Missing center tap

Hello all
Some years ago I built a copy of the famous John Linsley Hood class A amplifier. I built a version with no minus supply, so an output capacitor was required. At that time I doubted the negative influence of the output cap. I still do, but I would like to try removing the output capacitor, just to check if I can hear any difference. To do this I need to build I symmetrical power supply. Unfortunately my transformer does not have a center tap and my question is: Is there any simple and good way to make a symmetrical power supply using a transformer with no center tap?

Torben Herrmann

It is possible to create a pseudo-ground for low current circuits which enables a single polarity supply to appear as if it were a dual rail supply. There are also specific ics which will provide an inverted voltage but again these are only low current.

With the higher current requirements of the JLH, I am afraid that the only realistic option is to use a centre-tapped (or dual secondary) transformer if you want +/- rails.

Dual output votages

Two transformers of the same type with only one output winding can also be used. I would use a full wave bridge for each polarity and tie the postiive output of one supply to the negative output the other at the filter cap terminals. This technique can also also be used with two transformers with indentical dual windings for greater power. Tie the two secondary windings in parallel for each transformer with the correct polarity and wire supplies together as described previously.