TL Audio 5051 - Manual (Page 4)

1. INTRODUCTION
Congratulations on purchasing the Ivory 5051 Mono Valve Processor by TL
Audio!
The Ivory 2 Series consists of a range of hybrid valve signal processors, which
utilise low noise solid state electronics in conjunction with classic valve
circuitry to produce audio processing units offering very high quality signal
paths with the unique valve audio character. The units offer comprehensive
control facilities, whilst remaining straightforward to operate, and represent
excellent value for money.
The 5051 is a single channel voice and instrument processor with mic, line
and instrument inputs, a compressor, a four band equaliser and a noise gate.
A single illuminated VU meter monitors the input level, output level or the
compressor gain reduction. The optional DO-2 digital output card allows 24-bit
analogue to digital conversion via an RCA phono type SPDIF output, with
selectable 44.1 or 48 kHz sample rates and the option to clock the converter
to an external word clock source.
The block diagram of the 5051 is shown in Figure 1. A solid state,
electronically balanced input amplifier is used to achieve state of the art
performance with very low noise, low distortion and wide bandwidth. An
ECC83/12AX7A triode valve stage (run from a stabilised 150v DC supply) is
used as a second stage voltage amplifier, to obtain the classic valve sound
and gradual overdrive characteristics.
The preamp stage also features 48V phantom power, a 30dB pad and a high
pass 90Hz filter. A Drive LED gives a visual indication of the signal level
through valve stages (and thus the amount of ‘warming’ taking place) while a
Peak LED warns that clipping is about to occur, and this monitors the signal at
key points in the audio path.
The compressor section offers fully variable control of threshold, ratio and gain
make-up, with four switchable attack and release times and both hard and soft
knee options. A ‘Hold’ facility reduces LF distortion, and a side chain insert
point is provided for frequency conscious compression. Like all other TL Audio
compressors, the gain control element of the 5051 compressor stage is based
around a special transconductance amplifier, which avoids the use of VCAs
and helps contribute to the smooth, open sound of the unit. A stereo link
facility is provided to allow the compressor control voltages of two 5051s to be
linked, thus preventing image shift when processing stereo signals.
A four band valve EQ stage is included (with a triode valve stage in each
filter), providing up to 12dB of cut or boost and a choice of four pre-selected
frequencies on each band. The ‘EQ PRE’ switch places the EQ ahead of the
compressor in the signal path. A simple but effective noise gate (with variable
threshold) is provided to remove unwanted background noise.