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Voltage Converter Question

The Sad Mafioso

The Sad Mafioso

Guest
Dec 25, 2011
26
0
35
Greater Manchester, UK
#1
OK, so I need a voltage converter in order to get my amp working. From what I've worked out it needs at least 1k VA to get it up and running, so I assumed the converter would need to be compatible with that. I went to my local music store to try and find one and the guy told me that he was 'pretty sure' that the one he had would work. I was sceptical when I saw that it was marked at 100W (only a tenth of what I thought I needed), but he assured me that I could always take it back if it didn't work. So my question: is it worth me giving the 100W converter a try or would that just potentially do more damage to the converter and/or the amp? Thanks in advance for any help.
 
#2
If the transformer blows, you can damage your amp. Why take the risk. It sounds to me like the store has a unit that they want to sell and are trying to pawn it off on you.

What type of amp do you have and what are the power specifications?

100W / 220V = 0.45A is not a lot of current capacity for most amps. On the other hand, your estimate of a 1000W converter would provide 4.5A. Actually less because there is loss in the converter which is dissipated as heat. Calculate what you need and then add a 25-50% safety factor. When you turn on your amp and the power supply capacitors are discharged, there will be an initial surge of current. Your converter has to be able to cope with this. Some converters are designed to meet their specs, the better ones generally exceed them.

My advice is to get the right converter for the job. Go with quality. Be less concerned about the unit's size and weight.
 
#3
beans-on-toast said:
What type of amp do you have and what are the power specifications?
Click to expand...

I'm using a GK 800RB. It says on the back next to the power input '120V' '8A', so that means it would need a converter designed to handle at least 1k VA, right? (8 x 120 = 1,000) I'll just take the converter back, say it didn't work and order Invalid Link Removed unless anyone else has any input on the subject.
 
#4
The 1000W would work well for your amp. Carroll & Meynell makes a very good product. I don't think that you'll go wrong with their transformer.

My GK800RB schematic indicates that there are two different transformers available, a 110V and a 220V. The schematic is old and it is possible that your amp is newer and has a dual voltage transformer inside it. If this were the case, a couple of simple wiring changes inside, a new power cord and fuse would be all that you need. It might be a good idea to take the time to send GK an email, give them your serial number, and ask if your amp can be rewired from 110V to 220V operation. There is also the possibility of buying a 220V transformer that can be installed inside your amp from a local service center.
 
#6
Thanks for the info. I think that I'll opt to get the external transformer so that if I get any more American-made products in the future I'll have a way of stepping down the current. In terms of fuses, I'm guessing that the one that came with the amp should still be suitable. It's actually a 4A 250V fuse, so I'm guessing that could work with either current, but if I have any problems with that I'll just order some 8A 125V fuses (the type it suggests I use on the back of the amp).
 
#7
According to GK, they recommend a 3AG7A (7A 250V) for 115V, and a 3AG4A (4A 250V) for 230V operation. Best to get the correct fuse and some spares.

3AG specifies a standard cylindrical glass, 0.25" (6.35mm) diameter, 1.25" (32mm) length. The next number is the current spec, 7A is seven amps. It is a regular fast blow fuse. The 250V spec for 115V operation is normal.
 
#9
beans-on-toast said:
According to GK, they recommend a 3AG7A (7A 250V) for 115V, and a 3AG4A (4A 250V) for 230V operation. Best to get the correct fuse and some spares.

3AG specifies a standard cylindrical glass, 0.25" (6.35mm) diameter, 1.25" (32mm) length. The next number is the current spec, 7A is seven amps. It is a regular fast blow fuse. The 250V spec for 115V operation is normal.
Click to expand...

Thanks again for the help. I'll order up these fuses. Like you say, it'd be better to play it safe and get the exact fuses GK recommends.
 
#17
beans-on-toast said:
You'd think so. Some companies choose to not sell a product in Europe rather than go through or pending completion of the certification process.
Click to expand...

The 800RB would not pass CE due to the heat from the rear exposed heat sink. Would have required major redesign and RAG did not want to make any changes to the 800RB unless absolutely necessary. So Europe missed out on the 800RB.
 
#18
The Sad Mafioso said:
Thanks for the info. I think that I'll opt to get the external transformer so that if I get any more American-made products in the future I'll have a way of stepping down the current. In terms of fuses, I'm guessing that the one that came with the amp should still be suitable. It's actually a 4A 250V fuse, so I'm guessing that could work with either current, but if I have any problems with that I'll just order some 8A 125V fuses (the type it suggests I use on the back of the amp).
Click to expand...

What you need is an external 2:1 turns ratio step-down transformer to lower voltage. Because the voltage is going down while the Apparent Power remains constant, current increases, it does not decrease. Note that this lowered voltage and increased current consumption is exactly what the amp is expecting to see, to operate as intended. This means that it is not wise to change any fuses, since you are not changing any aspect of the amp's current draw.
 
#19
The Sad Mafioso said:
I'm using a GK 800RB. It says on the back next to the power input '120V' '8A', so that means it would need a converter designed to handle at least 1k VA, right? (8 x 120 = 1,000) I'll just take the converter back, say it didn't work and order Invalid Link Removed unless anyone else has any input on the subject.
Click to expand...

I don't think the converter needs to be defiant. It would be better to use a sanguine one, I think.
 

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