Anyone have experience with a Quad 405 amp with Quad 57s?


Recently bought my second pair of Quad 57s. In the ‘90d, I joyfully lived with Quads for a decade. The only non joy was blowing up amps and arching the Quads. Well, the amp problems seem to be gone with the new 57s with their protection circuits. However, I am clipping with my First Watt M3.

The 405 was recommended as “cheap and good”. The M3 sounds very good but big music is a bit of a problem. I understand that the 405 was designed to power Quads. Rolls off the highs, which are not there anyway. And only produces bass down to 40 Hz, which is where it ends in the Quads.

BTW-the new Quads have won me over my past dynamic speakers. So many records which were so so on the big ones are now terrific on the Quads. Especially the more low level ones. The Quads pull you in!

mglik

I have been using modded 405-2 amps with ESL 57s for more then 25 years.  I leave amps and speakers powered 24/7.

The 57 has a rollercoaster of an impedance curve. From 30ohms at 40hz to 1ohm at 20khz. The M3 is voltage-limited at 30ohms and runs out of power. A solution is to use a sub/x-over set around 80hz if you want to play power music like Mahler and Strauss loud.

The Quad 405 is an excellent amp and does not roll off the frequency extremes. I have a nicely restored/modded one to use with my 57’s. It actually is too powerful for the 57’s (27volts/90wpc) so a careful hand on the volume control is necessary to avoid damage. The stock 57’s will arc with more than 20 volts (50 watts). In the past I used a Bedini 25/25 (14 volts) with my first pair of 57’s. No problems. The 405 was designed for the about-to-appear 63. A safer amp for the 57 is the 303 (35wpc). I also have one. Your restored 57’s with the voltage clamp should be OK with the 405.