High quality 120V to 240V AC Mains transformer for permanent install

[ruairioflaherty]

Hi All,

I have a European client building a studio we designed (in a Frank Lloyd Wright home no less) and he wants to include a permanent wall mounted 240V outlet for his EU gear and visiting producers.

Does anyone have experience with high quality options for this?

Current draw will be relatively low, a guitar amp, or a few pieces of outboard etc.

Thanks.
Ruairi

 

[ruairioflaherty]

I understand code implications and an electrician will be doing the install. This is just to make permanent something he is doing wityh cheap wall warts right now.

 

[sahib]

Hi Ruairi,

I have used Avel Lindberg (in the UK) a number of times. Very high quality stuff. Their US web site

https://www.avellindberg.com/transformers/d4000_range_specs.htm

 

[abbey road d enfer]

I thought most places in the US had a 220V distro for the oven, range and other appliances that need extra power? At least, it's the case in my NOLA condo. In that case, it's a balanced distro, which should not cause any issues with european gear.
The other obvious solution is using a step-up xfmr, with the problem that it generates intense magnetic field (and also noise), so it needs to be installed at a distance.
In order to avoid undesirable confusion, the 220V should be on Schuko wall sockets.

 

[ccaudle]

I thought most places in the US had a 220V distro for the oven, range and other appliances that need extra power?

Yes, power to the premise is distributed as center tapped 240V. You could just run a 240V feed to the studio. I do not know if Schuko sockets are approved for permanent installation in the US, so depending on what the local building code stipulates you may have to install US style 240V sockets and use adapter cables.

 

[abbey road d enfer]

I was not aware of the existence of 240V domestic receptacles. The range in my condo is hard-wired.

 

[Brian Roth]

Indeed, something like this:

https://www.platt.com/p/0035220/lev...-6-20r-white-side-wired/078477249871/lev5821w
They are commonly used for window air conditioning units.

Bri

 

[ruairioflaherty]

I realize now my post was incomplete.

Yes, aware of the option to to use the 240V coming onto the property but my gut says the extra isolation of a set up transferring is a good thing.

Abbey is right re noise, and the potential for hum. With a good torrid I expect radiated EMI under small load would not be an issue.

Thanks everyone.

Cheers,
Ruairi

 

[Brian Roth]

Any idea of the anticipated maximum current load for the 240 VAC circuit(s)? Obviously, a 100VA toroidal xfmr costs less than (for example) a 2000VA.

I would also consider a "1:1" iso xfmr (240 VAC -> 240 VAC) which would be fed from the existing 240 VAC available in the building. I can't see a reason why a 120 -> 240 VAC xfmr would offer any advantages. In fact, going the 1:1 route would result in lower voltage drop/better voltage regulation on the incoming primary side from the circuit breaker panel, especially if the wiring run is long-ish.

Bri

 

[JohnRoberts]

I was not aware of the existence of 240V domestic receptacles. The range in my condo is hard-wired.

240VAC outlets are common for appliances, my dryer in the laundry room has a plug and outlet. Also my old in-wall air conditioner had a 240VAC outlet. OTOH my stove, wall oven, and hot water heater are hard wired, likely to save cost.

The euro gear should be happy at 60 Hz (less ripple voltage on PS capacitors).

[edit- you could rig up a 240v outlet to test. The typical 120v branch circuits are line with 120vac and neutral with 0V. About half the outlets will have the other polarity 120vac line. With a couple long extension cords you should be able to grab power from both polarities that will have 240VAC across them.

Of course if you are not comfortable messing with mains voltage don't . you could probably use a euro 230V outlet strip with a US 240V plug attached to the line cord. And plug that into a 240v outlet. That should keep the code police happy (but don't take my word for it). [/edit]

JR

 

[Brian Roth]

[edit- you could rig up a 240v outlet to test. The typical 120v branch circuits are line with 120vac and neutral with 0V. About half the outlets will have the other polarity 120vac line. With a couple long extension cords you should be able to grab power from both polarities that will have 240VAC across them.

Several months ago I had to test the main "DSP" rack of a Neve Capricorn desk in a temporary location with no convenient 240 VAC power source. So, a kludge wiring with two long extension cords wired into a junction box that then supplied another "pigtail" with the required 240 VAC female connector for the Neve rack.

Paraphrasing Mr. Rogers: "Can you say Cluster Fµck? I knew you could!"

Hey...I got the task completed....

Bri

 

[ruairioflaherty]

Any idea of the anticipated maximum current load for the 240 VAC circuit(s)? Obviously, a 100VA toroidal xfmr costs less than (for example) a 2000VA.

I would also consider a "1:1" iso xfmr (240 VAC -> 240 VAC) which would be fed from the existing 240 VAC available in the building. I can't see a reason why a 120 -> 240 VAC xfmr would offer any advantages. In fact, going the 1:1 route would result in lower voltage drop/better voltage regulation on the incoming primary side from the circuit breaker panel, especially if the wiring run is long-ish.

Bri

Unfortunately no solid sense of load but it's a small production studio, it will never be more than a guitar amp, a few pedals or maybe a vintage mic.

I think using the 240 coming into the property is the way to go, preferably with the 1:1 isolation transformer, even though it may be gilding the Lilly. If there is space we could locate that transformer at source and out of the studio to negate radiated noise.

Thanks all.

 

[ruairioflaherty]

The euro gear should be happy at 60 Hz (less ripple voltage on PS capacitors).

[edit- you could rig up a 240v outlet to test. The typical 120v branch circuits are line with 120vac and neutral with 0V. About half the outlets will have the other polarity 120vac line. With a couple long extension cords you should be able to grab power from both polarities that will have 240VAC across them.

The euro gear willl change with different visiting producers etc so no set roster to test, with that I am not giving any guarantees. Something like an analog tape machine may not be happy.

The electrician will be able to handle this no problem.

 

[Brian Roth]

I am a realist/pessimist. I recall back in the 1990's when I was involved with a new "home studio" that was being built in Tulsa, and the owner was a huge fan of vintage Euro mics and outboard gear. What began with a "few" 240 VAC pieces of equipment quickly ballooned with the addition of two Studer J37 4 track machines ("Hey! It's what the Beatles used!!") and the required large McIntosh power amps (and a HP audio generator) to supply the necessary 50 Hz power for the Studer transports (capstan motors).

EDIT: One large Mcintosh amp, with each channel feeding a 24VAC to 240 VAC step-up transformer for each Studer.

Never ASSume anything....

Bri

 

[Script]

Indeed, something like this:

https://www.platt.com/p/0035220/lev...-6-20r-white-side-wired/078477249871/lev5821wThey are commonly used for window air conditioning units.

Same in Japan (generally 100V). Electrician just hooked cables together for 200V outlet (takes 10 minutes) and used same socket as in the link.

 

[Tubetec]

I know a guy who bought a load 110V studio gear from a guy selling up here ,
So he ended up with a mix of 110 and 230 v gear running in the studio ,
There wasnt a good system in place to differentiate the 110 and 230 v circuits , like colour coded plugs /cables ,
clear labeling to tell him which pieces were 110v and some form of non mating recepticals to help prevent the wrong voltage being applied .
He ended up blowing the crap out of loads of stuff by connecting it to the wrong supply .

So lets say you have your 110v supply , neutral bonded to ground at the utillity in the usual way , then you have a 240 step up with a centre tapped ground , what happens if someone makes an audio connection between a 110v and a 230v powered device , or even makes physical contact to metal work at different potentials ?

So obviously the safety of the people using the gear is the primary concern ,
Theres inherent differences between the US 110v and the 230v EU system ,
I hesitate to give any advice in this respect , I'm not well versed enough .

Safety of the equipment is secondary , but again its difficult to make it fool proof when you want guests to be able plug and play , the safety requirement might fight whats best practice in terms of noise , what happens if someone arrives with a miswired bit of equipment plugs it in and the thing becomes unsafe in some way ?

The guy I knew who blew up much of his gear by applying 230v to 110v equipment could have saved so much trouble by simply
reconfiguring the 110v stuff to 230v on the back panel in many cases .

The safety convention here in Ireland is 110v is yellow , 230v blue and three phase is red , each system has its own unique keyed colour coded receptical and connector that wont mate with the others , and in the case of 110 and 230 they also use yellow and blue cable respectively .

We had a few non export model US made tube amps down in Sulan , each had its own 230-110v transformer installed , probably around 250-500VA , We kept a few smaller iso and autoformers for the clients to step down if they required it we'd figure out the best way to do it on a per case basis , more often that not they brought their own arangement to get 110v .
We didnt make 110v available to the client from the wall anywere in the building appart from the shaver sockets, If you do want to make your own 230v supply for the owners gear my advice is make it in such a way theres no possible way anyone can hook up without oversight of staff and a special adapter cable .

Nothings fool proof 100% , there are intrinsically safer ways to do things though .
Best of luck ,

 

[gyraf]

With a European moving over there, please persuade them to install a GFI relay regardless of what 230V-solution you come up with. These are mandatory in EU, so we kinda expect them to be there without thinking about it..

In our old studio we had a 500VA 115V outlet (from a simple step-down toroid) for visiting engineers - that size covered all the internationality we ever needed (but the 60Hz for hammonds)

/Jakob E.

 

[Whoops]

We had one of this permanently installed in our studio for visiting 110V clients.
It was great.
We had a 4000w model because we never knew what was coming in terms of power draw, but you have the same type of transformers with smaller Watts ratings.

 

[ruairioflaherty]

Thanks all for input.

The electrician is asking if we need the addition of a neutral and I"m reminded why I prefer mastering records to designing studios

He says a Euro 240V is Hot, Neutral and Ground. Whereas U.S. 240V outlets are 2 x 120V Hot with no neutral, and a ground.

He's pulled cable for the 240V but would need more if we add a neutral, and I'm out of my depth,

Is my intuition to have an isolation transformer overkill? I would prefer to proceed without if we can.

And noted re GFI Jakob, thanks.

 

[Brian Roth]

No requirement for a Neutral in this situation. You need two "hots", each at 120 VAC to ground/neutral but 180 degrees "out of phase" with each other which results in 240 VAC from hot to hot. A third conductor to the receptacle provides the protective grounding connection.

Sidebar: this assumes the building is fed with conventional "single phase" power, which is somewhat confusing in terminology. The ordinary USA residence or smaller sized commercial building is supplied with three conductors from the electric utility company. Two conductors are "hots" with 120V to neutral, but 240 V hot-to-hot as described above. In my pea-brain, that is TWO phase power, but it is called single phase in the USA.

I mention this because larger commercial buildings (and a few gigantic mansions) are supplied with three phase power which is another kettle of kippers. Three phase power in the USA is provided in two configurations, "Wye" and "Delta" which have oddball voltage combinations between the three hots and the neutral. Most likely a non issue in the current discussion, but something to be aware of.

An iso transformer is not a bad idea, but expensive to add. I did a quick online search for toroid transformer choices and saw that Equitech (better known for their "balanced power" devices) makes iso xfmrs.

https://equitech.com/isolation-transformers/
Another one that popped up was this company:

https://toroid.com/general-isolation-transformers/
Bri