Hi-End Push-Pull Amplifier - 10-20W no feedback!

Introduction

The my first Push-Pull amplifier was terrible, as many commercial products, if comparated to the my Single Ended amplifiers 2A3 PSE, 300B PSE ...
Here has been implemented a design where the first and driver stage is a Single Ended configuration and only the power stage is a Push-Pull.
This idea is visible in some amplifier designed by Mr. Sakuma but with more transformers and more passive components.
The my project is the most simple Push-Pull design and it has been created on the experience of the my Single-Ended designs.
The sonic result is impressive!

The main target are:

power output about 10-20W but could be increased without problems
very good damping factor
no feedback
no vacuum diodes
only 2 stages
no interstage capacitors
no anodic resistors
only 5 or 6 tubes for both channels
gain enough to be drive by any CD player

Components

All the audio transformers used in this project are Lundahl products:

LL1623/PP + PCB_B Output transformer
LL1649 Power supply transformer
LL1638/4H 500mA Power supply choke
LL1660/10mA Interstage transformers

Lundahl is one of the world´s leading manufacturer of audio transformers used in many professional studio recording and radio stations so He have a very big experince and all these products use a custom audio C-core.

The driver stage is a E182CC Mullard or Jan Philips and each channel use half of this.
If you don't find the E182CC or you want more gain you can use a 5842 Raythoen per channel with a cathode resistor of 180-150ohm (20mA).
It is possible use also 6C45, 5687 and D3A in triode connection (see PF2007 result test).

datasheet 5842 Raytheon (Adobe Acrobat format)

The output tubes used are the new Svetlana KT88.

datasheet KT88 (Adobe Acrobat format)

but I have tested with this circuit output tubes like the KT90 EI, KT88 Teslovac and 6550WE Sovtek.

About passive components types, I don't leave many choices: Holco or Caddock resistances on cathode, ELNA Cerafine capacitors on cathode and power supply.
For all my new projects, I am using the very good ELNA Cerafine capacitors that I love and which can be find at good price by AUDIOKIT.
The ELNA Cerafine capacitors contain super fine ceramic particles which, through chemical reaction, improve the discharging speed between the anode and electrolyte with very low distortion.
Any other electrolytic or polypropylene capacitor give very lower sonic performances introducing some alteration. Only the Blackgate WKZ could give better sound, but I have not tested it and I know of some problems during startup phase.

About wire forget the teflon ! use only stranded tinned copper wire with pvc isulator and for loudspeakers I am testing the elevator cables (paralleled wire with a good section).

A very good quality stranded tinned copper wire could be buy directly from E-Z-HOOK that carries an extensive line of fine stranded and extra flexible wire.

The schematic

Sonic results

Incredible performance for a Push-Pull ! very near to Single Ended sound but with higher dynamic !