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EB-201/168 |
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The “MILLENNIUM-200” (EB-201/168) driver, developed from the “RIBBON” and “MILLENNIUM” drivers, is an ALL-FET, high-speed driver circuit with exceptional resolution and dynamics. It is intended for 150W Class-A/AB power amplifiers. Its transparent and neutral sound makes it equally applicable in high-end home systems as in studio monitor and recording applications. Within its power rating, the EB-201/168 outperforms most high-end power amplifiers on the market in terms of sonic quality, irrespective of price.
The circuit diagram is shown in fig. 1.
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 |  | | Figure 1. |
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The circuit is a fully complementary design, using only FETs as active elements. The input stage is a complementary differential cascode FET circuit, using dual monolitic JFETs, cascoded first with low noise JFETs, and then with MOSFETs. Each of these is working with 2 mA drain current. The second stage consists of two JFETs in parallel and a MOSFET, connected in Cascode. The JFETs are operated at 10mA each, providing a total of 20mA drive for the output stage. The resistors are all high quality Caddocks and Welwyn or Vishay/Dale. The driver board can be operated with unbalanced input (input impedance: 100k) and with balanced input (both inputs: 2.2k).
The bias circuit (Q18 and associated components) is a Vgs multiplier, using a MOSFET. The MOSFET itself, a TO-220 device, is selected according to the MOSFETs used in the output stage and is mounted on the output heatsink, if necessary. This ensures proper bias tracking with the different output MOSFETs. The output offset is tracked and controlled by Q11, which is a JFET-input opamp. Two shunt regulators provide ± 10V supply voltage for the opamp.
The “MILLENNIUM-200” driver can operate with a regulated voltage of maximum ±65V. The maximum input voltage for the regulators is ±73V. With 8 pairs of Hitachi MOSFETs the “MILLENNIUM” can produce close to 200W in Class-AB into 8 Ohm and over 300W into 4 Ohm. Minimum heatsink requirement is SK157/200 or SK158/200, with a thermal resistance of 0.2K/W or less.
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