Over Christmas I've been experimenting with a low-voltage reverb circuit - a scrapbox special.
My PSU consists of a 12v-0v-12v transformer (24v) driving a standard full-wave voltage doubler. This gives me a B+ of 76v, which I'm happy with. It's on the high side due to UK/European voltage inconsistencies. The tube heaters are powered off 12vac (actually 14v) - one leg of the PT to the centre tap. That also works fairly well apart from excessive heater hum. If I power the heaters (with one side grounded) from an external transformer there's no hum.
So, the problem I have looks like the ground reference to the heaters, which are raised 38v with respect to the chassis and is difficult to resolve because of the lack of common ground path in the supply.
The simple answer would be to use a half-wave doubler with common grounding, but I'm wondering if anyone else has any ideas? I want to keep the simplicity of the existing transformer and avoid having a separate heater transformer.
My PSU consists of a 12v-0v-12v transformer (24v) driving a standard full-wave voltage doubler. This gives me a B+ of 76v, which I'm happy with. It's on the high side due to UK/European voltage inconsistencies. The tube heaters are powered off 12vac (actually 14v) - one leg of the PT to the centre tap. That also works fairly well apart from excessive heater hum. If I power the heaters (with one side grounded) from an external transformer there's no hum.
So, the problem I have looks like the ground reference to the heaters, which are raised 38v with respect to the chassis and is difficult to resolve because of the lack of common ground path in the supply.
The simple answer would be to use a half-wave doubler with common grounding, but I'm wondering if anyone else has any ideas? I want to keep the simplicity of the existing transformer and avoid having a separate heater transformer.
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