tfpro P10 Dual Mic Preamp / Stereo Compressor

P10 Dual Mic Preamp / Stereo Compressor description:

The TFPro P10 is a dual mic preamp and dual/stereo compressor and much more.

The TFPro P10 is a combination of the greatest of microphone amplifiers, the sound and effect of classic optical compression but with new engineering for even greater flexibility, and classic 1980s style equalisers, all in a dual package.

There's nothing quite like a transformer for an input buffer, it's the perfect isolator, and it eliminates the need for electrolytic capacitors at the audio input.. The P10 uses a substantial UK made transformer, but because of the novel design of the current mode input stage, the transformer operates with predominantly current. With almost zero voltage there is no possibility of overload or distortion at the input, so the input stage can handle outrageous levels with no distortion, even at very low frequencies.

The amplification after the transformer is shared across 4 gain stages so that no single amplifier is 'stretched', this minimizes impulsive distortion; the effect that makes so many so called 'good' preamplifiers sound over clean and brittle. The design of the input gain control ensures that gain is evenly proportioned across the 4 stages.

From the first experiments with optical compressors in the 1950s, the problem has always been the difficulty of achieving stable high ratio compression. TFPro took another look at the problem and designed a new circuit where the compressor forms one leg of a precision 'bridge'. This design makes it possible to achieve compression ratios up to 100:1, a true limiter. (Previous circuits have been restricted to ratios of about 6:1 maximum).The compressor make-up amplifier, which is normally a low noise op-amp, in the P10 it is a classic design class A discrete transistor amplifier, this adds to the cleanness and 'weight' of the sound.

The compressors work independently in the two channels, but a link switch takes the operation of the compression controls from channel two and makes them work from channel one. The stereo linking is accurate enough for precision mastering of stereo tracks. The EQ circuits are based around detuned gyrators subtracting or adding at specific selectable tuned frequencies. The 'Q' values are all around 1.5 giving detailed control of overlapping frequency bands that are particularly effective for drum recording.

VU meters show the audio level immediately before the output gain control circuit. When the 'READ GR' button is pressed, the VU meter shows the gain reduction of the compressor in dB. In addition to the large VU meters there are LED indicators showing 'signal present' (when there is a signal greater than -26dB in the system) and a channel overload LED that flashes on brightly when the signal hits a level within 6dB of a real overload.

TFPro P10 technical specifications:

• XLR input, transformer balanced, normal mode 800 ohm impedance to suit 200 ohm or lower microphones. In phantom power mode, 2Kohm impedance and 48V phantom power.
• Input level from -80dBu up to 0dBu.
• LINE input on XLR and jack, floating transformer balanced 20Kohm impedance. Input level -30dBu up to +28dBu.
• Instrument input, front panel TRS jack, transformer balanced 20Kohm impedance. Input level -45dBu up to +8dBu.
• Overload margin: Greater than 30dB on mic inputs. Other inputs approx 25dB.
• Max system gain 85dB
• Harmonic Distortion: Normally within 0.002%
• Outputs: All outputs balanced 150 ohm source impedance nominally 0DBu. Max output +24dBu.
• Compressor: Class A amplifier operating in 'Wien Bridge mode' Variable ratio 1.2:1 up to approx 25:1. Attack time variable from 0.5mS up to 20mS, not calibrated (varies with compression type). Release time variable 250mS up to 2 seconds.
• EQ: Gyrator controlled LF, MF1 and MF2 bands with overlapping frequencies.
• 230VAC and 115VAC operation.
• Housing: 3U rack case with heavy gauge aluminium front panel. Rear housing steel plate.
• Dimensions: 2U rack, depth 300mm. Weight 2.8 kgs