The L 15 amplifier compared to the old circuit board for size.
I have been comparing some of the amplifiers that I have worked with:
Size 200x41.5x?? mm
8 Ohm 100 Watts
4 Ohm 200 Watts
2 Ohm 350 Watts +-55VDC
Transistors 3 EA: A1943 C5200
Size 150x40x?? mm
8 Ohm 150 Watts
4 Ohm 300 Watts
2 Ohm 600 Watts +-55VDC
Transistors 3 EA: IRFP240/IRFP9240
Size 110x65mm (L-20)
8 Ohm 200 Watts +-65V
4 Ohm 350 Watts +-60V
Transistors 4 ea D1047 B817
Note: L-28 includes capacitors and speaker protection
Size 245x65x30mm (or 195x90 with 4 Capacitors)
8 Ohm 500 Watts +- 95VDC
4 Ohm 1000 Watts +-90VDC
2 Ohm 1000 Watts +-65VDC
Transistors 4 ea TTA1943 TTC5200
Note: Includes Capacitors and Speaker protection
Note there are 2 sizes one with 2 capacitors and one with 4 capacitors.
NJW0281/NJW0302 450W+450W HIF
4 Ohm 450 Watts +-85VDC
Gain Very Low - needs preamplifier
Transistors 4 ea NJW0281/NJW0302
I think I can fit the PR-800 amplifier version with two filter capacitors so I will try to upgrade to that amplifier instead. It is coming from China so it will take a while. Please stay tuned. The PR-800 version is in another blog post.
I am rebuilding the VU meters. I did purchase some LM3915 kits but they only have 10 LED's and I have 12 holes to fill. I also used round LED's instead of the flat ones that came with the kit. But that version only has 10 LED's. So I stripped a board from the amplifier bare and installed a LM3915 instead leaving room for more circuitry.
However the rebuilt VU meter was barely visible! So I had to replace all of the LED's with newer brighter models. Now to add the two top LED's. I am planning on using a dual op amp for that job.