Supra 2.0 main board (150616-1)
For those who like vinyl records this is the ultimate preamplifier for your record player. Standard configuration is for MM cartridges. Modification for MC is easy as all parts are through hole and only concerns resistors. As a power supply a separate transformer PCB (150616-2) can be used or a DC/DC converter module (PCB 150464-1). With the latter a standard 12 VDC/1 A AC adapter is needed.
NOTE: Apparently the DC/DC converter used in the original publication on PCB 150464-1 (JCE0612D24 from XPPOWER) is hard to come by. We didn’t find modules at other manufacturers with the same specifications (6 W, 12 V in, 2 x 24 V out and the same footprint). There is an easy solution to this problem. Instead of an output voltage of +/-24 V we use +/-15 V. A good alternative is module TEL 5-1223 from Traco Power. It’s maximum output power is 5 W which is more than enough, due to the lower output voltage. The outputs can deliver 200 mA, also more than enough. Input voltage is 12 V nominal (9-18 V). The voltage drop across the regulators should be more than 3 V. The voltage drop across the 1N4007 in the power input is close to 1 V. So the voltage output of regulators LM317/LM337 should be set to deliver +/-11 V. All it takes is to change R60 and R62 to 1.4 kΩ, that’s all. To be sure we performed new measurements and got the same results with the lower power supply. With this modification the power supply voltage of the opamps is roughly +/-10 V (he voltage drop across the filters (T1…T4) is also around 1 V).