Single Ended Pentode Audio Amplifier

Each Amplifier I build is a labor of love. One can choose to make the amp purely functional. Or....one can design some visual refinements , utilizing some fine woods, and cabinet maker's skills - requiring a complete woodworking shop in addition to an electronics assembly shop. I have both, which is fairly rare on the web - most amps are rather basic slabs of metal with perhaps a little wood adornment-but mostly pragmatic builds with homely transformers in view.

The Claus Byrith Designed Single Ended Pentode is a semi monobloc ~ meaning left and right channel amps are completely separate from each other. They do use the same power supply, but it is one with a massive amount of iron..including a Ten Henry Choke.

This is a fabulous sounding amp. I congratulate Mr. Byrith on this very successful design. Claus Byrith is/was the sound tech for the Danish School of Music.

I am still building and improving this page...more photos to come. I am also planning to mount this all on a cabinet which will contain some speakers I plan to build, and possibly a 22" flat screen TV...all in a nice tall cabinet which should stand about 6 feet in height; and roll on wheels. I am also considering utilizing a couple of 35 amp hour batteries to be installed in this entertainment center. With a little finnesse, the whole thing can be rolled where needed...including outside on the party/cookout patio.

See above the decibel level. You can improve this, slightly, with an indoor antenna, by rotating it...sometimes with the "V" shaped antennae -"v" shaped . Or perhaps the antenna spread flat, and rotated. This can only improve so much. In reality, wherever possible, you should strive to have an outdoor antenna. I will show an image of that antenna, and also show how greatly improved  was the reception ~ comparing before and after db readings-indoor vs outdoor.

I have installed an "Audio Attenuation Switch" on the back. it turns out this amp has such powerful "gain", the "line level" voltage from the Marantz components are a bit high ~ meaning even the lowest volume level is a bit too loud...so this remedies that situation, for folks who prefer soft background music.

Here is a shot of the 12AX7 input tube,which drives the EL34 Pentode

Below here, I wish to explain my "Three Scale Volume Control ". it is an identifying trait of my Bluebird Audio amp designs. I discovered that by switching in varying amounts of negative feedback, some improvements could be made for poorly reproduced CD's...and sadly there are too many of them around. But the ideal setting is for NO feedback at all. Audiophiles have long extolled the virtues of Zero Negative Feedback. First take a look at the dial:

The second row of numbers is the minus 3 db NFB setting. This range goes from : point 12 watts...to 4 point 8 watts