I am looking to build my first amp with help from a friend in electronics. Ive been looking around and found that the L20D is very popular, but on more searching have decided to go for the L25D although ATM i dont know the differences between them. Anyone got any idea's or comments ??
Also i was finding it hard to work out what power supply to use....
At first i was thinking im gonna need to get a toroid of about 60-70v, but thats why im here.
From what i am aware the actual peak voltage from a rectified ac power supply is actually 1.414 times the amount. i.e 45vac would get me about 63.6vdc ? Correct me if im wrong as im sure i read somewhere that you then times the peak by about 0.63 to get the actual output.
YES THIS CONFUSES ME......so any help would be appriciated.
I need to work out as well whether i can use a single say 600va supply for 2xL25D. Again it was suggested to provide about 1.25 times the required maximum power.
If i get a toroid with 2x50vac secondaries and connect the correct two wires together will i end up with a three wire 50-0-50 ??
Once again guys thanks for any advice and please feel free to enlighten me on anything i am clearly missing.
If you don't mind reading a bit, this link will answer most of your questions.....
Elliott Sound Products - Linear Power Supply Design
I've been reading this forum like crazy lately and the consensus seems to be that you can't beat these SMPS for price and quality
Re L25D vs. L20D vs. L15D, these are in decreasing order of suitable voltage ranges.
I believe in Table 1, p.4 of the below link that AMP7S-150 corresponds to thge L15D and AMP7S-200 to the L20D.
I get the impression that the designer of these modules favors the L15D for sound quality
I have enjoyed looking over these posts to try and get some clues I am looking for. I am running 2 L25D boards with +- 70 volts. They are both ocp'ing far too early in my opinion. I looked at the board, and it looks like the ocp resistors are the same as for the amp7s. Checking the transistor on voltage shows it to be pretty much identical to that for the original single package with two transistors design. So it appears to have twice as much transistor, but it uses the same heat sink, and the resistors defining the overcurrent are the same. This tells me that the board isn't prepared for a 4 ohm load even though it has enough transistor to do it. Of course, I could be wrong, and there could be some other reason why my boards are tripping so early.
it doesn't really work with 4 ohms
I tried a lot of stuff, and the L25D just doesn't really do 4 ohms, even if you play a lot of tricks. Single exception is ... if you are using it for a subwoofer only, it may do 4 ohms if you cut the gate resistors in half. ******* with the oc resistors can help a little, but to stop it from oc'ing, you have to remove them.. Install fuses for oc protection, and find out that they aren't reliable the hard way. My final decision ... scrap the L25D as a 4 ohm alternative move to at least an iraud 350 or iraud200 with irfb4227 transistors to get what you are after. .. these boards sport same size but higher gate charge hence lower internal resistance transistors, and the irs2092 chip should be capped with a heat sink to help it to supply the gate current. There are other boards with quad irfb4227's installed that amazingly cost around double (close to $100 each which doesn't make sense to me) but quad irfb4227s would probably promise more reliable behavior.
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