Micro 25R Tube Preamp

The Croft Acoustics Micro 25R is a valve preamplifier that builds on the design principles of the original Micro 25, offering enhanced performance through regulated power supplies and upgraded internal components. Like its predecessor, the Micro 25R features a moving-magnet phono stage alongside multiple line-level inputs, including CD, tuner, and tape. 

Construction and Features

• The Micro 25R uses three 12AX7 (ECC83) tubes: two dedicated to the phono stage and one to the line stage.
• The interior is fully point-to-point hand-wired, with audiophile-grade capacitors used in the RIAA equalization and coupling networks.
• The power supply section is fully valve-regulated, employing high-quality toroidal transformers and additional regulation valves, which help to lower noise and improve stability compared to the standard Micro 25.
• The preamplifier runs in pure Class A operation, contributing to its refined sonic character.
• The front panel includes dual-mono volume controls for precise channel balance, a mute switch, an input selector for three line-level sources and one phono input, and a power switch.
• The rear panel offers gold-plated RCA sockets for all inputs and outputs, a dedicated phono earth/grounding post, and a fused IEC power inlet.

Phono and Line Stage

• The phono stage is designed for moving-magnet cartridges and higher-output moving-coil cartridges, provided the connected power amplifier has sufficient sensitivity.
• The RIAA equalization is implemented with shunt feedback and high-grade capacitors for accurate frequency response.
• The line stage is configured as a cathode-follower buffer with unity gain, ensuring low output impedance and minimal coloration.
• The Micro 25R’s regulated power supply and upgraded components provide lower noise, greater transparency, and improved dynamics over the standard Micro 25.

Measured Performance and Specifications
(Where available; detailed measurements for the 25R are not widely published, but core electrical characteristics are consistent with the Micro 25, with improvements in noise and regulation.)

• Input Sensitivity:
  • Phono (MM): 1mV for 0.5V output
  • Line: 0.15V for 0.5V output
• Output: 0.5V nominal, suitable for direct connection to Croft Series 7 and similar power amplifiers
• Inputs: 1x phono (MM), 3x line-level (CD, tuner, tape)
• Outputs: 1x main (to power amp), 1x tape out
• Dual-mono volume controls for independent channel adjustment
• Regulated power supply for reduced noise and improved dynamic headroom
• All-tube signal path using ECC83/12AX7 valves

Sound and System Compatibility

• The Micro 25R is praised for its transparent, open, and three-dimensional soundstage, with a highly engaging and natural musical presentation.
• It synergizes particularly well with Croft’s Series 7 power amplifier but is compatible with a wide range of power amps.
• The regulated design and upgraded components yield lower noise and greater clarity, especially noticeable in demanding systems or with high-sensitivity speakers.

Typical Price and Value

• The Micro 25R is positioned above the standard Micro 25 in Croft’s lineup, reflecting its regulated power supply and higher-grade internal components.
• It is widely regarded as offering exceptional value for its sonic performance and build quality.

Here you find 6 models, 6 with images and 0 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.
All listed radios etc. from Croft Acoustics Ltd.; Birmingham