Backyard noisemaker
This started out as a 250w/4 ohms plate amplifier. While playing with it, I blew the original final up (not seen here) trying to make it's diff amp more linear. I didn't realize I jumped out the current source for the LTP! 
Since there were too many things that aggravated me, such as the bridge rectifier not mounted to the heatsink, no heatsinks for 7812/7912, filter caps too small and board too small to add bigger ones, I built a completely different final and a real power supply for it. Preamp also got good caps. The AC line wiring was a disaster. Transformer has dual primaries, for either 120 or 240v operation. As I received the unit, only one primary half went through the thermal fuse. The other half only had the line fuse for protection. I sure as hell fixed that!
The square board by the transformer has the two caps for the +/-72v supplies, rectifier, regulators and filters for the +/-12v op amp supplies as well as filters and isolation diodes for the fan power supplies. The rectifier for the main supply is a 35A, 400V on the heatsink.
It puts out 240W RMS into 8 ohms, 400W RMS into 4. Measured with a dummy load- no reactive power from a speaker inflating the reading. Transformer is a bit small- when it heats up after long periods of high output outside, output drops a little.
The cab has an Eminence Beta 12A-II and a Pioneer branded Fostex 1" horn. The XO was designed in ARRL radio designer by me. Dimensions are 16x17.5x23". 98dB 1W/1W and power capacity of 250W. The zero dB reference point in the plot is also 98dB. Full power SPL is 122dB, before power compression. That thing used to be a bunch of plywood shipping containers for circuit boards. It didn't have an Eminence or American flag sticker yet either...
Enjoy the pix. If anyone wants schematics, I'll have to scan 'em in.
PS- The amp was simulated in Multisim and built a year ago, the cab a few months after.
-Paul
Since there were too many things that aggravated me, such as the bridge rectifier not mounted to the heatsink, no heatsinks for 7812/7912, filter caps too small and board too small to add bigger ones, I built a completely different final and a real power supply for it. Preamp also got good caps. The AC line wiring was a disaster. Transformer has dual primaries, for either 120 or 240v operation. As I received the unit, only one primary half went through the thermal fuse. The other half only had the line fuse for protection. I sure as hell fixed that!
The square board by the transformer has the two caps for the +/-72v supplies, rectifier, regulators and filters for the +/-12v op amp supplies as well as filters and isolation diodes for the fan power supplies. The rectifier for the main supply is a 35A, 400V on the heatsink.
It puts out 240W RMS into 8 ohms, 400W RMS into 4. Measured with a dummy load- no reactive power from a speaker inflating the reading. Transformer is a bit small- when it heats up after long periods of high output outside, output drops a little.
The cab has an Eminence Beta 12A-II and a Pioneer branded Fostex 1" horn. The XO was designed in ARRL radio designer by me. Dimensions are 16x17.5x23". 98dB 1W/1W and power capacity of 250W. The zero dB reference point in the plot is also 98dB. Full power SPL is 122dB, before power compression. That thing used to be a bunch of plywood shipping containers for circuit boards. It didn't have an Eminence or American flag sticker yet either...
Enjoy the pix. If anyone wants schematics, I'll have to scan 'em in.
PS- The amp was simulated in Multisim and built a year ago, the cab a few months after.
-Paul
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