Voltage regulation for Joule amps

What am i missing here? Why are you using a variac? Why are you setting the voltage to 89 volts? Is this standard procedure with Joule products?

Out of curiosity, what is your standard line voltage? When it fluctuates, how far up and down does it vary? If there is a big swing in voltage, you may need to contact your power provider and have them assess the situation.

As a side note, i just went through this at my shop last summer. The voltage used to hover right around 118 but was sagging down to 104 at times. A new business just opened up and they had a machine that would pull 400+ amps at turn on. Needless to say, every time that they turned it on, the voltage would bottom out. After calling the power company and providing them with detailed reports, they replaced the pole transformer. All has been good since then. Only problem is that the voltage is now up around 125 volts all the time, which is a bit on the high side.

Same thing was happening here at my home a few weeks ago. When watching a movie on my HT system, my Pre-Pro started glitching and the lights on the amps were flickering during loud passages. On the next loud passage, the lights in another room started to blink. This told me that there was a problem with either the AC mains in my house or the power provider was having problems.

Not wanting to expose all of my equipment to potential damage, I ran downstairs and shut down the box feeding the AV systems. I then went to see if the neighbor was having problems or if it was just in my house. While walking over to the neighbors house, i saw that the AC pole transformer feeding my house was on fire. Needless to say, i ran back in and called my power provider and the fire department.

Believe it or not, they came out and repaired the problem in a matter of less than 45 minutes. Since then, my AC has been much more consistent and noticeably quieter.

Sorry to go so far off topic, but given my past experiences, you might be in a similar situation. You might want to monitor your AC and keep a log. The more documented info that you can provide for your power company, the more likely you are to get results.

In case you didn't know, the Monster AVS2000 produces audible clicking sounds during normal operation. I'm not familiar with the ExactPower unit. Sean
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Brian: Thanks for the clarification.

"Swampy": There's an easy way to get around this. It is called a regulated power supply and would work with ANY voltage that was above appr 95 volts or so. This approach may be more costly than a high current variac with the need to disippate more heat, but it would have surely been a FAR less clumsy and more convenient way to do things. That is, as far as the end user is concerned.

As far as the AVS2000 goes, the clicking is audible, but not real loud. The more that the voltage or current draw varies, the more clicking that you would hear. Sean
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I know that they commented about this in Stereophile during the review. I've seen these units many times since the review and i've always heard the "clicking" that they spoke of. I was also just looking at these units in a local dealer December 17th. The clicking was easily audible several feet away. Given that all of my experiences match those of the comments made in Stereophile, i assumed that all of these units made that noise. Maybe some are quieter than others, i don't know. Sean
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"I will, of course, contact Judd at Joule tomorrow."

Boy, i can already hear that conversation.... : )

The bias on most tube circuits will change due to both dynamic and thermal variations. As such, it is best to set them to where they should normally be and then re-adjust after the unit has thermally stabilized during NORMAL use. Better designs with tubes that are in better condition will remain within their nominal operating range once that is done. If the bias is all over the place during a normal listening session, the tubes aren't in very good shape, the circuit feeding them is unstable ( thermally or electrically ) and / or the voltage into the unit itself is far from regulated. Even if one has "good" tubes, a stable circuit and a regulated power supply, you'll still find that tube bias "wanders" just a bit. Tubes simply are NOT precision operating devices.

Other than that, i was not suggesting that you attempt to build a regulated power supply for this unit. To do so would be quite costly and require extensive electrical knowledge to do it right. This is probably most of the reason why we don't see precision regulation circuitry in most power supplies.

As far as temperature goes, i would be more concerned with the tubes & circuitry than the variac itself. So long as the variac isn't getting too warm, either through self-dissipation of energy OR your heating system blowing directly on it, don't worry about that.

I was looking for voltage fluctuations on the AC line itself, not after the variac. Due to the "step down" action of the variac, those variations will be reduced in significance, so we really need to see what is going on with the incoming power. Try measuring the AC voltage from the outlet feeding the variac with the system under load ( get some volume on it ) and then in another outlet or two around the house on other circuits. This will tell us if the wiring feeding your Joule is adequate and / or if the AC voltage is fluctuating from the provider. Sean
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