DHT LT Supply PCB

Introduction

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

First capacitor is for tuning between choke-input and cap-input supply depending on your choice.

The rectification stage is full bridge and can accommodate different type of Schottky rectifier from DO-41 to TO-220 and SMD. There is a snubber RC circuit for the transformer secondary.

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

It also provides two interesting options:

      • CLCLCLC – last L is a common-mode choke
      • CRCRCLC – L is a common-mode choke

There is a fuse holder on board as well as LED (TH or SMD) 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.

Overview

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

LT Supply PCBv03

The circuit can be broken down in the following parts:

      1. Input snubber circuit is R2 and C1. Typical values shown on the diagram below.
      2. Rectifier diode bridge D1 to D14 in either DO-41 (D5-D8), TO-220 (D1-D4) or SOD-128 (D11-D14). Please place only 4 rectifier (obvious but worth mentioning).
      3. C2 is the voltage “tunning” capacitor. Preferable Polymer Aluminum type. Make sure ESR and ripple current matches your needs.
      4. 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 L2 is used, R1 is omitted and R3 generally replaced with a simple wire.
      5. L2 and L3 external chokes connected via a 2mm bullet connector. You can solder straight wires to the board if preferred.
      6. R4 (3 to 5W size) works in same way as R1.
      7. C3, C4 and C5 are electrolytic SNAP-IN type capacitors. Make sure ESR and ripple current matches your needs.
      8. L1 is a common mode choke. There are 3 mounting case / lead spacing options to fit multiple suppliers. BOM provides 3 examples. Make sure that current and choke specifications match your needs.
      9. R5 is the bleeder resistor (3 to 5W size)
      10. D9/D10 are the LED (place only one) either TH 3mm type or SMD (1206). The resistor R6 limits the current through LED.
      11. F1 has a standard 20mm fuse holder for PCB. Note that the fuse should be rated to operate effectively at the current required.
      12. (+OUT and GND) Output can be taken out of a standard 2-pole block connector or a 2mm bullet connector.
LT Supply PCB layout

Building the board

The building is a straight-forward process and is expected the builder to be familiarised and competent in managing valve  supply 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.

LT supply for 300B

You can see a couple of examples here and here.

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 LT supply, this is not a board for you.

There are plenty of examples out there and you can check in DIY Audio for help if needed. I’d highly recommend you familiarise yourself with PSUD2 if you want to adventure in the design of your own LT supply.

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.

I will provide detailed BOM and basic build guide upon payment.

If you are interested ping me a message below: