Author Topic: Class AB amp designs in pedal format  (Read 4086 times)

Djentronio

Re: Class AB amp designs in pedal format
« Reply #20 on: October 22, 2017, 12:22:24 AM »
Quote
Class B requires both positive and negative voltages.

In any operational active electronic circuit we always have positive and negative voltages. Let's consider a basic "unipolar" power supply, say, with +9VDC and common 0V supply rails:

9V is positive in reference to 0V, 0V is negative in reference to 9V.



Wouldn't that be 0V is more positive in reference to the 9V side?  That's how you get -9V power rails for PNP littered designs or russian stuff after all.

rezzonics

Re: Class AB amp designs in pedal format
« Reply #21 on: November 02, 2017, 10:55:01 AM »
The different amp classes terminology does not refer mainly to power amplifiers?
Is it not the need to reduce heat in power amplifiers that created the need for B, C... topologies?
Does it make sense to talk about amp classes for a clean boost pedal?

PRR

Re: Class AB amp designs in pedal format
« Reply #22 on: November 03, 2017, 12:05:00 AM »
> refer mainly to power amplifiers?

Not fundamentally; but yes.

You always get the most amplification for the least cost with Class A. Also low distortion. If power output is small, and battery efficiency is not killing you, this makes Class A a no-brainer for almost all work.

When you figure out a job for big power output, and wonder "Where can I get a tube/transistor that big??" or "Jeez! That battery will go flat fast!", then you look into the other classes.

That's for "clean", which is the goal in almost ALL audio work. Distortion pedals are something else. The classic FuzzFace, among many others, idles in Class A but when you beat on it it de-biases through Class B into Class C. And not push-pull B (clean) but single-side B (half the wave into SE C (less than half the wave). So 2 bucks of parts covers all 3 "classes".
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