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Dual supply using 2 transformers +170-0-170
I am building an amp that requires +170 and -170v rails for b+ on the output tubes. The circuit calls for a typical dual power supply using a 230vCT transformer and a single bridge rectifier.
I have a stock of 115v transformers. Is there anything wrong with me using 2 115v transformers and 2 rectifiers to create this circuit creating a 0v reference to ground by connecting the + out of one bridge to the - of the second bridge creating my +170-0-(-)170? I have seen some discussions where the solution proposed is to parallel the 2 transformers to create something equivalent to a ct transformer feeding one rectifier. Cost of an additional rectifier is a non issue. What are pros and cons of the 2 configurations. Best sound quality is the ultimate objective. |
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As I understand it, the reason for using dual bridges when one would suffice is to enable better grounding arrangements for the caps. Having said that, I'm not sure I'm convinced of that anyway. |
There is an alternate solution using a dual diode-dual cap voltage doubler, if the current is low, and so , omit one less transformer and its interaction.
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Your method is the best way. The dual bridges mean that the transformer secondary is not directly connected to circuit ground. It is only connected when the diodes conduct. That reduces line induced noise. Although that is not normally an issue with vacuum tube amplifiers.
There are a few other advantages also, but that is one of the biggest. You will want to try switching which primary leads go to the AC hot. That will also affect noise level. |
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Thank you. Lots to consider. I should have mentioned that I am using fairly overspec toroids at 5A ea. Each is driving a pair of 6C33C so not light current.
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