Some time ago I’ve received a Technics SL-1910 turntable from a friend. At that time mine problem was that this turntable doesn’t have integrated RIAA network and my vacuum tube stereo doesn’t have too. I needed an external RIAA active network to equalize the audio from the turntable and rise it’s volume to the 1,5Vpp needed to drive the stereo amplifier. I’ve designed a simple active RIAA network powered by a low noise op-amp NE5534 or OP27 or other pin-to-pin compatible op-amp’s. I’ve made some PCB’s for it too. I sell the PCB at 5€/each plus shipping. Contact me for more info or buy.
The PCB populated
RIAA schematic.
The simulated circuit result and the result from the real circuit measure fits very well.
Frequency response simulation
Real frequency response, please note that actually the dB loss is a dB gain. +35dB at 20Hz and 0dB at 20Khz aprox.
All resistors are 1/4W
- All capacitors must be high-quality poliestere but I’ve used standard ceramic type without any issue
- IC’s are mounted on DIP-8 package
- I/O are made soldering directly coax cable from RCA sockets to the pcb
- The circuit is powered by 2x 9V battery to minimize noise from power supply. I use a connection like this to power the circuit. Just add a double trow switch to connect/disconnect the +9V and -9V supplies.
Battery connection diagram
- The output cap must be a 2.2uF polyestere non polarized from WIMA or high-quality equivalent.
- The PCB that I’ve realized is 100x50mm in size, 1.6mm FR4 thick, double layer professionaly made. There are 4 mounting hole at corners. The PCB is noise free without any enclosure thanks to my design but I sugest you to enclose it into an alluminium enclosure like this one, cheap, from banggood.com
- For I/O use only quality gold plated RCA connectors mounted on the alluminium front/real panels
Riaa_1 click here to read the BOM (bill of materials)
