SpeakerTalk

iso · Posted: Mon Sep 24, 2012 8:58 am Post subject: Quad 240

I bought Quad 240 built in 1992. It seems to be quite nice little amplifier.

However there seems to be some odd noise, like short 1-2 second burst of oscillation, 5-10 seconds after shut down. It seems that this noise is only from right channel when using Cantatas, when I used Tannoy LRM:s noise seems to come from both speakers.

I noticed that some other 240 user made note from similar noise. Does anybody have any idea if this noise is due to some design problem of 240 or is this amplifier somehow damaged. When looking at circuit diagram, it seems that the floating or regulated grounding system of PSU seems most likely cause of this unstable situation.

It would be also nice to know if there is some easy fix for this noise after shut down.

Best Regards

Kimmo

iso · Posted: Tue Sep 17, 2013 7:12 am Post subject: Quad 240

Shunting D3 zener diode that powers DC servo with 47uf electrolytic cured oscillation... but there is now turn on thump.

I have used 240 now for year as my AV amplifier with Cantata´s. It has performed quite well and dual volume controlls have not caused too much trouble.

Do anybody here have any idea what preamplifiers were sucessfully used to drive Quad´s with balanced inputs. Especially when 520 and 240 series amplifiers were new and in domestic systems?

Best Regards

Kimmo