Audio HiFi

I picked up this vintage Trio KA-4000A amplifier to use on my Desktop PC (DAW) to drive a small pair of book shelf speakers. However, the amp had a fault on testing so out came the iron and a box of spares. The fault was noise (hiss) and crackling on one channel. This turned out to be a faulty transistor, namely a 2SC458. This particular transistor is quite well known for failing and is a common part in many amplifiers and other audio equipment of this era. Therefore changing these is a must. If you have a vintage solid state Trio amp with a noise problem and it is not just a simple volume pot cleaning process then check for any of these 2SC458 transistors.

The Consonance Basie Pre-amplifier kits were originally available from Diy HiFi Supply. The Mk1 was a SRPP based unit with a cathode follower output stage that could be modified to use other tubes. In my original build I eventually by-passed the cathode follower and used 2 x Mullard E80CC driver tubes making it an Anode follower.

It is possible to make a SuperClamp plug using a standard UK mains plug and a few parts. Total cost is a few pounds. Simply take any UK mains plug, the MK ones are better since they have more space inside them but I managed with a cheap one. Inside the plug you need to connect a varistor across Live and Neutral. If there is enough space you should use 2 in parallel. That is it !! You can take this a step further and connect a varistor across Live and Earth and one between Neutral and Earth. They are very low capacitance like a typical Y-Class Cap and act as such here until clamping a spike. Blank the cable entry with a rubber grommet or some sealant if you wish.

In Use

This is a full mains filter build that can be made with or without the chokes if you wish. The first picture shows the unit I made in a simple ABS case. This filter is a complete DIY solution where you make the circuit yourself, either on a PCB, vero-board or tag strip.

The sonic benefits of any mains filter is subjective at the best of times. Some people swear by them and others dislike them. I have always preferred my system with some kind of filtering and cannot see the purpose of using high grade audio mains leads without a filter circuit before them. The filter isolates the audio grade mains lead from the yards of twin and earth grey cable under the plaster and the miles of cable to the local sub station on your phase.