Class A digital device?

fra77x · Post by **fra77x** » Fri May 12, 2006 6:00 am

Hello, i was talking recently with a friend of mine and he told me about a conversation with a guy with a lot of hardware tools. He told him that there is an identification for some devices the class "a". He told me that is about the material the clip is designed (or something else) that makes the particular device superior. Anyone has any details on this, is it a kind of a quality standard like ISO for audio devices, any info would be fine.

Mr Arkadin · Post by **Mr Arkadin** » Fri May 12, 2006 7:38 am

No, it's not a standard, it's different circuit types, usually applied to amps and pre-amps . There's Class A, Class B and Class AB. To be honest i can't remember the difference between them all - i think Class A is a better signal circuit but not very efficient in power, Class B is more efficient but can distort the signal, so Class AB is the compromise. i think Class D is used in connection with digital amps (hence the D i suppose). Or something. i have no idea what Class C amps are. There even seem to be circuits available for Classes E-H, but i've never heard of them in practical applications, maybe someone with more knowledge can elucidate.

Here's a little something to get you started.

<font size=-1>[ This Message was edited by: Mr Arkadin on 2006-05-12 08:48 ]</font>

Post by **irrelevance** » Fri May 12, 2006 11:36 am

I think class c amps are able to be run by low power sources like batteries. Class A amps are the standard for power amp design as I remember, slightly wasteful but overal good amplification and frequency response.

Post by **garyb** » Fri May 12, 2006 1:27 pm

here's a good explanation:
http://www.screensound.gov.au/glossary. ... enDocument

medusa13 · Post by **medusa13** » Sun May 14, 2006 9:16 pm

As far as I know, class a, b, or ab refers to the circuit type and how the signal is affected.
Supposing that a signal is made up of positive and negative values, a class b circuit will split the negative values and the positive ones to amplify them separately and sum them together at the end.
This adds distortion.
A class a circuit won’t split the signal. It will process the signal indepently of its value through the same path. The result will be more true to the original signal (no distortion) but class a devices are more inefficient at power handling. Hence, it's harder to design something and have good results.

Martín

DigiSUN · Post by **DigiSUN** » Tue May 16, 2006 8:09 am

Yes, Medusa is right (Also Mr Arkadin, althought i'm not 100% sure about class C/D...).

As far as I know, Class B Device aplifies the positive and the negative parts (polarities) of the signal seperately. The results are "summed" together in the output, and they may result in unaccurate zero-crossings - It's called crossover distortion. However, Using this method, signal is always centered around zero - which means high efficiency, and minimum power consumption when the signal is silent.

Class A uses a single amp over the signal - by first applying a high DC offset to the signal (making it a single-polarity), amplifying it and then removing the DC at the output. This method is linear and offers no crossover distotion at all. However, since even silence is converted to a non-zero DC value, it means that current flows in the amplification system all the time - resulting in permanent static power consumption and heat while the amplifier is on.

<font size=-1>[ This Message was edited by: digisun on 2006-05-16 09:14 ]</font>