Doc Lloyd Audio DLA-2A User manual

INSTRUCTION MANUAL
LEVELING AMPLIFIER
MODEL DLA-2A
DOC LLOYD AUDIO
CHICAGO, IL

DLA-2A
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2
WARNING
This product generates high voltage to power vacuum tube electronics.
Remove power before replacing tubes and whenever product is not in use.
INTRODUCTION
The DLA-2A Leveling Amplifier is a meticulous recreation of an iconic studio compressor. This includes the input
transformer, output transformer, high voltage tube audio path, and the T4B optical attenuator module. Two
sidechain tubes are replaced with high voltage solid-state circuitry to significantly reduce size without impacting
the audio path.
Typical studio compressors require line level signals from low impedance sources. The DLA-2A has the standard
transformer balanced line input as well as a high impedance input with a balanced gain stage, providing direct
compatibility with guitar and bass.
The compressed output signal is passed to a transformer balanced line output that can be connected to a mixing
console or headphones as well as an instrument level unbalanced output that can be connected to a pedalboard or
amplifier.
DC power is applied to the tube heater filaments and does not generate 60 Hz hum, resulting in lower noise than
the classic reference design.
COMPONENTS
– Lundahl 1922 Input Transformer
– Lundahl 5402 Output Transformer
– Kenetek T4B Classic Optical Attenuator Module
– JJ ECC803 (Long Plate 12AX7) Vacuum Tube
– JJ 12BH7-A Vacuum Tube
– Calibrated VU Meter with Backlight
– Vishay Beyschlag Thin Film Professional Resistors
– Non-piezoelectric Class 1 Ceramic and Film Capacitors
– Daka-Ware Bakelite Knobs

DLA-2A
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CIRCUIT BLOCK DIAGRAM
CONNECTIONS
DC Power: Connect 12 VDC, 1.5A, center positive power supply.
Remove power when not in use to prolong tube life.
Tubes remain powered in bypass mode.
Input: Connect source audio equipment to either instrument input or line input.
Line input will override instrument input if both are connected.
Output: Connect line output to line-level equipment and instrument output to
instrument-level equipment. Both outputs can be used simultaneously.
CONTROLS
Peak Reduction: Controls gain of sidechain amplifier. Set for desired compression.
Gain: Controls make-up gain of audio amplifier. Set for desired output level.
VU Meter: Displays compression level in dB. Backlight indicates effect is engaged.
Bypass: Passes audio directly from line input to line output.
Instrument input and output buffers remain active.
Emphasis: Set fully clockwise for flat sidechain response (default).
Rotate counterclockwise to increase high frequency sensitivity.
Mode: Down position is low ratio compress mode. Up position is high ratio limit mode.
1968 MODEL 2A
TUBE AUDIO PATH
SOLID-STATE
T4B DRIVER
UNBALANCING
BUFFER (-15dB)
BALANCING
BUFFER (+15dB)
INST
UNBAL
(HI-Z)
LINE
BAL
(600Ω)
LINE
BAL
INST
UNBAL
+275V
+15V
-15V
+15V
-15V

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NOMINAL SPECIFICATIONS
Inst Input Impedance: 2 Megaohms Unbalanced
Inst Output Impedance: 100 Ohms Unbalanced
Line Input Impedance: 600 Ohms Balanced TRS
Line Output Impedance: 10 Ohms Balanced TRS
Input Power: +12 VDC at 1.5A, Center Positive
Internal High Voltage: +275 VDC
Internal Low Voltage: +15 VDC, -15 VDC
Gain/Peak Reduction: Up to 40 dB
Inst Input Level: 0 dBu maximum
Line Input Level: 16 dBu maximum
Compression Ratio: 4:1, Soft Knee
Attack Time: 0.2 milliseconds for 50% of full compression
Release Time: 60 milliseconds for 50% release, 0.5 to 5 seconds for complete
release depending upon the amount of previous reduction
Frequency Response: 30 Hz to 15 kHz, +/- 0.1dB
Noise: 75 dB below 10 dBu output level
Tube Complement: 12AX7, 12BH7
Dimensions: 7.4” L x 5.1” W x 3.9” H
Weight: 2.6 lbs.
Accessories - Power Adapter, 100-240VAC Input, 12VDC Output, US Plug
- Inline Switch Adapter, DC Power Jack
- TRS to XLR Adapter, Male to Male
- TRS to XLR Adapter, Male to Female

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COMPRESS MODE, 1kHz
LIMIT MODE, 1 kHz
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
-45 -40 -35 -30 -25 -20 -15 -10 -5 0
Instrument Output Level (dBu)
Instrument Input Level (dBu)
PR=0%
PR=20%
PR=50%
PR=80%
PR=100%
-45
-40
-35
-30
-25
-20
-15
-10
-5
0
-45 -40 -35 -30 -25 -20 -15 -10 -5 0
Instrument Output Level (dBu)
Instrument Input Level (dBu)
PR=0%
PR=20%
PR=50%
PR=80%
PR=100%