Hi Beppe,
from post357
I could have observed that the "no noise" between supply phases is bound to sound better than the noise the amp produces when the PSU voltage collapses from Vpk down to badly regulated DC holds at this for a short period (10mS or so) and then jumps back up to Vpk again.
But, how does the regulator manage to supply DC when there is no supply to it's input? It seems that the diagram showing DC between phases is a figment and that my first observation "zero voltage" supply lines is more likely.
from post357
as shown in Eric's web site.
I could have observed that the "no noise" between supply phases is bound to sound better than the noise the amp produces when the PSU voltage collapses from Vpk down to badly regulated DC holds at this for a short period (10mS or so) and then jumps back up to Vpk again.
But, how does the regulator manage to supply DC when there is no supply to it's input? It seems that the diagram showing DC between phases is a figment and that my first observation "zero voltage" supply lines is more likely.
That's interesting. Maybe you just didn't have the right combination? My results are usually that the ringing will be reduced to a single period, and adding the parallel C to the RC slows that remaining peak or two so that it doesn't end up in other circuits. The way I do the RC filter is I estimate a value for C then I turn a pot in series with it while looking at the scope.jackinnj said:
Hi Nixie,Nixie said:
do you have a method for choosing your component values that avoids measuring the transformer inductance?
Hi beppe61,
A power amplifier can't work without smoothing capacitors.
Smoothing capacitors is a necessary harm. My article about SCPS (Shared Current Power Supply) is at first a concept. I dont give applicative solution, just comprehensive schema.
As AndrewT, (hello Andrew), if you have a three phase main (+ neutral) into you listening room, by using three toroidals transformers you can obtain a continuous power supply. You could experiment power supply with zero capacitors. You certainly obtain a very bad sound ! By adding small polypropylene values 10uF, 20uF, 47uF... smoothing capacitors with snubbers you certainly obtain a very nice, powerfull and expressive one.
Eric
beppe61 said:
A power amplifier can't work without smoothing capacitors.
Smoothing capacitors is a necessary harm. My article about SCPS (Shared Current Power Supply) is at first a concept. I dont give applicative solution, just comprehensive schema.
AndrewT said:
As AndrewT, (hello Andrew), if you have a three phase main (+ neutral) into you listening room, by using three toroidals transformers you can obtain a continuous power supply. You could experiment power supply with zero capacitors. You certainly obtain a very bad sound ! By adding small polypropylene values 10uF, 20uF, 47uF... smoothing capacitors with snubbers you certainly obtain a very nice, powerfull and expressive one.
Eric
AndrewT said:
Hello AndrewT
Where do you see ZERO volts on the supply line on my web site ?
Eric
AndrewT said:
Hello Mr Andrew, good evening !
Honestly all this discussion is too difficult for me.
Anyway I will follow this very interesting 3D.
Thanks and regards,
beppe
I can't understand Juaneda's argument. Maybe someone can explain it to me.
As an aside, why so much focus on class-AB designs? Unless you're making large amps (> 200 W/ch), it doesn't make sense to me. A gallon of gasoline is 30-40 kW.h, and how quickly do you burn one gallon in average driving? Do you really think you're saving much energy by not using class A? It pales in comparison.
As an aside, why so much focus on class-AB designs? Unless you're making large amps (> 200 W/ch), it doesn't make sense to me. A gallon of gasoline is 30-40 kW.h, and how quickly do you burn one gallon in average driving? Do you really think you're saving much energy by not using class A? It pales in comparison.
Eric Juaneda said:
Thank you Mr Eric. I think to understand better now.
Can we say that in order to upgrade a power amp power supply it is better to replace the transformer with a bigger one than to replace the smoothing caps with bigger ones ?
Thanks and regards,
beppe
Got it. Thanks for explaining it in a language that I can understand. 🙂AndrewT said:
I was probably right about these small ceramics being good at shunting the high freqs, but I had not thought about the wide range of frequencies between the 100Hz and the megaHz.
I'll do CRC filtering from my next amp onwards.
Can we say that in order to upgrade a power amp power supply it is better to replace the transformer with a bigger one than to replace the smoothing caps with bigger ones ?
Dear Mr Eric,
at least for me this is an extremely important statement.
Honestly I have wrongly thought the contrary.
Actually I have an amp at hand on which I would like to improve the power supply.
Now and finally I know where to start in order to elevate its performance.
It is a 120 W/4 ohm RMS thing.
By the way the present transformer looks of suspicious quality indeed.
I believe that a very good toroid of about 500VA (like Talema ones) could be a nice step-up.
Thank you very much indeed.
Very valuable advice.
My kindest regards,
beppe
Eric Juaneda said:
Dear Mr Eric,
at least for me this is an extremely important statement.
Honestly I have wrongly thought the contrary.
Actually I have an amp at hand on which I would like to improve the power supply.
Now and finally I know where to start in order to elevate its performance.
It is a 120 W/4 ohm RMS thing.
By the way the present transformer looks of suspicious quality indeed.
I believe that a very good toroid of about 500VA (like Talema ones) could be a nice step-up.
Thank you very much indeed.
Very valuable advice.
My kindest regards,
beppe
beppe61 said:
Beppe,
only if the original one is anaemic, the common thing in most of the Asian power amps, and only to a certain extent.
Sometimes i tend to concur with Mr Curl, where have you guys been the last 25 years ?
The transformer experiments by Mr Juaneda is a repeat of what has been verified by so many audio clubs and individuals, a sporadic audio manufacturer even made it a trademark.
Mr Juaneda's article lacks part II, the observation that the oversizing phenomenon doesn't live forever.
Hooking up a 3000VA transformer to a 100 watt in 8 Ohms amplifier does not deliver anything extra, compared to something like a 1000VA version or even smaller, not when i did it.
Several manufacturers offered the same power amplifier as a standard model and as a Special Edition, and that wasn't yesterday but some 20 years ago.
The Berendsen audio amplifier manufacturer on this continent called it the Blue and the Red editions, the standard 60 watt monaural models already boasted a toroidal transformer others would consider to be oversized.
Brands like the Australian Metaxas used special wound 1000VA transformers for each channel of an amplifier with an output power number below 100 watts, and a 1600VA for the 100 watt high bias monaural Soliloquy.
Even diy power amp kits had the option, for instance the German ALBS company that was very popular back then.
The same applied to pre-amps.
There are amplifiers on the market with 3-phase powersupplies, btw. I have a 3-phase mains connection on the premises, called Power Current overhere. Good point of Mr Juaneda to include that in his writings, i've tried a 3-phase powersupply setup and it's definitely worth it.
Class A is an entirely different ball game, imo.
Being French, Mr Juaneda will be familiar with the 65 watt class A Audio Analyse A9, biased at 50 and running on a 160VA toroid per channel.
Or the 120 watt A90 model, biased at 100 watt class A in 8 Ohms, on 330VA toroidal transformers.
To my surprise earlier this week, even Mr Grey Rollins did not seem to be aware that single ended class A amps, as manufactured by PassIncorp., have a near constant bandwidth from zero to maximum output power.
Any PP class AB afficinado is welcome to try his hand at the same.
Hi all
So Jacco, following the examples you kindly provided, a x-former with a VA at least three times (3X) the maximum power of the load is a practice on well designed equipment.
May I assume that your point is something like this: “ everything above 3X-4X will provide diminishing returns”?
(that is a 10X is no more better than a 5X)
Regards
George
So Jacco, following the examples you kindly provided, a x-former with a VA at least three times (3X) the maximum power of the load is a practice on well designed equipment.
May I assume that your point is something like this: “ everything above 3X-4X will provide diminishing returns”?
(that is a 10X is no more better than a 5X)
Regards
George
Originally posted by jacco vermeulen
Beppe,
only if the original one is anaemic, the common thing in most of the Asian power amps, and only to a certain extent.
Sometimes i tend to concur with Mr Curl, where have you guys been the last 25 years ?
The transformer experiments by Mr Juaneda is a repeat of what has been verified by so many audio clubs and individuals, a sporadic audio manufacturer even made it a trademark.
Mr Juaneda's article lacks part II, the observation that the oversizing phenomenon doesn't live forever.
Hooking up a 3000VA transformer to a 100 watt in 8 Ohms amplifier does not deliver anything extra, compared to something like a 1000VA version or even smaller, not when i did it.
Several manufacturers offered the same power amplifier as a standard model and as a Special Edition, and that wasn't yesterday but some 20 years ago.
The Berendsen audio amplifier manufacturer on this continent called it the Blue and the Red editions, the standard 60 watt monaural models already boasted a toroidal transformer others would consider to be oversized.
Brands like the Australian Metaxas used special wound 1000VA transformers for each channel of an amplifier with an output power number below 100 watts, and a 1600VA for the 100 watt high bias monaural Soliloquy.
Even diy power amp kits had the option, for instance the German ALBS company that was very popular back then.
The same applied to pre-amps.
There are amplifiers on the market with 3-phase powersupplies, btw. I have a 3-phase mains connection on the premises, called Power Current overhere. Good point of Mr Juaneda to include that in his writings, i've tried a 3-phase powersupply setup and it's definitely worth it.
Class A is an entirely different ball game, imo.
Being French, Mr Juaneda will be familiar with the 65 watt class A Audio Analyse A9, biased at 50 and running on a 160VA toroid per channel.
Or the 120 watt A90 model, biased at 100 watt class A in 8 Ohms, on 330VA toroidal transformers.
To my surprise earlier this week, even Mr Grey Rollins did not seem to be aware that single ended class A amps, as manufactured by PassIncorp., have a near constant bandwidth from zero to maximum output power.
Any PP class AB afficinado is welcome to try his hand at the same.
Dear Mr Vermeulen,
thank you sincerely as usual for your extremely kind and valuable reply and advice.
For me it was not so clear that the importance of the transformer prevails on the capacitance.
Honestly and wrongly I believed the contrary.
This is a very important result for me.
Just think that I have the house full of Sikorel that I wanted to use in the future.
I see a future full of huge toroids.
By the way I see your advice that at a certan point an increase in VA does not give any advantage.
I wonder if there is a very simple formula to calculate the VA needed for the transformer.
Can we say maybe VA =3*RMS power on 4 ohm ?
I mean, if an amp can deliver 100 W/4 ohm a 300 VA transformer could be enough ?
Thank you very much indeed.
Kind regards,
beppe
gpapag said:
It happens because the higher VA transformer heats less, remains more efficient, and is thus more "regulated" --
beppe61 said:
Without smoothing caps -- not likely -- some of NP's early designs in Audio Amateur (predecessor of AudioXpress) had inadequate power supply rejection -- so he recommended regulated supplies -- some tweaks to the Borbely amplifiers regulated the driver supplies...
jackinnj said:
Thank you very much Sir.
What would be your optimum amount of capacitance per channel and voltage rail ?
I think that a 4700uF per rail per channel should suffice in any case for a AB class power amp.
Am I wrong ?
Thank and regards,
beppe
the optimal amount is going to depend upon how much current will be drawn by the power supply -- does someone have a thumb with rules on it???
I think it's like 1,000 uF per 10 watts, but feel free to correct me if I am wrong. I am in a very forgiving mood today as it is 0 degrees Fahrenheit here --
I think it's like 1,000 uF per 10 watts, but feel free to correct me if I am wrong. I am in a very forgiving mood today as it is 0 degrees Fahrenheit here --
I'm with Jack on the regulation bit, as usual he can give it straight in a single sentence.
Efficiency of toroidal transformers are starting to look decent above 300VA and pretty good above 500VA, at 1000VA and above there's not really much to be gained.
The transformer efficiency and the spare power factor seem the only parameters of significance.
The French class A amps i mentioned might be a good example.
The amplifying circuitry of both models was similar with Motorola TO3 BJT output devices and not that fancy, not even then.
The lower powered type was more of an economy model, not that spectacular, and especially not for what it cost. The powersupply of that one had 20 electrolytic capacitors of 5500uF in parallel for both channels.
The high power model cost twice as much, and sounded 2 steps up the ladder.
Given that the total of it's capacitor bank was in line with the other model for the higher bias level and that also the power factors of the transformers used were close to identical, the higher efficiency of the bigger model seems to have had an important impact on the significant difference between the two.
imo, a car needs both the tires and the brakes.
Efficiency of toroidal transformers are starting to look decent above 300VA and pretty good above 500VA, at 1000VA and above there's not really much to be gained.
The transformer efficiency and the spare power factor seem the only parameters of significance.
The French class A amps i mentioned might be a good example.
The amplifying circuitry of both models was similar with Motorola TO3 BJT output devices and not that fancy, not even then.
The lower powered type was more of an economy model, not that spectacular, and especially not for what it cost. The powersupply of that one had 20 electrolytic capacitors of 5500uF in parallel for both channels.
The high power model cost twice as much, and sounded 2 steps up the ladder.
Given that the total of it's capacitor bank was in line with the other model for the higher bias level and that also the power factors of the transformers used were close to identical, the higher efficiency of the bigger model seems to have had an important impact on the significant difference between the two.
imo, a car needs both the tires and the brakes.
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