Is the YAQIN MS-12B (220v +-10%) safe to use in UK - diyAudio
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Old 1st October 2011, 11:04 AM   #1
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Default Is the YAQIN MS-12B (220v +-10%) safe to use in UK

Hi guys,
can you tell me if the YAQIN MS-12B is safe to use in the UK? Does it need adapting?

I think I read a thread somewhere that the Chinese amps are not safe in the UK that the transformers get saturated due to a mismatch in the voltage. It may have been on a different forum.

I know that the UK is supposed to be 230v now to bring us in line with Europe but I have also read that its still really 240v due to some sort of trickery.

I am afraid I have never really understood volts and amps despite having an O Level in physics many years ago. I think I learned Ohms law by rote and resistance etc but its all a bit fuzzy now.

I presume that the is the YAQIN MS-12B is 220v +-10% according to the sticker on it that it has a 22v safety margin either side of 220v which would allow it to work up to 240v if I am understanding correctly should be fine.

I have read somewhere of them failing in the UK. My Little Dot MKIVse headphone amp didn
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Old 1st October 2011, 12:01 PM   #2
Mooly is offline Mooly  United Kingdom
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All that changed in the UK was the tolerance limits... which in practice meant no changes to the network were needed.

The UK mains can still be as high as 256 volts worse case and so that puts your YAQIN as not officially suitable.

There would be no problem with mains transformers in themselves running on 220 or 256 volts. Where the problem arises is that the secondary output voltages are correspondingly higher... maybe enough to over run marginally specified components or cause excess heat generation in regulators etc.
A 63 volts cap that has around 61 or 62 volts across it on 220 volts will be over the limit at 240 or higher.

SMPS's are more imune to this as long as the main reservoir cap and primary side components are suitably rated... but these are usually specified as 90/110 volts to 240 with no adjustment.

For reference,
http://www.bis.gov.uk/files/file11548.pdf
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Old 1st October 2011, 01:56 PM   #3
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Quote:
Originally Posted by Mooly View Post
All that changed in the UK was the tolerance limits... which in practice meant no changes to the network were needed.

The UK mains can still be as high as 256 volts worse case and so that puts your YAQIN as not officially suitable.

There would be no problem with mains transformers in themselves running on 220 or 256 volts. Where the problem arises is that the secondary output voltages are correspondingly higher... maybe enough to over run marginally specified components or cause excess heat generation in regulators etc.
A 63 volts cap that has around 61 or 62 volts across it on 220 volts will be over the limit at 240 or higher.

SMPS's are more imune to this as long as the main reservoir cap and primary side components are suitably rated... but these are usually specified as 90/110 volts to 240 with no adjustment.

For reference,
http://www.bis.gov.uk/files/file11548.pdf
Thanks for taking the time to apply, I measured my mains voltage at around 236 to 238v ac on my multimeter at the mains socket.


Where does the 220v + or - 10% play its part? Do I have 22v margin on my amp?

Thanks again
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Old 1st October 2011, 02:44 PM   #4
data is offline data  Australia
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220v + or - 10% means that the transformer can tolerate the extra 10%, but the other components after the transformer may not, and with 250v+ as possible?
There are sellers on the bay and elsewhere that can order real 240v versions from the factory, just have to usually wait three weeks for them to get them in before they can be shipped to you.
It a matter of finding such a seller, contact and ask a few.
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Old 1st October 2011, 04:00 PM   #5
Cassiel is offline Cassiel  Libya
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It is not a problem because the filament voltage is regulated (phono stage) and the higher B+ isn't a problem either. The line stage filament voltage can be fixed changing a resistor. The big problem is that it's full of crappy parts: looks good on the outside and terrible on the inside. Pretty typical Chinese crappola.
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Old 1st October 2011, 08:10 PM   #6
Mooly is offline Mooly  United Kingdom
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Quote:
Originally Posted by eldarvanyar View Post
Where does the 220v + or - 10% play its part? Do I have 22v margin on my amp?

Thanks again
It means the product is OK on 220v -/+10% which is up to 242 volts.

I have no idea what the quality of the unit is like though
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Old 1st October 2011, 09:14 PM   #7
jonners is offline jonners  United Kingdom
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This amp has been discussed quite a bit on other forums - try an internet search. I had quite a bit of trouble finding valves that were clear of feedback and whistling problems with mine, and a couple of the heater voltages were on the high side. I have the 240V version.
I'm quite happy with it now, but I would be wary of buying it unless you are prepared to spend a bit more on valves, and to spend some time sorting it out.
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