Anthony DeMaria Labs Liquid Mu ADL-1700 User manual
ADL-1700
Introduction
Congratulations on your purchase of the 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.
The 1700 has many practical applications for recording studios, tracking, mixing,
stereo buss, vocals and instruments, live concert sound reinforcement as well as for film
and broadcast work.
Installation
Audio Connections for Transformer Balance Systems
Back panel, XLR audio input and output are transformer balanced and floating,
meaning there is no ground connection from pin 2 and pin 3. For optimum results your
input signal should have an impedance of 600 ohms. Use good quality audio cables for
best results (Mogami, Canare or Monster cable, etc) Pin 2 or pin 3 can be wired hot. Be
consistent: if you wire pin 3 hot on the input, make sure to wire pin 3 hot on the output.
Please follow diagram 1 for the proper audio hookup.
Diagram 1
Input Connector
12
3
Output Connector
21
3
GND
1
- (cold)
2
+ (hot)
3
Or vice versa if your studio is 2 pin hot
1
Audio Connections for Transformer Balance Systems
If the 1700 must be used in an unbalanced system please follow the three steps below:
1. Connect the ground or shield of your audio cable to pin 2 of the XLR
2. Connect the hot wire to pin 3 of the XLR
3. Repeat step 1 and 2 when using a 1/4” jack (see diagram 2)
Please note, this set up is for audio systems with pin 3 hot. If your audio system
is pin 2 hot then connect the ground or shield of your audio cable to pin 3 and the hot
to pin 2. Remember to keep it the same on both the input and output.
Diagram 2
XLR Connector
12
3
1/4” Jack
GND or Shield 2 or 3
+ (Hot)
GND
1
- (cold)
2
+ (hot)
3
Or vice versa if your studio is 2 pin hot
AC Connections
The vacuum tubes in the 1700 operate at high voltages, 285-V and 105-V so
please be careful. Disconnect power cable when servicing or changing tubes. Avoid
touching the tubes with your fingers; instead we recommend rubber gardening gloves.
All servicing must be performed by ADL or a trained technician. Do not operate with top
cover off. Do not use near water and avoid any moisture. Always use a grounded AC
receptacle.
2
ADL assumes no responsibility for possible injury from electric shock while
servicing this product or operating it with the top cover off. Turning the unit off while not
in use will increase component life. If you have any questions, please contact ADL. To
further increase component life, please allow for adequate ventilation at rear of unit.
Because of the heat generated by the tubes we also recommend one rack space above
and below remain vacant for additional air flow.
1. Provided is an AC cable, please connect to back panel.
2. Connect AC plug to a properly grounded AC receptable only.
3. Apply power and allow for 15 minute “warm-up” before using.
Fuse Replacement:
Should it become necessary to change the fuse, first turn the unit off and unplug the
AC power cable from the receptacle. The fuse is located on the rear left side. Gently remove
the fuse cover and discard bad fuse and replace with correct new fuse. Please note, if your
unit is in constant need of new fuse, it may require a servicing so please contact us.
For 120-V . . . . . . . . . . . . . . . . . . . . 2-Amp Slow Blow 5x20mm
For 220-V . . . . . . . . . . . . . . . . . . . . 1-Amp Slow Blow 5x20mm
Front VU Meter Lamp:
To replace meter lamp simply unplug unit, remove top, unscrew faulty lamp and
replace with new lamp. Radio Shack # 272-1128 or Chicago Lamp #606-CM 40.
Operations
The 1700 employs the 6BCA, variable Mu, dual triode to achieve its smooth, soft
knee type compression. Control of the 6BC8 is handled by a 6H6, dual diode vacuum
tube, which adds a musicality to the way the 1700 operates.
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!
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Controls
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 master select switch set to GR (Gain Reduction). As per the original design,
jumpers are located on the main circuit board near the 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 the 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.
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Bypass
The bypass switch allows for immediate A/B comparison between the 1700 and
the raw signal connected to the input XLR. The 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 changes accordingly. The remaining presets are 4:1, 8:1 and 12:1.
5
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 Potts
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.
6BC8 Balance Procedure
Although we have painstakingly inspected all parts, components and
workmanship, components and tubes do change over time requiring your unit to be
serviced. A thumping sound while in compression may require replacing and readjusting
the 6BC8 tube.
Depending on your warrantly period, servicing should be completed by a qualified
technician or sent directly to ADL. This balancing procedure requires that the unit is
plugged in and receiving power. Located on the main circuit board is a 2-position header
clearly marked ( 3-VAC test 3--J ). Connect an AC 3-volt supply and remove input and
output audio signal.
1. Set attack and release controls to approximate mid setting
2. Input and output attenuators fully counterclockwise (maximum gain)
3. Set meter switch to output
4. Turn output attenuator clockwise until an indication is observed in the meter
5. Located on the back and on both sides of teh 6BC8 are two trim pots
6. The right most trim is used to balance the plate voltage (105-VDC)
6
7. The left most trim is used to balance the cathode voltage
8. Start by first adjusting the plate balance, then the cathode balance trim for
minimum meter deflection.
9. Output gain fully clockwise (zero attenuation)
10. Repeat step 8. Note meter indication.
11. Adjust the plate balance trim slightly clockwise until a change in meter indication is
observed. Then adjust cathode balance for a meter indication less than that noted
in step 10.
12. If meter indication is less than that noted in step 10, perform step 11 repeatedly
until absolute minimum meter indication is obtained.
13. Once the balancing procedure is completed, detach the 3-VAC ( 3-VAC test 3--J )
cable, replace top and resume recording.
14. 6BC8 / 6BZ8, If this tube is changed or fails, it will effect meter reading requiring
new GR meter adjustment
Please note: A minimum meter deflection of -20 dB will yield the best performance. If the
two sections of the 6BC8 (high frequency twin triode) are not reasonably symmetrical,
the tube will be noisy and cause a thumping sound when in compression. In the event
that the balancing procedure does not yield a usable tube, it must be discarded and
repeat balancing procedure with a new tube.
Specifications
Frequency Response
Clip
Distortion
Noise
Input/Output Impedance
Dimensions
Fuse
Tube Compliment
Shipping Weight
Power Consumption
7
. . . . . . . . . . . . . . . . . . 10 Hz ------ 30 K hz
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +28 Dbu
. . . . . . . . . . . . . . . . . . . . . . < 0.1% --10-GR =< 0.5%
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . --75 Dbu
. . . . . . . . . . . . . . . . . . . . . . . . 600 ohm
. . . . . . . . . . . . . . . Standard 19” 2-U depth 11-1/8”
. . . . . . . . . . . . . . . 120-V . . . . 2-Amp Slow Blow 5x20mm
220-V . . . . 1-Amp Slow Blow 5x20mm
. . . . . . . . . . . . . . . V--1 6BC8, V--2 12AX7A
V--3 12BH7A/12AU7A, V--4 6CL5
. . . . . . . . . . . . . . . . . . . . . . . . . 13 lb. or 15 Kg
. . . . . . . . . . . . . . . . . . . . . . . . Watts 28-W
WARRANTY
Anthony DeMaria Labs, Inc.
845-255-4695
This manual was created 10-28-13. The content, wording, diagrams, photos, etc. of
this manual are the sole property of ADL and may not in any way be reproduced, copied,
transmitted, or transcribed in any language without written authorization from ADL.
Our warranty is express or implied and specific only for a new ADL 1700 clearly
marked with a serial number issued by ADL and is in lieu of all other warranties. The ADL
1700 is covered by limited and conditional warranty starting from date of purchase for a
period of one year. This warranty applies to the original client/owner (individual who first
purchased the product) and may in no way be transferred to a second owner. ADL will
perform multiple inspections, tests and burn-in procedure to insure you are receiving a
product that is free from defects in materials and workmanship. If you receive a defective
1700 or damage was incurred in shipping, please notify us and we will arrange an
exhange for a new unit. The terms and conditions of this one year warranty may only
apply of the product was received by the purchaser in full working condition. In the event
that your 1700 malfunctions due to improper installation, use in any way which would
compromise the design of the unit, improper ventilation, alterations or modifications of
any kind, it would immediately void/nullify your warranty. In the event that a 1700 is
received as defective it must be sent back to our factory for repair. ADL will not assume
responsibility or be held liable for any 1700 that is damaged in transit.
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