audio output transformer wiring color code

The transformer was made by Majestic Transformers in Poole UK and was sized to fit the original case but it had been bolted directly to the chassis as pictured because it would not fit with the mounting cheeks in place I had supplied replacement block capacitors to the 'repairer' of these amps and I was interested to see this new mains transformer which was causing the owner some concern Looking at the left hand side amplifier in the picture you would probably think the same thing The owner of an early pair of QUAD IIs was concerned that a repair to his amplifiers was 'not quite right' The project pictured above and described below started when I was contacted and quizzed on how a modern replacement QUAD II mains transformer should or could be fitted Some transformer manufacturers offer replacement mains transformers and chokes for the QUAD II valve amplifier but there are few that make a replacement QUAD II output transformer (OPT) and only one I know which currently (Oct 2020) makes a replacement core that fits the original case (can) and performs better than the original or the new parts fitted in the IAG 'quad classic' and its modern variants They used 1:1 to 1:3 turns ratio and classical push pull power amplifier in the output stage.~ QUAD II New Mains and Output Transformers ~ Interstage coupling transformers used to be popular in vacuum tube based designs. This requires both low resistance windings and very low leakage inductance. Therefore, a line output transformer should have low output impedance which remains low at high frequencies. Typically, audio transformer is driven by an amplifier and loaded by several thousand pF cable capacitance and high input impedance of line receiver. Hence, the transformer is used in step-up configuration so that amplifier sees an impedance of 600 W in order to achieve good noise performance. Due to this, it is very difficult to achieve good noise performance in an amplifier.

Moving coil phonographs are very low impedance devices (~3 W ). They also transform the impedance as microphone input transformers and have high CMRRs. Line input transformers are generally driven by balanced line and drives an unbalanced line.

Audio output transformer wiring color code