Circle Labs V1000 – Phono MM/MC

Description

The construction of the MC section of the phono stage incorporates our exclusive step-up transformer, designed and hand-crafted in the factory workshop. We always focus on creating our own solutions, rather than using widely available OEM parts. The SUT in the V1000 phono stage does not recycle existing designs: we made it from SCRATCH.

The primary winding is made of Litz wire containing 25 strands, insulated from each other by a silk braid. The secondary winding is made of high-purity copper wire. This sophisticated configuration has enabled us to obtain very low resistance figures (0.25 Ohm/22 Ohm), in order to minimise signal losses from the cartridge.

The signal from the SUT goes to the MM preamplifier section, which is based on ECC88/6922 valves (two valves per channel). Constant bias has been achieved through the use of cells. The circuit operates with zero negative feedback. The design is a 100% dual-mono configuration with independent and fully isolated circuits for the left and right channels.

In the power supply, we use Mundorf polypropylene capacitors and a two-stage cascade-type stabiliser with zero feedback. To reduce interference, the power transformers are housed in a separate enclosure.

From an input perspective, our phono preamplifier incorporates two independent inputs. It is ready to support a dual turntable/tonearm setup, accommodating cartridges with full impedance (10-1000 Ohm) and provides a wide capacitance adjustment range (0-320 pF).

On the front panel, the user can configure the classic RIAA curves via the two adjustment knobs, or apply their own custom settings to better suit the production of records released prior to standardisation. Additional knobs include MC/Mute/MM switching and an input selector.

Technical specifications

• Type: valve phono preamplifier for MM and MC cartridges
• Construction: dual mono, with independent and isolated circuits for each channel
• MM Gain: 45 dB
• MC gain: 65 dB, switchable to 70 dB
• Inputs: 2 × RCA, independently configurable
• Outputs: 1 × RCA and 1 × balanced XLR
• MC load impedance: adjustable between 10 and 1,000 Ω
• MM load capacitance: adjustable between 0 and 320 pF
• EQ curves:
  • Bass/treble: 230, 318 RIAA, 400 and 630 µs
  • Treble: 100, 75 RIAA, 50 and 25 µs
• Valves: 4 × E88CC/6922
• Circuit: open-loop
• MC step-up transformer: custom-designed SUT with dual nanocrystalline core
• Power supply: external, featuring Mundorf polypropylene capacitors
• Power supply regulation: two-stage cascaded stabiliser, without feedback
• Power supply cable length between units: 1.2 m
• Fuse: T400 mA anti-surge, 5 × 20 mm

Dimensions and weight

• Main unit: 430 × 130 × 365 mm —width × height × depth—
• Power supply: 98 × 83 × 210 mm —width × height × depth—
• Main unit weight: 9.5 kg