Latest project is a Stereo Amplifier for my MP3, CD Player and output to some desktop speakers or my headphones. Using 12AX7, to a 6AQ5 Single Ended output one for each Left and Right channel. Power supply is a full wave 6X4 rectifier tube and a 270 VAC Transformer.
The chassis I used is a Hammond Manufacturing 1441-24 Heavy Duty Chassis Case 20 Gauge Steel, 12x8x3. New old stock, probably not available any more. I will be making a faceplate for the front of my amp. The sides will be faced with maple, no back plate. The chassis is covered in green low tack tape and then things can get arranged over top. I actually pen on details and set locations for all the components. This gives me a chance to see if there is room and I am not going to run into conflicts for wiring.
It’s easy to see where I decided to cancel a location, where some items are xed out. The front face was not too much of a problem. Right and left tone controls, Lamp and Mains switch.
This is the rear face and it contains the mains plug and the fuse holder. On the inside there is a fuse block for high voltage DC and the Fuse holder is for a fuse for the main 120v mains.
First hole was the power plug hole and I was learning to use my nibbler tool. I am never impressed with the nature of these holes after cutting, they look ragged and raw. However, they do get covered up by the component that is installed in this location.
Further drilling completed most holes, and I was generally happy with how that went. I liked working in the steel chassis. It was more forgiving in the drilling process than aluminum was in some other projects.
Here is the chassis with all the tape removed and the holes cleaned up from any left over flashing from the drilling process. What I did not like was the minor dimpling of the metal from where holes were made. This would not have happened using aluminum.
Here is the chassis with the major components installed. Things begin to look much better with components added. Further to be installed are the tone controls on the front face.
Beginning stages of wiring, where the power supply section is completed. I used terminal strips near components for adding resistors and capacitors.
The completed amp in initial stages of testing. I realized then that voltages were all coming out low, but not low enough to keep things from working. I am suspecting that the power transformer is too small and will be looking into replacing it with something a bit larger. In the meantime I am enjoying this amp and have been playing my CD player through it.
Just recently, after testing I realized that the transformer that I was using in the previous images was not doing the job. This new one is much better and has more current capacity. It has made a big difference.
I also realized that I had wired the plate and grid #2 connections wrong and had to make that correction. This has made the amp cleaner and upped the output. I am much happier with the final product.