Class A simple valve amplifier
Single Ended, minimal basic.
general-purpose (flexible evolutive build)
This device can evolve towards superior versions. All possible upgrades.
I wanted to produce a simple basic valve amplifier in class A. stereo.
It was there is more than 20 years.
I had two output transformer for EL 34 (given by Didier De Bruynes)
My only problem was the power output valves' choice.
I tested the R120 triodes (not convincing, due to resonance at a certain frequency, and not enough power).
I placed two EL 504 (not convincing)
Then KT 88 (for the moment it is the tube which I prefer).
Here with EL 504 (abandoned).
In limps out of wood (with ventilation wire netting).
The lower part (It is badly made. I was beginner... excuse me!).
This build was useful for me to learn processes and craftiness of self build (DIY).
The sound is very good, but the low ones are a little weak, I prefer the EL84 push pull sound. But it is true for the EL84 amp I have quality output transformer.
Tube KT88, a success.
Result don't had waited value.
Vhy ? The cause is simple: my two output transformers were of insufficient quality , They were built for guitar cheap amplifiers, for small budgets.
I did not want to invest in two transformer of quality, of which I know the price: more than 152,45 euros or $ each part.
I wanted a food carried out with transformers and components of recovery.
This powerful tube, modern, manufactured by many marks, is a tetrode (like famous the 6L6) specialized audio.
Used in Single Ended it can deliver an audio power of 19 Watts.
In push-pull assembly the power can do 90 Watts.
SVETLANA TECHNICAL DATA
High Performance Audio
Beam Power Tetrode
he Svetlana KT88 is a glass envelope beam power tetrode. It is intended for audio frequency power amplification service. High plate dissipation rating, close manufacturing specification tolerances and thorough processing provides improved reliability and superior sonic performance. The Svetlana KT88 is manufactured in the Svetlana factory in St. Petersburg, Russia, and is designed to be a direct replacement for any KT88, KT90, KT99 or 6550.
The new KT88 features greatly enhanced sonic performance: Increased peak cathode emission from new cathode materials; Stable operation from extended processing and aging; Gold-plated grid; New tri-plate anode; Single-piece beam forming electrode; Precise grid/screen alignment; Improved vacuum processing; comprehensive static and audio amplifier testing before and after aging.
Heater: Min. Nom. Max. Voltage (AC or DC) 5.7 6.3 6.9 V Current 1.6 A
Cathode: Oxide-coated, unipotential Cathode-to-heater potential, max. -250*/250** V
Mechanical: Operating Position Any Base Large wafer octal 8-pin with metal sleeve
AF Power Amplifier
Maximum ratings: DC plate voltage 800 V Grid no.2 DC (screen) voltage 600 V Grid no.1 (control) voltage -300 V DC cathode current 230 mA Plate dissipation 42 W Grid no.2 (screen) dissipation 8 W