I joined this discussion with an open mind - not entirely sure what was meant by a "voltage doubler" in the context of a HT power supply of a valve amplifier. Having read with great interest the arguments being put forward - it is clear to me that some people like to argue for the sake of it, and have a very fixed view which is different to most other people on here who have amplifier and/or electronics experience. Santial has repeated (with great tact and diplomacy in fact...) - that it is more a matter of semantics than a proper technical discussion - in other words - calling something a name for that which is not (in this case calling a bridge rectifier power supply a voltage doubler). I can call a banana a potato if I like. Does that make it wrong? Perhaps not for me, if that is my view, but it does tend to cause confusion in the Greengrocers/ Supermarket! John has repeatedly failed to show what voltage is being doubled, or where in the rectifier circuit, yet he insists on calling it a "voltage doubler" Not really - I can't see any doubling anywhere, what voltage is being doubled? Where? I tried to explain, with the use of examples of a Simple bridge rectifier circuit with actual AV and DC voltages, but John has shown little interest in going down to this level of detail - yet accuses Santiago of being "light" with his responses: I don't see any clarity, just hundreds and hundreds of words..... This statement (quoted from another forum) is an attempt to explain why the bridge rectifier with bridge tap (which Santiago has already said is not fundamental to the operation of the circuit, but is a historic artifact, but also serving to keep the voltages on the series output caps balanced), is in some mysterious way, a voltage doubler: But this argument is like saying a loaf of bread is not a loaf of bread - it is a "half-loaf doubler" since if you cut it in half, and put the two haves together, you have a whole loaf! In-fact, I think from now on, when I buy bread, I am going to specifically ask for a "half-loaf doubler"! Imagine the fun and long protracted conversations I can have doing that!!! I have a little electronics experience, and have worked as a professional electronics engineer (although in the area of switched mode power supplies (where REAL voltage doubling is possible!) rather than audio amplification. My work these days is more Electrical (automotive) than electronics.... But if I was a layman (with little or no electrical or electronics experience) reading this thread, I think I would be more inclined to believe Santiago than John Hammond, - that there is nothing special or different about a bridge rectifier circuit with a centre tap, compared to one without, and that the neither circuit is called, or acts like a voltage doubler.... If anything I admire your confidence and self-belief, John. Santiago is well respected here for a reason - he designed some of the most revered modern Marshall amplifiers produced in recent times, including the JVM series, AFD and YJM amplifiers (plus some others...). I think he was head of his design department at Marshall while he was there? As I said before, if Santiago told me that I was mistaken about something, I would be inclined to believe him, and benefit from the learning being offered! So I don't think I am going to continue with this discussion (entertaining though it has been!) - I don't think anyone or anything is going to convince John that a simple bridge rectifier circuit with a centre tapped transformer is - well, just that and not some form of magical , fly-back boost regulator which doubles something, somewhere!