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Voltage Step Down Converters - HiFi Kit
scootz - 19/8/09 at 04:33 PM

I'm finding converters that satisfy the Voltage (120) and Wattage (100), but not the Hertz!

Every single converter that I see has a 50hz rate. The back of my two machines that I want to use, it states 60hz!

Would it hurt to run the machines on the 50hz converters?

Please only reply if you KNOW the answer... no guessing!

MakeEverything - 19/8/09 at 04:36 PM

It shouldnt.

If the frequency was higher, then id say possibly, but as long as the voltage is within tolerance you should be ok.

Bluemoon - 19/8/09 at 04:45 PM

Probably o.k. But if you have an oldfangled record player with a synchronous motor, it would run at the wrong speed!

Dan

scootz - 19/8/09 at 04:49 PM

Nah, it's a Yamaha Soundbar and Sub (both bought in the states).

Found this on eBay... seems to cover all bases, or is the advertiser just 'expanding' the ranges to attract dipsh*ts like me!



CONVERTER LINKY

02GF74 - 19/8/09 at 05:09 PM

it shouldn be ok since for hifi the ac voltage get converted to dc anyway.

not so good for a TV since the mains is the time base for the scan rate, or it used to be.

that same converter is £ 29.99 in maplins.

ChrisW - 19/8/09 at 07:05 PM

You'll never sort out the frequency unless you convert to DC then invert back up again. Not something that's going to happen in an off-the-shelf bit of kit, and something to do any kind of power will be very expensive.

As has been said though, hifi kit probably won't mind, and if it does, it probably just 'wont work' if run on the wrong frequency rather than doing any damage.

Having said that, I take no responsibility if smoke comes out!

Chris

smart51 - 19/8/09 at 07:53 PM

Mains voltage converters never change the frequency. Most stuff will work just fine. The voltage is converted to DC and 50Hz vs 60Hz makes no difference. As with all free advice, there's no warranty if it all goes wrong. Eveb as an electronics engineer, I wouldn't have even thought to worry about this.

MikeRJ - 19/8/09 at 08:46 PM

quote:
Originally posted by scootz
Nah, it's a Yamaha Soundbar and Sub (both bought in the states


Are you sure that lot takes well under 100 Watts? Must be a pretty tiny sub?

Running audio gear designed for 60Hz on 50Hz is definitely less than ideal. Assuming your kit uses a conventional power supply (which the majority of decent stuff does) there are two main issues:

A transformer (i.e. like ones used within the power supplies of audio equipment) must have enough iron in them to deal with the peak magnetic flux. For any given power requirement, peak flux is less at higher frequencies (which is why switched mode supplies can be made so small). Running a transformer designed for 60Hz at full power from a 50Hz supply could cause core saturation and overheating, depending on how much margin is built into the transformer. The power rating of the transformer should be reduced by 20% to retain the same design margins.

The other issue is that after the transformer is a rectifier and capacitor to turn the AC to a filtered DC. The size of the capacitor depends on how much ripple voltage is acceptable, and again can be made smaller at higher frequencies. The bottom line is running at 50Hz you will give more voltage ripple.

Running at moderate volumes neither of the above are likely to cause problems, but if you like to have it turned up to 11 on a regular basis you may find that the output clips more easily (due to the higher ripple) and the transformer gets hot.

My main concern is if you have the power rating correct for the converter.

Macbeast - 19/8/09 at 08:47 PM

In theory, an internal HI Fi transformer designed for 60 Hz would get slightly warmer when run on 50 Hz. Aircraft equipment used to run on 800Hz (ISTR ) because the core size, and therefore weight, was less than if run on 50Hz. But it shouldn't be a problem at the power levels you meet in a HI FI.

A TV set btw, never used mains for the scanning: the broadcasters used to lock the frame scan rate to mains because any hum effect on the receivers would be stationary, and thus less visible. This went out the window when colour came in.

MikeRJ - 19/8/09 at 08:59 PM

quote:
Originally posted by Macbeast
In theory, an internal HI Fi transformer designed for 60 Hz would get slightly warmer when run on 50 Hz. Aircraft equipment used to run on 800Hz (ISTR ) because the core size, and therefore weight, was less than if run on 50Hz. But it shouldn't be a problem at the power levels you meet in a HI FI.


The snag is a transformer rated for 50Hz is more expensive, so if a piece of equipment is never marketed in 50Hz countries, the manufacturers wouldn't spend the extra money. The absolute power level is not the problem, it's how close you get to the transformers design limits. Even a low power transformer can run hot enough to burn out (in fact it's more likely, small cheap transformers are almost always very marginal in design).

scootz - 19/8/09 at 09:28 PM

THe woofer takes 75w in and the soundbar 55w. Figured having each one on a 100w converter should be ok? No?

MikeRJ - 19/8/09 at 10:44 PM

quote:
Originally posted by scootz
THe woofer takes 75w in and the soundbar 55w. Figured having each one on a 100w converter should be ok? No?


Yeah should be ok, I didn't realise you were going to use two converters.

scootz - 20/8/09 at 10:51 AM

What the hell, I'll take the gamble!



Thanks for your help guys!