Power Conditioning

Rumored to be quite important for toobs?

AC is AC ... is not ...

The "standard" allows for some major fluctuations for what comes into the house from the street. I've got a whole house surge protector that takes care of the big lumps, and plugging a Kill-A-Watt tester into an outlet every now and then shows that the power here ain't all that bad, but ...

Tubes are another story I guess. Solid state can take a lot more abuse without going under. I understand voltage changes that might be considered normal can shorten tube life considerably, and I'm sure we've all noticed that bottles aren't all the inexpensive. So ...

I just ordered an APC Line-R 1200VA Automatic Voltage Regulator.



It's not a backup unit - I've got a couple of those collecting dust as the batteries don't last and cost almost as much as a new unit. It's got a relay that taps the transformer based on what's coming in and either bumps it up, tones it down, or passes it thru untouched. Real compact so I can put it in the cabinet. It has three outlets, which should be perfect for the ST-120 I got coming, a tube phono stage, and my Maverick D1+ DAC.

And ya ... I could go a lot better for a lot more, but I think this is better than nothing ... these get real good reviews for other stuff too, like computers and LCD tvs that tend to be a bit more sensitive to dirty AC.

Only complaint I've seen on the APC is the relay is a bit loud, but ... I imagine it's quieter than exploding tubes or me crying about them when they die. The APC was under $50, so I don't expect perfection ... just protection ...

Thoughts?

you're correct. tube systems don't like varying voltages. I use a variac. you can plug a good 6 outlet power bar into it so you can run up to 6 items through it. I have one system that has new and vintage items. I use 2 variacs with that system. one set at 120 volts and the other at 117 volts. they are dead quiet. if you're into restoring vintage gear a variac is a must have anyway.

Which variac units are you using?

check out ebay #221195867176. own 4 of them and have never had any issues with any of them. made in china but us models are a lot more.

I've got a Chinese variac on the bench that works nice for bringing up old stuff slow, but I never considered it a precision instrument and hadn't thought of it as a "power conditioner" ...

Mine is the common garden variety that has a manual adjustment knob at the top. Wouldn't the power out from the variac change as the line voltage fluctuates? You're basically setting the knob to whatever's available at the time you set the knob, so seems like you'd need to be checking it constantly.

I like the idea of "automatic" ...

wedg714 wrote:check out ebay #221195867176. own 4 of them and have never had any issues with any of them. made in china but us models are a lot more.

Yup ... that's the one I got. The baby blue adds a bit of "ambiance" to the bench, don't it?

Hey, I can derail my own thread if I want to!

How about thermisters?



I've gotten into the habit of adding one or two at the line in whenever I rebuild old radio transmitters and such.

I'd think a CL-80 on each side of the line in on the ST-120 would help protect the amp by bringing it up a bit slower ...

I have 123 volts at all of my outlets. the variac is used to lower that voltage. I have whole house surge protection so a spike is not a problem. even when my central system kicks on, I only get about a half volt bump. I live in a very rural area without any industrial users nearby so I get a very constant voltage. I agree that a variacs voltages can vary according to the voltage that is sent to it but it works in my situation. I've only had one tube blow on me and I have never lost an output tube. if I lived where the voltage coming in varied more than a couple of volts I would definitely own a power conditioner.

sKiZo wrote:Hey, I can derail my own thread if I want to!

How about thermisters?



I've gotten into the habit of adding one or two at the line in whenever I rebuild old radio transmitters and such.

I'd think a CL-80 on each side of the line in on the ST-120 would help protect the amp by bringing it up a bit slower ...

I use a CL-90 on a ST-35 build. I have high(ish) voltage at my place - usually around 122-123V. The thermistor knocks down the voltage to about 118, bringing voltage measurements more in line with original specs. Not using the thermistor, all readings were a little hot. And of course, you get a soft start-up.

OK ... I'll take that as a thumbs up on the "current inrush limiter" (maybe less confusing than thermister). Lotta less BANG for a very small investment I figure. I had the Kill-A-Watt plugged in all day today and it showed an average of 122.7, so the CL-90 might just be the way to go here too.

Does yours get hot? CL-90 is good for two amps - just realized I haven't a clue how many amps the ST-120 can pull under load ... anybody? Seems to be the missing spec ...

PS ... Bob ... if you're around, this picture is to confirm that the shipment has been delivered.



One question though. It's in the house, but it's just sitting there lookin at me stoopid like. I get the feeling there's something I have to do first before it'll work ... Hmmmmmm ...

sKiZo wrote:Solid state can take a lot more abuse without going under.

I must disagree. Tubes can handle more electrical abuse than SS gear can by a large margin. Yes, physically tubes are more fragile - but there's a reason that (as an example) tubes were used as the finals in a lot of commercial radio transmitters. Those big tall AM transmitting towers get hit by lightning all the time - and instead of blowing up they're tubes would just take it and keep working.

Tubes are used in circuits where the voltage and/or current exceed spec as a matter of routine. Does it shorten a tube's life? Yes, to a degree - but the same circumstance will END a transistor's life in many cases.

Tubes are essentially immune to static electricity issues - certainly that's not the case with many SS devices (MOSFETs anyone?).

Tubes are resistant to EMP (electro-magnetic pulse) such as would occur if a nuclear device was detonated - SS gear gets destroyed unless very extensive/expensive precautions are in place to prevent it from happening.

I could go on... I'm not sure where that idea came from, but I assure you that other than the fragility of the glass envelope, tubes are much more abuse resistant than SS gear, all else being equal.

wedg714 wrote:you're correct. tube systems don't like varying voltages. I use a variac. you can plug a good 6 outlet power bar into it so you can run up to 6 items through it. I have one system that has new and vintage items. I use 2 variacs with that system. one set at 120 volts and the other at 117 volts. they are dead quiet. if you're into restoring vintage gear a variac is a must have anyway.

Please see my previous post. Tubes tolerate varying voltages at least as well as SS does - and that's being VERY conservative.

Unless the AC line voltages differ significantly from the "spec" primary voltage a variac is not needed for healthy tube gear. When you see a "spec" for voltage, etc., you have to learn to ask "what is the tolerance". No power grid EVER operated at exactly 115 volts, 117 volts, 120 volts, or whatever the "specified" voltage was. So a mark of well designed gear was its ability to function properly over a wide range of AC line voltages. There's no need to use a variac unless you have quite large deviations from normal voltages that take you outside the design tolerances...

wedg714 wrote:I have 123 volts at all of my outlets. the variac is used to lower that voltage. I have whole house surge protection so a spike is not a problem. even when my central system kicks on, I only get about a half volt bump. I live in a very rural area without any industrial users nearby so I get a very constant voltage. I agree that a variacs voltages can vary according to the voltage that is sent to it but it works in my situation. I've only had one tube blow on me and I have never lost an output tube. if I lived where the voltage coming in varied more than a couple of volts I would definitely own a power conditioner.

It's good to have spike/surge protection, power line spikes can go into the 1000s of volts range. With so much electronic gear around the typical house nowadays the whole-house protection is a good idea. Sure beats replacing expensive SS circuitry in the dishwasher, stove, refrigerator, etc.

But I do not see any reason why you need a variac with 123 volt mains. That's well within the tolerance of all but the most poorly designed and executed audio gear, let alone well designed tube gear.

BTW, just FYI - "Variac" was a General Radio trademark for their specific brand of adjustable output autoformer. I'm not sure who owns the trademark now.

Yet you can run a solid state amp for 30 years without any issues, and be constantly replacing tubes ... granted, in theory tube rigs should be more durable, but ... real life disagrees. I ran a lot of big rig tube gear in my Navy days and yes, it could handle larger loads, but we always made sure we had lots of spares handy as they had a tendency to go blooie on a regular basis. I suppose a lot would have to do with how you treat tubes too - I'll freely admit I spent a lot of time in shall we say somewhat impaired condition twiddling stacks of 2kw transmitters just to see if I could get them to go boom ...

Even more important ... replacing a transistor isn't anywhere near as expensive as replacing a tube can be, so a bit of extra insurance is a good thing?

Back to power conditioning. I did a bit of digging, and really, only thing I can find is that the ST-120 has a 5a slow blow fuse. Basing max load on that is iffy, but, hey, we work with what we got. On that basis, I figure a 5A inrush limiter should do the job gracefully and 20ohm should allow plenty of time to ramp up power before it goes open.

Theoretically of course. Somebody correct me if I'm wrong ...

Digikey 570-1007-ND (can't post links yet, but that should get you there if yall want to take a peek.)

sKiZo wrote:Yet you can run a solid state amp for 30 years without any issues, and be constantly replacing tubes ... granted, in theory tube rigs should be more durable, but ... real life disagrees.

Yes sometimes tubes need to be replaced - but tubes are easy to replace and can often be done without professional help. Not too many people can go in to their SS gear and replace a power transistor.

As well quite a few tubes last 30 years. A lot of SS parts don't. But yes, SS devices do generally outlive tubes- tubes are consumables.

In any case you aren't describing abuse here, you are talking about variances in lifespan. The fact that tubes eventually wear out is not an indicator of inability to take abuse.

Jim McShane wrote:Yes sometimes tubes need to be replaced - but tubes are easy to replace and can often be done without professional help. Not too many people can go in to their SS gear and replace a power transistor.

OK then ... in a roundabout way, I guess that was the major point of this discussion for me ... protecting what (at least in my case and to me) a rather large investment in bottles. I got around $300 into them right now. Compare that to the $35 I spent recently to replace the finals on an old Sansui SS. Also, based on what I read to be fairly average results, I can expect to have to replace tubes on a regular cycle of maybe three years based on my listening habits. Yeowch, but I'm hoping it's all worth it.

All in all, seems worth a bit of extra protection ...

Oh. And while we're talking inrush, let's not forget those transformers. Rumor has it those aren't cheap either ...

sKiZo wrote:

Jim McShane wrote:Yes sometimes tubes need to be replaced - but tubes are easy to replace and can often be done without professional help. Not too many people can go in to their SS gear and replace a power transistor.

OK then ... in a roundabout way, I guess that was the major point of this discussion for me ... protecting what (at least in my case and to me) a rather large investment in bottles. I got around $300 into them right now. Compare that to the $35 I spent recently to replace the finals on an old Sansui SS. Also, based on what I read to be fairly average results, I can expect to have to replace tubes on a regular cycle of maybe three years based on my listening habits. Yeowch, but I'm hoping it's all worth it.

All in all, seems worth a bit of extra protection ...

Oh. And while we're talking inrush, let's not forget those transformers. Rumor has it those aren't cheap either ...

Neither are the monster filter caps used in the power supplies of SS gear - and their trafos are subjected to the same stress as tube gear trafos.

You might pay a few bucks more to buy new output tubes - but there is no labor involved since you can do it yourself. Compare that to the labor involved with replacing the SS outputs - if you can even get them anymore. How much does it cost to have the output transistors or IC chip replaced in an SS amp, parts and labor?

BTW, there are FAR more - by a very large number - of obsolete and difficult/impossible to find SS devices than there are power tubes, that's a real problem in a lot of cases.

SS devices have a place in the audio field, no question about it. I use them in my designs and rework parts sets. And they do have some advantages over tubes that are important - small size, no heater current requirements, and so on. But ability to take abuse? Definitely the edge goes to tubes.

Speaking of tubes ... just got an email that PartsConnexion is knocking 20% off all new tubes ... sounds like a deal, but I'm not sure how well their regular prices compare to others ... might be worth checking it out for anyone in the market.

Just sayin' ...

OK then ... back to the original post ... I got the APC LE1200 in today and plugged it in. The Kill-a-Watt shows an average of 122.5 going into the "regulator" ... and 122.5 going out. Just got off the line with APC and they pointed out in the small print that it won't trigger unless it's more than 6% out of tolerance, which makes it kinda sorta useless in this application.

Here's a fun test ... the box has presets for 110v-120v-127v to match your region. I tried all three and at 127v, nothing ... as expected because 122.5v (what I'm getting out of the wall) is within the 6% tolerance. Here's where it gets interesting - on the 110v setting, 122.5v IS outside tolerance, so yes, it does kick in, indicates a voltage overload condition, and (drumroll please) cuts the power to 108v. Huh.

I did ask if there were any internal adjustments I could make to get the tolerance more to my liking or move the center of the ranges, and "Bob" from New Dehli couldn't come up with anything.

Anyway. Enough of that. I'll use the LE1200 on my video system and be done with that. Big screens especially seem to benefit from minimal regulation ... which is what this box does. Minimal ... yeah ... minimal.

So, on to varactors ... I've got one on the bench so I'll play with that a bit. Set it to 117v as per what I'm hereing hear ... er hearing here ... and plug the Kill-A-Watt into that to see what comes out the other end. Can a Kill-A-Watt average line in? I'd have to read the book ... actually have to find it first.

EDIT > > Was down cleaning up the bench from the last project, getting ready for the ST120 build. Plugged the Kill-A-Watt into the variac and set it for 117a ... was down there a couple hours with an occasional glance and it looked pretty steady +/- a half volt ...

Never really thought of using a variac as a long term solution towards power regulation ... seems obvious now, but thanx all for pointing it out to me.

** Too many projects lined up right now ... Gotta make a store run for a couple more tackle boxes ...

?




Oh!

sKiZo wrote:Here's a fun test ... the box has presets for 110v-120v-127v to match your region. I tried all three and at 127v, nothing ... as expected because 122.5v (what I'm getting out of the wall) is within the 6% tolerance. Here's where it gets interesting - on the 110v setting, 122.5v IS outside tolerance, so yes, it does kick in, indicates a voltage overload condition, and (drumroll please) cuts the power to 108v. Huh.

That seems to be common with these cheap power "regulators". My APC H15 does the same. I suspect that they're little more than a variac with a control circuit that chooses from a limited number of settings -- e.g. -10%, pass-through, +10%.

I've had a lot of APC stuff over the years, and other than batteries going bad, they've seemed pretty reliable. Unlike their tech support. Next best thing to useless. Try sifting thru their online "knowledge base" sometime. That takes pitiful to a whole new level.

Have no fear! You CAN get automatic, reliable, AND accurate regulation if you're willing to spend a few extra dollars. Just add a couple zeros to the end of the check is all.

Note to self ... and anyone else who cares ...

Variacs DO drift until they warm up. I set mine to 117.0 today while I was working on the bench, and after an hour it had drifted up to around 118.5 ... Not unreasonable. I get that a lot on older radio transceivers, shortwave and such. Centered it again and it stayed at 117 +/-2 for line fluctuations.

My AC line in is relatively stable then, based on random tests over the last few days. Just higher than I expected at 122.5 average. Surprising in that it used to read significantly lower. Couple years back, the entire neighborhood was upgraded from 4000Kv to 14.4Kv for a new development. New substation, transformers, etc ...Wonder if that's got anything to do with it?

If I do use the variac to power the VTA ST-120, I may just leave it on then. Not much draw on idle, and that would eliminate the warm up time. I'll also leave the Kill-A-Watt plugged in to monitor things for a while and make sure the thing doesn't turn into a Kill-A-sKiZo ...

skriefal wrote:

sKiZo wrote:Here's a fun test ... the box has presets for 110v-120v-127v to match your region. I tried all three and at 127v, nothing ... as expected because 122.5v (what I'm getting out of the wall) is within the 6% tolerance. Here's where it gets interesting - on the 110v setting, 122.5v IS outside tolerance, so yes, it does kick in, indicates a voltage overload condition, and (drumroll please) cuts the power to 108v. Huh.

That seems to be common with these cheap power "regulators". My APC H15 does the same. I suspect that they're little more than a variac with a control circuit that chooses from a limited number of settings -- e.g. -10%, pass-through, +10%.

Many have different taps they can switch to in response to a large enough change in voltage. I know of none that use a continuously variable autoformer ("Variac").