Quote:
Originally Posted by barretter
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.
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Hi again Barretter
Yes you are quite right, I have a SPA9 phono preamp (MM) to do this.
The Ortofon OM Pro S will be on an interchangeable headshell (4HF), for modern 33/45's, and the channel select will be on the new rotary switch fitted to select amp input between the following:-
1. The new ext input (with RIAA bias adjustment as described)
2. The headshell for the Orotfon (with SPA9 in circuit)
3. Headshell for GC8 mono ceramic cartridge (with no signal correction).
This is all in place and seems to work out ok, i just need to find a way to provide a small amplification trim to the ext input as described in my previous post.