Class G & H audio amplifiers - How they work

I even didn't heard about G and H classes. Thx for the information. Interesting video as always.

I have 4 RPA-16 amps. from Rockville and they are class H amp.s love them.. they weight 47 lbs. each and each for right around $400. I can get with a 4-ohm. load 1.7K. watts per side..at max output.. Great value for the money!

Enjoyed the series, John. Thanks and happy holidays!

In the later 1970's Hitachi pioneered the class G amps and Soundcraftsmen used class H. I purchased a Hitachi SR-804 class G receiver in 1979 and still use it as my main amp. It's weight (for a 50wpc receiver) is under twenty four pounds. Most similar units from that time were well over thirty pounds and didn't have 3dB's of headroom. The Hitachi SR-804 runs cool. Even after several hours pushing my Ohm L's (4 ohms) to loud levels in my 1,700+ cu/ft living room, the receiver top is barely warm. I did use a Marantz 2252B for a few months during 2015 but like the seemingly effortless power of the Hitachi. Great video, a lucid explanation of amp classes.

I just went to see about getting Bob Cordell's book. I'm in Canada, $115CAD+.. wow. Great video series btw.

I have a late model Phase Linear design, DRS900, designed by Carver. By their description it sounds like it would be a class H; 6 supplies (3 per channel) with separate plus high and minus high supplies, rated 150W RMS and 900W peak. I never knew of the class G & H designations though. Bought it at a nice discount when Jensen bought and discontinued the line. A very nice amp for the early 1980's.

I was vaguely aware of these topologies but certainly had never heard of them being called class G & H, thank you for sharing !!

Thanks for another interesting video, John! I had to fix one of the power amps for the subwoofers in my home stereo. Class H - low, mid and high rail and to top it off, the 12 output transistors is configurated as sziklai pairs. Took some re-engineering before I could start the troubleshooting and repair.

I owned a couple Carver amps. The first was a receiver, I forget the model. After a week or two I sent it back because I was sensitive to a very high frequency it seemed to be emmitting. They did tests and said they found no such signal in the output. I traded it in for a 400t, no such problems. I think in hindsight it was a spurious reverse microphonics issue in the power supply, only audible outside the output signal. Being a newer product the 400t probably had these issues designed out.

Awesome series. Thank you for putting this series together, really enjoyed every minute and learned so much. I aspire to following your footsteps.

Thanks John keep uploading more videos, you and your fellow electronic techs keep Youtube alive at least for us IMHO.

Very interesting. So the distinction between G and H is that (using your letters), H just turns the Hi supplies on and off, whereas G uses the top and bottom transistors to provide pseudo Hi+/- supplies at voltage slightly beyond what the middle transistors need to avoid clipping. Essentially G provides to the middle transistors a supply voltage that tracks their needs.

I really enjoyed these explanations and now I know the difference.

Very nice and clear presentation. Another outcome I experience with these designs, specifically with the Carver M1.5t, is a large amount of digital/switching noise from the thyristor switches. This noise made the amp impossible to use with early digital sampler keyboards like the Ensoniq.

Good series, John. I’ve seen you work on those Carvers, now I understand how they work. I believe they used thyristors for switching to the higher rails. I suppose they would use mosfets or igbt’s today, if class d had not taken over..

Your among the few channels that keep me using YouTube. Thanks! This series has helped me clerify a lot. That being said. Efficiency is over rated in my opinion. In the real world, for me anyways, my audio battery use is my phone. Aside from that I've swapped enough light bulbs out for led to more then compensate for the very limited use of all my amplifiers combined plugged in. So for me efficiency isn't a factor in most cases. It does play a factor in size and cost though at high watt output but at some point cost goes out the window too for the right project.

A number of manufacturers these days are saying something like "our amp produces 75 Watts in Class-AB, of which the first 10 Watts are in Class-A". Would you consider doing a video to explain what that means exactly? With one of these beautifully simple schematics?

Thanks John!! Great series!

EXCELLENT

Hi JohnAudioTech Are you going to do a video on the amplifier circuit configuration for Bridge tied Load.