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Today I received two SMPSs (Switched Mode Power Supply) instead of the above kind of hopeless solution.
I came to the conclusion that while the SMD (Small Motor Drive) stopped switching due to some strange reason at 16V (before linear regulation which resulted in 12V out) I had 21V with 7Vpp ripple at input to the SMD. Some (24Vrms-16V)*6A would then mean 48W dissipation. This while the SMD isn't a heat sink...
I really like my new SMPSs. The brand is nicely enough Mean Well (RPS-75-12), which I really do
Best regards, Roger
I came to the conclusion that while the SMD (Small Motor Drive) stopped switching due to some strange reason at 16V (before linear regulation which resulted in 12V out) I had 21V with 7Vpp ripple at input to the SMD. Some (24Vrms-16V)*6A would then mean 48W dissipation. This while the SMD isn't a heat sink...
I really like my new SMPSs. The brand is nicely enough Mean Well (RPS-75-12), which I really do
Best regards, Roger
Hi folks!
I'm seldom here nowadays because I have fallen in love with my swedish electronics forum (elektronikforumet.com) and is really not so keen on writing about the same stuff in english.
Don't get me wrong, I love writing in english it's just that it consumes energy
Anyway, I wish to present some pictures of my since a few month finished JFET-Amplifier.
I also want to say that it did not turn out so well.
I was aiming at 12W (12V supply) and got 4W
A couple of watts was lost in the common source resistans (had to double it so I lost 4V there) and a couple of watts I lost in the transformer copper windings (0,7mm Cu@3A), to my great surprise.
It should be pointed out that the Power JFETs (LU1014D) I use, as a nice tip from this forum actually, can be run at 24Vds maximum (which gives me an idea of improvement).
And the source loss could be eliminated with a huge capacitor (some 220mF)
The copper loss (at same current) may be minimized whith the aid of a bifilar 1mm winding (not so keen on that due to its stiffness).
If we consider the good parts for a while instead, here is the data:
BW(BF=4): 7Hz-30kHz (-3dB)
BW(BF=0): 35Hz-12kHz (-3dB)
BW(BF=0): 20Hz-20kHz (-6dB)
Looks rather good, yes?
The only problem here is reality.
Feedback is magic but it can''t compesate if there are no voltage margins.
So even if I can produce 4W at 1kHz, I can only do that in the middle of the band(width).
And while the level is down 6dB at both preferred ends, maximum power output at those ends are 1W only.
So I now have an amplifier that only can produce 1W over the whole audible bandwidth.
So to say that I've built a 4W JFET amplifier is to exaggerate a bit
Fiasco?
Best regards, Roger
I'm seldom here nowadays because I have fallen in love with my swedish electronics forum (elektronikforumet.com) and is really not so keen on writing about the same stuff in english.
Don't get me wrong, I love writing in english it's just that it consumes energy
Anyway, I wish to present some pictures of my since a few month finished JFET-Amplifier.
I also want to say that it did not turn out so well.
I was aiming at 12W (12V supply) and got 4W
A couple of watts was lost in the common source resistans (had to double it so I lost 4V there) and a couple of watts I lost in the transformer copper windings (0,7mm Cu@3A), to my great surprise.
It should be pointed out that the Power JFETs (LU1014D) I use, as a nice tip from this forum actually, can be run at 24Vds maximum (which gives me an idea of improvement).
And the source loss could be eliminated with a huge capacitor (some 220mF)
The copper loss (at same current) may be minimized whith the aid of a bifilar 1mm winding (not so keen on that due to its stiffness).
If we consider the good parts for a while instead, here is the data:
BW(BF=4): 7Hz-30kHz (-3dB)
BW(BF=0): 35Hz-12kHz (-3dB)
BW(BF=0): 20Hz-20kHz (-6dB)
Looks rather good, yes?
The only problem here is reality.
Feedback is magic but it can''t compesate if there are no voltage margins.
So even if I can produce 4W at 1kHz, I can only do that in the middle of the band(width).
And while the level is down 6dB at both preferred ends, maximum power output at those ends are 1W only.
So I now have an amplifier that only can produce 1W over the whole audible bandwidth.
So to say that I've built a 4W JFET amplifier is to exaggerate a bit
Fiasco?
Best regards, Roger
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