What is a predriver?Class A

phipiper10
phipiper10 Posts: 955
edited February 2009 in Electronics
I've not spent much time reviewing different amp classifications but have some understanding.

The B&K manual says:

operates class A predriver and AB high current MOSFET power
output stages.

What does the predriver do? Does this actually operate in class A for some brief period up to x watts or something before switching to AB?

My google search didn't yield much so maybe this is better known by some other name?

Thanks!
Analog Source: Rega P3-24 Exact 2 w/GT delrin platter & Neo TT-PSU Digital Source: Lumin T2 w/Roon (NUC) DAC: Denafrips Pontus II Phono Preamp: Rega Aria MK3 Preamp: Rogue RP-7 Amp: Pass X150.8 Speakers: Joseph Audio Perspective 2, Audio Physic Tempo Plus Cables: Morrow M4 ICs & Audio Art SC-5 ePlus, Shunyata PCs Misc: Shunyata Hydra Delta D6, VTI rack, GIK acoustic panels
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  • megasat16
    megasat16 Posts: 3,521
    edited February 2009
    phipiper10 wrote: »
    operates class A predriver and AB high current MOSFET power
    output stages.

    What does the predriver do? Does this actually operate in class A for some brief period up to x watts or something before switching to AB?

    Thanks!

    Most High Power High Current Amplifier has different several gain stages. The early gain stage / the 1st gain stage refers to as the pre-driving stage for the later gain stages. B&K said it uses Class A topology for the predriver stage and then the Class A signal from predriver stage is fed to the later gain stage which is Class AB topology. This allows purer signal transfer between 1st gain stage and later gain stage. I think it also known as Class A biased Class AB amp.

    It does not necessary means that it operates in Class A for a first few watts and then switch to Class AB. I know some Parasound amps do that but not in every model. I don't know about B&K. You need to ask B&K with the specific model about it.
    Trying out Different Audio Cables is a Religious Affair. You don't discuss it with anyone. :redface::biggrin:
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  • phipiper10
    phipiper10 Posts: 955
    edited February 2009
    Thanks Mega that helps.
    Analog Source: Rega P3-24 Exact 2 w/GT delrin platter & Neo TT-PSU Digital Source: Lumin T2 w/Roon (NUC) DAC: Denafrips Pontus II Phono Preamp: Rega Aria MK3 Preamp: Rogue RP-7 Amp: Pass X150.8 Speakers: Joseph Audio Perspective 2, Audio Physic Tempo Plus Cables: Morrow M4 ICs & Audio Art SC-5 ePlus, Shunyata PCs Misc: Shunyata Hydra Delta D6, VTI rack, GIK acoustic panels
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  • Systems
    Systems Posts: 14,873
    edited February 2009
    phipiper10 wrote: »
    What does the predriver do? Does this actually operate in class A for some brief period up to x watts or something before switching to AB?
    The input and driver stages of Class AB amps are routinely operated in Class A because unlike the output stage ,the amount of current required is only in the tens of milliamps.Therefore heat dissipation is not an issue and the benfits of operating the voltage gain stages in Class A are many.


    An amp with an Class AB output stage will operate in Class A up to a certain power level determined by the actual amount of bias current ,then it switches to Class B at higher levels.
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