At a glance
- Phone stage for all kinds of systems (Low-output MC, high-output MC, MM)
- Symmetrical/asymmetrical input
- Symmetrical/asymmetrical output
- No capacitors in the signal path
- Wide range of input capacitance and input resistance
- PCB available in our shop
platINA is a universal RIAA preamp for MC and MM system. It uses a low-noise instrumentation amplifier that can be configured for a wide range of gains. Therefore platINA is more flexible than the VSPS (MM only) and the PhonoClone (low impedance MC only). It also provides symmetrical and asymmetrical inputs and outputs. Signal-to-noise ratio is better compared to VSPS and PhonoClone. Commercial phono stages with a similar topology and sound quality do not sell for less than $500, some even in the range >$1000.
The platINA PCB can be ordered in the shop.
The circuit consists of 5 stages:
- Input stage that provides linear amplification of the MM or MC signals between 20 and 40db.
- A DC servo stage that implements a high pass filter. 2 filter frequencies are possible: a RIAA compatible 20Hz subsonic filter or a “flat” frequency response with 2.5Hz corner frequency.
- A passive low pass filter implementing the 75µs pole.
- Amplification of the low frequencies in the feedback loop of another OP amplification stage.
- Symmetrical line driver stage (can also be used as unsymmetrical line driver)
platINA doesn’t come with its own power supply. The power supply rejection ratio (PSRR) is very good, but an appropriate power supply is always a good idea. I have good experiences with the combination of UniSieb and a shunt voltage regulator. Place the voltage regulator close to platINA and the rectification & smoothing PCB close to the power transformer. If you like, you can split the device into 2 independent cases: one for power transformer and UniSieb and the other for voltage regulator and platINA.
- platINA circuit diagram
- platINA PCB
- platINA component placement
- platINA part list
- Sourcing RIAA capacitors
- RIAA online calculator – use it if you want to use different capacitor values
Pingback: platINA page is now ready
Pingback: Project introduction: DigiPot | Crazy Audio