Stabilising Wall Voltage (Without Breaking the Bank)

Discussion in 'Tube Audio' started by Crang, May 12, 2018.

  1. Crang

    Crang Active Member

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    I am looking very very hard at entering the world of tubes and kits both by building Bob Latinos M-125 monoblocks. About ready to start selling some gear to fund this endeavor. In all my reading one thing that is very clear is that these amps can not be supplied by more than 122 volts or bad things happen. I have been measuring my wall voltage and it typically fluctuates from 122 to 126 volts over the course of a day. I need to correct this before ever plugging in one of Bobs kits.

    The ideal solution would be something like PS Audios power regenerators with a perfect 120v 60hz sine wave coming through. Even used these go for $1400 or more, and thats just not in the cards right now. At the low end I can get cheap chinese made variacs for under $100 which will step down the voltage say 6 volts so I will be getting 116 to 120 out of the wall.

    I am looking for ideas for something in between these two extremes. I don't have a specific budget but $300 to $500 feels about right. Curious what the members here have done to solve this issue? It may be a tall order but ideally the solution can keep a stable 120v not just stepping it down a fixed amount. Of course it needs to provide enough juice for 2x 125 watt amps. Some type of filter would be appreciated- its a rental house at the moment so I can't add new circuits or change a whole lot that happens before the outlet.

    Is this possible?
     

     

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  2. willyrover

    willyrover Super Member

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    What does Bob have to say about this? With 120V +/- 5% being nominal (at least for my utility), 114 - 126V should be expected at the outlet. I would think (hope) that Bob's amps, being updated/modern designs, would be able to handle these voltages.

    I can understand some concern in older amplifiers, with tired components that were running close to their ratings from day one, on sagging power grid voltages - but not on modern equipment.
     
  3. Retrovert

    Retrovert AK Subscriber Subscriber

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    An autotransformer is the perfect solution if your voltage is always high by a fixed amount. (The trademarked brand name is "Variac".)

    The better UPS units will regulate line voltage and an autotransformer may then be used after that to further regulate.
     
  4. Hi-FiGuy

    Hi-FiGuy Well-Known Member

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    Location:
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    If your measuring your wall voltage without a load it will always measure high. Once you plug in the amp the line voltage may drop a bit, unless your house is right next to a substation. I like to use Ferroresonant power transformers from SOLA when the voltage and currents are on the lower side. These work great with Line Pre's, Phono Pre's, DAC's and Optical Disc Players. They give you constant voltage out of usually 118 when the line fluctuates from 95V to 130V. The problem is they are noisy and run hot. Another solution is just called a voltage regulator, most of them come from China and they have a tapped power transformer inside with a relay and some circuitry for selecting the primary tap that leads to 120V on the secondary winding. Most of these are for smaller more sensitive equipment, and when the relay clicks sometimes you will hear a pop. You could always just build the amps and use a current inrush limiter to slow the current and eat a couple of volts when the amp is running.
     
  5. primosounds

    primosounds Parallel single ended EL84 ,EDCOR OPT

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    Variacs are ok but are not the best solution. There is a current limit to the unit but even before that is reached the amount of current flowing through the wiper contacts can eventually erode and also limit the current flow. I did a test with my amp plugged into 118 vac wall voltage, a line conditioner and a variac. The dynamics were noticeably reduced thru the line conditioner and even more so thru the variac. So, unless you have no choice i would not use that for reducing wall voltage. Some guys build a bucking transformer set up to get the raw voltage to 117 or whatever they want.
    Line conditioners keep the voltage output to 118v, or you can set the voltage on the expensive models. I use one on my flat screen and home theater stuff. The new ones are made in China but you can get them used for pennies on the dollar at the Goodwill and other second hand stores. They are mostly an isolation transformer and some surge suppressor circuitry so are very reliable.
     
    Last edited: May 12, 2018
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  6. dB happy

    dB happy Active Member

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  7. Tim D

    Tim D AK Subscriber Subscriber

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    :)

    You neighborhood isn't going to notice your amp turning on unless you are talking huge wattage and you are running 240VAC - even then it would only happen on a neglected Electric Utility distribution leg. My Fisher tube amp draws 1.3A @ 120VAC. This is small stuff. If you turn your amp on and you see any drop at all then you better check your house wiring.

    Having said that, the voltage will vary during the day while "EVERYONE" is out there turning things on and off. The Electric Utility tries to match the electric supply with the load, but it is normal for the voltage to vary over the course of the day due to this dance between electric supply and load. (Will your one amplifier be noticeable? In general, not at all unless you have a wiring problem and then the voltage drop will only be local.)
     
    Last edited: May 12, 2018
  8. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    Finding one of these used is probably cheaper than an audio specific power regenerator. I have one running my HT with a quieter fan installed in the case because the stock fan is crazy loud

    https://www.tripplite.com/smartonli...mpwebcard-option-usb-db9-serial~SU1500RTXL2UA

    I did have to replace all four batteries but that was easier for me as I get distributor pricing through my employer.

    Looks like the new ones have the option of setting output voltage to 110V but mine I'm pretty sure is 120V only as it's old.

    Edit: it does actually work. Voltage on power conditioner on sideboard shows as 116, reads 116.9 because the A/C is running; output of Tripp-Lite is 121.2 according to my cheap meter that I happened to have sitting here. However, if you have a hard limit of 122V, that might be too close for comfort.
     
    Last edited: May 12, 2018
  9. whoaru99

    whoaru99 Epic Member

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    Right on!
     
  10. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    Now that I think about it though, if you got something like that and then bucked down one recep for the tube stuff, that would be a good solution.
     
  11. Crang

    Crang Active Member

    Messages:
    147
    Location:
    Austin, Texas
    Bob is actually the one who says never more than 122 volts and that has been confirmed by a number of people that run his amps. A lot of them run variacs but the voltage will still fluctuate with a fixed amount of step down and as one member here just noted, it negatively effects sound quality. There are some auot biasing boards which just came out that can be added to his amps, so I assume that will help with voltage fluctuation but still doesnt fix the need to drop the input voltage probably 2 to up to 8 volts at any given moment.
     

     

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  12. Yamaki

    Yamaki Not For Hire Subscriber

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    Given your budget, I'd suggest one or more of these:

    https://www.panamax.com/product/max-5300-power-management-2ru-11-outlets-M5300-PM

    I have two of the M5400-PM units in my main system & a M5300-PM protecting a second smaller system in another room. Never had a problem with them protecting the equipment. I've been present during 4 or 5 electrical surges and shutdowns in the area and these units protected my gear. Nothing has ever been damaged in any of those incidents.

    Good luck!
     
  13. EngineerNate

    EngineerNate AK Subscriber Subscriber

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    This is basically what I was going to suggest. I use a Liebert 2200va unit for my servers. It's also double conversion so it's generating it's own AC sine wave output 100% of the time like your tripplite. I also put new cells in it, that ran $75 or so on eBay.

    When I was looking into buying it, one of the top forum hits I found was a Gearslutz user who used it in his home recording studio to provide clean power to some mic preamps and recording gear that he was having trouble with hum in.
     
  14. arts

    arts Super Member

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    My recommendation would be,based on your stated voltage levels,to build yourself a bucking unit for each monoblock.Many of the available voltage regulators only work in five volt steps,so they aren't all that precise in any event.

    Actual regulation is (relatively) unimportant,you just need an overall reduction in the five to seven volt range. This is easily acomplished with readily available,inexpensive,off-the-shelf transformers,and makes for a nice easy little construction project.

    For some info and giggles,please refer to this thread:
    http://audiokarma.org/forums/index....r-vintage-tube-equipment.705805/#post-9471055
     
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  15. Hi-FiGuy

    Hi-FiGuy Well-Known Member

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    Location:
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    Thats true. I was thinking about my Citation II the original fuse is rated at 8A and after installing a current inrush limiter Jim McShane recommends using a 6A fuse. This is enough current to dim the lights at turn on. Most tube amps dont consume this kind of current. The beast is an exception.
     
  16. Tim D

    Tim D AK Subscriber Subscriber

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    Hmm, >6A at 120VAC? Does this still happen after you installed the in-rush limiter? If so, how old is your house? I would suggest you have a wiring problem or at least out of date wiring. Do you have 240VAC service? Microwave ovens and hair dryers draw more at 120VAC. You should see a correspondingly bigger dimming of your lights if higher draw appliances are started.

    (I trust Jim McShane, but just curious...) How many watts is a Citation II at the output terminals? The 6A sounds like a lot, but I am not familiar with the Citation II's. I used a "Kill-A-Watt" meter to measure the current of my Fisher KX-100 and sized my fuse accordingly. The in-rush limiter should make the ramp-up nice and gentle. Did Jim recommend a slo-blow? (Slo-blows are typical). Which in-rush limiter did you use? I'm thinking that a CL-80 (typical) is too small for something nearing 6A.
     

     

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  17. Legrace

    Legrace Member

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    My M125's initially gave me a lot of grief. Flash overs, redplates, several tube failures; all within first few months. Here I am thinking I must have really screwed up the builds! Nope, was all about this wall plate issue. Solution involved assembling a rather simple device called a bucker transformer. Shown below, with my two M125's plugged into it.

    I bought a 20A (plenty for pair of M125's) rated 6.3v center tap transformer, cut the power cord off an old dead appliance in my stuff to take to the landfill pile, and of course one needs an outlet. The box I made from some old lumber I had lying around. Just a matter of connecting a few wires. The bucker plugs into the wall outlet and drops my volts to a consistent 117-118v. After which my problem children are now so well behaved, night and day change.

    bucker.jpg
     
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  18. N8Nagel

    N8Nagel AK Subscriber Subscriber

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    Just curious, now that you've got me thinking about this, what would you recommend for a "mild" bucker? Wall voltage here ranges from 116-121 (looking at the display on the one power conditioner I have equipped with same) so a 10V drop would be too much, 4-6V would probably be OK, as I stated above I would probably be running off a Tripp-Lite regenerating UPS so voltage would then be held supposedly +/-2% of 120V (117.6-122.4)
     
  19. Tom Bavis

    Tom Bavis Audiophool Subscriber

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    If you're buying new, why not get transformers with 125V primary? Edcor will do a custom transformer for $40 extra - many other transformer companies will do the same. (Hammonds have 125V taps already). Why add something external?
     
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  20. dB happy

    dB happy Active Member

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    Why not just order an industrial buck boost transformer with multiple taps? The one I posted earlier is good for 13.8a, comes in it's own metal box, and has wide selection of voltages. For $70 you can't beat it.
     
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