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I’ve had my A3’s for almost 25 years, and in the beginning, I always left them plugged in with the bias set to the threshold of “crackling”. Unfortunately, I also experienced many insulation breakdowns. Then I started turning the bias down after each listening session, and I haven’t had a single breakdown since.
I like leaving the bias on as the electric field repels dust, and cutting the bias voltage roughly in half dramatically reduces the stress on the insulation. Since I have a monoblock amplifier situated behind each speaker, I simply give each bias pot a clockwise twist after switching the amps on, and a counter-clockwise twist when I turn them off.
With hindsight I suspect that the breakdowns were probably caused by the very high output resistance (300Meg) of the original bias modules. On humid summer days I had to turn the bias way up to get the same effective stator voltage, so a drop in humidity resulted in the stator voltage increasing beyond the voltage rating of the insulation. I only figured this out years later out when Roger sent me different bias modules that had 10x lower output resistance (30Meg), so humidity is no longer a factor. However, I still reduce the bias between listening sessions to minimize the voltage stress on the insulation.
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I also turn my whole system off after listening. My A1s are connected approx. 10-20 hours a week. Since I bought these 5 years ago I have noticed that the bias screw gets really hot as soon as I plug in the power cord. There are no anomalies of any kind but I would like to know if this is normal.
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Tom’s (tailspn) detailed explanation, thanks Tom, regarding possible degradation of materials constantly exposed to a high voltage electric field is exactly the reason why I turn off the bias supply of my panels when not in use.
Also, I unplug all of my equipment, including antenna wires, when there is the possibility of thunderstorm activity in the area. I have more than adequate HO insurance coverage but who needs the hassle of a claim submission when it’s so easy to be proactive to safeguard your equipment with such a simple step.
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Physical capacitors, as opposed to chemical (electrolytic capacitors), are simple devices consisting of parallel conductive surfaces separated by a dielectric insulation. In the case of SoundLab speakers, one “plate” is a bias voltage charged conductive surface consisting of a plastic film with a very high resistance conductive layer sputtered onto it. The other ‘Plate(s)” are conductive spaced wires on either side of the conductive film. Additionally, there are “window frames” that support and partition the conductive bias charged film, made with an insulating material. Air, and the window frame supports make up the speaker’s dielectric.
IMO, the high source resistance of the bias supply, added to the very high resistance of the surface sputtered film conductor of the plastic film, creates a RC time constant of several seconds. Dr. West estimates about 10 seconds to reach equilibrium. While I agree that charging a capacitor from a low impedance source can result in a very high inrush current, with subsequent stress on the capacitor components, this is not the case with electrostatic speakers with their very long charging time constants, and minimal charging current.
A factor that I do believe somewhat significant is the continued stress and ageing (if any) on the dielectric components subjected to a continuous high voltage field. While the air dielectric poses no degradation problem, the material used to frame and insulate the conductive film is of concern to me. For that reason alone, I unplug my five 845 speakers when not in use. My brother, on the other hand, having 10 SoundLab M1’s in a large home theater system, leaves his running all the time, with no apparent degradation.
As always, UMMV
Tom
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There can be a shortening of capacitor life with each on/off event. As with most things in life… lunches are certainly not free.
I did have the unfortunate experience of sending a full volume “digital noise” signal thru my system which resulted in needing to replace the brilliance controls.
I was a bit surprised that they are Dayton Audio Units. The bias controls are simple devices. These speakers are robustly built.
I sent my backplates in for a little custom work and updates. The one thing I has them do was replace the A/C plug with a high quality locking plug. And “better” speaker terminals.
Making sure you keep the speakers from crackling with the bias controls is really the only housekeeping you need to do.
I need to keep mine set fairly low….
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I have my backplates connected to an ifi power strip that I turn on/off at the beginning and end of each session.
I go back and forth on this because I am neurotic. I even purchased a third backplate as back-up in the event of a failure.
Does anyone think the bias circuit is more susceptible to damage from the influx of power at turn on? I don’t know much about how this stuff works but it’s always the argument made for keeping audio equipment on.
This November will be 5 years with my M645s. Haven’t had many problems, knock on wood.
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It is said that lightening never strikes the same place twice. That was proven incorrect at our home. We had a 70’ Sycamore tree that was nailed by lightening. The next year it was dying, so we had a tree trimmer out, who tied a ribbon around the tree, marking it for removal. Between then and the removal date (a couple days later), the tree was struck again. The marking ribbon around the tree evaporated. Plus, it wasn’t like the Sycamore was a lone tall tree. Surrounding it, were dozens of equally tall trees.
The initial lightning strike to the Sycamore, did little damage. Other than a PC’s Ethernet card, nothing else was harmed.
With the 2nd. strike to it, we weren’t so lucky! The strike took out many items, including blowing an irrigation controller off of the garage wall. Not the least of those items, was a custom $10K DAC and a $5K pre-pro. Our insurance paid it all (of course, minus our deductible). The payment process was fairly painless and the angst was minimal. Our homeowners insurance didn’t have a rider for our expensive audio equipment, because none was needed. I’ve found that to be the case here in the U.S. If one has a decent homeowners policy that pays for the home’s value, plus the home’s possessions, all audio equipment — including custom and expensive audio components — are covered as long as replacement cost doesn’t exceed the possession maximum amount.
Thus, I’m not too terribly concerned by the frequent thunder storms we have here in the Midwest. And for me and our experiences, leaving equipment plugged-in (on or off), isn’t a worry regarding power surges of the severe lightening kind.
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When I was a child, lighting struck my home and basically destroyed everything plugged in. I didn’t know any better and was confused as to why my mom thought it was a wonderful thing.
Unless you have a very detailed insurance policy, if you were to have that happen today.. in my case, with custom/rare non replaceable components I don’t take that risk and unplug my system when not in use.
Warm up and sound quality do not seem to be an issue and in a few hours, everything is stable and sounds just fine.
I’ve also had a preamp power supply blow up while listening to music. Thankfully I was there when it happened so there is something to be said about leaving equipment powered and not there for these situations…
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Dr West told me that our panels are basically big capacitors, which probably explains why he’s not concerned about leaving them on. The debate about whether it’s best to turn off electronics has gone on for a long time. I prefer shutting down my AV rig when I’m done.
To make it easy to turn everything on and off, I use a smart power strip that turns on all switched plugs when it senses current flow to one component – in my case, the TV monitor. So anyone who can use a Roku stick remote can watch TV. Listening to music is more complicated. But turning everything on and off happens by touching the Roku power button…
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Like some of the writers above, I’ve never switched off the HV sources, even when going on vacation. Likewise, I also leave my tubed preamp and SS power amp on also, so take that for what it’s worth. I might mention that the first pair of A1s I owned (I think it may have been the first production pair out of the factory) was left on for about 30 years solid. After replacing the panels with the PX upgrades in 2007 or so, they’ve been left on again since that time. A couple of years ago, I experienced a power surge that knocked out both HV sources. Dr. West provided me with a new set, but with voltage regulation, and I believe that they actually sound a bit better than the old ones. Just my 2 cents.
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Knowing Dr. West and his attention to detail, I would assume that he would install a switch or an automatic on/off (based on a signal), if SoundLab’s longevity were effected by leaving them fully powered 100% of the time as he instructs.
Moreover, I’m sure that Dr. West’s understands the capabilities and durabilities of his speakers and that he would not want their premature failure any more than we do.
So, with that said, I’ve been a SoundLab owner for over 20-years and have left them powered the entire time without detrimental effects. However even still, I recognize that I suffer from audiophile nervosa and I must admit that leaving my speakers powered, has posed a tad bit of a concern from time to time, especially in the early years of my ownership.
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When I bought my Sound Lab speakers about 2 years ago, I inquired about a power switch on the speakers, and Dr West said that there was no power switch and I could just leave them on and plugged in unless I’m out of town for more than a few days.
For the first year, I left them plugged in permanently. For the past year, I’ve been unplugging them after each listening session.
Presently, I’m sticking with unpluggging them after each use, and would think that would add to the longevity of the speakers. I’m curious how many others are doing the same.
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