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Reider Class G

Harald Reider's class G design (2004) offers a very low component count for an amplifier of this size (output power up to 1.3kW/4 ohms and 650W/8 ohms) compared to, say, the Giesbert Titan 2000, with a frequency response of 10Hz-40kHz (+0/-0.5db), THD <0.05% (1kW, 10kHz, 4 ohms) and a quiescent output stage dissipation of <10W (with supplies shown).

Harald's web-page includes a Spice simulation and the following comments;

"All MJE340 and MJE350 transistors must be mounted on a heat sink that can dissipate at least 5W, or on the main heatsink. The MJE340 bias-transistor must be mounted on the main heatsink or (even better) on top of one of the power transistors connected to the inner supply rails. The current limit is set to 32A. The zener diodes BZX84 (5V6) in series to the 1N4148 can be changed to a different value for other current limits. The bias current can be set to 20mA/transistor or (even better) can be set by measurement to minimum distortion on low output voltages.

The supply voltage can be set to lower levels for lower output power, ±20V inner and ±65V outer supply for 400W at 4 ohm, ±30V and ±85V for 800W at 4 ohm."


"In your gif the higher supply rail is 80V, but it should be 125V (you already need over 100V Peak for 1000W). In the design the resistor values for the biasing transistor are not chosen that good, you should take other values to reach the typical 4x diode voltage...

The biggest thing about this design is that it only uses 2 current amp stages, with 3 stages the whole thing won't work stable, so transitors with high beta should be used.

Limiting bandwith should be done, as always, so that the R of the RC network on the output is limited in dissipation, thats all."

Another class G design can be found here.

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