This tube amplifier uses the dual triode 12AX7 tube to first amplify the small signal voltage that comes from audio in. As long as the circuit diagram is closely followed, this tube amp should work. Make sure all the solder joints are secure and make sure that all the necessary components have been used. When wiring, pay special attention to the voltage and wattage ratings of the capacitors and resistors. Wire all the ground connections to the the copper clad plate on the bottom and isolate any connections and solder joints from the ground using nails hammered into small wood cubes. Follow the lines in the diagram and connect the different shown components together by way of the the lines in the diagram. If you click through the photo below, you can get a glimpse of the copper clad enclosure sticking off the output of the amp.To wire the audio circuit, you mostly have to just follow the circuit diagram.
#Homebrew amplifier plans software
I was going to use 7-pole low-pass filters until I realized that everybody else uses 5-pole filters because push-pull amps already suppress the even-ordered harmonics by at least -30 dBc.Ī bit of work with the new LADPAC software in EMRFD enabled me to crank out a table of filters for all of the bands (160 m 6 m) using the silver mica caps in my junkbox plus T68-6 toroids.
#Homebrew amplifier plans series
Without doing any actual measurements and calculations, I dropped in the broadband transformer pair used in the TF3LJ amp, and immediately improved my output power by a few watts.Ī bit more searching showed that I might need another compensation cap on the output, so I experimented a bit more until I found that a 1200 pF silver mica in series with the drain transformer outputs worked wonders and boosted my power on 6 meters to nearly 15 watts CW. My initial iteration of the amp used a transformer similar to the one in the Pennywhistle amp (this is a configuration that Ive also successfully used before in a push-pull class-C CW amp). The input return loss measured quite good -15 to -20 dB across all the bands. I figured it had to be something with the input or output network. Not too great when you are putting in 2.5 watts. More troubling was the fact that output on 6 meters was only 2.8 watts. I didnt get quite as much output power as I initially liked (only got about 10 watts), but the amp was working correctly. I nibbled a nice square area right out of the middle of the copper clad I used to build on, soldered the RD15HVF1 devices to some pads etched out with a Dremel, then bolted the MOSFETs and copper clad directly to the lid of the enclosure.ĭrilling the holes for the BNCs and the LED was a piece of cake with the aluminium box material. Homebrew Amplifier Plans Plus Stores AroundĪ bit of scrounging at the surplus stores around town led me to some cheap heat sinks that looked like they might be suitable for this project.Īfter attacking them with an angle grinder to get a lip off of the bottom side, I was able to bolt two of them to the lid of an aluminum Hammond enclosure. I dont have a scehematic to post at the moment, but if you click through on the photo to the right, you can see a close-up with descriptions of major circuit blocks.īelow, Ive posted links to the two circuit resources that I used the most for this design. I know, not the best method, but sometimes the desire to just put out some RF trumps proper procedure. Not surprisingly, the real focus of the design is in optimising the input and output networks.įeeling lazy and anxious to just get on the air, I pretty much did cut and paste from some different circuits to find out what works best. There isnt a ton of creativity to be used when designing a linear of this class (Push-pull Class-AB). These things can also take quite a beating from poor mismatches, and have the convienice of having the source connected to the metal tab on the case, making for a nice solid ground connection.
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