sgg5e@krebs.acc.Virginia.EDU (Stephen G. Graber) (05/03/91)
I'm considering purchasing some isolation transformers for my hi-fi gear and am looking for some feedback regarding what sorts of sonic benefits might be had, as well as what reasonable prices and qualities might be. In the summer in Charlottesville we often have near "brown-out" power conditions with line voltages as low as 105 (so I'm told). My power amp is an Aragon 4004 and I'm told it operates in class B when the line voltage drops- hence an isolation tranformer ought to keep it in class A more of the time, right? So far I've seen 1 and 5 KVA units. Both are made by TOPAZ, the 1 KVA unit is model 95210-52. I can have them both for $150. What do you think? Any and all replies appreciated. Thanks in advance.
miker@polari.UUCP (Mike Ranta) (05/06/91)
In article <11715@uwm.edu> sgg5e@krebs.acc.Virginia.EDU (Stephen G. Graber) writes: >I'm considering purchasing some isolation transformers for my >hi-fi gear and am looking for some feedback regarding what sorts >of sonic benefits might be had, as well as what reasonable prices >and qualities might be. In the summer in Charlottesville we often >have near "brown-out" power conditions with line voltages as low >as 105 (so I'm told). In general, I don't believe you'll gain _any_ sonic benefit from just an isolation transformer. The power transformer(s) in your amp already isolate it from the line, and another stage of isolation is only going to degrade the regulation of the power supply in your amp (there will be a voltage drop across the isolation transformer directly proportional to the load on it). If anything, this will make things sound worse! TrippLite makes several "line stabilizers/conditioners" including a few in 19" rack format intended for audio use. They range in price from a few hundred dollars on up. These units will put out 120 volts +/- 5% with input voltages ranging anywhere from 84 volts to 140 volts. I believe they operate by electronically changing taps on an internal transformer as the input voltage changes. I would assume there has to be some noise associated with these "steps". In other words, as your line voltage fluctuates, and as your amp attempts to draw more power (say during a heavy bass note at high volume) the TrippLite unit is going to be hunting around trying to find the right tap to keep the output voltage steady. I would think this would have more of a negative effect on the sonics of the amp then any power problems you might have in the first place. > >My power amp is an Aragon 4004 and I'm told it operates in class B >when the line voltage drops- hence an isolation tranformer ought >to keep it in class A more of the time, right? I simply don't believe that a minor line voltage drop will change the bias point in your amp. This doesn't make any sense. Typically the driver circuitry in a high quality class A amp is regulated. This means that line voltage fluctuations will not effect the operating point of the output circuitry. Even with 105 volts input, the bias point should not change much. There is a big difference between class B and true class A. > >So far I've seen 1 and 5 KVA units. Both are made by TOPAZ, the >1 KVA unit is model 95210-52. I can have them both for $150. >What do you think? > Overall, as you've probably guessed, I can't recommend _any_ transformer based power devices for audio systems. I can recommend a simple RFI/EMI/ Surge filter (which TrippLite also makes). This will help prevent damage caused by surges (rare) and help keep junk on the power line from ending up in the audio signal path (more common, like light dimmer noise). A good filter shouldn't set you back more than $50.
maxc1158@ucselx.sdsu.edu (Greg Penetrante) (05/06/91)
In article <11715@uwm.edu> sgg5e@krebs.acc.Virginia.EDU (Stephen G. Graber) writes: >I'm considering purchasing some isolation transformers for my >hi-fi gear and am looking for some feedback regarding what sorts >of sonic benefits might be had, as well as what reasonable prices >and qualities might be. In the summer in Charlottesville we often >have near "brown-out" power conditions with line voltages as low >as 105 (so I'm told). > Perhaps you can try the transformers from TRIPPLITE: LCR - 2400 LCR - 1800 The first one can optimize up to 2400 watts of power, with complete brown-out protection, filtration (up to 120db) and surge protection. I use one of them in my ssystem and I tell you they are EXCELLENT! The LCR1800 does up to 1800 watts. -greg