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Re: RIAA design dilemma, need your opinions.
Posted by Kurt Strain on February 19, 2002 at 13:20:45:
Despite my daft idea for using the large coupling cap before the RIAA network, I think it works fantastic. See the schematic below for my phono stage design, then replace things as follows:
* Change bipolar CCS with new MOSFET CCS in http://www.sonic.net/~ktstrain/MOSCCS.jpg
* Change V1 to 6ER5, also change its cathode resistor where you want the plate voltage and current to be (I chose 90V and 2.5mA for Vp and Ip) and remove the cathode bypass cap entirely.
* Change V2 to 6GK5, change the cathode resistor again for your desired operating point (I chose 110V and 2.5mA) and remove the cathode bypass again.
* Change the first coupling cap to two 0.22uF TRT teflon caps in parallel.
* Change the 0.01uF cap in the RIAA to a TRT teflon.
* Change the 0.22uF output cap to TRT teflon.
* Change all resistors in the RIAA to Caddock TF020 film. Change cathode resistors to Caddock MK132.
This is a MM input phono preamp. Use a high quality MC step-up transformer for MC input. I never heard tube or transistor do as good a job as my EAR MC-3 for this function - zero noise, great sound.
That's what I use. I think it's totally first rate. Better than anything else I have heard. But's it's an expensive setup with those parts.