The SOHA's power supply is quite simple. It's quite clever how it obtains the ~40 volt B+ for the tube - it basically stacks two full-bridge rectifiers, decoupling them with big caps. To make case layout and circuit debugging easier, I decided to put the power supply on its own board and use various salvaged connectors to hook up to the main amp board. The only mod I made to the original SOHA circuit was use a bigger transformer (1000 mA) to power some eye candy (and put a bigger heatsink on VR3 to handle the extra power). Oh, I also removed the power LED (I've got other plans). I much prefer surface-mount assembly to through-hole (no drilling a thousand little frickin' holes), so I found equivalent SMT parts to the recommended through-hole parts. Here are the part numbers I used for the power supply (refer to figure 4 on the HeadWize page here). Note the connectors are absent from this list - I have no idea what I used. A few years back, some jerk broke our dorm TV. Silver lining: it contained lots of sweet surface mount connectors!
|C7, C8, C11||47u 16V||667-EEE-HDV470XAP|
|C9, C10, C12||470u 35V||667-EEE-TKV471UAQ|
|BR1, BR2||100V 1A Bridge Rect.||625-DF02S-E3|
|VR1||12V 0.1A Positive||511-L78L12ACU|
|VR2||12V 0.1A Negative||511-L79L12ACU-TR|
|VR3||1.5A Neg Adj Vol Reg||512-LM337T|
|D3, D4||1N4002 1A 100V GP||583-FM4002|
|T1||30.0V CT @ 0.83A||553-VPT30-830|
Laying this thing out was a bit of a pain due to those large caps. Also, the kicad library archive didn't have modules for most of these parts. Oh well. Here's what I came up with:
SOHA power supply board. About 3.5" by 2".
Attached are some pics from the build. PCB made via toner transfer via laminator.
I've uploaded a KiCad project containing a schematic and the board layout.