Will Step down transformer affect HiFi's performance??

Friends,

This question is hitting me whenever I think abt electronic Item purchase in USA.

Friends Tell me "Will Step down transformer affect High end HiFi's(120V) perfomance?"......If it is, what is the performance difference compared to standard Voltage(230V) HiFi Items?

Is there any good&economy brand transormers available in India?..
What is the role of Voltage stabilizer and UPS in Hi Fi setup?....

guidance please..

Thanks,
Pandiyan

Hi Pandiyan
There may be an affect if your step down rating is not much higher. For .e.g. if you have an amp with max consumption at 500W, you should get a transformer that is rated much higher (remember there is an inefficiency also associated with the transformer itself). Even then, your performance may likely deteriorate. However, how much you can make out/hear is dependent also on the quality of the setup that you have...ranging from a simple receiver to a higher end receiver/amp.
A Power conditioner is used to remove noise from the line and a UPS is used to provide uninterrupted power supply although you can get a good one and use it as a UPS + a top notch power conditioner.

cheers

Let us get some fundamentals in place.

Electricity is all about the flow of electrons in wire. "Voltage" is a measure of how hard the electrons are pressing to get through--it's like water pressure in a pipe, or like the rotational force in our car's wheels. "Current," measured in amps, is a measure of how fast the electrons are flowing--it's like the gallons-per-minute flow in a pipe, or the feet-per-minute rate of spin of the tires on our car. Total power delivery, in an electrical circuit, is measured in watts, which are simply the volts multiplied by the amps; in the same way, the total power delivered by the car in our example is the amount of rotational force delivered by the wheels, multiplied by the speed of rotation. A number of watts may represent a very high voltage with relatively low current (such as we see in high-tension power lines) or a low voltage with very high current (such as we see when a 12-volt car battery delivers hundreds of amps into a starter).

To all this let us add a new dimension. This dimension is called 'frequency'. Unlike direct current (DC) that flows in one direction all the time, alternating current changes direction (represented as +ve and -ve) at a predetermined cycles per second. In the US it is 60 cycles per second or 60Hz. In India, it flows in 50 cycles per second or 50Hz.

How does this affect us? Well most AC equipment such as tube lights, heaters, and motors have been designed to work with these cycles. Are you aware that a tube light flickers (comes on and off) at the same frequency as the AC current?

What does this mean to me? Well, if you take a US made motor designed for 60Hz and run it in India at 110 volts but at 50Hz, it just wont even turn or at best will turn erratically.

Step down transformers, as with any transformer, are usually around 96% efficient. They can never be 100% efficient as there is loss of energy and current in the windings. But the catch is most step down transformers do not worry about frequency. So if you take a step down transformer and convert 230 volts to 110, what you will get is 110 volts but at 50Hz.

Now we come to the best part. Your audio equipment should not be affected at all? Why. Simply because all audio equipment work on direct current. Power supplies inside the audio equipment contain a TRANSFORMER which converts the mains AC supply to a safe low voltage AC. Then the AC is converted to DC by a bridge RECTIFIER but the output is varying DC which is unsuitable for electronic circuits. So the next step is SMOOTHENING of the voltage. This is performed by a large value electrolytic CAPACITOR connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. Even this will only supply DC current with small ripples in voltage that yet cannot be fed to the electronic circuits. So a last step is a REGULATOR. This is usually an IC that consists of a zener diode regulator and resistors. Irrespective of what voltage is fed to the diode, it always sends out constant voltage that can be fed to the electronic circuits.

Ideally you should try to get equipment that can take both 110 and 230 volts at 60 and 50Hz respectively. This way you eliminate the need to bring in another step in your supplying power to the audio equipment. For example literally every mobile phone charger can be used across the world without any hassle as they can switch between 230 and 110 volts. These would generally be rated as 100-240~ with frequencies FROM 50 TO 60Hz.

Since the HiFi equipment does an internal conversion from AC to DC and from high voltage such as 110/240 to somewhere around 5 to 25 volts, most equipment can, by themselves, perform well with mildly varying input voltages (voltage fluctuation). So if you do put a step down transformer between your power supply and the equipment, it should not make too much of a difference to the equipment. If the frequency is not properly managed, highly sensitive parts such as DC motors (in a CD player) could be affected. This is where PSRR of the equipment's power supply plays an important part.

Why are we then talking about stabilisers and UPS? Most equipment manufactured in the US, Europe and other advanced countries depend upon a stable power supply that does two things - ONE they supply power without fail; and TWO have very low fluctuation usually +/- 5 volts. In India, unfortunately, the power supply is both very erratic, and falls in voltage as the power is withdrawn by the consumers. For example, let us assume there is a mela or a political program running near your house. This will draw huge amounts of current from your supply albeit for a short time. When this happens, the power supply to your house will be affected by a huge drop in voltage as the EB is incapable of compensating for the additional load. In addition, at times, because of low production (as compared to demand) the EB will deem it fit to present you with a power cut.

A step down transformer that is given erratic power supply will in turn supply erratic voltages to the power supply of the audio equipment. This will put a strain on the power supply's capability to generate steady DC voltages sometime leading to a fuse blowing up or the whole power supply burning out.

Another important factor to understand and build for is good earthing. Many US and European equipment are earthed to the body of the equipment. You might get mild shocks when you touch a live equipment. Secondly the static electricity created by a equipment not properly earthed could create electro magnetic waves that could affect nearby equipment. In TV you will usually see this as noise lines moving across the screen at an angle of 45 degrees or more. Good earthing and line filters will help remove this problem.

I am showing below an interesting article from a US based magazine called The Audio Critic. Their 26th issue had an article on the 10 Biggest Lies In The Audio Industry.

The 8th Biggest Lie in Audio

The Power Conditioner Lie

Just about all that needs to be said on this subject has been said by Bryston in their owner's manuals:

"All Bryston amplifiers contain high-quality, dedicated circuitry in the power supplies to reject RF, line spikes and other power-line problems. Bryston power amplifiers do not require specialized power line conditioners. Plug the amplifier directly into its own wall socket."

What they don't say is that the same is true, more or less, of all well-designed amplifiers. They may not all be the Brystons' equal in regulation and PSRR (*), but if they are any good they can be plugged directly into a wall socket. If you can afford a fancy power conditioner you can also afford a well-designed amplifier, in which case you don't need the fancy power conditioner. It will do absolutely nothing for you. (Please note that we aren't talking about surge-protected power strips for computer equipment. They cost a lot less than a Tice Audio magic box, and computers with their peripherals are electrically more vulnerable than decent audio equipment.)

The biggest and stupidest lie of them all on the subject of "clean" power is that you need a specially designed high-priced line cord to obtain the best possible sound. Any line cord rated to handle domestic ac voltages and currents will perform like any other. Ultra-high-end line cords are a fraud. Your audio circuits don't know, and don't care, what's on the ac side of the power transformer. All they're interested in is the dc voltages they need. Think about it. Does your car care about the hose you filled the tank with?

(*) Power supply ripple rejection ratio (PSRR) is a measure of how well a circuit rejects ripple coming from the input power supply at various frequencies and is very critical in many RF and wireless applications. In the case of an DC linear voltage regulator (LDO), it is a measure of the output ripple compared to the input ripple over a wide frequency range (10 Hz to 10 MHz is common) and is expressed in decibels (dB).

Venkat,

Thx a lot for your wonderful reply .... It is like a mini seminor on Current conversion...It reminds my Physics degree !!!...I appreciate it..Great !!!

Odyssey, Thx 4 u'r reply aslo..

Pandiyan

I forgot to add some conversion factors. This has been explained to some extent by Odyssey, but let me see if I can make is clear.

Generally speaking KW and KVA are units of power. The ampere is a unit of current. If you divide power by the voltage involved, you can determine the current involved, in amps.

Power (watts) = volts x amps

A volt-amp(vA) is a watt (W). (A volt times an amp is a watt.)

The main difference between watts and volt amps is that the watt rating determines the actual draw of power from a power source and the heat generated from equipment. The VA rating is used for sizing equipment such as circuit breakers, stabilisers, wiring, and UPS. The VA rating is normally equal to or higher than the watt rating, as it includes the power factor in its calculation.

Power Factors

The Power Factor is a calculation used to account for the difference in power supplies used to convert AC power into DC for use in electrical appliances. There are two types of power supplies - the capacitor input supply and the power factor corrected supply.

Power factor corrected supplies are used in most high end equipment, and have a ratio of 1W:1VA, allowing a very simple calculation for scaling electrical equipment and UPS. Thus, in theory, if your power factor is 1:1, and your load is 100 watts, you need an UPS that is rated at 100vA or 0.1KvA. You would be loading the UPS to 100% of its rating.

Older electrical equipment, as well as most audio and video equipment use capacitor input power supplies and have a power factor anywhere from 0.55 to 0.75 times the VA rating.

Typically when scaling a UPS for use you will use a 60% load factor on the UPS. If you overload a UPS it is almost certain to fail during a power outage, as the draw on the batteries will exceed the capacity of the UPS. Most new UPSs will automatically go into battery bypass when an overload condition occurs. The 60% load factor accounts for the high probability that most of the equipment drawing power through the UPS will be of a category that has a power factor of between 0.55 and 0.75.

Let us assume we have a brand new amplifier whose power consumption is shown as 500 W. You divide this by 0.60 (Point Six Zero) to get the KvA of the UPS/Stabiliser. Thus the load capacity on the UPS for your amplifier will be 500/0.60 which equals to 833 vA or 0.8KvA.

For step down transformer, all you have to compensate for is the energy loss due to heat dissipation, which is usually around 10%. So if your power consumption is 1000 watts, make sure that the step down transformer is rated at 1.10KvA.

I think you need to revisit the calculation. For 500 W power consumption, current rating would be 2.71 A which could be steady state current drawing, while during cold start , the amp draws heavy current (called as In rush Current) as well as while playing complex / dynamic music the amp again draws much higher current than this 2.71 A!

Your calculation suggests putting 0.8 KVA UPS to power this amp (500 W power consumption) , means this UPS can supply 3.48 A, which is not enough. In order to take care of In rush current and dynamic current requirements one has to provide at least 3 times the normal (steady State)current . In this example it should be 2.71 x 3 = 8.13 A!

Now after applying that UPS safe opering margin of 60%, this becomes 13.55 A! Which is 3.11 KVA UPS.

Put anything less, amp will work but dynamics will suffer.

And one more important thing here if it is UPS then it must be of Pure Sine wave UPS. (Not the quasi / Stepped Sine wave type). And 3 KVA Pure Sine wave UPS will cost a bomb!!

One can power HifI compoent through Servo Voltage Stabilizer with optional Ultra Isolation Trasformer. (Calculations reamins the same as I explained above).

Hope this helps.

SUhas

Thanks SuhasG. You could be right.

But then again, the figures I mentioned were under the assumption of peak or maximum usage. Most amplifiers would mention clipping power (maximum continuous power/channel) and this is the figure we have to take to do our calculation.

Sorry I also agree that an UPS will cost a bomb. Please replace all 'UPS' with 'UPS/Stabiliser'.

This brings up a question in my mind - will a AV receiver work well with inverters without any issues? I have already blown up a cooler and a spike guard (running pc speakers) but blowing up a av receiver wil be a costly affair.

Venkat,

Very nice write up mate. I think its the audiophelia (much abused term, I know) inside the head that do not let us go by logic and steer us into believing something that only the “golden ears” can experience!

Quote-
An example of this type of marketing, and the associated reviews in magazines, is the $1499 power cord, for which the reviewer states that "The choice of power cord one makes to transmit AC over the final feet to a component has the potential to be the most influential sonic link in a music system's power chain.

Roger Russell—a former engineer and speaker designer for McIntosh Labs—describes the introduction of expensive speaker wire brands, and critiques their performance in his online essay called Speaker Wire - A History.

In pursuit of happiness – bliss!

Check this out, incase you want to get more confused
Speaker Wire