Disco Volante
Well-known member
The young man I mentor a little bit in tinkering has recapped this old Beomaster 900. It now works quite well by its own standards (6W of true Germanium power!).
We've managed to reduce the noise somewhat by removing some resistors and rewiring it a bit, also replaced a few Rs with metal film.
All that's lacking is a proper RIAA preamp. These machines are meant to be used with crystal pick-ups.
So, I had this old Velleman thing in the drawer, and adding in a 7815 to drive it on a piece of vero-board is easily accomplished.
Now, what to do about the positive chassis? Reverse the supply on the riaa-pre? If so, how do we avoid shorting the -24V via the input socket? Yes, we can separate signal ground from chassis, but what if someone plugs in a DIN-plug where shield and signal ground is connected?
Or am I barking up the wrong tree here?
Cheers, V



We've managed to reduce the noise somewhat by removing some resistors and rewiring it a bit, also replaced a few Rs with metal film.
All that's lacking is a proper RIAA preamp. These machines are meant to be used with crystal pick-ups.
So, I had this old Velleman thing in the drawer, and adding in a 7815 to drive it on a piece of vero-board is easily accomplished.
Now, what to do about the positive chassis? Reverse the supply on the riaa-pre? If so, how do we avoid shorting the -24V via the input socket? Yes, we can separate signal ground from chassis, but what if someone plugs in a DIN-plug where shield and signal ground is connected?
Or am I barking up the wrong tree here?
Cheers, V


