A call for some advice please. I have a chinese music angel 845 single ended valve amp which sounds surprisingly clear and pure. However switch-on with 240volts here in the uk produced a loud thump from the amp (not from the speakers). I overcame this by fitting a switched box between the amp's power plug and the wall socket. The box swiches in resistors until the caps are charged then switches in the full 240v, which has stopped the loud thump. Recently I made up another box with 5 x 100ohm ww resistors which lowered the voltage to 217, more in line with the voltage of 220 which the amp is designed for. All sounded fine for a while. Now the tonality of the amp has suddenly changed. The treble is greatly reduced, bass is reduced, and the upper mid is prominent, giving the sound a megaphonic quality. Transparency is greatly reduced. I can't see any connection between the boxes and the resultant sound. Returning the amp to 240v supply does not cure the problem. Methinks signal capacitors may have failed but the incorrect tonality is on both channels. I intend shortly to measure all the capacitors and resistors to see if any are out of spec.
Before I begin examination I thought I would invite thoughts and observations from you. Have you come across this problem? Can defective valves bring about such altered tonality? I shall be most grateful for guidance and advice.
Yours sincerely,
Peter Parsons. Cornwall UK.
Before I begin examination I thought I would invite thoughts and observations from you. Have you come across this problem? Can defective valves bring about such altered tonality? I shall be most grateful for guidance and advice.
Yours sincerely,
Peter Parsons. Cornwall UK.