mains Voltage

[Floyddroid]

We recently had a new substation installed in the village and a lot of the overhead cables updated/replaced. since then i have noticed that the power supply for my pre-amp has become noisy and replaced quite a few light bulbs. I didn't think about the mains voltage until i recently bought a headphone amp and it was humming like a b......d. I contacted the manufacturer of the headphone amplifier who after some debate suggested that i had my mains voltage checked by a fully qualified electrician which i did. It was discovered that my mains voltage is running at 247 volts which is getting on towards the top end of the recommended voltage. I contacted the appropriate agency to discuss the matter and was told that it was in the range and therefore nothing could be done to lower the voltage by them to my property. With this in mind i contacted the electrician who informed me that the only thing he could suggest was wiring in an Optimisier on my distribution board in the garage. This would cost about £500 which is a lot of money. Any suggestions chaps?

[Arkless Electronics]

Nowt wrong with 247 and it will probably vary a fair bit from day to day. As low as 230 and high as 250 is not unusual at all and mains will often vary this much on a daily basis.

[killie99]

One of these, seen them for sale for as little as £125. It'll supply everything except your power amp.

http://www.powerinspired.com/ag500-ac-regenerator-500w-with-pwm-fan-control-p-1811.html

[struth]

One of these, seen them for sale for as little as £125. It'll supply everything except your power amp.

http://www.powerinspired.com/ag500-ac-regenerator-500w-with-pwm-fan-control-p-1811.html

thats the one ive got. works well

[rubber duck]

One of these, seen them for sale for as little as £125. It'll supply everything except your power amp.

http://www.powerinspired.com/ag500-ac-regenerator-500w-with-pwm-fan-control-p-1811.html

I run all my amps + active sub through my AG1500 without any issues. But then all my amps are 10-16W except for my Croft S7 and that's also fine.

[Dynamics]

Id try one of the slightly better power inspired regenerators which I've heard people say who live in villages or rural locations, are very good. I think it was the ag1500 regenerator he was saying was very good. Depends on your system mind. I'm trying a conditioner at the moment and started a seperate thread on this. An isol-8 minisub axis. But I've no idea if a conditioner would do the same job if the mains voltage is high and their is him. Only one way to find out - Try various devices at home.

[Macca]

I'd send the headphone amp back and and get a refund. It shouldn't buzz just because the mains is a bit higher than optimal.

[Barry]

I'd send the headphone amp back and and get a refund. It shouldn't buzz just because the mains is a bit higher than optimal.

Agree - any competently designed piece of kit ought to operate without problem when connected to the UK mains supply.

[337alant]

UK mains is 230VAC + 10% - 6%
216.2 - 253VAC so nowt we can do about it mine has been as high as 253V as well but recently is around the 230VAC
Mains regeneration could be a good idea ?.
IMO Don't but anything with a 220v transformer they buzz like shi% for me

Alan

[SPS]

I worked in the pub trade, many 24 volt bar transformers buzzed, we could swap one out and it cured it, it was only down to poor quality windings that vibrated.
I agree that anything sold in this country should be up to working on the mains voltage that is specced, but its far cheaper for them to suggest you spend money that may stop the buzzing than replace the faulty item
Best of luck...

[anthonyTD]

Unfortunetly,these days most equipment [Still using a normal mains transformer, not switched mode] designated to be used within the EU' is supplied with a power transformer that is designed for 230v, the theory is; that it should work fine between 220v, and 240v, however, a lot of the equipment I have had in for repair, and tested needs only 220v, and sometimes less to work optimally, so in theory, it has at least 20v over what the equipment is designed for!

[struth]

Ive used a few 220v things and found 230v is fine. 240v isn't. either a regenerator or a bucking tx/variac are needed.

[Ali Tait]

Steve, you could contact Airlink, who should be able to supply a balanced mains transformer with 220v output. Be cheaper than a mains regen unit.

[anthonyTD]

Good sugestion Ali.:)
A...
Steve, you could contact Airlink, who should be able to supply a balanced mains transformer with 220v output. Be cheaper than a mains regen unit.

[RothwellAudio]

You could fix the buzzing in the headphone amp by stopping its mains transformer from rattling. Basically the laminations that make up the transformer core are rattling/chattering as they are magnetised by the mains. Sometimes you can tune out the rattling by adjusting the tightness of the screws which are holding the transformer laminations together. Sometimes the transformer hasn't been potted well - maybe not all - but you can still do something about that. Transformers are dipped in varnish to pot them. You could do the same, or maybe even just drip some varnish on the top so it soaks into the laminations. Use oil-based varnish, not the modern "quick drying, low odour" water-based stuff.

It's possible that the problem isn't so much the high mains voltage as an effective DC component on the mains.
This explains it: http://www.isol-8.co.uk/dc_on_the_mains.html

[anthonyTD]

Yes,agree, Noise, and DC element on the mains can cause transformers to sing along with the mains, especialy toroids, and it can be worse at diffrent times of the day, this is definitely something to be considered!
You could fix the buzzing in the headphone amp by stopping its mains transformer from rattling. Basically the laminations that make up the transformer core are rattling/chattering as they are magnetised by the mains. Sometimes you can tune out the rattling by adjusting the tightness of the screws which are holding the transformer laminations together. Sometimes the transformer hasn't been potted well - maybe not all - but you can still do something about that. Transformers are dipped in varnish to pot them. You could do the same, or maybe even just drip some varnish on the top so it soaks into the laminations. Use oil-based varnish, not the modern "quick drying, low odour" water-based stuff.

It's possible that the problem isn't so much the high mains voltage as an effective DC component on the mains.
This explains it: http://www.isol-8.co.uk/dc_on_the_mains.html

[Ali Tait]

Yes indeed. Steve, if you go the Airlink route, get them to fit a DC blocker to the input.

[Barry]

In times past electronic gear used to be fitted with mains voltage selectors which selected the appropriate tapping on the transformer primary. This was because the transformers used were designed deliberately to be run close to saturation to improve regulation. If extra turns were wound on the primary to increase the saturation margin, the increased resistance would result in poorer regulation.

When a transformer saturates the inductance falls and the primary current rises. Saturation can be caused either by running the primary on too high a mains voltage or by having some DC on the mains (which is effectively is similar, but only occuring each cycle, rather than every half cycle). It only takes ~100mV of DC offset to cause toroidal transformers to buzz (owing to a lack of air gap in the core, toroidals 'hard limit' when saturated).

Early power supplies were unsophisticated, so it was important not to compromise regulation, but modern regulated power supplies can be supplied with a transformer that has a much larger saturation margin, and hence no need for a mains voltage selector.

However regardless of the margin of saturation, if the laminations are loose they will buzz, simply due to the AC nature of the mains supply.

[anthonyTD]

:)
In times past electronic gear used to be fitted with mains voltage selectors which selected the appropriate tapping on the transformer primary. This was because the transformers used were designed deliberately to be run close to saturation to improve regulation. If extra turns were wound on the primary to increase the saturation margin, the increased resistance would result in poorer regulation.

When a transformer saturates the inductance falls and the primary current rises. Saturation can be caused either by running the primary on too high a mains voltage or by having some DC on the mains (which is effectively is similar, but only occuring each cycle, rather than every half cycle). It only takes ~100mV of DC offset to cause toroidal transformers to buzz (owing to a lack of air gap in the core, toroidals 'hard limit' when saturated).

Early power supplies were unsophisticated, so it was important not to compromise regulation, but modern regulated power supplies can be supplied with a transformer that has a much larger saturation margin, and hence no need for a mains voltage selector.

However regardless of the margin of saturation, if the laminations are loose they will buzz, simply due to the AC nature of the mains supply.

[Floyddroid]

A lot for me to think about here folks. Many thanks.

[Arkless Electronics]

In times past electronic gear used to be fitted with mains voltage selectors which selected the appropriate tapping on the transformer primary. This was because the transformers used were designed deliberately to be run close to saturation to improve regulation. If extra turns were wound on the primary to increase the saturation margin, the increased resistance would result in poorer regulation.

When a transformer saturates the inductance falls and the primary current rises. Saturation can be caused either by running the primary on too high a mains voltage or by having some DC on the mains (which is effectively is similar, but only occuring each cycle, rather than every half cycle). It only takes ~100mV of DC offset to cause toroidal transformers to buzz (owing to a lack of air gap in the core, toroidals 'hard limit' when saturated).

Early power supplies were unsophisticated, so it was important not to compromise regulation, but modern regulated power supplies can be supplied with a transformer that has a much larger saturation margin, and hence no need for a mains voltage selector.

However regardless of the margin of saturation, if the laminations are loose they will buzz, simply due to the AC nature of the mains supply.

Excellent!

[Floyddroid]

Steve, you could contact Airlink, who should be able to supply a balanced mains transformer with 220v output. Be cheaper than a mains regen unit.

Which one Ali the bus 1500 or the bps2000?

[Edward]

Interesting thread.

For the past few weeks I have been trialling a friend's Isotek 2k "Qube" powering my preamp, amp, DAC and music computer.

In a word - transformative.

Much cleaner sound, insightful, rounded, more natural.

Took it out of circuit for a few days and difference very clear.

After Munich I may well get a trail unit of the Power Inspired AG1500 to see if another step change.

E

[Ali Tait]

Which one Ali the bus 1500 or the bps2000?

Either would be fine, I'd probably go for the larger, just cos. :-)

[Edward]

What is an easy way of measuring the quality (with audio in mind) of domestic mains electricity?

Ed

[struth]

possibly the easiest is to borrow a mains regenerator. if it improves things then your mains isnt perfect. if it doesnt, then dont worry

[Edward]

possibly the easiest is to borrow a mains regenerator. if it improves things then your mains isnt perfect. if it doesnt, then dont worry

True. However I'm always wary of the placebo effect - no doubt having been caught out many times. Nice to have reassurance with measurable stats. But having said that I do think I got a marked difference using an ISOtek Qube recently so perhaps an AC regen (such as that provided by Power Inspired) will be as obvious.

I see that you have the AG1500 regen unit. Did you notice a significant difference?

Interestingly in June's edition of HiFi News' there is a relevant comment (p116) on this subject. The comment also discusses the idea of "Variable MultiWave" which, to me as a layman, seems contra intuitive to a pure wave (as done by say the AG1500). But like you the comment says to try things out.