I like listening to headphones. Especially later in the evening. That's when I'm still awake, and the other people in the house are already asleep. When I listen through headphones, it doesn't wake the other, and I can still enjoy music.
I've built two other headphone amplifiers, and when this is finished, it will be my third and last for a while. The idea for this headphone amplifier was born when my previous mosfet amp was finished. It worked, but still left a lot to be desired. With this amplifier, I tried to build an amplifier that fullfills all the wishes I have for an amplifier.
Here's a description of this headphone amplifier. It's almost done now, read on to find out what has been and what needs to be done.
First, I will give all the schematics, and pcb layouts. On the next pages you can read about the construction and find some images.
I'm busy learning a lot about transistor design at the moment. It's my plan to replace the mosfet output stage (which is a simple mosfet follower) with a BJT output stage. This is also the reason why I didn't improve the current headphone amplifier last year: I'm planning for a major redesign in the next months. Please keep that in mind when reading this article :)
This is the powersupply for the 5670 twin-triode, it is designed using PsudII:
This is the powersupply for the Mosfet part of the headphone amplifier. Its basic design is the same as used in my previous headphone amplifier:
This is the schematic of the headphone amplifier itself. The output is switchable between normal and High Z (with a resisitor in series):
I have designed pcb's for the lm337/lm317 powersupply's, and for the Szekeres headamp. I have also built them, and they work just fine.
These are the images for the LM317 part of the supply. The images are resized for better layout, but are in fact larger. I have designed them to be printed on a 300DPI setting:
These are the images for the LM337 part of the supply. The images are resized for better layout, but are in fact larger. I have designed them to be printed on a 300DPI setting:
The lm317/lm337 are well known voltage regulators. I expect that I will make several powersupplies based on these IC's in the future. That's why I made the PCB's generic, so they can be used in pairs to form a dual supply. But also seperate, to give a positive or a negative powersupply. Therefore, there is room for 4 rectifier diodes on each board, but when they are to be combined to form a dual supply, only 2 per board are needed and the spare holes can be used to make the necessary links between the boards.
And this is the PCB for the DC coupled Szekeres:
The images are resized for better layout, but are in fact larger. I have designed them to be printed on a 300DPI setting.