ADL 1700 Tube Limiter

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  • ADL 1700 Liquid Mu Tube Limiter
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Price: $2,650.00
Product ID : 1700
Manufacturer: ADL
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ADL 1700 Liquid Mu Tube Limiter

ADL 1700 Liquid Mu Peak Limiter, often referred to as the little brother of the Fairchild 670.  The 1700 employs an all discrete tube design modeled after and a cross between the vintage UA 175-B and 177 limiter except we enhanced some features for added flexibility.  Unlike an opto limiter, the 1700 uniquely reduces the Mu or gain as the input signal is increased.

Like many classic tube compressors, the 1700 has a fixed point of threshold before compression.   This means that Increasing or decreasing the input level will vary the point at which the 1700 begins to compress.

The warmth and clarity of the 1700 is beneficial to everything from tracking to mastering.  Please try not to over do it!


Input gain knob
    Continuously variable, controls the amount of compression by altering the resistance in the grid circuits of V-1 (6BC8).  Gain reduction is easily visible on the VU with the meter select switch set to GR (Gain Reduction).  As per the original design, jumpers are located on main circuit board  near input transformer, clearly marked GAIN SELECT.  Factory settings are for low gain or line level.  High gain (microphone level)  setting will deliver an extra 20 Db of gain.

    Internal jumpers may be quickly reconfigured by removing the jumper that ties pins 2 and 3 and connecting pins 1 and 2.  Limiting is accomplished as a function of jumper position, low gain position is -12db and high gain position is -22db.  Please note any time the top is removed and a change is made the unit must be off and the power cable must be detached. 

    Also located near the input transformer is an INPUT IMPEDANCE SELECT.  Choosing the center most pins will configure the input transformer for hi impedance (200 ohms)  (5:1 turns ratio) and using two jumpers is for low impedance (50 ohms)  (10:1 turns ratio)

Output gain knob
    Continuously variable, controls that amount of overall gain that the unit can produce.  The amount of output gain is easily viewed on the VU meter with the meter select switch set to output.  Once the input gain is set for the desired amount of gain reduction, the output gain may be increased or decreased depending on the amount of overall gain needed.

    The bypass switch allows for immediate A/B comparison between the 1700 and the raw signal connected to the input XLR.   This switch is clearly marked and also has a red LED tip to indicate when you are bypassing the 1700.

90hz High Pass Filter
    Used to keep frequencies below 90hz from affecting the action of the compressor, resulting in a more dynamic low frequency spectrum when the compressor is in use.  An indicator LED shows when the HPF is engaged. 

On/Off power switch
    Located on the front panel.

Meter select switch
    This is a three position high quality Grayhill switch linked to the VU meter.  Each switch position is independently displayed, one at a time on the large VU meter.  Input indicates the amount of gain entering the 1700.  GR  indicates the amount of  gain reduction that is controlled by the input gain knob.  Output  indicates the amount of output gain and is controlled by the output knob.                       

Ratio switch
    This is a four position Grayhill switch.  Each setting will send your music to an independent tap located on the output transformer.  Each tap is specially designed to compress a portion or a preset amount of your music.  2:1 ratio setting means that for every 2dB of music entering the detection circuit (6AL5) , only one dB is allowed through the unit.  As we move to the remaining three positions the formula remains the same but compression amount change accordingly.  The remaining presets are 4:1, 8:1 and 12:1.

Release switch
    This is a five position Grayhill switch.  This switch is set according to taste and music type.  The slow setting is generally used for vocals and narration, while the faster setting is best suited for program material with more extreme dynamic range. 

Attack switch

    This switch is a six position Grayhill switch.  Similar to the release switch, settings are to taste.  The off or default position is a factory setting designed to produce the most organic compression characteristic unique to the 1700.

Balancing and adjustment trim pots
    Gain reduction adjustment is located below the VU meter.  To set the GR, first set meter switch to GR which will indicate current reading on the VU meter.  A reading above or below zero on the VU meter may be adjusted via GR adj.
For Input adjustment, set  meter switch to input and adjust via meter adj until VU meter reads zero

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