R.R. Amplifiers MLP4 User manual

Before using this unit, carefully read the sections entitled: “USING THE UNIT SAFELY” and
“IMPORTANT NOTES” (p. 2; p. 4). These sections provide important information concerning the
proper operation of the unit. Additionally, in order to feel assured that you have gained a good
grasp of every feature provided by your new unit, this User manual should be read in its
entirety. The manual should be saved and kept on hand as a convenient reference.
Version
Date
Auteur
V1.1
26-2-2021
Remco Ranschaert
Copyright©2021 R.R.Amplifiers
All rights reserved. No part of this publication may be reproduced
in any form without the written permission of R.R.Amplifiers.
User manual
MLP4
R.R. Amplifiers

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USER MANUAL MLP4
1. Using the unit safely
INSTRUCTIONS FOR THE PREVENTION OF FIRE, ELECTRIC SHOCK, OR INJURY TO PERSON
About WARNING and CAUTION Notice
WARNING
Used for instructions intended to alert the user to the risk of death or severe injury
should the unit be used improperly
CAUTION
Used for instructions intended to alert the user to the risk of injury or material
damage should the unit be used improperly.
* Material damage refers to damage or other adverse effects caused with respect
to the home and all its furnishings, as well to domestic animals or pets.
-----------------ALWAYS OBSERVE THE FOLLOWING-----------------
WARNING
•Do not open or perform any internal
modifications on the unit.
•Do not attempt to repair the unit, or
replace parts. Refer all servicing to only
R.R.Amplifiers.
Never install the unit in any of the following
locations:
•Subject to temperature extremes (e.g.,
direct sunlight in an enclosed vehicle, near a
heating duct, on top of heat-generating
equipment); or are
•Damp (e.g., baths, washrooms, on wet
floors); or are
•Exposed to steam or smoke; or are
•Subject to salt exposure; or are
•Humid; or are
•Exposed to rain; or are
•Dusty or sandy; or are
•Subject to high levels of vibration and
shakiness
WARNING
•Make sure you always have the unit
placed so it is level and sure to remain
stable. Never place it on stands that
could wobble, or on inclined surfaces.
•Do not allow any objects (e.g., flammable
material, coins, pins); or liquids of any kind
(water, soft drinks, etc.) to penetrate the unit.
Immediately turn the power off, and request
servicing by R.R.Amplifiers, when:
• Smoke or unusual odour occurs
• Objects have fallen into, or liquid has
been spilled onto the unit; or
• The unit has been exposed to rain (or
otherwise has become wet); or
• The unit does not appear to operate
normally or exhibits a marked change in
performance.
•Protect the unit from strong impact.
(Do not drop it!)

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USER MANUAL MLP4
WARNING
•When cleaning the unit, only use a water
moistened cloth. Do not use a wet cloth, or
use other liquids, see Maintenance.
•This device needs proper grounding for
a save use.
CAUTION
•Try to prevent cords and cables from
becoming entangled. Be good for your
cables.
•Disconnect all cords coming from
external devices before moving the unit.
•Make all connections to the unit before
powering the device(s). This can prevent ear
or unit damage because units can produce
hard plopping or clicking noises while
powering up.

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USER MANUAL MLP4
2. Important Notes
Power Supply
Before connecting this unit to other devices,
turn off the power to all units. This will help
prevent malfunctions and/or damage to
speakers or other devices.
Placement
•Using the unit near power amplifiers (or
other equipment containing large power
transformers) may induce hum. To alleviate
the problem, change the orientation of this
unit; or move it farther away from the source
of interference.
•Noise may be produced if wireless
Communications devices, such as cell phones,
Are operated in the vicinity of this unit. Such
Noise could occur when receiving or initiating
a call, or while conversing. Should you
experience such problems, you should
relocate such wireless devices so they are at a
greater distance from this unit, or switch them
off.
•When moved from one location to
Another where the temperature and/or
humidity is very different, water droplets
(condensation) may form inside the unit.
Damage or malfunction may result if you
attempt to use the unit in this condition.
Therefore, before using the unit, you must
allow it to stand for several hours, until the
condensation has completely evaporated.
•Depending on the material and
temperature of the surface on which you
place the unit, its rubber feet may discolour or
mar the surface.
You can place a piece of felt or cloth under
the rubber feet to prevent this from
happening. If you do so, please make sure
that the unit will not slip or move accidentally.
Maintenance
• For everyday cleaning wipe the unit with a
soft, dry cloth or one that has been slightly
dampened with water. To remove stubborn
dirt, use a cloth impregnated with a mild,
nonabrasive detergent. Afterwards, be sure to
wipe the unit thoroughly with a soft, dry cloth.
• Never use benzine, thinners, alcohol or
solvents of any kind, to avoid the possibility of
discoloration and/or deformation.

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USER MANUAL MLP4
3. Additional Precaution
•Use a reasonable amount of care when using the unit’s buttons, switches, or other
controls; and when using its jacks and connectors.
Rough handling can lead to malfunctions.

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USER MANUAL MLP4
Table of Contents
1. Using the unit safely ....................................................................................................................................................2
2. Important Notes ...........................................................................................................................................................4
3. Additional Precaution..................................................................................................................................................5
4. What’s in de box...........................................................................................................................................................7
5. Introduction ...................................................................................................................................................................8
Key Features................................................................................................................................................8
Website.........................................................................................................................................................8
6. Top Panel Description.................................................................................................................................................9
7. Front connection Panel Description ...................................................................................................................... 10
8. Back connection Panel Description ........................................................................................................................11
9. Connections..................................................................................................................................................................11
10. Midi.................................................................................................................................................................................11
11. Unit Specifications...................................................................................................................................................... 12
12. Power supply............................................................................................................................................................... 12
13. Midi channel setting .................................................................................................................................................. 12
14. Warranty....................................................................................................................................................................... 13
Exclusions................................................................................................................................................... 13
Limits of Liability....................................................................................................................................... 13
How to Obtain Service Under this Warranty..................................................................................... 13

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USER MANUAL MLP4
4. What’s in de box
When you open the box, please check that al items are present. Please contact R.R.Amplifiers when
something is missing.
•MLP4
•This User manual printed.
Tips & Tricks for best results
Use a good quality power supply (isolated outputs) for you effects.
This will prevent groundloops that may cause hum or other unwanted noises or side
effects.
Use good quality (patch) cable.
When good quality (patch) cable is used, with good quality TS ¼” connectors, the best
results in eighter quality and reliability will be achieved.
You can use an MD or DAT digital recorder to record digital audio, but a cable for
connecting your digital device to the UA-25EX is not included. You’ll need to obtain this
separately.

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USER MANUAL MLP4
5. Introduction
Congratulations on choosing this R.R.Amplifiers device. Our devices are developed and build with the
highest attention and quality possible.
We are very confident that you will be familiar with the MLP4 very quickly, and will appreciate the
versatility and high quality of this unit.
By using the MLP4 every effect will be treated as if it’s the only one in the chain. It will “see” and “feed”
the same impedance, no matter how many effects are active. And only the active loop puts its effect
into the signal chain. This ensures a very transparent sound without any tonal losses. The small size
enclosure will make it easy to implement it in your system (pedalboard or rack system).
Remco Ranschaert
R.R.Amplifiers
Leeuwenlaan 8
4532AD Terneuzen
[phone]
[email protected]
www.rramplifiers.nl
Key Features
•Small-sized unit
•High quality audio components are used
•High quality input buffer
•Independent line drivers for every loop
•Relay switching
•Midi In and thru
•340 pre-sets in PC. (CC mode available on when ordered)
•Midi channel set thru dip-switches
Website
This User manual is also available on the website: rramplifiers.nl/mlp4

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USER MANUAL MLP4
6. Top Panel Description
1. Channel
With this Dip-switches you can preset the midi channel (see table in 13 for settings)
You need to reboot after adjusting de setting.
2. Buttons loop 1 -4
Select/monitor the loop. Press to activate. When a midi program change has been received,
and one or more loops are selected, the Save button will blink. Press the Save button to save
this preset/program change.
3. Save button
When you press the button while blinking, that loop(s) is saved for that specific Midi Program
Change. By ignoring the Blinking Save button, the Program Change will not be saved.
4. PWR
Led to monitor power supply.
5. Midi indicator
Blinks when a midi message is coming in.

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7. Front connection Panel Description
1. Input/output
Input from guitar or other device , and output to an amp or other device. This path utilizes a
high quality buffer.
2. Sends
Mono ¼” Jack’s. All these Sends utilizes our high quality line drivers for best and stable
impedance. Every effect “sees” and “feeds” the same Impedance. When the loop is not
selected, the send to the effect is grounded by relay.
3. Returns
Mono ¼” Jack’s. From your effect, it “sees” always a 50kΩ impedance. When a loop is
selected, a relay puts also your effect into the chain.

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8. Back connection Panel Description
1. Power supply
Input 12VDC centre negative, 250mA
2. Midi In
Standard Midi din-connector. .
3. Midi Thru
This a copy of the incoming midi.
9. Connections
All connections are TS ¼”jack connections.
Please use good quality signal/guitar cable for best results.
10. Midi
The Midi Thru is a copy of the incoming Midi-in signal.
The Unit responds to PC’s.
the units can process PC’s till PC#340.
Note: CC’s is possible, please note this when ordering. Standard loop 1 = CC#1, loop 2 =CC#2, loop 3
= CC#3 and loop 4 = CC#4. When you order, we can program your desired CC’s.
When you want to change this later, please contact us for support.

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11. Unit Specifications
Input Impedance >1MΩ
Loop returns Impedance 50kΩ
Crosstalk Level <120dBu
Noise Floor <120dBu
Frequency Response 20Hz to 80kHz
Max Input Level +24dBu
Gain unit is unity gain
loop Switching (electromechanical relay switching)
Dimensions 134 x107 x 56 mm
Use between 0°C and 40°C
12. Power supply
Input Voltage 12V centre negative
Required Current 250mA
13. Midi channel setting
X = on
Channel 1 2 3 4
1 o o o o
2 x o o o
3 o x o o
4 x x o o
5 o o x o
6 x o x o
7 o x x o
8 x x x o
9 o o o x
10 x o o x
11 o x o x
12 x x o x
13 o o x x
14 x o x x
15 o x x x
16 x x x x
Channel dipswitch setting

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14. Warranty
R.R.Amplifiers warrants the product to be free from defects in material and workmanship for a period
of two (2) year from the original date of purchase. If the product fails within the warranty period,
R.R.Amplifiers will repair or, at our discretion, replace the product at no cost to the original purchaser.
Exclusions
This warranty covers defects in manufacturing discovered while using this product as recommended
by R.R.Amplifiers. This warranty does not cover loss or theft, nor does the coverage extend to damage
caused by misuse, abuse, unauthorized modification, improper storage, lightning, or natural disasters.
Limits of Liability
R.R.Amplifiers will not be held liable to any party for damages that result from the failure of this
product. Damages excluded include, but are not limited to, the following: lost profits, lost savings,
damage to other equipment, and incidental or consequential damages arising from the use, or
inability to use this product. In no event will R.R.Amplifiers be liable for more than the amount of the
purchase price, not to exceed the current retail price of the product. R.R.Amplifiers disclaims any other
warranties, express or implied. By using the product, the user accepts all terms herein.
How to Obtain Service Under this Warranty
For all customers: Contact R.R.Amplifiers through our website at http://www.rramplifiers.nl, or
dropping a email to inf[email protected] . Proof of original ownership may be required in the form of
a purchase receipt.