Tag: LT supply PCB

DHT Supply PCB

I took me a couple of years but eventually found the time to build the BOM and a simple documentation guide for the DHT LT supply PCB. I’ve been using this PCB for a long time on most of my DHT preamps and in my current 300B SE Amplifier.

It’s a 16 x 8 cm board which can be stacked for a stereo DHT stage. Enough flexible is provided for all sort of filtering combinations (either choke to cap input supplies).

Some may say is a killer, but I add a common-mode choke to suppress HF noise from mains. I design my supplies with a no-compromise thinking and best possible components (e.g. including split-bobbin main transformers), chokes and capacitors to deliver the lowest noise possible to the filament supply.

This board doesn’t replace the filament regulator (e.g. Rod Coleman regulator), it’s just the raw supply circuit needed before them.

I will sell the remainder of my stock of these lovely ENIG finished PCBs. You can order them here.

300B filament supply

In the process of rebuilding my old 300B amplifier, I decided to make a new filament power supply. It all came up around the components I had at hand, so it could’ve been improved but that meant extra cost:

I have a pair of custom-made JMS transformers with multi-taps secondaries. This helps me tweaking the right output voltage. Anyhow, any 15V transformer would do. Perhaps you want 14V to ensure you don’t dissipate too much on the filament regulators (e.g. Rod Coleman regulators)

I used my flexible LT supply PCB which allowed me to build this in less than 1 hour. I also used some existing chokes made in the UK by “Spirit” which are ok for this purpose. The Lundahls are in use, so can’t reuse them:

300B filament board ready

I used some SOT-128-2 schottky rectifiers but any other should work as well. Resistors are wirewound and the CMR choke is what I had in stock as well. A simple 15mH/3A should do fine.

The output measured well at 9V with a 6R load which dragged 1.5A. A bit more than the 300B but should be a good indication of performance. Also ripple level is good at 2.5mVrms. The rest will be cleaned up by the regulator itself 🙂