Ultra Fast High Power Single Ended Amplifier
by Andrea Ciuffoli - 17 Jun 2002
Introduction
The main target are:
-
high power output: about 13W
-
medium power supply voltage: about 430V
-
very good damping factor: output resistance about 1 ohm
-
no feedback: only local feedback on output stage
-
no vacuum diodes: normal diode bridge
-
only 2 stages
-
no anodic resistors
-
Ultra Fast signal transfert: with the use of an SRPP (Totem Pole) and the
Tetrode in the final stage
-
only 8 tubes per both channels
-
gain enougth to be drive by any CD player
After the experiments made with the
20W
Push Pull converting this many times from a push pull to a single ended
only connecting a grid of an output tube to ground (instead of the interstage
transformer) the result has been always the more superiority of the Single
Ended sound because the sound is more natural and any instrument is more
true.
The my idea was to create a project with the same normal and low cost
output tubes with enougth output power to drive normal loudspeakers (with
an efficiency about 88-89db) and without high power supply voltage.
So a project for beginner but high performance at low cost.
Components
All the audio transformers used in this project are
Lundahl
products:
-
LL1627/185mA
+
PCB_B
Output (price about 148$ each)
-
LL1669A
Power supply transformer (price about 117$ each)
-
LL1638/8H
Power supply inductance (price about 65$ each)
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 are two 12AX7/ECC83 Mullard or Jan Philips
The output tubes used are the new Svetlana KT88.
but I have tested with this circuit output tubes like the
KT90 EI.
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 main schematic
