Does anyone use a variac with their OR120?

BayofPigs · Post by **BayofPigs** » Sat Nov 18, 2006 9:31 pm

My band is finally going to be playing some shows within the next few months. The bars are dives and I was wondering if it would be wise to use a variac with my OR120?

I read this article on the Plexi Palace website and was wondering what you guys think? Would I be wasting my money?

http://plexipalace.com/va/service.html

fiveightandten · Post by **fiveightandten** » Sat Nov 18, 2006 10:27 pm

Any variac that can provide power for an OR-120 is going to be big and heavy. The positive side of it is that you'll be able to control the line voltage going into the amp. The negative aspect is weight, and one more thing to carry around, and more cable, and one more thing to worry about breaking or getting bumped (*watch out* if the setting on the variac gets nudged while you're playing!)

That being said, a variac will not protect you against voltage spikes, or outlets with faulty grounds, or anything like that. It's just a Variable AC transformer that lets you adjust the line voltage.

IMO, if you're looking to make your amp perform consistantly and safely in places with shotty power, pick up a power conditioner that has a regulated line voltage feature. It'll be more expensive than a variac, but I think that's what you're looking for. They're less bulky as well.

Hope that helps.

-Nick

BayofPigs · Post by **BayofPigs** » Sat Nov 18, 2006 11:44 pm

Hey Nick, good to see you back around here.

I have the cheapest power conditioner that Fuhrman makes and don't think I can afford one with the line volatge feature. How about an autotransformer? Is there a big issue with the voltage mismatch on the old Oranges?

I have to take the OR120 to a tech and get the tubes changed and get everything checked out, would you reccomend that I add a standby switch? Opinions seemed to be mixed. I was thinking about printing out the article you wrote about it and giving it to the tech. Anything else you would reccomend I get checked out?

BTW, those articles you wrote on the F.A.C. and Baxandall tone stack were the cat's pajamas and helped out a lot.

fiveightandten · Post by **fiveightandten** » Sun Nov 19, 2006 1:42 am

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by BayofPigs
 Hey Nick, good to see you back around here.

I have the cheapest power conditioner that Fuhrman makes and don't think I can afford one with the line volatge feature. How about an autotransformer? Is there a big issue with the voltage mismatch on the old Oranges?

I have to take the OR120 to a tech and get the tubes changed and get everything checked out, would you reccomend that I add a standby switch? Opinions seemed to be mixed. I was thinking about printing out the article you wrote about it and giving it to the tech. Anything else you would reccomend I get checked out?

BTW, those articles you wrote on the F.A.C. and Baxandall tone stack were the cat's pajamas and helped out a lot.
<hr height="1" noshade id="quote"></blockquote id="quote">
To be honest, i'm not even sure what you mean by 'autotransformer'. The old Oranges, from my experience, don't have the problems other old amps (Hiwatts and Voxes, for instance) do with present day wall voltages.

Some of the old Oranges had PT's with US primary taps designed for 120V, some 118V, some 117V. But I haven't seen any that had only 115V or 110V as an option for us. My '71 pics only head has a 110V selection, but it also has 118V, which is what I run it on. I have an old 1964 Vox AC-50 head, for which the schematic specifies a 465V B+. The last time I checked the amp, it was at 515V. That's 50V higher than it should be, and a full 15V above the rating on the filter caps. The amp hasn't had any problems, but my Oranges never had any voltage issues like that.

I'm pretty sure the thinking with Oranges not having a standby is that the amps were originally designed to be stadium amps and were intended to be played at loud volumes, probably for long periods of time. The main source of tube wear would be from that, and any premature wear from not having a standby would be neglegable. Then came the master volume models, as people needed that Orange overdrive at more reasonable volume levels.

Nowadays, I think the way most people use the amps, they can benifit from having a standby switch. It's not a necessity, but I certainly have one on both my OR-120's (Though I actually sold one not too long ago).

Back on the original topic, if you have a power conditioner already, and intend to use it still...it couldn't hurt to carry around a variac if you wanted to. Though I don't think it's necessiary. The power conditioner should take care of any damaging voltage spikes, even though it doesn't have line regulation. But if you're worried about it, have the tech measure the B+ voltage at the highest constant wall voltage you would see in your area. I know around here I see 122V or 123V, but not really any higher than that. My 70's head has never risen above 517V or so on the plates, and all the filter caps are rated a fair deal above what they're seeing. The heater voltages have never been too high either. If you're concerned about any of that, just tell him to take a few minutes to measure it out and let you know what things look like.

Hope that helps.

-Nick

Andy H. · Post by **Andy H.** » Sun Nov 19, 2006 2:04 am

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by fiveightandten
[brI'm pretty sure the thinking with Oranges not having a standby is that the amps were originally designed to be stadium amps and were intended to be played at loud volumes, probably for long periods of time. The main source of tube wear would be from that, and any premature wear from not having a standby would be neglegable. Then came the master volume models, as people needed that Orange overdrive at more reasonable volume levels.

Nowadays, I think the way most people use the amps, they can benifit from having a standby switch. It's not a necessity, but I certainly have one on both my OR-120's (Though I actually sold one not too long ago).
<hr height="1" noshade id="quote"></blockquote id="quote">I agree there. I've never really worried about not fitting one to my OR120, but then again my policy is that it goes on at the start of the night and stays on until I'm done with it. Most of the valve wear is me enjoying putting out the bass...

Andy.

BayofPigs · Post by **BayofPigs** » Sun Nov 19, 2006 3:22 am

The autotransformer is just a step up transformer to run the amp at 240V. That is what they called it on the Plexi Palace page.

The voltage taps on my amp are 115, 200, 220, and 240. It is a 75 OR120. I run the amp on the 115 tap. Does the actual voltage equal what is labled on the chasis or is the only way to know for sure is to test it?

I think I just freaked a little when I read the article. Thanks for the help. I will definetly take this information to the tech and see what he thinks.

Andy H. · Post by **Andy H.** » Sun Nov 19, 2006 10:32 am

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by BayofPigs
 The autotransformer is just a step up transformer to run the amp at 240V. That is what they called it on the Plexi Palace page.

The voltage taps on my amp are 115, 200, 220, and 240. It is a 75 OR120. I run the amp on the 115 tap. Does the actual voltage equal what is labled on the chasis or is the only way to know for sure is to test it?
I think I just freaked a little when I read the article. Thanks for the help. I will definetly take this information to the tech and see what he thinks.
<hr height="1" noshade id="quote"></blockquote id="quote">What do you mean exactly? The US mains supply is (in theory) 120v these days I believe, so yes you want to use the 115v tap - it is closest.

The actual voltage coming out of the wall will vary, (sometimes by a surprising amount), under different user load conditions such as day to night, and when the adverts come on during the big game. To be sure of the voltage you'd have to measure it. If you do that then make sure it doen't measure you up for a wooden box while you're at it!

Bear in mind that as the mains varies, so will the voltages output from your step up or variac transformers. If not a regulated box, (as 5/8/10 suggested), then its output voltage will vary by the same percentage, high or low, as the mains supply itself did.

Andy.

fiveightandten · Post by **fiveightandten** » Sun Nov 19, 2006 3:34 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by BayofPigs
 The autotransformer is just a step up transformer to run the amp at 240V. That is what they called it on the Plexi Palace page.

The voltage taps on my amp are 115, 200, 220, and 240. It is a 75 OR120. I run the amp on the 115 tap. Does the actual voltage equal what is labled on the chasis or is the only way to know for sure is to test it?

I think I just freaked a little when I read the article. Thanks for the help. I will definetly take this information to the tech and see what he thinks.
<hr height="1" noshade id="quote"></blockquote id="quote">
Ahh. Gotcha. Autotransformer = step-up transformer. Fair enough.

Andy explained it pretty well, but just to reiteriate...

It's like the gearing in your car. If you're in 5th gear on the highway and the tach is reading 3,000 RPMs at 80MPH...if you bring the tach up to 3,500RPM, you may be going 85MPH. The gearing ratio in the transmission determines how much of an increase in speed you get from an increase in engine RPM. A different car may only increase speed from 80MPH to 83MPH with the same change in RPM in the same gear, just the same as a Vox may see a bigger change in internal voltage from the same change in wall voltage.

In the amp world...

The power transformer does exacly that. It transforms the wall voltage...in 2 ways actually. First, it ramps the wall voltage UP, from our US voltage in your case of about 120V or so...up to maybe 350V or so for the B+ supply to the tubes. The actual B+ is around 500V or so, but the rest of that ramping up is done by the rectifier.

The 2nd transformation that occurs is the PT ramping DOWN the 120V wall voltage to about 6.3V for the tube heaters. (I'm ignoring bias taps completely, for simplicities sake...you don't want to have to factor that in!)

This is accomplished by 2 seperate 'windings' on the transformer. An abridged way of thinking about the windings would be that a set amount of wire is wound around the core of the transformer. That amount of wire pre-determines the ratio of voltage change. In our case (in your amp right now in 2006), we have the following:

-120V coming in to what we call the primary winding, the side commected to the wall

-364V (or so) coming out the 1st "secondary" winding for the B+. So we'll say that this winding multiplies the input voltage by about 3.04.

-6.6V (which is slightly high, as it supposed to be 6.3V. But within reason) coming out the 2nd secondary winding, for the tube heaters. So we'll say this winding multiples the input voltage by about .055.

...

So, hop in your Delorian and turn the clock back to 1970 when your amp was made. They designed those ratios based on the wall voltage at the time. Say they were expecting 115V...they designed that primary tap on the PT to have a ratio that would turn the input voltage of 115V into the desired output voltage. Take a look at the difference:

In 1970 (as things were intended):
-115V in
-115V x 3.04 = 350V out for the B+ (again, this is AC and would get ramped up again when the rectifier changes it to DC)
-115 x .055V = 6.3V

In 2006:
-120V in
-120V x 3.04 = 365V
-120V x .055 = 6.6V

Or let's say you go to a club where the wall voltage is 122V:
-122V in
-122V x 3.04 = 371V
-122V x .055 = 6.7V

Now...not to completely discount all the stuff above, but don't be worried about the numbers you see above. They're there more for conceptual understanding than actual real world situations. There's other things to take into consideration, like how the rectifier affects things, and how the load the tubes put on the amp affects things. If I calculate a 21V increase over 'normal' at a wall voltage of 122V, it doesn't mean you'll necessiarily get that in the amp after all is said and done. Again, just use the above examples to understand how things work...not as real world calculations.

But now you know. And if you have a tech measure what's going on in the amp at a specified input voltage, you can make a determination as to weather or not it's something that concerns you (intended voltages can me found on schematics). My guess is that you'll find there's not much to worry about with these amps.

Hope that helps.

-Nick

BayofPigs · Post by **BayofPigs** » Mon Nov 20, 2006 1:24 am

That definitely helps. Thanks, Nick and Andy.

ironlung40 · Post by **ironlung40** » Sat Jan 28, 2017 3:07 am

Hey Nick and Andy,

I know I am resurrecting and old thread, but I know you guys are still active in here.

So, I just want to be clear, and a just in case you guys have learned something new since this thread:

I am running my OR120 on the 115 tap. My voltage in my home is anywhere from 120 to 123 volts, usually.
Am I risking damaging my power transformer doing this, or am I probably o.k.? I am a bit worried now as I just recently bought a Laney Supergroup 100 and from the internet lore I have read I am afraid to plug this guy up without a variac or step up transformer. It only has a 110, 210, 230, and 250 selector for voltage.

Would you pick a variac over a step-up transformer to run my OR at 115 and the Laney at 110 or at 240 and 250 if you were to filter the power?

Thanks,

Ironlung

Post by **bclaire** » Sat Jan 28, 2017 3:29 am

No experience with it but how about this:

https://www.sweetwater.com/store/detail/Brownie" onclick="window.open(this.href);return false;

or

https://www.sweetwater.com/store/detail/BrownBox" onclick="window.open(this.href);return false;

ironlung40 · Post by **ironlung40** » Sat Jan 28, 2017 2:14 pm

Wow, those brownies look great! They are fuse protected too, which would be a must for me. It seems they also act as a power conditioner which is really cool too. They are expensive though! An old variac can be had for way south of $100 usd and a step up transformer for south of $50 usd. But, the wattage capability, the power conditioning, a/b ability, and the size probably justify the cost of these.

Thanks for the link, Billy. I would not have known these were on the market or an option without it.

Gladmarr · Post by **Gladmarr** » Sat Jan 28, 2017 6:05 pm

Here's the poor man's DIY version of either a variac or that brown box dealie.

http://www.angelfire.com/electronic/fun ... Boost.html

ironlung40 · Post by **ironlung40** » Sun Jan 29, 2017 3:00 am

Sweet!

That could become a project.

fiveightandten · Post by **fiveightandten** » Sun Jan 29, 2017 4:43 pm

ironlung40 wrote:Hey Nick and Andy,

I know I am resurrecting and old thread, but I know you guys are still active in here.

So, I just want to be clear, and a just in case you guys have learned something new since this thread:

I am running my OR120 on the 115 tap. My voltage in my home is anywhere from 120 to 123 volts, usually.
Am I risking damaging my power transformer doing this, or am I probably o.k.? I am a bit worried now as I just recently bought a Laney Supergroup 100 and from the internet lore I have read I am afraid to plug this guy up without a variac or step up transformer. It only has a 110, 210, 230, and 250 selector for voltage.

Would you pick a variac over a step-up transformer to run my OR at 115 and the Laney at 110 or at 240 and 250 if you were to filter the power?

Thanks,

Ironlung

Just to be clear, it's not really the power transformer that is at risk. The transformer just "transforms" the wall voltage to a higher voltage, which feeds the rectifier in the amp. It also has taps to transformer wall voltage into a lower voltage for the bias supply and heater circuit. I'd say the potential for PT damage is very very low due to a slight increase in wall voltage.

What CAN be at risk are the components in the amp. If you have caps that are rated at, say 500V, and they're seeing higher than expected voltage due to an increased input voltage, they can fail.

That being said, the components in your Orange should be fine. For the Laney, I would measure the B+ and see if it's exceeding the rating of any of the caps in the power supply. That's the biggest concern.

BTW, the Brownie is definitely underpowered for an OR-120 or Supergroup. The brown box might cut it. I haven't done the math, but EL34 heaters draw a ton of current, and a 4 x EL34 power section is pretty hefty. Be sure that unit can handle it.

Here's the thing about altering input voltage. You would have to set your amp up for whatever voltage you want to run it at. So if you buy a Brown box and run the OR-120 at 115V (or the Laney at 110V), you are married to that voltage. You can't forget to bring it to a gig and run the amp, you'll overcook the tubes, as they'd be biased for the lower voltage. If a knob gets bumped on that unit and increases the voltage, you're in trouble.

IMO, your OR-120 is totally fine. For the Laney, it would be wise to have a look at what's happening at your wall voltage and make a decision that way. I mentioned it above back in 2006, but I run my Vox AC-50 heads at modern wall voltage and those are running on their 110V taps. The B+ is way higher than it is spec'd for, but I made sure the components in the amp aren't being pushed beyond their limit. The amp doesn't sound the same as it would running at 110V, but they run reliably.

There's merit to running amps like this at the intended voltage. But you do need the right equipment to do it, and it's a commitment in terms of adding complexity to your rig, and making sure you always keep an eye on the power that's feeding the amp.

Another option is installing a high powered Zener diode to drop the voltage in the amp. You can google that and read up on it a bit.

-Nick

Does anyone use a variac with their OR120?

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