Quad 405 405-2

Brand: Quad

Model: 405-2

Technical data

• Sine power: 2 x 100 W into 8 Ohm
• Distortion at 1 kHz: < 0.001%.
• Intermodulation at nominal power: < 0.01%
• Signal to noise ratio: >95dB
• Frequency response over all: 20 Hz - 1 dB to 20000 Hz - 0.5 dB
• Outputs: 4 - 16 Ohm
• Dimensions: 341 x 115 x 195 mm
• 100-120V or 200-240V
• Weight: 9 kg

Remarks

Other models of the same series:

Quad 303

Quad 405 power amplifier : The 405 "current unloader" is based on the "feed forward error correction" principle of 1928. This principle is based on the requirement that the output signal may only differ in magnitude from the input signal. Deviations from the original, such as those caused by the usual negative feedback, are undesirable distortions. The "current dump principle" avoids this problem by subtractive comparison of the input signal with a matching part of the output signal. This produces a correction signal which is added to the "distorted" output signal and cancels out its distortion. The amplifier inverts the signal, a positive input signal is opposed to a negative output signal. With a quad preamplifier, which also inverts, this behavior is compensated.

to the device:

The device has no power switch and is switched on by the Quad Preamplifier 33 via a special power cable. If you use a standard mains cable, you have to switch the amplifier on and off at the power strip. The input socket is a 4-pin Din socket, the pin assignment of which is printed on the rear panel of the unit. If you want to connect a "foreign" preamplifier, you need a DIN/Cinch adapter, or you have to install 2 Cinch sockets (which is quite easy, because there is enough space, 2 holes and the DIN socket is right next to it). The LSP sockets are simple clamping mechanisms and difficult to access with thick cables, as the DIN socket is awkwardly located next to it and the clamping mechanism also only allows cables up to 4 mm². The actual power of the Quad 405 has been measured by renowned hi-fi magazines at 120 watts into 8 ohms. The transmission bandwidth is only 20-20000 hz. This "limited" transmission range was intentionally carried out with the Quad devices, in order to be able to exclude disturbances below and above the range reliably. The rise time is only 0.1 µs. The input sensitivity is 0.5 V.

I can really recommend the power amplifier with the corresponding preamplifier, but the operation, especially of the preamplifier, is English "splinig", as well as the unusual wiring of the devices among each other. To prove that this concept is sound-neutral, the importer at that time, Thomas Wegner (Scope, Hamburg, later Schaulandt), connected 10 units in series and demonstrated them in public. QUAD's own DIN wiring "forces" the user, so to speak, to combine with QUAD. If one connects with other manufacturers via adapter cables, the inversion should be taken into account.