IGS Audio Double Triode Limiter

The IGS Audio Double Triode Limiter is an expanded version of the Double Triode microphone preamp.

The limiter is based on classic solutions used in the 60's and 70's. The component in charge of compression is an IGS Audio custom designed photocell. It consists of an electroluminescent subcomponent and a photo resistor. This subcomponent illuminates the photo resistor which reduces the audio path amplification. The limitation of the amplification is directly proportional to the light intensity in the photocell. The limiter threshold is indicated by a diode labelled "Limit" on the front panel.

Audio path is a 2-stepped tube amplifier with the individual drive of both steps. The saturation of the first step is dependent on the input signal (with the possibility to use Pad -20dB). The saturation of the second step is dependent on the Output regulator. Inputs and outputs are balanced with Sowter and Edcor (USA) transformers (custom selection possible). The anode voltage is close to 300V DC.

For each of the channels Gain, Output and Limiter threshold can be regulated smoothly. The featured switches are +48V, Mic/HiZ, Phase, Pad -20dB. Hiz inputs are located on the front panel. The meters show output signal level.

Usage:

The DTL is a typical double microphone preamp. It is adapted to work with any type of microphone. A wide range of amplification makes it possible to record drums as well as the quietest ribbon microphone. The Pad -20dB makes it possible to work with line signals as well. In this case the DTL does a great job of recording tracks from external devices such as synthesizers or drums machines (like Akai MPC). Great results are achieved through resampling tracks from DAWs. The DTL adds a tube saturation as well as an Opto-compression to the sound. The high impendence inputs (HiZ) enable connecting a guitar or bass guitar directly into the grid of the first step of amplification (Typical HiZ solution).

Additional device capabilities are activated by the Limiter section. This can be used to limit peak levels of the input signal. The wide range of Limiter settings goes from slight compression to hard limiting. This is especially useful in vocal recording where the wide range of signal dynamics is controlled. The limiter controls the louder parts and prevents digital audio path distortion. Another trick could be using the DTL as a drum compressor or sum compressor. It can increase the overall dynamics of the mix and give it a brighter sound. This is a very versatile device for audio processing.

Technical specification:

• Inputs: 2 Mic/Line XLR and 2 HiZ Jacks on the front
• Outputs: 2 XLR
• Tube Only audio path
• Operating Level +4dB
• Maximum Output +29 dBV,
• Meters reads Output VU,
• Max. Limiter Reduction 18dB
• Gain Boost 60dB
• THD < 0.1% @ 1Khz
• S/N Ratio: 104dB
• Mains consumption: 80 watts
• Soft Start Power Tube Timer
• Shipping weight: 8 kilos