I'm so excited about the Millett Hybrid group buy I can't stand it. I'm in for a few boards, but I couldn't wait two weeks with those tubes staring at me so I made one without the PCB.
The power LED is in a hole halfway through the half inch thick milky plastic. I wanted a color like an old neon pilot lamp. My 10 year old digital camera doesn't do it justice. Hey, the Kodak DC-50 was the best for about a week in the '90s!
I used as many parts from the surplus store as I could. The pots- volume and bias were $.99 each. I think the knob was $.35 and the power sw was a buck. They had the teminal strips too (unbelieveable!).
The top plate is a piece of .125 Al I cut from a plate with a saber saw and drilled and tapped for the 4-40 screws. The bottom and the rollbar for the tubes is made of some machinable plastic I've had kicking arround for ten years. Its tapped and screwed together with 4-40 screws as well. The hole to the left of the vol was a mistake. I'll think of something to put in it. I ran out of 4-40s before I could fill in all the plate to base holes so there are some unfilled holes on the top right now.
The little proto board for the buffers is the unused half of a CMoy project (Tanget, you rock!). The switch on the board is to change the bandwidth mode of the buffers. I'm hoping to learn what the heck that means. The bundle of white wire is the tube bias test points so I can pull it out and clip the multimeter to them.
I've been curious about what kind of difference the parts quality really makes, so I built this one as the low buck (gumwrappers and spit) version. The caps are mostly the values Peter Millett calls for and are the less pricy Panasonics. I also skipped all the film caps except on the output stage. The pots are all probably 20+ years old from the magical wonderland we call Surplus City on route 66 here in Albuquerque. The power suply is the 6 clam wall wart from Digi-Key.
It took me about two solid days to put it together and it worked the first time
It was making a distinct 60hz buzz that went away after I shoved the input cable in harder. I haven't listened to it with the good phones yet, but it sounds as good as the 'go ahead and blow these up' phones are capable of. Right now I'm just happy it hasn't burned the garage down. The real critical listening will come after I build one with spendy bits on the PCB from the group buy (Nate and Drew- you rock too!). This is the second amp I've made after a couple of very fun CMoys.
Thanks to everyone who has been answering my questions and everyone who makes this site such a fun place. Thanks Rick and Pete for pointing me at enough tube wisdom of the ancients to keep me busy for a few years.
Oh, look! It flew over to the bird feeder!
