For a long time Metrum Acoustics has used hybrid (triode) amps for pleasure listening and critical evaluations. What we did not like was the fact that triodes suffer aging problems. In simulation software, we started to simulate triodes with fets instead. The good thing with triodes is their low gain and a lot of bandwidth without any need for feedback. As a result we realized a full class A high voltage fet circuitry having the right gain ,very good open loop bandwidth and low noise figures. A similarity is the high voltage of 350 Volts to get this circuit running. As a result an amazing linearity without any feedback was realized. From this point the circuit is driving a class A/B output section (10 watts in class A). Some little feedback is necessary to get the right gain but also improves the damping factor at the same time . Compared to our old hybrids, there’s no sonic difference, just less noise and lower distortion.
After two years of prototyping and testing, we’ve now turned this into a commercial product. The circuits are quite over-dimensioned to be sure that no errors occurs. Still we added a lot of protection to avoid any damage to your loudspeakers in case of malfunction. A soft start procedure is added to charge the amazing capacity of 176000µF. This huge capacity is available during complex and dynamic transients. As known hybrids combine tube sound and amazing control as realized by transistor designs. Here you have the solution. The “Forte” power amplifier will serve you without problems as known with normal hybrids but still having the holographic sound as known from good tube designs. The Forte is an addition to our awarded Adagio digital amplifier.
Voltage & Color
110V Silver Line, 110V Black Line, 230V Silver Line, 230V Black Line
50 Watt to 8 Ohm, 100 Watt to 4 Ohm, 170 Watt to 2 Ohm Class A/B, 10 Watt Class A
Distortion 0.03% THD
Damping Factor 200
110/115V AC 220/230V AC 60/50Hz
Output Noise 300 µV RMS
Frequency Response 10-60.000 Hz – 3DB
Slew Rate 50V / µSec
Input Impedance RCA 15 KOhm, XLR 60 KOhm
Input Sensitivity RCA 240 mV RMS for 1 Watt, 1.75 V for 50 Watt, XLR 480 mV RMS for 1 Watt, XLR 480 mV RMS for 1 Watt, 3.5 V for 50 Watt