• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

GU-46 push-pull & single-ended amplifiers

There is no need to re-invent the wheel, you can use the PS design from the Philips EL6470/6471, substitute a power transformer with lower voltage, and scale the components (HV rating) accordingly.
No, not seriously. Sorry. Remember the EL6471's three-phase PSU! Of course I know that it could be rewired for common (one phase) AC supply, but there's still this tiny 4 µF filter capacitor left, which may suit for 300 Hz ripple with it's notches never getting close to 0 V, but will fail filtering a two-way 100 Hz ripple sufficiently.


Best regards!
 

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Thanks! That's about ten times the price of GU-50's. As we can easily extract about the same power form three pairs of these with a modest 800 V plate supply, they offer the better bang for the money, I'd say. We'd need a more elaborate driver section, though, as they must be operated in class AB2 to get 120 watts per pair and need a larger grid voltage swing.


Are the GU-46 valve holders also available in the East?
Best regards!
 
I have seen sockets in Russian eBay-alternatives, but they are far too expensive since they are military material.
There seems to be an alternative made of some carton material (see thread of ClassZ, linked in an answer somewhere in the beginning of this thread). I will make these sockets on my own from procelaine material.


I have seen these GU-50s too, but i was somehow more impressed by the large glass bottles of the GU-46, even if it might become quite tricky to build something "economic" and useful.
 
Guys let`s not forget expensive E80CC at AF input on that Philips power amp , also input AF transformer to ,

If balanced AF input is not necessary same as balanced GNFB as is by Philips amps but only SE AF input maybe something like this configuration of input/driver stage can also work and sound well to ?
 

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Hi Douglas

Well that configuration with EL34 DC coupled to g1 grids of GU46 do not automatically mean constant grids currents flow and constant A2 class of operation , that effect will appear on full excitation of OPS , but is good solution to avoid blocking distortion caused from coupling caps and g1 resistors network ,and to get instant overload recovery in case if grids currents starts to flow ,
that my proposed schematic also do not means tons of applied GNFB , maybe just 5-10db max.

Regards
 
With EL34's in circuit, I'd just use 'em as voltage amps. Full pentode rigging...and they won't be so worried about possible high plate voltage. Use the g2 voltage to tune them to their loads...:) On top of that I'd still do away with the gNFB, local as in Schade resistor, or direct from U-L tap E-Linear is useful for several reasons.

Split C-T grid chokes and coupling caps that are not small will take care of the finals.
cheers,
Douglas