Step down transformer

[vinothkumar]

Hi guys,

I got a sudden doubt after reading some posts in the forum regarding the step down transformer which I purchased for my SONY STR DN1050 receiver bought from US.

I bought MAXINE 500 WATTS SDT and here is the link : 500 WATTS AUTO WOUND STEP DOWN TRANSFORMER MAXINE: Amazon.in: Electronics

My doubt is, my receivers power consumption is 240W. The total power of all channels are 7*165 = 1155W. Now forum said that you have to choose SDT with receiver total power * 1.5 / 2 times of watts.

Should I choose 1155W *1.5 / 2 = 1732 / 2310 or
240 * 1.5 / 2 = 360 / 500 Watts.

I am totally confused here. I already bought 500W SDT for my receiver. Did I select wrong transformer? If yes then what is the correct SDT for me?

What is the required watts?

Thanks in advance.

 

[Fantastic]

No home theater amp produces full power on all channels. Usually the surround channels will be at much lower average levels than the front channels. The main channels itself will be running at an 'average' level much lower than it's rated full output power. Assuming worst case conditions you still might not cross 30 watts average on the main channels. Remember that the occasional peaks could be hitting over 150 watts !
so 30 x 7 = 210 watts. So the 240 watts figure is for normal use.
Your transformer at 500 watts should do fine !
My only reservation is if the auto transformer is genuinely rated at 500VA ! You might not be able to check this out easily at home. Many manufacturers over rate their transformers ! But nothing to worry. You can easily know if what you bought isn't OK as it will heat up quite a lot . It should get quite warm to the touch if you play your home theater amp very loud. But if it's hotter than you can touch ( over 55 deg C ) you might need a bigger transformer than what they 'call' 500 VA. But Maxine has been around a long time and I think it should be OK.

 

[vinothkumar]

Thank you Fantastic for your awesome comments. What do you mean by heating?
Are you telling about the receiver gets heat or SDT gets heat?

So far my SDT never gets heat but my receiver would get heat if I increase the level settings and play loud.

 

[panditji]

It's the same with my amp as well...I have a SDT rated at 500VA and my amp has a maximum power consumption rating of 270Watts...My amp gets heated quickly and gos into protection mode but the SDT does not....DO I also need a bigger SDT maybe a 750 VA?

 

[vinothkumar]

I called SHAH ELECTRONICS guy and asked about the SDT. He said that SDT are based on only the power consumptions not the wattage of all channels. And he said the same that if the SDT gets heat up then I should change it to more watts. It is fine then no need to change.

Still I am confused because forum says it is based on ALL CHANNELS * 1.5 but these guys are telling only the power consumption * 2.

Please make us clear on which basis we should buy SDT. I can still change my SDT and get new one.

 

[Fantastic]

Heating of the EDT. ALL transformers heat up as current flows through them. There are normal losses in the transformer that cause them to heat up....this is governed by laws of nature !

The transformers are designed to operate up to a 'safe' temperature when handling the rated load. The safe temperature depends on various factors but for us can be safely taken as below " too hot to touch " which is usually below 60 Deg C . Note that the core temperature can be 20 to 30 deg hotter than the outside ! So as your receiver produces more output power, it draws more power from the transformer and hence causes it to heat up. If it remains cool , it means that you are operating well within the ratings.

The receiver WILL get hotter as about 30% of the out power of the amp is converted to heat and you will find finned heat sinks in the amp to dissipate this heat. So a pretty hot amp means you are playing very loud and it IS expected to get hot ! That's why you should have good ventilation for the amp. At the same time the SDT should NOT get very hot as the efficiency is much higher than an amp ( over 90% for toroid transformers like you have ). So heat generated in the SDT is very much less .

panditji : Your SDT is fine ! YOU are the problem !
You seem to be playing VERY loud , OR you are using very low impedance speakers ( 4 ohms or less) at high volume OR you don't have enough ventilation for the amp OR the amp is inside a closed cabinet OR the cabinet has no free air flow !
Generally all large power amps should be kept on top of a cabinet or shelf and NOT inside them, there should be free air flow. Keep it where it gets a draft of air from the fan OR place a small fan near it blowing air around the amp. Maybe it will not shut down after that.
However if you ARE playing it very loud then something else might shut down overtime.....your ears !
Be careful ! You need them to work well for about another 100-your age , years ! No replacements are possible !

The SDT rating should be based on the 'average power output' of the amp.
Your manual says 240 watts and that's what you should use. The individual channel wattage is what each channel can deliver individually ! All channels cannot simultaneously deliver the single channel rating x no of channels.

Like 7 x 165 is 1155 watts. Your amp cannot produce 1155 watts continuously ! It's internal supply will not permit that AND it will not be able to dissipate the heat generated if there was no electrical limitation.
The company rated the amp consumption at 240 watts ( under normal use!). That means it will generate only less than that as audio power with ALL channels working at the same time. No single channel has a constant wattage while playing music or movies. They all combine together to form an average consumption . The front two channels are rated highest ( continuous power) as they produce most of the power in stereo music or in movies.

Both you guys seem to have SDT's that are working well in your system. No need to change it.

 

[vinothkumar]

Fantastic.. You comments are fantastic too. Thank you so much for your detailed information about the SDT.

Some post made me confused with my SDT.

 

[panditji]

Thank you sir...You are right that my amp is kept on the bottom shelf and the wood shelf on top is only 3 inches from the top of the amp...Alos since I stay on the top floor, my room is very hot and maybe that is why the amp heats up quickly as the average room temperature is above 30 degrees to start with.....

Many thanks sir for clearing my doubt and saving me some money as well..

 

[vinothkumar]

One more doubt.
Please look at the following links where they are calculating it based on the all channel watts * 1.5..
http://www.hifivision.com/what-should-i-buy/19632-step-down-tranformer-av-receiver-2.html
http://www.hifivision.com/surround-...p-down-transformer-my-avr-sony-str-dn840.html

Please make me clear friends...

 

[Fantastic]

What you have is working fine !
You can go round in circles reading lots of material that you don't fully understand.
The explanation to your question was already given but apparently you didn't understand.

If you read that your system is OK and IT IS OK in actual use , it's time to just sit back and enjoy the system.

 

[mbhangui]

You shouldn't be looking at the sum of the output wattage of all the channels. The actual power consumption will be far less than that. A 100 Watts output means that the amp is capable of delivering 100 W during peak demands. There is no music which will cause an AMP to deliver that sustained output. The peak demands usually come when there is low frequency notes (drums, etc). During these times, the extra power comes from the power supply capacitors which gets fully charged during a lull.

The average power consumption is far less than the rated output of the channels. Also the transformer and the power supply in avr's are not capable of giving a sustained max rated output. Hence, even if you put a very high wattage SDT, the power supply inside the AVR cannot take advantage of it. If you want to save your money, just buy a SDT which is 1.5 times the rated power consumption of the AVR/Amp.

Another example. Your mobile phone will not get charged faster by plugging your power adaptor into a 15 amps socket. The max power consumed is limited by the minimum impedance of the transformer/power supply in the AVR and governed by a law formulated by George Simon Ohm. This law appeared in the famous book Die galvanische Kette, mathematisch bearbeitet (tr., The Galvanic Circuit Investigated Mathematically) - 1827

Ohm also dabbled with Music with Ohm's acoustic law, sometimes called the acoustic phase law or simply Ohm's law, states that a musical sound is perceived by the ear as a set of a number of constituent pure harmonic tones. It is well known to be not quite true. Take a good look at Ohm, remember him and thank him for saving your hard earned money

 

[vinothkumar]

Thank you mbhangui.

My receiver has 240 watts power consumption. I already have Maxine SDT with 500 watts. The same thing is suggested by Fantastic too.

Thanks for both of your comments guys.

 

[Fantastic]

Ohm also dabbled with Music with Ohm's acoustic law, sometimes called the acoustic phase law or simply Ohm's law, states that a musical sound is perceived by the ear as a set of a number of constituent pure harmonic tones. It is well known to be not quite true. Take a good look at Ohm, remember him and thank him for saving your hard earned money

What's the connection here ? I didn't get it !

All sounds are made up of pure tones ( fundamental frequency) plus it's harmonics with different amplitudes and relative phase relationship. Even a square wave is just a combination of pure frequencies ! Every sound is just a combination of several 'pure' tones. What isn't conclusive is if changes in relative phase are easily audible or not. What they observed is that in the lab they can be made slightly audible but on musical signals it's very hard for most people to notice the difference between the original signal and one with slight phase changes .

 

[ForgottenLegend]

Hello,

I have a yamaha 477 receiver which is rated 120v/60Hz and 260 watts.
Cant decide between Maxine 500watts and 750watts (Auto Wound Toridial). Can you please suggest. I dont mind spending on the 750watts btw but is it a waste of money?.

Also there are SDT models with built in stabilizer and costs a bit more. Do you think the stabilizer versions would be really helpful?. Any reviews from the users already using Maxine step down transformers would also be helpful.

Cheers!

 

[Fantastic]

You need only a 500 watt unit.
Stabiliser is useful only if your voltage varies beyond +10/-15 % . Variations in between this range can be handled by the amp. Use a stabiliser only for very high or very low mains voltage. Typically over 260V or below 200 V. Otherwise skip it.

 

[ForgottenLegend]

Thank you Fantastic!
I ordered the Maxine 500watts SDT with stabilizer from Mr. Amit Shah.