PHOM is a tube phono preamplifier for MM and MC cartridges, designed and manufactured in Poland by IGS Audio. The signal path is fully tube-based and all-analog, operating without global negative feedback. Two gain stages in cascode configuration bracket a fully passive RIAA equalization network placed between them – not inside a feedback loop. Passive inter-stage RIAA eliminates the phase distortion artefacts and nonlinearities that active equalization introduces. Four 6N1P-EV tubes from NOS military-grade stock form a hand-selected matched quartet. The power supply uses a GZ34 tube rectifier with choke filtering for soft-start behaviour, extended tube life, and stable DC rail delivery. The UTM Industry mains transformer is substantially oversized relative to the power consumption of 55 W. The finished unit weighs 9 kg and sits in a 380×290 mm enclosure built from 3 mm CNC-machined aluminium.
Transformer-coupled MC input – why it matters at this signal level
Moving-coil cartridges output signals ranging from tens of microvolts to a few millivolts – far lower than MM cartridges. Any noise introduced at this stage is amplified through every subsequent gain stage along with the signal. PHOM addresses this with a transformer-coupled MC input: a step-up transformer raises the MC cartridge signal before it reaches the first tube, without adding active electronic noise in the process. Resistive loading for MC cartridges is adjustable across 16 steps from 56 ohms to 1000 ohms, covering the full range of internal impedances found in real-world MC cartridges and allowing precise impedance matching for each specific unit. MM cartridges receive 16-step capacitive loading from 22 pF to 390 pF to correct resonance behaviour in the upper frequency range. Gain exceeds 60 dB for MM and reaches up to 80 dB for MC.
Passive RIAA network and component selection
The RIAA correction network in PHOM is passive and placed between the two gain stages rather than inside a feedback loop, preserving the open-loop character of the amplification. Three capacitor types are combined in the network: NOS Paper in Oil capacitors, Silver Mica, and Mundorf EVO. Paper-in-Oil types are chosen for their natural, fluid dielectric behaviour and low microphony; Silver Mica for thermal stability and tight value tolerances; Mundorf EVO for low ESR and consistent frequency response across the audio band. Nominal output is 0.775 V RMS (2 Vpp) with maximum gain of 62 dB. A turntable ground terminal on the rear panel eliminates inductive hum without adapters. The front panel uses a minimalist layout with a single LED power indicator; all cartridge loading adjustments are accessed from the rear.
KEY FEATURES
- Fully tube, all-analog signal path without global negative feedback
- Passive inter-stage RIAA equalization – no active correction loop artefacts
- Two cascode gain stages with matched quartet of NOS military-grade 6N1P-EV tubes
- Transformer-coupled MC input – minimum noise at the first gain stage
- 16-step resistive MC loading: 56 Ω – 1000 Ω
- 16-step capacitive MM loading: 22 pF – 390 pF
- Gain: above 60 dB (MM) / up to 80 dB (MC)
- RIAA capacitors: NOS Paper in Oil, Silver Mica, Mundorf EVO
- Power supply: GZ34 tube rectifier + choke filter, UTM Industry transformer
- Designed and manufactured in Poland, weight 9 kg
TECHNICAL SPECIFICATIONS
- Type: tube phono preamplifier MM/MC
- Signal tubes: 4× 6N1P-EV NOS (military-grade, matched quartet)
- Rectifier: GZ34 (tube), choke-filtered power supply
- RIAA equalization: passive, inter-stage
- Gain: max. 62 dB (MM) / up to 80 dB (MC)
- Output level: 0.775 V RMS (2 Vpp)
- MC loading: 16 resistive steps, 56 Ω – 1000 Ω
- MM loading: 16 capacitive steps, 22 pF – 390 pF
- MC input: transformer-coupled
- Connectors: RCA input/output, turntable ground terminal
- Power consumption: 55 W
- Enclosure: 3 mm CNC aluminium, 380 × 290 mm
- Weight: 9 kg
- Manufactured in Poland
