Class C amplifiers

[gtirard]

Warning: silly topic

Ever wondered about class C amplifiers? I mean, we know about Class A, B, A/B… and D.
What about class C amplifiers?

So, I asked to ChatGPT

What about class C amplifiers for audio applications? I mean, we know class A, B, A/B and D, but what about class C?

Answer:

ChatGPT - Class C Amplifiers Audio

Shared via ChatGPT

chatgpt.com

Spoiler: Bottom line

Comparison summary​

Class	Conduction	Audio use	Why
A	360°	Yes	Best linearity
B	180°	Yes	Efficient, crossover distortion
AB	180–360°	Yes (most common)	Best compromise
D	Switching	Yes	High efficiency
C	< 180°	No	Requires tuned load

---

Bottom line​

Class C amplifiers are fundamentally incompatible with audio signals.

They're brilliant for RF power amplification, but for audio they:

• Cannot handle wide bandwidth
• Produce extreme distortion
• Offer no advantage over Class D

That's why you almost never hear about Class C in audio—even in experimental or boutique designs.

 

[S-Bigbottom]

They are for amplifying wireless signals not making loud.

Not one better than A/B or one less than D.

 

[fdeck]

Class-C is intended to be operated with heavy filtering to suppress the harmonics, in single frequency applications, notably radio transmission.

 

[agedhorse]

At least Chat GPT got the conclusion correct.

 

[baxter_x]

So class C is all about filtering?
That I guess is not interesting at all for our purposes here?

 

[frankie5string]

When I was really young, I had a neighbour up the street that built his own HAM and AM transmitting gear. The amplifiers he used were "Class-C" based on 6V6 tubes. It was all from the 50s-60s. I think it ran around 10-12 watts.

Can't really say it was good or bad at anything - but it worked.
He was very keen to convince kids that HAM radio was something we should all get involved in. This was early 1980s. My parents refused to let him build me anything that was going to run on mains power. That's probably the only time I heard anything about Class-C.
Companies like Harris and Nautel did all sorts of cool stuff for broadcast where an array of RF Amplifier elements could be fired up and down dynamically to follow the incoming audio and increase transmission efficiency and reliability. Pretty need to see/read about.

 

[TeaTime]

I think they are still used in radar systems?

 

[monsterthompson]

Classy amplifiers? Sign me up!

 

[agedhorse]

So class C is all about filtering?
That I guess is not interesting at all for our purposes here?

It's all about many things unrelated to audio.

 

[MultiScaleMale]

AI is getting better. Basically it's that friend that thinks they know something because they read it on the internet. And that's essentially what AI is, a conglomeration of things that it read on the Internet. Add in some hallucination where it just makes up things and you get a quick summary from multiple sources that would take you a lot of time. ChatGPT doesn't give sources but other LLMs will. Check sources!

 

[fdeck]

So class C is all about filtering?
That I guess is not interesting at all for our purposes here?

When tuned to operate at a single frequency, it can be much more efficient than Class-AB. This is important for, like, multi-kilowatt radio transmitters.

 

[gtirard]

ChatGPT doesn't give sources but other LLMs will. Check sources!

I don't know why it didn't give sources this time, but it often does (with links). And when it comes to bass topics, sources often comes mainly from… Talkbass! But it finds infos better than the internal TB search engine, and it summarises.

When I'm searching bass related content, I usually:

1. Search with the Talkbass search (with advanced criteria most of the time)
2. Search in Talkbass with Google. I type : "site:talkbass.com mysearch", in google search bar - it asks Google to find "mysearch" within talkbass only. Often works better than the Talkbass search.
3. If I can't find relevant results, I try ChatGTP, but I'm aware the answer is not reliable so I try to check.

I agree with the rest of your comment.