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).
