After successful building ACA with a laptop power supply, I am interested into building another amplifier. I'm interested into building a JLH 1969.
Can I power up the JLH 1969 with a laptop power supply. I have 2 laptop psu rated at 80w each.
I saw a JLH 1969 boards selling in ebay which only takes Vcc and GND.
Can I power up the JLH 1969 with a laptop power supply. I have 2 laptop psu rated at 80w each.
I saw a JLH 1969 boards selling in ebay which only takes Vcc and GND.
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I don't recall the numbers but I think the JLH has a low PSRR (Power Supply Rejection Ratio).
Perturbations of the power supply get onto the signal output.
SMPS are very poor for high frequency interference and I suspect you will find this to affect the JLH output, rather badly.
You will need to add in some form of interference attenuation. A capacitor multiplier might be good enough and JLH designed at least one. He also designed a ripple eater.
Maybe he found these to be necessary to get the best sound from some of his circuits.
Perturbations of the power supply get onto the signal output.
SMPS are very poor for high frequency interference and I suspect you will find this to affect the JLH output, rather badly.
You will need to add in some form of interference attenuation. A capacitor multiplier might be good enough and JLH designed at least one. He also designed a ripple eater.
Maybe he found these to be necessary to get the best sound from some of his circuits.
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Many (+many) years ago I had such an amplifier and it had a rather poor PSRR such that I could hear the supply ripple. If you want good performance, you should probably use a linear regulated power supply. That is the best way to keep noise down.
Laptop PSUs could suffer from heating problems because they are often designed not to supply maximum power continuously without important heating. For normal class D or AB it is not a problem because the average power content in music is considerably below the peak power that determines the maximum volume use. But, class A is different in that it just pulls a lot of power disregarding the output power being used and the type of music. Thus, on top of possible ripple problems you may run into PSU overheating.
Laptop PSUs could suffer from heating problems because they are often designed not to supply maximum power continuously without important heating. For normal class D or AB it is not a problem because the average power content in music is considerably below the peak power that determines the maximum volume use. But, class A is different in that it just pulls a lot of power disregarding the output power being used and the type of music. Thus, on top of possible ripple problems you may run into PSU overheating.
Another link
Not a laptop PS but a SMPS. A laptop PS is a species of SMPS, of course.
SMPS powered JLH 69 - quick and dirty results
Not a laptop PS but a SMPS. A laptop PS is a species of SMPS, of course.
SMPS powered JLH 69 - quick and dirty results
Thank your for all the comments.
I have a spare toroidal transformer here but I am not sure will this under power or not. The transformer rated at 0-15v dual primaries @200VA. What will be the power I get from this transformer? My plan it making a 10watts JLH.
I have a spare toroidal transformer here but I am not sure will this under power or not. The transformer rated at 0-15v dual primaries @200VA. What will be the power I get from this transformer? My plan it making a 10watts JLH.
Yes.
moppy said:
At what impedance?? To get 10 Watts, the supply voltage may be 17V or 36V, depending on load impedance.
With one 15VAC winding you get about 21V of DC. In 8 Ohms or higher you will get less than 10 Watts. With two 15VAC windings you get say 41V, which is off the chart, and will need *massive* heatsinking.
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Strongly suggest someone move this material to the big JLH 10 Watt class A thread.
JLH 10 Watt class A amplifier.
They are currently discussing PSU (among other things).
Cheers Jonathan
JLH 10 Watt class A amplifier.
They are currently discussing PSU (among other things).
Cheers Jonathan
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