Musical Fidelity A1 Integrated Amplifier Repair/Upgrade

Looking at a Musical Fidelity A1 and some of its classic problems which are well documented by Mark Hennessy. We take some reference plots before we do anything then compare with results after our modifications. A power supply upgrade helps with supply ripple and the input amplifier modification reduces the noise floor at higher levels. Noisy volume control and selector switch issues are also exterminated!

Some thoughts after completing this video:
1. The scope noise before modification was horrendous. The input of the amplifier was terminated but its possible that the termination wasn't doing its job due to the precarious input selector switch. This may account for the results being so bad.
2. The non-linearity that I showed on the scope at higher levels before the modifications was not there after the modifications. You can see when I vary the volume control that the output easily goes up to 20v and clips in the traditional way. Possible there was some other fault present before the mod.

These modification and tests take a fair chunk of time. Its unlikely to make economic sense to have these amplifiers modified in this way. The only feasible approach would be DIY.

Marks web page : https://www.markhennessy.co.uk/mf_a1/

Serial number of this amplifier: 16580