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Changing an amps voltage?

paulscape

Member
Messages
3,548
I know nothing about this. Are some amps able to switch between various voltages (110-240) on the fly or are specific transformers needed for each voltage? How safe is it to use an external voltage converter with an amp? The reason I ask is because I often see amps I want to purchase on the emporium but I live in a 240v country.
 

michael patrick

Loud and proud
Silver Supporting Member
Messages
10,992
Depends on the amp. Some amps have a switch for choosing which voltage to run on. Others you'd need an outboard voltage step up/step down transformer.
 

StompBoxBlues

Member
Messages
20,246
In my experience, the outboad voltage converters (that are safe!)
are heavy-duty transformers that bring the 240 down to 110. They work fine, but if you play out, it is a pain in the rear.

As MP answered, there are some amps that have a switch (usually you have to make sure to change the main fuse as well...when you double the voltage, you halve the current, so usually a 2 amp fuse (at 110vac) will change to a 1 amp fuse (240vac).

Usually when they do this, they put this info on the back.

Depends how much a deal you get I guess, but generally, amps that are only 110, you can have a tech change out the power transformer. Transformers cost a little..
 

paulscape

Member
Messages
3,548
Ok so an amp like a marshall plexi, which has the voltage selector switch on the back, all Id need to do is change the fuse to 1 240v...but I wouldn't need to change transformers aswell would I?
 

StompBoxBlues

Member
Messages
20,246
Ok so an amp like a marshall plexi, which has the voltage selector switch on the back, all Id need to do is change the fuse to 1 240v...but I wouldn't need to change transformers aswell would I?
Probably need to double check, but if I get you right, yes. If it was set to 110 and had the correct fuse in it (rated, or it says on the back most likely) then you would have to switch it to 240, and am pretty sure you would have to get the same type fuse (slo-blo usually) but rated for 240 v. and half the value of the one that is in there for 110.

BUT...I wouldn't listen to just me. If you are contemplating getting one, contact Marshall!! Either they have that info in the manuals, a FAQ, or just email them or call. Best to hear it from the horses mouth...

Just one other thing I was wondering...when it comes to Marshall amps...they were made in the UK, where it is 240...so I'm just wondering when you factor in shipping (expensive and risky with overseas) etc. can you really get a better deal than you can where you are...or from England where it already is either set to 240, or only 240v?
 

paulscape

Member
Messages
3,548
Probably need to double check, but if I get you right, yes. If it was set to 110 and had the correct fuse in it (rated, or it says on the back most likely) then you would have to switch it to 240, and am pretty sure you would have to get the same type fuse (slo-blo usually) but rated for 240 v. and half the value of the one that is in there for 110.

BUT...I wouldn't listen to just me. If you are contemplating getting one, contact Marshall!! Either they have that info in the manuals, a FAQ, or just email them or call. Best to hear it from the horses mouth...

Just one other thing I was wondering...when it comes to Marshall amps...they were made in the UK, where it is 240...so I'm just wondering when you factor in shipping (expensive and risky with overseas) etc. can you really get a better deal than you can where you are...or from England where it already is either set to 240, or only 240v?
Oh Ive already got a nice marshall - was just using that as an example of an amp I know that has the switch selector on the back between 110-240. My other amps Ive bought have come straight from the factory 240v. What Im mostly looking at is older second hand BF or good SF clean fender amps - all the bargains are usually in the US. For better or worse a lot of people in the states 'won't ship internationally' so my wallet is kept shut even before thinking about voltage issues haha. As you mentioned before I can use an external voltage converter but yeah its an extra hassle.
 

StompBoxBlues

Member
Messages
20,246
Oh Ive already got a nice marshall - was just using that as an example of an amp I know that has the switch selector on the back between 110-240. My other amps Ive bought have come straight from the factory 240v. What Im mostly looking at is older second hand BF or good SF clean fender amps - all the bargains are usually in the US. For better or worse a lot of people in the states 'won't ship internationally' so my wallet is kept shut even before thinking about voltage issues haha. As you mentioned before I can use an external voltage converter but yeah its an extra hassle.
Where are you by the way? You know what probably would be the best thing to do is just call one or two of your local amp-repair places (if you don't know any, just ask at the music stores, they must have someone) and ask them what it would cost to replace the power transformer. Just pick a BF and SF example you know you might want.

Once you know what it costs (I have no idea, but guessing that the trafo is the lions share of the cost) THEN you can really calculate if the savings are worth it for you.

Like I said, those power converter boxes are really heavy, pain in the...and I don't now you but for me really not worth it. I'd figure out the diff between buying locally, or getting from the US, factoring in shipping (which will be expensive!), and either cost of converter or repair shop shifting the trafo...against prices local.

Of course, like you say, folk are so weird about shipping overseas. I don't see a huge difference between shipping from NY to LA, or from NY to Europe...other than customs. But it can be hard. Maybe the best bet there is to check music stores that will ship internationally, that have used amps, etc. (they may even be able to outfit with the right trafo before shipping?).

I know here in Norway, ALL music prices are way higher than the states, but when you factor in the hassles, risk, and extra work...I usually end up just buying here.

Oh yeah...don't forget to factor in the VAT taxes (import tax)...here in Norway it is like 25% I think.
 

xroads

Member
Messages
2,464
3 options:
- amp has a voltage selector => easy to switch
- amp has no voltage selector, but its transformer can be rewired to different voltages (transformer coils have different tabs, a tech can do the rewire)
- amp has no voltage selector, and transformer can't be rewired => you need a different transformer in the amp, or an outboard voltage transformer.
 

StompBoxBlues

Member
Messages
20,246
3 options:
- amp has a voltage selector => easy to switch
- amp has no voltage selector, but its transformer can be rewired to different voltages (transformer coils have different tabs, a tech can do the rewire)
- amp has no voltage selector, and transformer can't be rewired => you need a different transformer in the amp, or an outboard voltage transformer.
That is a good point about some trafos that have the wires, they just aren't being used. Saves money.

Anyone know if fender amps generally have switchable trafos, or the wires are there just unused, or is it some do and some don't?
 

paulscape

Member
Messages
3,548
3 options:
- amp has a voltage selector => easy to switch
- amp has no voltage selector, but its transformer can be rewired to different voltages (transformer coils have different tabs, a tech can do the rewire)
- amp has no voltage selector, and transformer can't be rewired => you need a different transformer in the amp, or an outboard voltage transformer.
So if the amp has a voltage selector I don't need to change transformers - just flip the switch on the back?

Stompboxblues - I'm in shanghai so it's hard to get transformers...well good ones anyway! Gear that's here though is about the same price as US, just no old fender amps floating around :)
 




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