I better idea could be to look at power bricks such as this one
https://www.amazon.co.uk/Laptop-Cha...8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
Or other external DC power supplies however I have never tried smoothing one to remove noise. The above type have a filter on the lead which will help and not many uF's should be needed in the amp but other smaller none electrolytic in parallel are likely to be needed to smooth higher frequencies.maybe even adding ceramics to other types. Others maybe polycarbonate foil and film or other higher frequency types. All types loose performance in respect to frequency as they get larger so a few values may be needed.
The above brick would drive the original design down to 4ohm, some loss of power with 8. There are all sorts of power bricks around,
Toroidal transformers were widely used in audio amp as they have a far more contained magnetic field than the usual type. Best bought with a mounting kit or the method copied somehow. It avoids creating a shorting coil on the transformer.
https://www.amazon.co.uk/Laptop-Cha...8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1
Or other external DC power supplies however I have never tried smoothing one to remove noise. The above type have a filter on the lead which will help and not many uF's should be needed in the amp but other smaller none electrolytic in parallel are likely to be needed to smooth higher frequencies.maybe even adding ceramics to other types. Others maybe polycarbonate foil and film or other higher frequency types. All types loose performance in respect to frequency as they get larger so a few values may be needed.
The above brick would drive the original design down to 4ohm, some loss of power with 8. There are all sorts of power bricks around,
Toroidal transformers were widely used in audio amp as they have a far more contained magnetic field than the usual type. Best bought with a mounting kit or the method copied somehow. It avoids creating a shorting coil on the transformer.
A peer is your equal. You are definitely not my peer. You obviously do not know that the JLH class A amplifier draws approximately constant current. To obtain the steady state output voltage, the current is equal through both output devices and is the quiescent current. They form a voltage divider. If a signal is applied, the current increases in one device while decreases in the other and vice versa. Hence, the total current remains the same.
My personal preference would be a linear PSU
[ that is one with a transformer / rectifier / smoothing capacitor(s) ]
However for convenience Laptop ‘ Bricks’ are very useful. As I’ve been trying to find redundant Laptop PSU’s for a little while now as initially it was the easiest option to power my single 1969 JLH Prototype , the most useful was the 12 volt one for testing , the best sounding one is the Bose 20 Volt, but the Samsung 24 Volt gave more power into 8 Ohms but all wouldn’t deliver enough current to use on anything other than single original 1969 JLH with pair 3055’s
William
I didn’t say I was your peer & you only are slightly older than myself and have forgotten most of my Op Amp Theory & Audio Amplifier Classes. As you have proven that you don’t know anything about me either.
However that aside thank you 4 elaborating your understanding of Class A.
Kind regards to you Mr Nico Ras let’s keep things amicable.
William
In class A you define your output by calculating the output current requirement. Furthermore, you define your power supply by the efficiency of the amplifier, which is roughly 25%, then only can you determine the transformer ratings. Assume 2 x 15 watt, with a quiescent current of around 1.4 Amp per amplifier (stereo). Remember to add the diode bridge voltage drop to the rail voltage you have calculated. Also consider that the transformer will always be under load, so you cannot simply say that the supply rail will be 1.4 time the transformer voltage, in fact it will be around the transformer RMS rated voltage. Now go and calculate all these values. Then calculate the smoothing capacitor value at the allowable ripple voltage @ 100Hz (the line voltage). In fact, JHL provides you a chart in his 1969 publication in wireless world regarding the power supply, just follow his instructions. Physics have not changed since then.
Nico is amicable, but honest, straightforward.
The best friend will tell you when your hopes are false. In that sense Nico is your the best friend.
Ignorant and false friends will feed your selective and deceptive hopes. God save me from false and ignorant friends.
No offense meant but try to be honest with yourself. Read the data from your "bricks" and apply simple calculus. (No mathematics is needed to see the obvious.)
There have been many posts previously in this thread about SMPS of all varieties & my personal preference as I have already expressed is a powerful linear supply as a PSU for my DiYJLH Build.
Data in a readable form presented in image below :
I was only considering using ‘Bricks’ above for testing my JLH 69 Prototype as I’m painfully aware of their limitations as the laptop power supplies I have obtained, range from 40 to 60 watts. Unfortunately I haven’t been able to find anything better due to my current location on the African continent. When I return home I will be looking 4 a case , large heat sinks, quality semiconductors & a massive toroidal transformer with capacitors up to the job of smoothing the ripple.
William
By the way, I qualified as EE before there were op-amps.
I sincerely envious as you were obviously taught vacuum tube theory instead which is far more useful.
I had great difficulty in staying awake during the lectures about Op Amp’s in University.
Probably due to late nights in the bar of the students union playing video games.
Kind regards to a fellow EE
There is no escaping the fact that I botched my explanation of class A operation badly and so, thanks actually, to Nico for the roasting which I deserved and may I offer my humble apologies to all here, for that post. I can't think what possessed me, apart from having had a lot of trouble with cheap Chinese SMPS units which would not regulate properly when there was any audio output. On the positive side, there were no problems with good quality MeanWell SMPS units, that I can recall.
They are likely to need rather different "filtering" than a mains transformer but I can't see why that would rule them out.
I wondered what Hood suggested on power supplies. He's effectively using a capacitance multiplier. Not a bad idea considering the cost of big electrolytics He mentions the supply will reduce ripple to less than 10mv. Using a page that uses a decent ripple estimation that would need >0.7F to achieve the same thing. The transistors he uses wont be critical. Just need similar power rating and gain. They are only handling 100Hz
This page IMHO gives some reasonable approximation or ripple.
https://www.electroschematics.com/capacitor-input-filter-calculation/
It also shows how to handle the same problem when a regulator is used.
The wiki has a page on capacitance multiplication which explains the principle.
This page IMHO gives some reasonable approximation or ripple.
https://www.electroschematics.com/capacitor-input-filter-calculation/
It also shows how to handle the same problem when a regulator is used.
The wiki has a page on capacitance multiplication which explains the principle.
AjohnL, actually some of the Meanwell products mentioned earlier, I have implemented very successfully into audio products. Remember people had terrible views and opinions of Class D as well. Everything gets better eventually as designers understand the issues and start designing around them. One has to keep in mind that different topologies sound different, but none of these are actually bad, they are simply different. My opinion of class A is that it sounds very relaxed smooth and "accurate". Class D on the other hand can sound very revealing, sometimes even harsh if paired with some speakers. But, a lot of hi-end manufacturers are changing their attitude, making use of class D efficiency versus cost and weight. One can to some extent design your own characteristic sound into an amplifier of any class, as you can with speakers. JLH came up with a recipe that really stood the test of time, being both simple and very appealing to a wide audience. Only problem is that speaker efficiencies has dwindled making way for tonal accuracy and hence 10 - 15 watt is sometimes a little lean when selecting speakers that you may like. I am still a huge fan of John’s 1969 design, it is not only elegant but highly innovative. There are many EE that will not be able to explain exactly how it works. His later designs however, were far less innovative and more main stream.