The TFPRO P82 is a dual channel switched precision analogue mastering equaliser with 5 stages of response tailoring in 2U rack mount format.
The P82 is constructed in a heavyweight steel chassis. It is designed for dual mono or stereo use giving detail sound correction of precise frequencies with particular attention to response extremes. It is an original design by Ted Fletcher and is assembled and tested in the UK.
The TFPRO P82 EQ achieves smooth click-free repeatable operation by using specially made notched control pots and rotary frequency switches. The system offers exceptional sound quality with extremely low noise and distortion; a pure analogue sound that can be described as ‘luxurious’.
The line level XLR and jack input goes via a balancing transformer with an input impedance of 20Kohms designed to operate best at a level between -10dBu and +8dBu and with a flat response (within 0.1dB) from 8Hz to above 25KHz . The unique design of input circuit eliminates low frequency distortion and retains flat amplitude and phase response far beyond digital equipment.
The EQ sections operate in frequency bands that that are important to musicality; this EQ brings together the physics of sound reproduction and ‘what sounds right’, it is a harmony of experience and careful design.
Technically, the audio signal is controlled in bands that are defined by analogue electronic inductors. Frequencies are determined by 6-way switches while lift and cut are controlled by notched rotary potentiometers so that accurate settings are easily recoverable.
This is an inductor-based equaliser with switchable ‘shelf’ or ‘peak’ response. When switched to ‘shelf’ mode, it becomes a ‘Baxandall’ type EQ circuit. Frequencies covered are 20Hz to 125Hz in 6 steps with switching lift and cut in 19 steps with fine resolution from -12 to +12dB. Care must be taken as lifts of extreme low frequencies are possible. Alteration of sub-sonic balance has a profound effect on the spaciousness of sound.
This is similarly inductor based. Frequencies covered are 125Hz to 700Hz in 6 steps with switching lift and cut in 19 steps. With small amplitude changes the phase shifts in the music are kept under control producing a harmonious sound. When large amounts of correction are necessary, the ‘Q’ (intensity) of the selected frequency tightens so that effect spread is controlled.
This is also inductor based. Frequencies covered are 700Hz to 4KHz in 6 steps with switching lift and cut in 19 steps. These frequencies are normally thought of as ‘high’ and must be treated carefully to retain smooth sounds, the ear is most sensitive to these frequencies. Small lifts and cuts significantly affect the apparent ‘depth’ of sound.
This is a fourth inductor-based type with controlled peaking response. Frequencies 2.8KHz to 12KHz with switching lift and cut in 19 steps. The HF section is used to control the clarity of the sound without seriously affecting acoustic depth.
SUPER HI SECTION (AIR BAND)
This is a ‘Baxandall’ based circuit with shelving response. Frequency (3dB point) switchable between 15KHz and 18KHz with lift and cut from -12dB to +12dB in 19 steps. The purpose of adjustable ‘air-band’ is to introduce or control the extreme high frequencies; what we used to call the ‘fairy dust’.
A pair of IN/OUT illuminated by-pass push-button switches hard-wire bypass the 5 EQ stages by relay. When power is removed the audio input directly connects to the audio output.
The gain of the EQ sections are carefully set-up so that the volume remains precisely the same when by-pass is operated.
LED meters show peak levels in 10 steps up to +10dBu. The top LED is red but does not necessarily indicate ‘overload’; The electronics are capable of a very high overload margin to allow for transient spikes in the audio signal.
The meters are set to indicate peak signals and have controlled release characteristics similar to broadcast peak meters.
Low noise low distortion output stages provide floating balanced outputs via XLR and standard jack. With EQ set to nominal ‘0’ the frequency response and operating level is maintained to within 0.5dB 20Hz to 20KHz.
The P82 is mains powered with LED indication of ‘on’. The internal supply works at any mains voltage without adjustment.
- INPUTS XLR and 3-pole standard jack. 20K impedance, transformer balanced.
- OUTPUTS XLR and 3-pole standard jack. 300 ohm source impedance electronic floating balanced.
- SYSTEM GAIN 0dB within 0.2dB.
- SIGNAL/NOISE RATIO approx. 120dB.
- HARMONIC DISTORTION (THD) within 0.04% 20Hz to 20KHz at operating level.
- AMPLITUDE FREQUENCY RESPONSE +0 -0.1dB 8Hz to 25KHz.
- EQUALISER 5 band with 6 switch frequency selects on 4 bands, 2 frequency selects on High HF band.
- LIFT and CUT controls have 19 ‘click’ points defining amount of lift or cut. Maximum lift or cut is 12dB at the defined frequencies.