UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Adding a selectable line input to valve radiogram

barretter · 15th Nov 2020, 12:20 am

If you want to use an Ortofon OM Pro S it will have to have its own dedicated pre-amplifier. The Ronette BF40 has an output of 800 millivolts, the Garrard GC8 has an output of 800 millivolts for 78s and 200 millivolts for 33/45s ; the output of the Ortofon is 5 millivolts. The Ronette and Garrard cartridges have to have an input resistance of 1M whereas the Ortofon has to be loaded with 47K. The Ronette and Garrard sort of do the necessary equlization by themselves but the Ortofon needs an electronic circuit to do the needed equalization and amplification. There isn't any way you can feed a line source into the RIAA circuit used for the Ortofon.

15th Nov 2020, 12:20 am	#123
barretter Heptode Join Date: Jan 2006 Location: Todmorden, West Yorkshire, UK. Posts: 870	Re: Adding a selectable line input to valve radiogram If you want to use an Ortofon OM Pro S it will have to have its own dedicated pre-amplifier. The Ronette BF40 has an output of 800 millivolts, the Garrard GC8 has an output of 800 millivolts for 78s and 200 millivolts for 33/45s ; the output of the Ortofon is 5 millivolts. The Ronette and Garrard cartridges have to have an input resistance of 1M whereas the Ortofon has to be loaded with 47K. The Ronette and Garrard sort of do the necessary equlization by themselves but the Ortofon needs an electronic circuit to do the needed equalization and amplification. There isn't any way you can feed a line source into the RIAA circuit used for the Ortofon.