Introduction

This PCB is intended to provide HT rectification and filtering for any pre-amp or amplifier. It has some flexibility to accommodate various sizes and types of capacitors (e.g., from PIO to film to electrolytics) depending on your choice and preference.

The rectification stage can be either a full silicon bridge (either SiC or not) or valve. Valve rectifiers are external to the board. You can also configure the rectifier to be a hybrid one. There is a snubber RC circuit for the transformer secondary.

The filtering stage has the flexibility of either be LCLC or RCRC depending on your whether you want to use chokes or not. Chokes are external to this board.

Final stage is intended to use a DC-Link type Film capacitor solely due to its impact/contribution to the amplifier sound based on my personal experience.  There is a fuse holder on board as well as Neon indicator.

It’s your choice to decide what elements of the board you would use. The board may be a bit bigger than expected, however this way you can fit a wide good range of capacitors in it. It feels to me it has a good compromise in terms of flexibility and size.

Circuit Overview

The circuit is very straight-forward and well known so I will just reference its parts. You should be knowledgeable on HT supplies and I recommend highly you use PSUD2 software to model and confirm the dynamic response of your supply.

 

The circuit can be broken down in the following parts:

1. 1. Input snubber circuit is R2 and C1. Typical values shown on the diagram below.
   2. Rectifier diode bridge D1 to D8 in either DO-41 (D5-D8) or TO-220 (D1-D4).
   3. External connection to valve rectifiers (A1, A2 and K) with the addition of the CT (transformer center tap). These are connected via a 2mm bullet connector. You can solder straight wires to the board if preferred.
   4. C2 is the voltage “tunning” capacitor. Fits from PIO and film to mid-size electrolytic caps (e.g. 7.62mm lead pitch).
   5. R1 and R3 (3 to 5W size) used as part of first RC and/or ripple current dampening and protection of the C3 capacitor. When L1 is used, R1 is omitted and R3 generally replaced with a simple wire.
   6. L1 and L2 external chokes connected via a 2mm bullet connector. You can solder straight wires to the board if preferred.
   7. R4 (3 to 5W size) works in same way as R1.
   8. C3 and C4 are electrolytic capacitors for filtering
   9. C5 fits a small value (e.g. 100nF or smaller) film or PIO capacitor
   10. C6 is the final cap for a DC-Link WIMA capacitor of 10-45uF. This is the most audible capacitor in the chain, therefore opted for the WIMA DC-Link film one.
   11. R5 is the bleeder resistor (3 to 5W size)
   12. F1 has a standard 22mm fuse holder for PCB. Note that the fuse should be rated to operate effectively at the voltage required.
   13. N1 is a Nixie indicator INS-1. It has a current limiter resistor R6.
   14. (+B and GND) Output can be taken out of a standard 2-pole block connector or a 2mm bullet connector.

Circuit examples

Below are 2 examples for a DHT Headphone Amp / preamp power supply. First one has only valve rectifiers and second one uses a hybrid one:

Building the board

The building is a straight-forward process and is expected the builder to be familiarised and competent in managing high-voltage circuits. Please don’t attempt building this board if you are not.

Given the flexibility of the board, the BOM contains drilling size as well as lead space / pitch as guidance for component selection. There is also a spreadsheet provided with some examples of the capacitors that can be used and fit in the board.

Important note

The board is sold as-is for you to work on based on your design. Please don’t ask me for design advice as don’t have the time am afraid to help. If you don’t know how to design your HT supply, this is not a board for you.

Order

The board is high-quality PCB with ENIG gold finish.  I made a small batch for my personal use and now am selling the rest of them.

If you are interested ping me a message below: