RFB-02 for the pre amp

Here is my "low current" version of a double rectifier unit built on the RFB02's. It can handle an amp or so without any heat sinks. This time with ONsemi fast recovery diodes (FRED's), MRS820, soft recovery diodes.
In my oppionion only Schottky diodes can do without snubbers. Therefore, I have used snubbers for each of the 8 diodes used in this dual low-noise rectifying bridge. The schematic is shown in figure 13. If you compare this schematic to the one for the power amp, I have added one more capacitor to filter the AC voltages even better. This is because a low noise power supply is more important the lower the signals are.

Figure 13 Schematic of the dual, low-noise rectifying bridge for my pre amp.

The capacitors on the DC voltages did not fit on the PCB, so I have put them together with the big electrolytics instead. If you are a bit handy, you can surely find a way to fit these capacitors on the PCB, too.

Figure 8 Here, the snubbers are mounted on the PCB. Note that I have used golden spade connectors.

Figure 9 Soldering tin flows far better on the golden spade connectors compared to plain tinned ones.

Assembly is shown in figure 10 and 11. Note that there is a short wire between the two PCBs. This wire creates the virtual ground between the two rectifying bridges. See also the schematic.
To be able to mount solder the three capacitors on the AC voltage, you need to scrape off some green laquer first. I usually presolder this bare copper surface before I solder the legs on the capacitors. This is because the copper surface is very, very large and one needs to heat the copper a comparatively long time. When presoldering is done, soldering the legs is a small task.

Figure 10 Assembly.

Figure 11 Assembly. PCB is now finished.

This ends this article about filtering out noise on the transformer seconodaries on Per-Anders Sjöström's RFB02 (replaced by RFB03) rectifying designs, and how I how assembled two different dual rectifying bridges. One for a power amp with Schottky diodes, and another for a pre amp using soft recovery FREDs.

Sigurd Ruschkowski