at 400+W is wasteful of money and equipment longevity. The answer I was looking for was finally posted recently - use a variac to reduce the voltage given to the amp when idling, and hence reduce the power dissipated. Now the question is: has anybody used their class A amp in conjunction with a variac? Does it have any unwanted audible side-effects? Also, a recent poster noted that he couldn't tell the difference when his amp had preheated for half-an-hour versus a whole day. Has anybody else performed a similar experiment and would like to comment? And, as always, let us all try to be polite in our discussions here. -- thomas willett Georgia Institute of Technology, Atlanta gt4586c@prism.gatech.edu "Violence is the last refuge of the incompetent." - Salvor Hardin (Foundation)
sjc@fmg.bt.co.uk (Steve Colwill) (09/28/90)
thomas willett (gt4586c@prism.gatech.edu) writes: >poster noted that he couldn't tell the difference when his amp had preheated >for half-an-hour versus a whole day. Has anybody else performed a similar >experiment and would like to comment? I run a system bi-amped with Musical Fidelity (I think they may be ``British Fidelity in the US) A372 Class-A amps. They get through a lot of heat! I have not noticed that that there is a difference in sound quality between minutes from power-on and hours thereafter. Steve Colwill BT Research UK
jank@ttidca.TTI.COM (Michael Jank) (10/01/90)
It would be simple to design a class A amp with a juice saving mode. Put a switch on the front: Standby/Listen. When in the standby position, the amp would just keep the current flowing through the heaters of the tubes and shut down everything else. The amp could be left running like this to extend tube life.
mikes@iuvax.cs.indiana.edu (Michael Squires) (10/02/90)
In article <6688@uwm.edu> jank@ttidca.TTI.COM (Michael Jank) writes: > >this to extend tube life. All audio tube amps that I'm aware of run class A until they reaach something like half-power, then go to AB mode (one side cut off, no currently flowing on the control grid) for the rest of the cycle. A Dyna MKIII runs in Class A if you don't ask for more than 30watts out of it; between 30 and 60 watts it runs in AB. The distortion products when the amp runs into AB is worse than when it's in A, but it's much better than the hard clipping of a 30 watt amp driven hard. I don't remember a class A amp being popular until the advent of solid-state gear, where class A was used to eliminate crossover distortion. Since vacuum tubes don't suffer from that problem it was never (infrequently?) used.
rogerk@uunet.uu.net (Roger Knopf 5502) (10/03/90)
In article <6688@uwm.edu> you write: > >It would be simple to design a class A amp with a juice saving mode. >Put a switch on the front: Standby/Listen. When in the standby position, >the amp would just keep the current flowing through the heaters of the >tubes and shut down everything else. The amp could be left running like >this to extend tube life. The Kinergetics goes into this mode when you power off - it runs a trickle charge to the electronics, or so I am told. -- Roger Knopf <standard disclaimer applies> SCO Consulting Services "If your controller will talk to a uunet!sco!rogerk or rogerk@sco.com cow pie, we can store data on your 408-425-7222 (voice) 408-458-4227 (fax) cow pie." --Scott Deardorff