DIY - Shure M65 Phono Preamp

[sann]

I had been happily using DIY EAR 834p phono stage for many years, and wanted to try a vintage phono preamp preferably without the cathode follower, then I stumbled upon JE labs (who I follow and admire since I built JE Labs Simple 45/2A3 amp) forum thread Shure M65 phono preamp
A simple circuit, without a cathode follower and with around 5k output impedance, I immediately decided to build.




The stock RIAA network has a HF boost at about 10khz, and though it sounds very lively, on some recordings it sounds a bit bright, I did a lot of experiments with the values of capacitors even made an excel sheet to calculate the RIAA poles based on the capacitor and resistor values, and settled on changing the 470pf to 750pf which is parallel to 100k resistor.

Happy listening
-sann

 

[raj12345]

Which is your Preamp/power amp/amplifier used along with this phono ? Are using a valve based amplifier along with this phono ?
The capacitance loading adjusted to 750pF is used with which cartridge & phono cables combo ?

 

[sann]

Which is your Preamp/power amp/amplifier used along with this phono ? Are using a valve based amplifier along with this phono ?
The capacitance loading adjusted to 750pF is used with which cartridge & phono cables combo ?

I am not using any preamp currently and directly feeding the phonostage output to JE Labs Simple 45/2A3 amp with 100k load.

750pf is used to bring down the HF roll off to 2123Hz from 3386Hz.

I am using Denon DL-103 cartridge hence cable capacitance is not a concern for me.

 

[sann]

PS: About hum - Initially I used a toroidal transformer also installed a metal cover to suppress hum, however it still didn't solve the issue, then I thought about putting the power supply in a seperate box as done by JE Labs, then I thought about giving Kolarkar Audio power transformer a try which was built with a medical grade shield and darn accurate HV and heater secondary even with load. This solved the hum issues, and I didn't need to worry about making a seperate PS box.
This phono is popular known as Chrome Cutie and it really looks cute with a small footprint.