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    Building, troubleshooting and testing of these amplifiers should only be
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Level Five 2A3 SE schematic : opinions ?

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Also, there's a missing decoupling capacitor after the dropping resistor (R6) feeding the upper plate of the SRPP driver tube (pin 5, marked +280 V). A 47µF/400V electrolytic from this point to ground should fit. Nothing new or innovative in this very basic circuit but it should work, though don't expect much more than 2 watts output power with the values and operating points shown.
 
Parallel driver tubes - not my kind of taste... I find paralleling tubes bring slightly blur sound compared to non paralleled tubes.

On the PSU side, choke-input is preferred over cap-input for better regulation.

With the cheap stepped attenuators available on eBay, why still use a carbon pot?

Using 3.5K OPT will give you lower power for 2A3, which is already pretty low. Why not go for 2.5K OPT?

2A3 bypass gives ~6Hz @ 3dB. i'd prefer it to be lower so that the speakers would be the limiting factor instead of the amplifier. 100uf bypass is what i'd prefer. it's not expensive either, why save on that?

C5 can be smaller if R7 is 470k. i'd prefer C5 of 0.22uf and R7 of 100k-200k. grid resistor is better to be kept lower.

I'd prefer another RC filter for the driver stage. Sharing the same rail without further bypass is not really preferred.

I've seen someone posted a 2A3 design from diy-audio-guide if not mistaken. Looks quite decent. Check it out.

Just my grudges... :)

tubeworld.
 
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