The time has come for me to finally jump in and build me a tube power amp. I've got nearly a dozen preamps kicking around, so I figure I'm ready for something bigger. Up until now I've been using low-gain preamps with no-gain SE mosfet buffers (huge szekeres circuits, basically) but finally decided to build my own integrated tube amplifier. I have quite a pile of tubes, but settled on el84 power tubes, as I can do with 10 ~ 15w easily. As for my circuit, I decided to go like this:
Basic grounded cathode
Split-load phase splitter (both will be either 6cg7 or 12at7, depending on whether I want to use cathode feedback or not))
El84 output stage in pentode mode (with edcor budget trafos, as they work hard for the money)
I'm shooting for a B+ of around 320v. I will use a ez81(6ca4) rectifier. As for regulating my screen currents, I was thinking of using another el84 or half a 6cm7 as a cathode follower, with a 1meg pot at g1 to set output voltage and therefore idle current, will this work well in this application? I've used this type of setup as an adjustible PSU for a couple Aikidos with good results. The only silicon in this amp will be the leds under the tubes
A couple other things. With a 10k plate-to-plate trafo, and 120 ohm cathode resistor, what formula(e) should I use to determine a good value of bypass capacitor?
Any help in getting the values and ideas down will be greatly appreciated!
Basic grounded cathode
Split-load phase splitter (both will be either 6cg7 or 12at7, depending on whether I want to use cathode feedback or not))
El84 output stage in pentode mode (with edcor budget trafos, as they work hard for the money)
I'm shooting for a B+ of around 320v. I will use a ez81(6ca4) rectifier. As for regulating my screen currents, I was thinking of using another el84 or half a 6cm7 as a cathode follower, with a 1meg pot at g1 to set output voltage and therefore idle current, will this work well in this application? I've used this type of setup as an adjustible PSU for a couple Aikidos with good results. The only silicon in this amp will be the leds under the tubes
A couple other things. With a 10k plate-to-plate trafo, and 120 ohm cathode resistor, what formula(e) should I use to determine a good value of bypass capacitor?
Any help in getting the values and ideas down will be greatly appreciated!
+1
You are going for a very well-tested, tried-and-true amplifier design. MJ uses his "Bevois Valley" project to teach each stage of the design process for an amp like this in great detail. It is an EL84 PP design using a split-load "concertina" phase splitter. It is probably well worth your time to pick up this book and use that chapter to walk you through the design process for your amp. You will learn a great deal along the way. I know I did...even though I didn't build that amp, the same steps apply to similar PP designs.
I have the 2nd edition that I picked-up about 8 years ago, which does not really talk much about SE power amplifiers. MJ is not very fond of them and concentrates mainly on PP designs. However rumor has it that he reluctantly goes through a simple SE PA project in the 3rd ed. I've been meaning to pick up the 3rd ed, but I end up balking at the price given that I already have the 2nd ed and his 3rd ed seems to be split into 2 books.
You are going for a very well-tested, tried-and-true amplifier design. MJ uses his "Bevois Valley" project to teach each stage of the design process for an amp like this in great detail. It is an EL84 PP design using a split-load "concertina" phase splitter. It is probably well worth your time to pick up this book and use that chapter to walk you through the design process for your amp. You will learn a great deal along the way. I know I did...even though I didn't build that amp, the same steps apply to similar PP designs.
I have the 2nd edition that I picked-up about 8 years ago, which does not really talk much about SE power amplifiers. MJ is not very fond of them and concentrates mainly on PP designs. However rumor has it that he reluctantly goes through a simple SE PA project in the 3rd ed. I've been meaning to pick up the 3rd ed, but I end up balking at the price given that I already have the 2nd ed and his 3rd ed seems to be split into 2 books.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.