Hello

Does someone know the consumption of voltage for computer and what kind of current computer use (AC or DC)? Also what usage have radio and telephone?
Thanks a lot

Voltage is not consumed, so I presume you are asking how much power is being used. Look carefully at each device, somewhere there will be electrical information that includes either watts or volt-amps (VA) which is roughly (there is no exact conversion) comparable to watts.

Voltage input into any computer I ever met was AC which is converted to DC.

Tom

All computers contain a transformer/power supply which converts AC to DC-many new computers, with large display terminals and speakers connected can consume up to 400w-large SCSI hard disks run at up to 10,000 rpm.
Not sure about phones, but I do know that they actually run on batteries in normal operation, sort of a UPS, as it were. Radios, stereos can be determined by looking at the nameplate on the unit. Their consumption varies according to the speaker rating/volume. Some high end systems with monster speakers attached will actually deliver straight AC to them. They contain no transformer, and generate considerable heat. I believe they are known as Class B, with regular stereos known as Class A/B switching Amplifiers.

Exchange battery voltage is 48 to 50V, positive pole grounded. A standard tel. line is fed through a relatively high resistance, so current is limited to the tens of milliamps range and off-hook voltage across the phone is typically 5 to 12V, depending to a large degree on line length. Power consumed by the phone itself is therefore minimal. Ringing supply is AC at up to 100V, but again power consumption is very small.


A push-pull audio output stage can operate in class A, B, or A/B.

Class A means that both transistors (or tubes) are conducting all the time. As one conducts more heavily the other conducts less, and vice versa.

With class B, the transistors are biased to cut-off point, so with no signal there is no (or very little) current. One transistor then conducts for positive parts of the signal, the other for negative portions.

Class A generally offers better fidelity, but because of the quiescent current it is much less efficient than class B.

Class A/B is a compromise between the two. With a low-level signal, both transistors conduct and the amplifier works in class A. At higher levels, one transistor cuts off during positive peaks, the other during negative, effectively changing the mode to class B.
While class A/B isn't as efficient as class B, it avoids crossover distortion which can sometimes be a problem with class B.

Thanks for the much more informed responseto the original post, Paul. Am I being misleading about one class of amp being transformerless, or is it a different animal altogether?

Glad to be of service.....

There is no specific link which requires any particular class of operation to use or not use a transformer to couple to the speaker. It's possible to build an amplifier in any of the three classes A,B, or A/B either with or without such a transformer.

With old tube amps a transformer was almost always used, as it's the easiest way to couple power from the high-impedance tubes to the low-impedance speaker.

Many early transistor amps also used a transformer. The higher-quality units ran class A or A/B. Class B was especially common in battery-powered portables, due to the higher efficiency & thus lower battery drain.

Because transistors are lower-impedance devices than tubes, direct coupling is also easily achieved, and is the norm in modern amplifiers. The absence of the transformer is said to remove a possible source of distortion, but another advantage is that transformers for high powers and bulky and expensive.

It's still possible for a transformer-less output stage to run as class A, B, or A/B, however.

There is also a class C, but this is not suitable for audio applications.

now they've got class D amps for subwoofers in car audio systems. I hear they are very efficient and generate less heat, so cooling is not as big of a factor. they are also cheaper than class AB amps. They can only be used for subwoofers though