Vermes
Advanced Member level 4
Presented here acoustic amplifier was based on popular LM3875TF. It is a stereo system with buffer made on Tesla ECC88 tubes.
Buffer:
It is a system of common cathode with active load 2x ECC88 Tesla (small noise, high gain, quite large anode current, low operation voltage and clear sound). Those tubes are also easy available. Capacitors (for example WIMA, Sinecon), all resistors 1%. Power supply of the buffer: anode voltage smoothed on a MOSFET power transistor, high voltage capacitors from SAMSUNG. Tubes glow with alternating voltage ~6,3V. A capacity of separate transformer to the buffer is 60VA.
Degree of power:
Degree of power was designed accordingly to a well known and very good schematic. It uses 2xL LM3875TF. Resistors used were bought from Beyschlang, Vishay – 1% or less. Capacitors: NICHICON MUSE 1000uF/50V in GOLD version.
Power supply:
The power supply consists of:
- transformer on EI profiles ~2x 21V on secondary winding
- 8x fast LEDs MUR 860 (max 8A)
- sockets with fuses for 3A
Housing:
Front panel was made of polished 4mm aluminum, painted with clear lacquer in spray to prevent prints of fingers on aluminum. Sides were made of a chipboard. Back and bottom were made of painted metal sheet. Bottom was made of a net, which improves the system ventillation. It is not good to use fans because of their vibration and interference. Heat sink is large enough so that even at maximum volume it receives the heat very well. The tubes are warm. Outputs: you can use popular banana plugs or an unskinned cable. Inputs: gold chinches. 3 channels.
Link to original thread - Wzmacniacz GAIN CLONE LM3875, PREAMP ECC88
