Voltage regulation for Joule amps

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
>

I read the review when this avs2000 came out. I have never heard a tiny peep out of mine.(even if my head were on top of it) But it did emit the odor;at first.

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
>

Sean, I know that I am not technically knowledgeable to go around making changes in this unit, if what you are saying is that a "regulated power supply" would be a replacement for the variac. esp. since the variac is connected to the main amplifier by two different power cords with different terminations (one male and one female, IIRC). That is the reason I was looking for something like the the Monster AVS 2000 of the Exactpower since I think what I need is something that would supply a constant voltage. The fluctuation at the amp (downstream of the variac) is about+1, -5 volts. I just double checked the manual and the indicated range is about 83-87 volts. It generally seems to sag more than go up, both in the magnitude of the change and the frequency of the change (i.e., it most frequently reads below the initial nominal setting). This causes the bias on the output tubes (6C33C-Bs) to drop from 27/28 to 23/24, and compromises the sound. The variac is near a warm air outlet and the amp itself is on an outside wall. Of course, it runs quite hot and I am sure alters the ambient temp around itself by several degrees. The variac is about 2-3' away and slightly lower down, but as I said, close to a warm air duct. Could these temperature fluctuations be having an effect on the voltage the variac delivers? As you can see, my knowledge of things electrical is quite limited. TIA. I will, of course, contact Judd at Joule tomorrow.

"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
>