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ReSEPP Design: 5 Tubes 4 Natural Sound


my idea is Reverse standard Single Ended Push Pull

just to have input and output in ground level

and put a low ratio transformer on big power tube



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Stee said:

my idea is Reverse standard Single Ended Push Pull

just to have input and output in ground level

and put a low ratio transformer on big power tube


Definitely not a SEPP at all. There's no phase splitter, so all you have is a cathode follower with an active triode load. I have my doubts as to how that's going to work as is. Might be better to use a White cathode follower since that restores active pull up/pull down.

The A Number One problem with all SEPP-like designs is that they are balanced for one specific load impedance. Let the load change (and speeks are anything but a constant load) and it goes out of balance with rising distortion.
Your schematic doesn't show a SEPP, it show a cathode follower output stage with active load.

A SEPP is unbalanced, the upper part is a cathode follower and the lower part is a normal cathode grounded amplifier. The SEPPs that have been made commercial, (like Philips with EL86) give a lot of 2nd order distortion, ~10%

The Camoroni document is full of unsubstantiated claims about output power etc. A SEPP without phase splitter can only work in class A meaning that the output will be very low.


There is nothing about SEPPs in this link.

Best Regards Hans
PPP Design

Thanks for your reply

may be the discussion is about name of architecture, i'm wrong

i would like to focus quality of sound
not the power or rendering

my idea is concentrated on benefits in pure complementary configuration, especially in class A, like this drawing

the link of Susan Parker show how is good have load on cathode
in particular to have local NFB (she named this "zero feedback")
What you have drawn is just series connected cathode followers which means that the total gain from input to the output cathode will be less than 1. Maybe you intended to draw series connected SEPP or SRPP stages, the difference is then that the input is the lower grid and the output is the upper cathode on each stage.

However A SEPP doesn't work as if it would be a complimentary configuration even if if it look like that, the SEPP is inherently unbalanced as has been described before, (the gain of the lower and upper tube are different). The way to provide a complimentary function where both the upper and lower tubes provide same gain is to introduce drive to both tubes and a gain compensation method whereof the Futterman connection is the most well known although there are several others.

How Susan Parker can call a cathode coupled stage, (that have infinite feedback) as zero feedback is interesting in itself but it is of course nothing new to use a cathode follower output stage.

Regards Hans