Arcam and the TDA1541

[a.palfreyman]

Eventually got around to doing the back-to-back listening but found that my CD160#2 had developed an unusual fault that could only be heard when stood near the speakers. This was a random crackling noise (i.e. not a specific frequency like a buzz) so whipped the lid of and had a poke around the regs. There is a lot of noise (clock splatter) on the supplies but measuring at pin 15 of the TDA1541 (the -15Vdc supply which has RC on the feed that cuts a lot of this noise) a random, stepped up-and-down of about 3mV was seen on top of the dc voltage. Took it out and soldered up a little circuit to make sure it was the reg and not something else and hey-presto, faulty reg. Putting a new 7915 in tonight. Although this supply powers the output opamps and the mute circuit after the opamps I suspect that it has most effect on the TDA so it shows how critical the -15V supply is on the TDA chip.

 

[davidsrsb]

The 7915 is not a very good reg as it uses internal feedback resistors to set the output voltage.
A 7905 with a 10V zener in the common would be better or a 337 with decoupled adjust

 

[a.palfreyman]

The 7915 is not a very good reg as it uses internal feedback resistors to set the output voltage.
A 7905 with a 10V zener in the common would be better or a 337 with decoupled adjust

Thought about doing that ^^ but just wanted a 'replace original' solution for ease. Increased cap value before has helped to reduce residual feedthrough of rectified voltage swing and this is further cut with RC in front of TDA input as I wanted to keep near original for comparison to my modded one which I still need to do.
Thanks,
AP