- #1
famousken
- 108
- 0
Hello everyone, I'm in the design process of building a 100W/ch audio amplifier. I would like it to sound as good as possible (willing to sacrifice power output for sound quality) and am looking for some design pointers. The output stage and driver stage will be solid state using 2sd845/2sb755 complimentary pair for the output transistors (120v,12A,Hfe=15) and c2235/a965 for the drivers (complimentary) (120V,800mA,Hfe=180). From that point I would like to use tubes as the required drive current is within realistic ranges (Aprox. 60mA) The tubes I was considering using are 5963 dual triodes simply because I have a bunch of them and they seem to have the right specs http://www.tubebooks.org/tubedata/HB-3/Receiving-Type_Industrial_Tubes/5963.PDF.
Where I am having trouble is in two areas, the first being the biasing of the driver transistors for class AB operation. Should I bias at the driver transistors, after the tube amplifier stage? I am worried about stability problems at power on/off as the tubes need to warm up. Also, any suggestions as to coupling the tubes to the driver transistors? I'm thinking that I will need to use pure class A, cathode follower, biased to 0V relative to the power supply rails (+65V-0- -65V) and this would mandate capacitor coupling between stages and biasing of the final stage at the driver transistors (I think) however I would like to use direct coupling in all stages if possible, so if there is a way around this please let me know!
Here are the datasheets for the driver and output transistors:
http://www.datasheetcatalog.com/datasheets_pdf/2/S/B/7/2SB755.shtml
http://www.datasheetcatalog.com/datasheets_pdf/2/S/C/2/2SC2235.shtml
Where I am having trouble is in two areas, the first being the biasing of the driver transistors for class AB operation. Should I bias at the driver transistors, after the tube amplifier stage? I am worried about stability problems at power on/off as the tubes need to warm up. Also, any suggestions as to coupling the tubes to the driver transistors? I'm thinking that I will need to use pure class A, cathode follower, biased to 0V relative to the power supply rails (+65V-0- -65V) and this would mandate capacitor coupling between stages and biasing of the final stage at the driver transistors (I think) however I would like to use direct coupling in all stages if possible, so if there is a way around this please let me know!
Here are the datasheets for the driver and output transistors:
http://www.datasheetcatalog.com/datasheets_pdf/2/S/B/7/2SB755.shtml
http://www.datasheetcatalog.com/datasheets_pdf/2/S/C/2/2SC2235.shtml