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Non switching class B power amplifier

russel

russel

./_dazed_and_confused
I have put this as a separate thread, here is a cheap way to get that class A sound for not much money.



Tony has kindly put the files on pinkfishmedia.net/resources/NS.zip and pinkfishmedia.net/resources/NSSimple.zip the simple version contains the basic circuit with no current limiting, good for I guess 50-75 watts and the second one a dual FET version for more power, there are PDFs of the schematic and plots of a suitable PCB layout. There are also KiCad files for anyone that wants to build one, if you do check carefully as its a modification of another board. The bias circuit is a non switching design based on Tanakas work described in "New Biasing Circuit For Class B Operation" AES 65th convention paper no 1615 feb 25-28 3-6 1980.
 
Why?, how many non-switching AB amplifiers have you designed, measured and listened to?.
 
russel said:
There is an update to this if you are thinking of building it.
Click to expand...

I'm not a builder, but I have been wondering lately about the future of Class A amps, given the deepening ecological crisis. An amplifier that achieved the sonic benefits of class A in an efficient manner would be very interesting indeed.
 
eastone said:
I'm not a builder, but I have been wondering lately about the future of Class A amps, given the deepening ecological crisis. An amplifier that achieved the sonic benefits of class A in an efficient manner would be very interesting indeed.
Click to expand...


If you run a class A amplifier in winter there is little ecological damage. Very few people are into hifi these days, the young listen on headphones and can't afford places that could house a hifi anyway. Current dumping is pretty efficient and sounds nice as does non switching, even class D although not quite as good as the above reaches a very high level of performance if done well and is really cheap to boot. Most commercial systems will be class D soon.
 
Let's just put things in context:

200W of electrical input power (drawn continuously from the UK grid mix) is about 68g/CO2 per hour (at 340gCO2/KwH at time of writing*, calculated from this http://gridwatch.co.uk/co2-emissions)
Leave it on all year, 24/7/265, and other than having an interesting bill, that's 600Kg of CO2 added.

Yet
-That's just 3500miles in a Prius (from the min-spec 106g/km in, 2018 figures), or
- 6/10ths of the way across the Atlantic on a commercial economy flight Heathrow-JFK New York (calc: https://co2.myclimate.org/en/portfolios?calculation_id=2054043)

Both are also avoidable, or all three can be balanced - up to the individual.
Conclusion - for 2-4 of hours a day of pleasure, a practical Class A amp (retail, or DIY) is not on the list of things to worry about, nor demonise, when there are far lower-hanging fruit in each of our lives.



ETA: * I did similar calcs 9yrs ago for a hospital design, and project eng advised the UK grid mix was accepted as 460-500gCO2/Kwh - that's just how far the growth in Renewables, and consequent closure of coal stations has brought us in that short time.
 
I fear that the commercial growth of class D will soon mean that good output transistors for linear amps will become expensive NOS trinkets on forums such as this and no longer available from usual sources... it's happening already in as much as there is less choice of decent parts for non class D amps and for analogue audio in general than there was 10 years ago. Already almost all new TV's, radios, phones, car stereos, bluetooth speakers etc etc are class D!
 
Buy all the good parts while you can now Jez as I suspect they will be very difficult to obtain in the future. I've noticed this in the short time I have been making SS designs. Never had a problem getting anything Valve/Tube related in the last 35+ years, but definitely had problems obtaining solid state parts in the last few years...
 
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Interesting stuff.
Martin,
Don't want to go off-piste but one of the things that really annoys me is that "electric cars are emission free". Unless you are using "green" energy, they clearly aren't. The CO2 is just "moved" somewhere else. And every time you convert energy, you lose some of it.
Any thoughts as I think this is just a massive fallacy.
AP
 
a.palfreyman said:
Don't want to go off-piste but one of the things that really annoys me is that "electric cars are emission free". Unless you are using "green" energy, they clearly aren't. The CO2 is just "moved" somewhere else. And every time you convert energy, you lose some of it.
Any thoughts as I think this is just a massive fallacy.
AP
Click to expand...

True, but they are now saying that a lot of the UK's electricity is from green renewable energy sources... Not sure how true that statement is?
 
G T Audio said:
True, but they are now saying that a lot of the UK's electricity is from green renewable energy sources... Not sure how true that statement is?
Click to expand...

http://gridwatch.co.uk/

I have some concerns about counting biomass as renewable, it depends what they are burning, where it comes from, and whether it is really renewable, but still, a lot is now from renewable.
 
Quite - last time I read-up on it, Drax - at 2.5MW of biomass with more capacity to convert yet - is burning timber pellets grown and shipped from Canada...
 
Yes I understood something similar, the renewability and transport both being overlooked. I am not sure what the state of it is now, but originally a lot of what was called biomass was actually cofired with coal. This allowed coal stations to keep running as so called biomass stations but really they were still mainly coal with a bit of biomass chucked in too.
 
So we are told "some" of the facts but not the ones that might make you think. Partial truths eh? Twas ever thus.
Cheers,
AP
 
G T Audio said:
So about 1/3rd of our power is "renewable". Ok, that's better than I expected...
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Renewable? Such as? If we’re talking wind power for example the generators are huge and mounted on big steel columns both of which consume large amounts of energy to make. They sit on big rafts of concrete and what about transportation to site? When I look over the valley from where I live I can see a large windfarm in the distance and more often than not nothing is moving.
 
do get carried away (metaphorically), what you say is often not considered. Robbing Peter to pay Paul, or something like that!

And someone 'up country' is buying up oak trees in the UK to burn, so that oak timber has to be imported from Europe (or even wider afield) to satisfy demand for lumber. Bummer. After you know what, oak will be almost unobtainium.
 
Chops54 said:
Renewable? Such as? If we’re talking wind power for example the generators are huge and mounted on big steel columns both of which consume large amounts of energy to make. They sit on big rafts of concrete and what about transportation to site? When I look over the valley from where I live I can see a large windfarm in the distance and more often than not nothing is moving.
Click to expand...
Wind, solar, hydro, biomass http://gridwatch.co.uk/Renewables
Of course there is a period of generation where the power produced is effectively just offsetting the power taken to build the things, but the figure seems to be in the order of months for wind turbines and you have an asset that you would hope lasts decades.
Sure when the wind does not blow they don't spin and don't generate, but when it does ...
 
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