As promised, here is the summary post, complete with schematics, for the entire 300B stereo amp.
Specifications:Peak power out : 7.5W/channel
Input sensitivity for peak output : 5.1Vpeak (3.6Vrms)
Frequency response (-3dB BW) : 20Hz to >20KHz
Distortion at full output : 3.3%
Distortion per watt (Ds) : 0.44%/W
Output impedance : 8Ω
Input impedance : 200kΩ + 69µµf
Amplifier Schematic (2 channel)Attachment:
Schematic Final Amp.png
Power Supply Schematics (120v and 240v mains versions)Attachment:
Schematics PS final.png
300B Filament Supply SchematicAttachment:
Schematic Filament Final 240.png
Thermal Design Note:The bridge rectifiers need to be heat sinked to a heat sink with a thermal resistance of no more than 39.5˚C/W (including interface layer thermal resistance). I recommend the Comair Rotron 822202B00000 heat-sink with a thermal resistance = 13˚C/W (
http://www.alliedelec.com/search/productdetail.aspx?SKU=5990351). The LT1085 rectifiers need to be heat sinked to a heat sink with a thermal resistance of no more than 11.8˚C/W (including interface layer thermal resistance). I recommend the Aavid Thermalloy 529802B02500G heat-sink with a thermal resistance = 3.7˚C/W (
http://www.alliedelec.com/search/productdetail.aspx?SKU=6190109). The thermal design is based on a peak ambient temperature of 75˚C at the heat sink. As such, the case containing the filament supplies should be vented but forced air cooling should not be required.
Now I'll be handing this thread off to Mark so he can keep us up to date as the amplifier comes together. I'm really looking forward to seeing how this comes out.

I see that the Rk-Ck are connected to pin 4 of the 300b filament with the positive of the filament voltage. Not sure why but i have used pin 1. should i move it to pin 4 or is either side ok. Thanks for assisting.