E♦N, AudioSonic, Monarch, Monacor NF-718
LoFi mini-amplifier

 

General:

Around 1965 issued amplifier made in Japan.
This amplifier was issued with several names on the front: E♦N, AudioSonic, Monarch, Monacor and more.
E♦N "Electronics Nederland NV" was a Dutch company importing and rebranding Japanese audio gear.

 

Front ^

^ Front Monacor version with type-# SA616. Monacor was imported in The Benelux by "Makuport".

 

Owners manual:

User manual in PDF of the E♦N AudioSonic mini amplifier click here
 

special futures:

There are models of this amplifier with DIN input/output sockets on the back side.
Light and small footprint amp. Wood case.
Good build, good pcb's and good parts used.
This amp employs all Sanyo germanium transistors.
Separated volume control for R & L channel.
 

Specifications:

Distortion (THD 20Hz - 20kHz) < 3% at continuous output per channel: 3 Watts RMS per channel.
Maximum output power 3,5 Watts per channel,
Speaker impedance: 8~16ohms
Signal/noise ratio: 40dB
1 x Cinch input.
 

Schematic:

User manual with schematic diagram in PDF of the E♦N AudioSonic mini amplifier click here

 

Modifications:

You may replace some capacitors in the signal path & the power supply and power rail.
The amp has Germanium power transistors that can get noisy and break down when not properly heatsinked.
Check idling current through the power transistors, they may break down when not set properly,
the standard idling setting by the factory is too high, check and reduce.
The Monacor version has a lower grade blank aluminium, not black painted, heatsink.
 

interior after update ^

^ Smaller heatsink in the Monacor version.

Power transistor ^

Data Sanyo 2SB405 green:

Package: TO-1
Ucb = 25V
Ic max = 1A
hFE = 100 @ 200mA
Ft = 700 kHz
Ptot = 750mW
Tjmax = 85°C
 

Monacor used SA616 as type number for this amplifier ^,
but they issued some years later a second different model with the same type number.
Below an example of this other model in the Monarch SA-616 issued version. v

 

Sound:

The sound is very good for such a small amplifier.

 

© Hans Hilberink - ON9MMK, PE1MMK® 2003 - Last update: 20-01-2018.