The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Dynaco VTA tube amp kits, all Tubes4hifi.com products and all Dynakitparts.com products


    Variac's on sale right now at Circuit Specialists in AZ

    Share
    avatar
    j beede

    Posts : 394
    Join date : 2011-02-07
    Location : California

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by j beede on Sat Dec 31, 2016 6:35 pm

    monkuboy wrote:Another question here... I plugged in the Variac and then plugged the ST-120 into the Variac.  When I turned on the ST-120, the voltage in the Variac dropped from 120.0V to 119.3V.  Isn't the voltage supposed to remain the same?   Same thing with trying the TV - there was a slight drop in voltage when turning it on, and an even slighter drop when just plugging in the TV without turning it on (it was in a ready state with the LED light on showing it was plugged in).  Shouldn't the Variac keep the voltage constant?

    A VariAC is a transformer with a mechanically variable secondary tap facility. It provides variable voltage via the big knob on top--it does not provide automatic, feedback-based voltage regulation. When you load the output of a transformer there will be an observable voltage drop versus the no-load voltage. Simply set the voltage to your desired level after applying the load. It sounds to me like you have a VariAC that is doing what it is supposed to do. Does it hum? Does it run cool? Those would be of greater interest to me.

    ...j
    avatar
    Peter W.

    Posts : 411
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Peter W. on Sat Dec 31, 2016 11:01 pm

    OK..... A few things here. And from the perspective of one who has fiddled with the audio/radio hobby for now well over forty (40) years. So forgive me please if I ramble a bit on the pendantic side.

    a) A line conditioner is a good thing whether your AC line is typically contaminated or not. It maintains a steady output voltage within a very wide range of input voltages.
    b) It puts out a pure sine-wave at 60 hz (50 if in other zones). Not necessarily grid-tied (a few more $$ gets you that), but close enough that your on-board transformer will be happy.
    c) It is generally very quiet in normal operation, not so much if your incoming power is very nasty. Few here in the US will ever notice, in other words (unless the newly empowered Russians get their way - as demonstrated in Vermont lately. This is not political - look it up).
    d) It will protect your equipment against spikes, brown-outs and other artifacts far better than a mere surge protector. Or a V-A-T.

    So, if you have one, keep it!

    Now as to a Variable Auto-Transformers (!!ONLY!! General Radio and its heirs may call their devices "Variacs", please keep that in mind). They are mechanical devices that reduce/manage/increase incoming voltages by taking off a simple coil at varying points. And the output-to-input voltage variation *AND PROPORTION* is fixed by the position of the wiper on that coil. Loads can cause voltage sags if the incoming line is not of sufficient capacity to carry that load. If you are getting a small voltage drop, that is normal - VERY!~!~! small. 0.583 % is very, very small. Variable Auto-Transformers DO NOT have any voltage regulating capacity whatsoever.

    And, cutting to the chase, why it is that I would prefer an audio-grade line conditioner over a V-A-T 100% of the time. If your local voltage varies, a V-A-T is useless as the output is a fixed proportion to the input. Today, you are OK at 123 V-in, to 118 V-out. Tomorrow at 128 V in, not so much unless you are constantly (hour-to-hour) checking. Hence a set-and-ignore range of 85 - 145V becomes quite desirable.

    As to bucking transformers - they also have one singular virtue: They will _always_ drop the incoming voltage by a specific amount, and do not admit to adjustment on the fly. Still not as good as a line conditioner, but far, far better than a V-A-T.

    So, as John Muir once stated: Come to terms with your ass, for it bears you!. Understand what each tool is for, use it for that purpose, and let other tools provide as necessary for other functions.

    End mini-rant.
    avatar
    pedrocols

    Posts : 96
    Join date : 2014-11-24
    Location : Western MA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by pedrocols on Sun Jan 01, 2017 2:05 am

    Peter W. wrote:OK..... A few things here. And from the perspective of one who has fiddled with the audio/radio hobby for now well over forty (40) years. So forgive me please if I ramble a bit on the pendantic side.

    a) A line conditioner is a good thing whether your AC line is typically contaminated or not. It maintains a steady output voltage within a very wide range of input voltages.
    b) It puts out a pure sine-wave at 60 hz (50 if in other zones). Not necessarily grid-tied (a few more $$ gets you that), but close enough that your on-board transformer will be happy.
    c) It is generally very quiet in normal operation, not so much if your incoming power is very nasty. Few here in the US will ever notice, in other words (unless the newly empowered Russians get their way - as demonstrated in Vermont lately. This is not political - look it up).
    d) It will protect your equipment against spikes,  brown-outs and other artifacts far better than a mere surge protector. Or a V-A-T.

    So, if you have one, keep it!

    Now as to a Variable Auto-Transformers (!!ONLY!! General Radio and its heirs may call their devices "Variacs", please keep that in mind). They are mechanical devices that reduce/manage/increase incoming voltages by taking off a simple coil at varying points. And the output-to-input voltage variation *AND PROPORTION* is fixed by the position of the wiper on that coil. Loads can cause voltage sags if the incoming line is not of sufficient capacity to carry that load. If you are getting a small voltage drop, that is normal - VERY!~!~! small. 0.583 % is very, very small.  Variable Auto-Transformers DO NOT  have any voltage regulating capacity whatsoever.

    And, cutting to the chase, why it is that I would prefer an audio-grade line conditioner over a V-A-T 100% of the time. If your local voltage varies, a V-A-T is useless as the output is a fixed proportion to the input. Today, you are OK at 123 V-in, to 118 V-out. Tomorrow at 128 V in, not so much unless you are constantly (hour-to-hour) checking. Hence a set-and-ignore range of 85 - 145V becomes quite desirable.

    As to bucking transformers - they also have one singular virtue: They will _always_  drop the incoming voltage by a specific amount, and do not admit to adjustment on the fly. Still not as good as a line conditioner, but far, far better than a V-A-T.

    So, as John Muir once stated: Come to terms with your ass, for it bears you!.  Understand what each tool is for, use it for that purpose, and let other tools provide as necessary for other functions.  

    End mini-rant.
    Several Amp manufacturers do not recommend the use of any line conditioners. Once again I am not an engineer so don't ask me why.
    avatar
    Blitzen

    Posts : 48
    Join date : 2009-07-10

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Blitzen on Sun Jan 01, 2017 7:11 am

    [/quote]
    Several Amp manufacturers do not recommend the use of any line conditioners.  Once again I am not an engineer so don't ask me why.[/quote]

    Can you remember which manufacturers are saying this? I'm curious as to why they might say this.
    I'm using a line conditioner on my home rig, and on virtually every piece of equipment in my work recording studio. There it is invaluable, because where I work a time signal is sent through once an hour to keep clocks in sync. The Tripp Lite filters that out!
    My take on Variacs: if you use one, you should also have installed a meter that tells you the AC power out level, otherwise it's rather pointless. Every time you turn the amp on, it should be referenced. Something such as a "Kill-A-Watt" is perfect for this, and cheap.

    monkuboy

    Posts : 30
    Join date : 2016-03-23

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by monkuboy on Sun Jan 01, 2017 1:02 pm

    Thanks to those who replied to my questions. I think I'll be sending the Variac back as I was under the impression it kept the voltage constant rather than it being proportional to whatever the incoming voltage is. Also, I'm a bit concerned about quality since the dial is so poorly calibrated, having to turn it down to 105V in order to output 120V (at 120V on the dial it actually outputs 134V).
    avatar
    bluemeanies

    Posts : 183
    Join date : 2015-02-09
    Age : 67
    Location : Folsom Pa.

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by bluemeanies on Sun Jan 01, 2017 2:49 pm

    Jumping in here a little late but I thought I would share.
    My line voltage in my house is from a low 115 to a high of 125.
    That is why I purchased a VARIAC. Heavy duty I bought one on eBay for $100.00. It came with a 30 amp fuse which I changed out to 10 amp fuse. I have a Kill a Watt that is connected to the Variac and the m125's connected to the Kill a Watt. At least now I have some control over the line voltage coming into my 2channel system.
    I also have a Furman Elite but found that the Elite was not enough. deepee recommended in a post a ground fault interruptor. I procrastinated and suffered a surge which burned out a transformer in my Grace Design m920. Fortunate I was the unit still had four years left on the warranty.
    I went to Home Depot and purchased two ground fault interruptors that have three outlets on each of them. They cost $26.00 each and have a manual reset.
    I have some equipment connected to the Furman and from the Furman to the ground fault interruptor. The rest of my equipment is connected directly into the ground fault interruptor and I fell a lot better than I did a few weeks ago.
    Every piece of equipment is protected but I am a realist...you cannot stop Mother Nature or control her, but I feel prepared for the worst.
    avatar
    pedrocols

    Posts : 96
    Join date : 2014-11-24
    Location : Western MA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by pedrocols on Sun Jan 01, 2017 3:31 pm

    Several Amp manufacturers do not recommend the use of any line conditioners.  Once again I am not an engineer so don't ask me why.[/quote]

    Can you remember which manufacturers are saying this? I'm curious as to why they might say this.
    I'm using a line conditioner on my home rig, and on virtually every piece of equipment in my work recording studio. There it is invaluable, because where I work a time signal is sent through once an hour to keep clocks in sync. The Tripp Lite filters that out!
    My take on Variacs: if you use one, you should also have installed a meter that tells you the AC power out level, otherwise it's rather pointless. Every time you turn the amp on, it should be referenced. Something such as a "Kill-A-Watt" is perfect for this, and cheap.[/quote]


    I do not precisely remember who. However, they argued that any amp with a properly design power supply should suffice. Thus the need or use for a power conditioner will be redundant.
    avatar
    bluemeanies

    Posts : 183
    Join date : 2015-02-09
    Age : 67
    Location : Folsom Pa.

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by bluemeanies on Mon Jan 02, 2017 11:57 am

    pedrocols wrote:Several Amp manufacturers do not recommend the use of any line conditioners.  Once again I am not an engineer so don't ask me why.

    Can you remember which manufacturers are saying this? I'm curious as to why they might say this.
    I'm using a line conditioner on my home rig, and on virtually every piece of equipment in my work recording studio. There it is invaluable, because where I work a time signal is sent through once an hour to keep clocks in sync. The Tripp Lite filters that out!
    My take on Variacs: if you use one, you should also have installed a meter that tells you the AC power out level, otherwise it's rather pointless. Every time you turn the amp on, it should be referenced. Something such as a "Kill-A-Watt" is perfect for this, and cheap.[/quote]


    I do not precisely remember who. However, they argued that any amp with a properly design power supply should suffice. Thus the need or use for a power conditioner will be redundant.[/quote]



    I heard arguments on both sides but my 7700 is plugged directly into the wall outlet as recommended by the manufacturer. My m125's are connected to a Kill a Watt which is connected to a VARIAC.
    avatar
    10-E-C

    Posts : 103
    Join date : 2014-02-12
    Age : 63
    Location : upper east tn

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by 10-E-C on Fri Jan 06, 2017 10:13 pm

    I've been running two of these Chinese VARIACs for years, the 20 amp model runs my main system with the M125's, Holger's Janis and Aretha. The unit test good with a checker. Now the 5 amp runs my ST-70 system, it was wired incorrectly, so I transposed the hot and neutral wires. My house voltage runs in the high 123 VAC, so I set both VARICs to 118 VAC allowing for a little voltage drop under load when the amps are running. Every time I check my bias I also check my voltage out of the VARIAC and it is always spot on where I set it. 3 years running the 5A and 2 years running the 20A with no hint of a problem.

    TM

    eickmewg

    Posts : 77
    Join date : 2014-08-29

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by eickmewg on Sat Jan 07, 2017 7:10 am

    So this is the third mentioned 5 amp model with reversed hot and neutral lines. Do we see a trend?

    monkuboy

    Posts : 30
    Join date : 2016-03-23

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by monkuboy on Sat Jan 07, 2017 12:49 pm

    eickmewg wrote:So this is the third mentioned 5 amp model with reversed hot and neutral lines.  Do we see a trend?

    I tested the Variac I received the other day and it was wired correctly. That said, I ended up sending it back for a refund because for one thing, the dial calibration was so far off (measured 134.4V at 120V setting) and also, I was under the mistaken impression it regulated the voltage and kept it constant, whereas it doesn't keep it constant. I feel it was defective, though, because of the dial being incorrect.

    ramon68

    Posts : 96
    Join date : 2009-04-12
    Age : 76
    Location : naples fl

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by ramon68 on Sat Jan 07, 2017 1:46 pm

    Monkuboy, did the voltage of the variac vary more than the incoming a/c? Or did it go up and down with the wall voltage?
    It wasn't designed to lock in a voltage, but simply to reduce the incoming voltage.

    monkuboy

    Posts : 30
    Join date : 2016-03-23

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by monkuboy on Sat Jan 07, 2017 11:23 pm

    ramon68 wrote:Monkuboy, did the voltage of the variac vary more than the incoming a/c?  Or did it go up and down with the wall voltage?
    It wasn't designed to lock in a voltage, but simply to reduce the incoming voltage.

    It varied with the wall voltage, which now I know is normal but I was under the mistaken impression it kept the voltage constant at whatever the dial was set at.
    avatar
    Bob Latino
    Admin

    Posts : 2537
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Bob Latino on Sun Jan 08, 2017 9:35 am

    Two things that are true about these Chinese variacs ...

    A. Yes - The meters on these variac's are simple analog meters and are not particularly accurate. You always check the outgoing voltage on the variac's AC outlet with a multimeter.

    B. Once set .. the variac's outlet voltage will vary with your incoming line voltage. If your incoming line voltage goes up, the variac's output voltage will also go up. Usually at most locations, you will find a pattern. Lets say that you find over a period of a week that your wall outlet line voltage ranges from 121 to 124 VAC at any given time and your incoming line voltage today is 122 VAC. You should set your variac's output on that day to 118. If you do, then your variac's outlet voltage may vary from about 117 to 120 at any given time but will always top out at 120 VAC.

    Another thing to remember > Line voltage changes will cause bias setting changes. As your line voltage goes UP, your bias setting will also go up. Bias settings that "wander" are almost always related to line voltages that wander.

    Bob
    avatar
    Peter W.

    Posts : 411
    Join date : 2016-08-07
    Location : Melrose Park, PA

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Peter W. on Sun Jan 08, 2017 1:35 pm

    Bob Latino wrote:

    >>Snippage<<

    Another thing to remember > Line voltage changes will cause bias setting changes. As your line voltage goes UP, your bias setting will also go up. Bias settings that "wander" are almost always related to line voltages that wander.

    Bob[/b][/size]

    And why it is that I prefer to use an audio-grade line conditioner in situations of varying voltage. The output is fixed against a widely variable input, and the output is also a pure sine wave.

    avatar
    Bob Latino
    Admin

    Posts : 2537
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Bob Latino on Sun Jan 08, 2017 3:21 pm

    Peter W. wrote:

    And why it is that I prefer to use an audio-grade line conditioner in situations of varying voltage. The output is fixed against a widely variable input, and the output is also a pure sine wave.

    Consider though that many line conditioners do not offer "true RMS voltage regulation" .. They do filter and reduce noise on your incoming AC line and filter out AC power spikes but many do NOT regulate and/or adjust the AC voltage. They won't jack up a lower than 120 VAC and they will not bring down a higher than 120 VAC down to 120 VAC. Those that do offer true RMS voltage regulation tend to be expensive. Deepee's Furman 20i power conditioner is $3000+. I think Furman's smallest power conditioner that does offer true RMS voltage regulation is over $1000 in pricing. So .... Yes > some power conditioners are also VOLTAGE REGULATORS but in general only the very expensive power conditioners can regulate voltage ..

    Bob


    Sponsored content

    Re: Variac's on sale right now at Circuit Specialists in AZ

    Post by Sponsored content


      Current date/time is Wed Jul 26, 2017 8:35 pm