Well, it started with this : http://www.diyaudio.com/forums/headp...amplifier.html
However, things turned out in such a way that I did have neither time nor money to pursue it further.
A few days ago I decided to take a look at it again and there has been some rather major changes.
List of changes :
Dual matched NPN monolithic SSM2212 transistors for the input pairs.
Dual matched PNP monolithic SSM2220 transistors for the current mirrors.
BC850C are used in the LED based current sources.
BC860C for the VAS.
Semelab ALF08NP16V5 dual N+P channel Lateral FET is used for the output transistor.
LTP bias current is 2.6mA through each of the input transistors, VAS bias current is 5.2mA, output stage bias current is 115mA.
Almost everything is SMD so the board is a lot smaller this time. Old board were 100mm X 100mm for 1 channel, the new board is 90mm X 50mm, which is 45% of the previous size and it might end up even smaller. Something like 70-80mm X 50mm should be a possibility.
Smallest components are the SOT23 BC850C/BC860C transistors, resistors and capacitors are 0805 and up.
The input RC filter will be using either a C0G/NP0 ceramic capacitor or a PPS film capacitor. The same goes for the Cdom capacitor, that is also either C0G/NP0 or PPS film. I have not decided yet.
100nF bypass capacitors will either be some kind of film capacitors or X7R ceramic capacitors.
I know a lot of people do not like ceramic capacitors for audio use but X7R are great for supply bypassing and NP0/C0G are just as good as some of the best film/silver mica capacitors when it comes to low distortion. On top of that they are extremely stabile over temperature and are free from the usual piezo electric effect seen in X5R/X7R and lower quality ceramic capacitors.
However, things turned out in such a way that I did have neither time nor money to pursue it further.
A few days ago I decided to take a look at it again and there has been some rather major changes.
List of changes :
Dual matched NPN monolithic SSM2212 transistors for the input pairs.
Dual matched PNP monolithic SSM2220 transistors for the current mirrors.
BC850C are used in the LED based current sources.
BC860C for the VAS.
Semelab ALF08NP16V5 dual N+P channel Lateral FET is used for the output transistor.
LTP bias current is 2.6mA through each of the input transistors, VAS bias current is 5.2mA, output stage bias current is 115mA.
Almost everything is SMD so the board is a lot smaller this time. Old board were 100mm X 100mm for 1 channel, the new board is 90mm X 50mm, which is 45% of the previous size and it might end up even smaller. Something like 70-80mm X 50mm should be a possibility.
Smallest components are the SOT23 BC850C/BC860C transistors, resistors and capacitors are 0805 and up.
The input RC filter will be using either a C0G/NP0 ceramic capacitor or a PPS film capacitor. The same goes for the Cdom capacitor, that is also either C0G/NP0 or PPS film. I have not decided yet.
100nF bypass capacitors will either be some kind of film capacitors or X7R ceramic capacitors.
I know a lot of people do not like ceramic capacitors for audio use but X7R are great for supply bypassing and NP0/C0G are just as good as some of the best film/silver mica capacitors when it comes to low distortion. On top of that they are extremely stabile over temperature and are free from the usual piezo electric effect seen in X5R/X7R and lower quality ceramic capacitors.