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In Reply to: RE: I'm not sure posted by Ugly on June 02, 2017 at 10:26:03
Just use ground as a reference for the servo, so the DC output is 0V.
As far as the input, each preamp side will have its own resistor to ground so that the preamp can function; that value should be 23.5K so that the load on the cartridge is 47K.
Thank you for your replies. They are very much appreciated. I had some ideas about things to try but it sure instills confidence to talk to someone who has tried some of this stuff.
The plan all along has been to make it easy to try either ground referenced or floating referenced servos via jumper setting.
My desire to leave the servos referenced to a floating , non ground node was triggered by these fully balanced/differential op amps, apparently targeted at the audio market, such as the OPA1632.
These parts have integrated servos to set output common mode voltage. The app notes suggest common usage being tying the Vocm pin to the ADC reference. To my mind this implies there are must be audio market ADC's out there using external non ground voltage references.
My concern is that if I wanted to use one of these ADC's and I had my front end servos referenced to ground I may exceed the common mode range of my of my output stage under certain large signal swing circumstances.
My thinking was that floating front end servo references or tying it to my own version of a Vocm reference pin and an output stage that allows setting output common mode voltage (similar to OPA1632 et al) gets me around that problem.
Well, building may be putting it just a bit strong. I just sit around using gigawatt/hours simulating then changing my mind and then do that some more.
I think I might be getting close...but I've said that before and then it evolves.
At the moment I'm fairly excited about some breakthroughs I'm having on the bass processing circuitry I'd like to include.
It's always something.
Who knows, maybe someday I'll start laying out a PCB. haha
Zoooo.. a daydreamer speculating on what if.. and a man with a horse in the race .. hoping to make 10s of $.
Not the most enlightening of threads.
And yet you read to the end.....lol
I would guess the general life misery level must be pretty high for someone as apparently clueless to feel the need to comment in such a worthless manner.
I hope things turn around for you soon.
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