Vermes
Advanced Member level 4
It is a design of audio amplifier based on well known LM3886 with original effect of „Magic Eye” on the front panel.
Main power supply consists of a 150VA transformer; 2x23V + 6,3V additionally winded, 4x4700uF MKT, bridge 10A. The power amplifier is based on application from AVT 2 x LM3886. You can use systems in insulated housing, heat sinks are sufficient for that power. Preamplifiers are standard application of system LM1036. Delayed turning on the columns was implemented as a very simple system on double relay 8A. Switch of A/B inputs was also based on a simple relay.
„Magic Eye” EMM801 and additional ECC81 tube indicate the level of input signal. It is powered by a small transformer 10VA 27V connected conversely to the secondary winding of the main transformer. As a result, you have voltage approximately 255V after the capacitor 47uF/400V, which is enough for the tube used. 6,3V DC glow, filtered by 8200uF capacitor. Backlighting the knobs was made by 8 white LEDs connected in series of two and powered from 6,3V.
In addition, there is a relay which is responsble for turning on the main supply and switching inputs in B position after giving 24V to its coil.
Electronics is mounted to a large textolite board. It is easy to thread it and holds the components.
Housing was removed from an old casette player. Front panel was made of 1,8mm aluminum sheet, bent to the dimensions of the housing. Holes for knobs were milled and knobs of duralumin were made on a lathe.
Dimensions of the knobs:
- 28mm dia - Balance, Bass, Treble
- 53mm dia – Volume
- 16mm dia – Power
Thin rings made of plexiglass are glued around the knobs. „Magic Eye” stands behind a wall made of plexiglass. Descriptions were made in the same method as thermal transfer for PCBs. Behind the „Magic Eye” there are pieces of a mirror.
Pictures:
Videos of operation:
Link to original thread - Wzmacniacz 2xLM3886 z magicznym okiem