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220V amp on its way for use here in the UK

badger748 said:
http://www.isoteksystems.com/cgi-bin/products.pl?id=19

I often wondered how these Power Inspired things compared against say an Isotek unit like this
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Lee,

The Isotek stuff is essentially a very smart filter, which cleans, but does not alter the incoming AC waveform. Regenerators like the Power Inspired kit turn the AC input into DC and then regenerate it into a new sine wave AC output. If I'm wrong, please correct me (and my apologies to any manufacturers if I have got it incorrect).
 
Thanks Charlie.
I guess the $65k question is, is it "better" to filter what you have (a la Isotek) or to regenerate like the PI unit you mention?

Hmmm! Harry Hill needed?!
 
swamp said:
You need a bucking transformer. Very easy to make. They work different from a normal transformer and at first would seem too small in size to handle the load but once you understand the concept.

http://sound.westhost.com/articles/buck-xfmr.htm

http://www.dms-audio.com/node/12

If you cannot make one. I have one I made a few years ago. You can have it real cheap but post will be about £4 due to weight. No use to me now. I used it to drop the voltage to 220V ish to power an 845 amp from HK.

Just pm if you want it.

Have said that most amps are ok on the extra 20V, just some tube amps end up running HOT esp on the heaters since the 6.3V ends up too high and it shortens the life of the tubes. SS is less of an issue.
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This is very informative and helpful. Do you have detailed instructions on how to build one? I understand the subtractive nature of bucking trannies, but an idiot-proof guide would be very useful. I have a 220V amp that I'd dearly like to do everything to preserve.
 
Would one of these work? Its been discussed in another thread but has the capacity to put out 220 from 240.
 
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RobbieGong said:
Thanks guys. Thanks for the attached link to the service manual David, much appreciated. On page 3 of the manual it shows the different 700 es models. There are two that are rated at 390w consumption and both look as though they are switchable up to 240v - am I right in reading it that way ? If so it looks as though you switch internally as there is nothing obvious on the rear of the amp to switch. The one I will be receiving clearly shows 390w on the rear although it also has 220v printed on the rear sticker as well...
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See if you can switch it internally first. If not then my bucking tx will work fine for you as your amp is only 1.6A load.
 
That Goldsource ST-1000 would be ideal also. That should also isolate the unit from the mains if its a TRUE step down with dual windings and and not an autoformer design. An isolated version gives you the advantage of DC blocking and noise immunity.
 
swamp said:
That Goldsource ST-1000 would be ideal also. That should also isolate the unit from the mains if its a TRUE step down with dual windings and and not an autoformer design. An isolated version gives you the advantage of DC blocking and noise immunity.
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Looks to be only 240 - 120 or 120 - 240, not 240 - 220.

Some cheap step down transformers can be audibly noisy as well.
 
So the ultimate best solution is a mains regenerator. A cheap solution is the bucking tx and a mid cost solution would be a decent step down but as Barrymagrec said, these can be noisy. These can buzz and be annoying in a quiet listening room.
 
RobbieGong said:
Here's a link to the exact item: http://rover.ebay.com/rover/1/707-5...0001&campid=5338728743&icep_item=151611263162

If you scroll down you can see pictures of the rear panel and all the exposed circuitry. Maybe someone can make something out by the electronics on view....
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That label is ambiguous as it doesn't correlate to those in the service manual. When you get the amp open it up and look for a VS board (voltage selector). If you have that you are in business. Otherwise as has been mentioned earlier on you need a bucking transformer. Thats easily made from a step down transformer but needs to be put in a sealed box with a 13A socket. A 500VA toroidal xformer is about £50. However if you don't know what you are doing someone in the pfm DIY section may build you one. However you'll need to measure your mains voltage and thats a hazard if you don't know what you are doing.

Cheers,

DV
 
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Hmmmm, built my first bucking transformer today to drop 240VAC to 220VAC. My maths says that the M-22 running at 220VAC consumes 280W, which means around 1.27A of current draw. So, I figured a small tranny with paralleled secondaries rated for 1.33A would be sufficient. Well, it works well enough, but I'm not sure I have sufficient current headroom with a 20VA tranny. After one album, it felt slightly warm.

I have ordered a new 120VA tranny just to be sure. That should be good for at least 6A continuous. A bit of overkill is probably not a bad thing.
 
you should reckon on about double the nominal current rating as your amplifier is not a resistive load and you need to account for the peak charging current of it`s caps.
 
Barrymagrec said:
you should reckon on about double the nominal current rating as your amplifier is not a resistive load and you need to account for the peak charging current of it`s caps.
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That sounds about right. 3A should be plenty.
 
I got a 670ES 220-230v from Austria last year, so far I've not encountered any issues with it. I have often wondered though if I should get something, just always seem to spend the cash on more music.

If I do, I'd narrowed it down to an AG500 or 1500 from Power Inspired or thought this from APC might work

http://www.amazon.co.uk/dp/B0000C88CR/?tag=pinkfishmedia-21

Oh, the 670 came with a nice bulky Schuko attached which needed a bigger than I'd expected adaptor casing.
 
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James said:
Hmmmm, built my first bucking transformer today to drop 240VAC to 220VAC. My maths says that the M-22 running at 220VAC consumes 280W, which means around 1.27A of current draw. So, I figured a small tranny with paralleled secondaries rated for 1.33A would be sufficient. Well, it works well enough, but I'm not sure I have sufficient current headroom with a 20VA tranny. After one album, it felt slightly warm.

I have ordered a new 120VA tranny just to be sure. That should be good for at least 6A continuous. A bit of overkill is probably not a bad thing.
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2x secondary winding current rating should be enough. It will still get warm. The main issue is the insulation strength on the secondary winding since it now has mains on it were it was intended for whatever lower voltage (12, 24 etc). 6A is overkill but gives you plenty scope for use on other 220V units.
 
Back in 1999 I bought a European import Sony TAFB920R from Richer Sounds.

It worked just fine rated at 220 Volts.

I would not buy a Chinese valve amp rated for 220 Volts though as the components don't have tolerances to cope with UK voltages up to 253 Volts. These are actually dangerous as they can set on fire.
 
swamp said:
2x secondary winding current rating should be enough. It will still get warm. The main issue is the insulation strength on the secondary winding since it now has mains on it were it was intended for whatever lower voltage (12, 24 etc). 6A is overkill but gives you plenty scope for use on other 220V units.
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Thanks for that, swamp.

What's the worst thing that can happen if the insulation breaks down? I'm just pondering if I should continue to use the 20VA tranny whilst I wait for the 120VA replacement.
 
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