US 115V rated gear in 100V rated country?

[Matt Syson]

Hi
You should aim to get the 'nominal' voltage withing the rated voltage band. The main isues you would have would be power line frequency related 'ripple' (typically double the mains frequenct predminantly).
Valve gear that does not have 'regulated' supplies will change performance slightly. For example a TubeTech unit is mostly regulated but the HT for the final output stage is not so there is a possibility that you may 'lose' a dB or two OUTPUT headroom. Since this is well in excess of +28dBu into a load greater than 600 Ohms this is not exactly an issue.
Other kit such as a LA2a for example would also alter slightly as it's supplies are not regulated.
It should be relatively cheap to get a 'step up' transformer sorted out so that your supplied 100 Volts can be made up to 115 Volts. You may actually find that the '100 Volts' is actually 'high' so making conversion not worthwhile.
ALL gear is designed to tolerate a range of supply, typically around 10 percent so you are almost in the range anyway.
To be told that reducing the supply for gear that uses REGULATED internal supply rails is total £$^& for the simple reason that unless the mains is too low, the GEAR inside won't know what the actual mains supply is until it is so low that it drops out of regulation.
Matt S

[solidstate]

Thanks Matt! So do you think I could get away with a standard step up transformer? I'm no expert, but won't it make worse noise-wise? Like hum o buzz? I do have a couple of furman power conditioner to prevent this kind of things though..

[Matt Syson]

Hi
You only need a decent 'step up' autotransformer. In essence it is a 100 Volt mains transformer with a 15 Volt (say) secondary at (say 10 Amps) which is wired such that the 15 volt secondary ADDS to the 100 Volt mains that is coming in. Thus this transformer only adds the DIFFERENCE which is 15 Volts as I propose, not the full power that an isolated step up transformer would give. In this scenario the transformer is rated at 15 Volts X 10 Amps which is 150 VA which are quite cheap. A transformer to provide 10 Amps at 115 Volts in a 'conventional' way would need to be 1150 VA, MUCH larger.
ANY big transformers must be placed at least 1 metre away from audio gear / cabling.
Power conditioners should not really be necessary in any half decently wired studio and they are a 'band aid' for sloppy design.
Matt S

[solidstate]

Hey Matt,

thanks for helping me with this. You mean a "stepdown autotransformer" right?

I've found this: (sorry Japanese only, I used google translator and looks like this one might work)

SH (

Will it be ok to use it in the same room with my other gear? If not, do you have any suggestion?

Here a few more, I can't tell which one is good though!

http://www.soundhouse.co.jp/shop/Sea...ategory_cd=380

[Speedskater]

If you live in an area with 100V available and the piece of equipment is designed to operate on 115V (newer equipment might be 120V or even 125V) then you need a step-up transformer to raise the voltage to a higher level.
But I think that most equipment (with the exception of power amplifiers) that are designed for 115/120V operation will work OK on 100V.

The bigger question is are you in a 50 Hz or a 60 Hz area. A transformer designed for 60 Hz will not be happy on a 50 Hz supply. But a 50 Hz transformer is OK with 60 Hz.

[Matt Syson]

Hi
You actually need to step UP as just posted above.
Japan is super technical and has lots of good egineers, if you can find them, to help with specific problems. You need to get talking to some guys near you.
Sorry I can't remember the name of one tech I was friends with who was at AMEK's dealer in Tokyo as it was about 14 years ago when I was last there (more's the pity as it was fascinating).
Matt S

[solidstate]

Indeed I asked a tech to come over next week. I just wanted to get more educated on the subject meanwhile.. Now Except from 1 piece of gear(namely the UA dcs preamp) all my equipment is 50/60hz. As far as I understand there is no way to convert the input frequency. So I guess my only solution is ask to the tech to change the transformer(ua already say they don't have one for the Japanese market). Now, about that stepUP transformer can someone post a link just so I understand what to look for?

Thanks in advance!

[gingataff]

The link you posted is a step up. 100v in, 115v out. Presumably the bigger, chunkier and more expensive the transformer the better.

FWIW I contacted Furman's tech support recently asking them if it's ok to use their US power conditioners in Japan (which are rated to run on something like 90v~130V).
He said that the only problem might be that 50Hz mains would cause the unit would see a higher voltage than normal and this might trip the surge protection circuit.
If that's the case perhaps other equipment would also see a higher than 100v voltage and a transformer wouldn't be necessary?
I'm thinking aloud so someone please correct me before someone gets hurt.

[Matt Syson]

Hi
A transformer rated for 60 Hz will not produce a significantly higher voltage when run at 50Hz, in fact slightly the opposite.
The frequency MAY cause a problem if there is insufficient iron core (it may buzz, overheat perhaps) but the voltage out should be much the same, certainly within tolerance.
The Furman conditioners MAY have an issue and you HAVE to contact them directly for their comments. DO NOT use website / forum info for this as it could be dangerous.
Having a LOWER frequency mains will REDUCE the DC available slightly as the reservoir capacitors have LESS time to 'recharge' during the mains cycle.
I have not seen the link but 100 Volt in and 115 Volt out sounds good to me. Work out the power requirement for your studio (or at least the units that are to be fed with this transformer) and allow plenty for new toys you may get in the future.
If it is only the UA gear that is unhappy with 100 Volts but is rated for 50 / 60 Hz, you could use a much smaller step up transformer for that unit only.
Matt S

[Speedskater]

The difference between 50Hz power transformers and 60Hz transformers is that the 50Hz have more iron in the core and are heaver. Many 60Hz transformer will have their core saturate (overload) when operated at 50Hz.

If you have a skilled technician, you may talk about using a buck/boost transformer to correct the voltage.

Bucking Xfmrs

[Matt Syson]

Hi
That 'Bucking transformers' link tells you practically all you need to know. As I said earlier a 15 Volt 10 Amp (output specification) transformer would give you about 10 Amps at 115 Volts which would power a reasonable amount of gear (1150 VA) and as they should be available as 'standard' transformers near you they should be cheap. You MUST of course have it put in a proper box of some sort with fuses included for safety.
Matt S

[solidstate]

I guess I'll have the tech look into this.. It's waaaaaaaaaaaaaaay over my head

Thanks for trying folks