Optonica SM-4646

1 9 7 7 1977
1 9 7 8 1978

Launched by Sharp in 1975, Optonica was to Sharp's high-end audio display, much like Technics was to Panasonic.

Becoming really visible in '76/77, Optonica however came up just a bit too late to get a firm grasp on a market that was about to slide down after 1978...

If Optonica is well remembered for its 1980/81 futuristic designs, often embodying the electronic audio & design research Sharp was heavy into, it made excellent separates before its most "visible" peak.
The SM-4646 is one of those efforts, available in silver (SM-4646H) or black (SM-4646B).


Three power transformers for "Delta Power", DC Class A stages (preamp + pre-driver), two big 13,600µF main caps, low-noise FETs & differential amps everywhere, a 4-gang volume attenuator and 16kg in toto.
The center transformer feeds the preamp and driver stages in Class A, the other two, independently, the L and R output stages in Class B.
It doesn't look like that from the outside, right ?

Indeed - but either it wasn't enough to start trekking the upper part of the scale or too much to keep low prices and get a strong grip onto the mid-end market...

Looks-wise a bit heavy and mostly clearly leaning toward the 1960s instead of the upcoming 1980s, too. Which is quite charming.

Despite receiving a french Laurier d'Or (Golden Laurel) for "outstanding function, design and performances" in 1977, Sharp's Optonica series never sold much... in France or elsewhere - pity.

Optonica SM-4646, image 1 Optonica SM-4646, image 2
Optonica SM-4646 specifications
Title Value
Power Amp Section Power Amp Section
Circuit : all-stage DC
pure complementary OCL
Music power : 2x 145W (4 Ohm, 0,05% THD)
2x 90W (8 Ohm, 0,05% THD)
RMS power : 2x 95W (4 Ohm, 1Khz)
2x 70W (8 Ohm, 1Khz)
2x 85W (4 Ohm, 20Hz...20Khz)
2x 60W (8 Ohm, 20Hz...20Khz)
THD / IMD : 0,05% (1Khz, rated power)
0,02% (1Khz, 50W output)
Power bandwidth : 10Hz...45Khz (IHF, 0,1% THD, 45W output)
Frequency response : 10Hz...100Khz (+0 / -2dB)
Input : 650mV / 47kOhm
Outputs : 4...16Ohm (A or B)
8...16Ohm (A+B)
Damping factor : > 50 (8 Ohm, 1Khz)
Residual noise : 0,5mV
S/N ratio : 100dB
Preamp Section Preamp Section
EQ amp circuit : 1st stage differential amp
Control amp circuit : NF type tone control amp
Inputs : 2,5mV / 22 / 47 / 100kOhm (phono 1)
2,5mV...5mV / 47kOhm (phono 2)
150mV / 47kOhm (aux, tuner, tape 1/2, DIN 1/2)
Max phono input : 350mV (RMS, 1Khz)
RIAA curve : 20Hz...20Khz (± 0,3dB)
Outputs : 150mV (RCA tape 1/2 out)
30mV (DIN tape 1/2 out)
Frequency response : 10Hz...70Khz (+0 / -1,5dB)
Bass control : ±10dB at 100Hz (600Hz turn.)
±10dB at 50Hz (300Hz turn.)
Treble control : ±10dB at 10Khz (1,5Khz turn.)
±10dB at 20Khz (3Khz turn.)
Low filter : -3dB at 10Hz (12dB/octave)
High filter : -3dB at 20Khz (6dB/octave)
Loudness contour 1 : +6dB / 100Hz
+4dB / 10Khz
Loudness contour 2 : +6dB / 100Hz
+?dB / 10Khz
Residual noise : 25mv (phono)
3mv (tape mon.)
S/N ratio : 70dB (phono)
90dB (lines)
General General
Componentry : 8 FETs
2 ICs
27 transistors
25 diodes
1 LED
PC : 520W max.
Dimensions : 44,2 x 14,4 x 36,3cm
Weight : 16kg.
Optonica SM-4646 : 0 topic
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page online since : 2009
page updated : august 2010
page type : LGT / KNB
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