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    Voltage regulator vs VARIC vs Power Conditioner

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    jsl1234

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    Voltage regulator vs VARIC vs Power Conditioner

    Post by jsl1234 on Wed Oct 17, 2018 4:37 pm

    I see lots of discussion regarding incorporating a VARIAC as part of the DIY workbench. I get that it allows for the user to bring up the AC slowly, and ensure it doesn't top out at a voltage greater than safe for a given piece of equipment.

    Do people use a VARIAC just on their bench? Will a VARIAC step-up/step-down an incoming voltage to a set point?

    The line voltage in Richmond VA seems to run anywhere from 114 to 122 at any given time--is this a problem with the VTA ST120? Does this variability in line voltage effect bias?

    Is a VARIAC the solution? Or should I invest in a particular voltage regulator and/or power conditioner (which don't seem to hold to a particular voltage but focus more on AC filter and surge protection).

    Thanks in advance...

    wildiowa

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by wildiowa on Wed Oct 17, 2018 5:57 pm

    Variac! This comes up frequently on the forum. Best bet is to get one online, Amazon or eBay, set it at 118 or whatever you prefer, and forget it. Saves a lot of blown tubes and fireworks. My voltage sometimes tops 126v, since getting the Variac absolutely no problem. The voltage coming out will vary slightly along with changes in your line voltage, but no biggie....main thing is to get it down below 120. Others prefer other devices but the Variac is best for me.
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    Bob Latino
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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Bob Latino on Wed Oct 17, 2018 8:03 pm

    Some power conditioners do not put out a TRUE SINE WAVE. A tube amp will choke big time if fed anything but a true sine wave. A variac always puts out a true sine wave.

    Variacs are inexpensive. A $60 5 amp unit will handle any ST-70 or VTA ST-120 amp. A 20 amp unit will handle TWO M-125 amps easily. Check out the link below. Disclaimer - I have no interest in the company that sells these units. Yes - they are made in China but customers tell me that they work well. Some of these at the link below have analog meters and some have digital meters. If you get one with an analog meter, just check the AC output with your multimeter. I would set up your variac so that you get about 118 VAC coming out of the variac.

    Variacs at Circuit Specialists in Tempe, AZ

    Bob
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    Peter W.

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Peter W. on Thu Oct 18, 2018 7:33 am

    A few things:

    a) A Variac as a stand-alone bench-tool is dangerously worse than useless. More on this later. As a bucking device to control high wallplate voltage, it has some few virtues. 'Few' chosen carefully.

    b) A Variac follows the line voltage. So, if you set it to buck by 5V, you will get 120V @ 125V, 119V @ 124V and so forth. You describe your wallplate voltage varying from 114V to 122V, or abou 8 volts. If you want to buck by only 2V, you will be at 112V at the low point. So, keep an eye on it at the beginning of a listening session and adjust as-needed.

    c) There are true RMS line conditioners. They are not cheap in a form as rugged as needed for tube audio equipment. But they are a permanent fix and handle both low and high wallplate voltage:

    https://www.performanceaudio.com/item/furman-p-1800-ar-voltage-regulator-power-conditioner/15997/    is one. Bob is absolutely correct that a tube-rectifier device will not be happy with square-wave or triangle-wave power. Solid-state rectifier devices are a bit more resilient - but only a bit.

    d) Dangerously worse than useless: How many here have been told that equipment should be tested by "bringing it up slowly on a variac"?  WRONG!  If the unit has a tube rectifier, it will not see B+ until the rectifier passes current - at about 75% to 85% of full power. Not a soft start by any means. And if the Variac does not have current metering, a dead or partial short at 50V will do damage long before the  unit under test starts to pass signal, or not. Bare Variacs are an excuse to let out the magic smoke, not much else. Even a dim-bulb tester that limits current will not disclose a say.... 10-watt error. Oops!

    This goes back to my "Spend Da MONEY!" rant. if you want a bench Variac, go with one that has the proper meters. I keep this one:  

    http://www.byan-roper.org/steve/steve-at-play/antique-electronics-and-2/heathkit-ip-5220-variable.html      Thanks again, Bryan!

    But they were made by VIZ, RCA, and many others. And, if you wish to forego isolation (bad idea on a test bench unless you have a stand-alone isolation transformer), this may be done:

    https://www.youtube.com/watch?v=2mrlha-uzro    Nice ability to read fractions-of-watts.

    We are blessed with pretty steady 118V at home. So I don't need bucking. Others are not so lucky.
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    cci1492

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by cci1492 on Thu Oct 18, 2018 8:42 am

    I could be wrong, but if you're looking to nail the voltage at 120VAC like the Furman unit linked by Peter, this one is cheaper and does that:
    https://www.amazon.com/gp/product/B000FBF08Q/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
    I purchased one earlier this year for my HT stuff. Tested it on my variac (duck..incoming!) and it will boost up or cut down to 120VAC output as needed. It has a very large toroidal transformer and has been working great. For the tube stuff (Bob's amps) I use a bucker.
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    Peter W.

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Peter W. on Thu Oct 18, 2018 8:51 am

    cci1492 wrote:I could be wrong, but if you're looking to nail the voltage at 120VAC like the Furman unit linked by Peter, this one is cheaper and does that:
    https://www.amazon.com/gp/product/B000FBF08Q/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
    I purchased one earlier this year for my HT stuff. Tested it on my variac (duck..incoming!) and it will boost up or cut down to 120VAC output as needed. It has a very large toroidal transformer and has been working great. For the tube stuff (Bob's amps) I use a bucker.

    Have you put a scope on it to look at the output? If a true sine-wave, that is a great option.
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    cci1492

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by cci1492 on Thu Oct 18, 2018 9:25 am

    It didn't occur to me to check for that Peter. I'm pretty sure it's not a modified sine wave. I guess I can test it. Keep in mind, it's not a UPS.

    wildiowa

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by wildiowa on Thu Oct 18, 2018 10:20 am

    There are more expensive and sophisticated solutions but for the $$ the Variac does exactly what you are looking for. Kinda old school and bulky, but set it up and stuff it away in back somewhere and forget it...worry no more. Less than $100. If you are a purist you can measure your line voltage each listening session and tune in the Variac exactly where you want it....often imitated but never equalled.

    jsl1234

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by jsl1234 on Thu Oct 18, 2018 4:05 pm

    Thanks for the input. I ordered the following (out of stock until mid-Nov)

    https://www.circuitspecialists.com/tdgc2-2d-variac-with-digital-display.html

    I thought the VARIAC held power at a constant number, not a percentage or fixed offset from the input voltage. Given that is the case, how does it address the issue of holding the power to the amp at 118 with precision? Sounds like a power conditioner is a more 'complete' solution?

    Or am I missing something...

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    Peter W.

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Peter W. on Thu Oct 18, 2018 4:13 pm

    jsl1234 wrote:Thanks for the input. I ordered the following (out of stock until mid-Nov)

    https://www.circuitspecialists.com/tdgc2-2d-variac-with-digital-display.html

    I thought the VARIAC held power at a constant number, not a percentage or fixed offset from the input voltage. Given that is the case, how does it address the issue of holding the power to the amp at 118 with precision? Sounds like a power conditioner is a more 'complete' solution?

    Or am I missing something...


    You are not missing anything. That is the case.

    Note from the Pedant in me (From Wikipedia):

    From 1934 to 2002, Variac was a U.S. trademark of General Radio for a variable autotransformer intended to conveniently vary the output voltage for a steady AC input voltage. In 2004, Instrument Service Equipment applied for and obtained the Variac trademark for the same type of product. Instrument Service & Equipment reserves all rights of use of the trademark VARIAC for variable transformers and related devices. https://iseinc.com/

    All other devices are Variable Auto-transformers. And, as the unit posted is Made in China, not by Instrument Service and Equipment, it is an example of Chinese theft-of-trademark and intellectual property.
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    Bob Latino
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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Bob Latino on Thu Oct 18, 2018 5:01 pm

    jsl1234 wrote:Thanks for the input. I ordered the following (out of stock until mid-Nov)

    https://www.circuitspecialists.com/tdgc2-2d-variac-with-digital-display.html

    I thought the VARIAC held power at a constant number, not a percentage or fixed offset from the input voltage. Given that is the case, how does it address the issue of holding the power to the amp at 118 with precision? Sounds like a power conditioner is a more 'complete' solution?

    Or am I missing something...


    A variac will not "hold a steady voltage". It is normally used to drop a voltage to a workable level that a tube amp can deal with. What you do is find out through trial and error what your average highest line voltage is ? Set the variac to put out about 118 VAC when your line voltage is at its highest. When your line voltage goes up and down, the variac's line voltage will also go up and down but > will be in a range that is easily handled by your tube amp. The variac is low cost solution to the problem. This solution that Peter W. recommends is nice and will regulate voltages but will cost a lot more > $756 power conditioner solution ..

    Bob

    jsl1234

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by jsl1234 on Thu Oct 18, 2018 5:07 pm

    Clear Bob, thanks. Like I said, the digital 20 amp unit is on back order, so will be a while before I get to play with this in practice.

    Jay

    wildiowa

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by wildiowa on Thu Oct 18, 2018 5:31 pm

    Did I read correctly in the specs the Furman provides a constant 120 volts...plus or minus 5 volts? So, you could still be feeding your stuff up to 125 volts, or as low as 115?

    jwb474

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by jwb474 on Sat Oct 20, 2018 5:16 am

    I find Variacs useful, reliable and safe. I use single versions of these to control fan speed and back in the day when I needed lighting control near am receivers.
    Studios today still use these.



    [/u

    If you want the advantages of a Variac with voltage stability these are available. Used them in previous job.

    You just "Set it and forget it" They also come with remote setting and monitoring options.


    audiobill

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by audiobill on Sat Oct 20, 2018 6:42 am

    US made variacs come up regularly on Craigslist -I bought a $700 unit for $100, in great shape.
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    cci1492

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by cci1492 on Sat Oct 20, 2018 9:32 am

    I had bad luck with the Chinese variac. After maybe a year it started tripping the breaker when switching on. Did some testing, breaker tripped on several outlets, added a giant thermister and corrected the issue. But after thinking about it I made a bucker with a Hammond TA. So, yeah, if you can find an American made used one for the same money IMHO it's a better choice.
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    Peter W.

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by Peter W. on Mon Oct 22, 2018 8:46 am

    wildiowa wrote:Did I read correctly in the specs the Furman provides a constant 120 volts...plus or minus 5 volts? So, you could still be feeding your stuff up to 125 volts, or as low as 115?

    I do not believe so:

    Voltage Regulation: continuous 120 volt AC output (+/-1.0 volt) with input from 113 volts AC to 126 volts AC (the SPR-20i will regulate well beyond 113 to 126 volts, but not within +/-1.0 volt)

    This is from one of their lower end regulators. It is my understanding that they regulate very well with the +/- 1 V range. Some of their more expensive devices allow the user to set the output voltage (within a range) as well.

    Keep in mind the difference between a Line Conditioner and a Voltage Regulator.

    And, then there is this:

    https://www.sweetwater.com/store/detail/BrownBox--amprx-brownbox-tube-amplifier-input-voltage-attenuator
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    deepee99

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by deepee99 on Tue Oct 23, 2018 1:54 pm

    Peter W. is right about the Furmans. I have two of them: one SPR-20i and one P-1800-AR. (*NOTE* There are two 1800 models; you want the P-AR -- this straight from the Furman tekkie -- for tubes). Long before I bought the 20i (which I use for my main system) I spoke at length with their English-as-a-first-language tekkies. Basically the thing is an autoformer; all the switching and associated racket occurs on the input side, so the output is pure unfettered sine wave.
    The 20i shuts down at 138 VAC but as mentioned, maintains its 119-121 VAC output through a 113-126 VAC range. (Voltage beyond 126 or below 113 VAC coming from the wall, a tube stereo won't be your only problem.)
    It's also very, very fast. We had a spike roll through about a month ago here that blew up a manual-reset-GFCI-protected modem. That same spike caused the main stereo's Furman to shut down but the GFCI on that circuit stayed live. (I have the Furman plugged into the GFCI). Now that's fast!
    I have all solid-state stuff on my smaller 15-amp Furman now, GFCI protected, on a circuit that's never measured above 122 VAC, so the Furman's basically acting as an expensive power strip. If someone wants it, PM me with an offer. (A caveat: these suckers are heavy.)

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    bluemeanies

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    Re: Voltage regulator vs VARIC vs Power Conditioner

    Post by bluemeanies on Wed Oct 24, 2018 4:53 am

    I have spikes in voltage constantly as well as severe drops in voltage due to (according to my electric company) Boeing and the International airport nearby. I never realized those spikes while having SS equipment with both Monster and Furman conditioners and surge protectors.
    Within a few months of getting my tube monoblocks I invested in a kil-o-watt ($30.00) and purchased a Staco (made in the USA) Variac on e-bay. New this Variac had a over thousand dollar price tag. It was listed at $185.00 on e-bay and I picked it up to my surprise for $100.00.
    Works flawlessly after changing the 20amp fuse to 10amps.
    The combination...Variac & kill-o-watt make things a lot easier.

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