Question about Hybrid Tube/SS Bridge Rectifier

[makinrose]

Hi Guys

Post-2 paragrapph-3 describes the use of parallel and nonparallel tube rectifers and the resulting sag produced.

In a way, saying that the parallel rectifiers "allows more current" is correct but also a bit misleading. The current has to be available from the PT to begin with, so what is really happening with parallel tube rectifiers is a reduction of the net diode resistance and thus a reduction of the sag. It is an attempt to overcome the imperfection off the device itself; current is increased for any given amount of sag compared to the use of a single rectifier.

It should also be noted that Fender was still following hifi rules and a hifi ethos for its amp designs up until the 1970s. Eliminating or reducing sag by adding a second expensive rectifier tube falls into that ethos. That players would remove one rectifier tube shows the difference of attitude between the designer and the user

I did leave out the critical important point about the power transformer. Thanks for clarifying.

   I've seen the dual tube rectifier setup on a few old Fenders but mostly in old hi-fi and in some organs.  

Just an aside:  The only original Low Power Tweed Twin I've worked on once belonged to a guitarist in Waylon Jenning's band and someone had removed the tube rectifiers and added SS diodes---I'm guessing to make it more reliable on the road. It raised the voltage quite a bit though.   I ended up reducing the voltage to the correct levels with some zener diodes and adding a sag resistor---basically what was in TUT2.  It worked out really well.