Heritage Audio 73 JR II User manual

USER MANUAL
MONO MIC/LINE PREAMP & D.I.
500 Series Module
73 JR II
August/2022)Rev.)1.0.)

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INTRODUCTION
CONTENTS
DESCRIPTION
GETTING STARTED
APPLICATIONS!
SPECIFICATIONS!
SIGNAL FLOW!
TROUBLE SHOOTING
WARRANTY STATEMENT
REGISTRATION!
RECALL SHEETS
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TABLE OF CONTENTS
Thank you for choosing the 73 JR II. Heritage Audio is dedicated to bringing you ´the sound of yesterday for tomorrow´.
We specialize in capturing that unique, enticing sound that everybody has fallen in love with. For years engineers,
producers and musicians have been yearning for that classic vibe. Usually the only option is to search for old, used
original equipment that is almost always in a questionable state of operation. This brings with it a whole lot of other
issues, making the experience less than desirable. Not to mention the very high prices asked for this equipment, which
makes them virtually unobtainable for the great majority. Now it´s possible to obtain that same sound with a brand new
piece that will give you all the problem-free, heavy-duty use you´ll need for years of music making history.
Peter Rodriguez
CEO!
Heritage Audio - Madrid, Spain
INTRODUCTION
© 2022 Heritage Audio S.L. is the sole owner of the copyright of all information and drawings contained in this manual which are not to be copied or
reproduced by any means or disclosed in part or whole to any third party without written permission.
Heritage Audio reserves the right to alter specifications without notice. The information in this manual has been carefully checked and is believed to
be accurate at the time of publication. However, no responsibility is taken by us for inaccuracies, errors or omissions nor any liability assumed for any
loss or damage resulting either directly or indirectly from use of the information contained within it.
73 JR II

DESCRIPTION
The 73 JR II is the 2021 update to the already classic 73 JR, a true 73 style mic preamp in a single 500 series slot with
some added features that will cover all the recording needs for engineers and musicians that don´t find the need to track
with eq.
Employing only discrete circuitry and conventional components, the 73 JR II is a faithful 3 stage all class A 73 preamp.
Styroflex and tantalum capacitors have been used throughout. No corners were cut.
The useful all discrete class A hi pass filter has been updated, making it sweepable from 20 to 220 Hz. Now it is even
easier to make your low end tighter without affecting desired frequencies.
The Line mode allows for re-amping of prerecorded tracks and it´s perfect for adding some class A color to lifeless
recordings.
The smart switched DI (automatically switches from MIC to DI mode when inserting a MONO ¼” jack) is an all discrete
Class A JFET circuit ahead of the MIC transformer, so all the juice is there. Since its introduction in 2013, it has become
a classic DI for bass.
Finally, special care has been taken with power handling, implementing internal +24 V slow turn on regulation (about 20
seconds to reach full voltage).This makes your 500 series enclosure´s power supply healthier and makes the 73 JR II
independent of the rest of the slots.
WHAT TO LOOK FOR IN A 500 SERIES 73 PREAMP:
There are several compromises usually made when adapting a 73 preamp for the 500 Series, especially the following 3.
You won´t find any of these in the 73 JR II:
•Eliminate one gain stage and run only up to 70 dB of gain. A “real deal” 73 mic pre must have 3 gain stages for a total
of 80dB of gain. Taking the first gain stage out and maxing out the other 2 allows for up to 70 dB of gain, but noise
figure and low end at high gain are seriously compromised.#The 73 JR II uses the full 3 gain stage circuit for up to 80
dB of gain with noise of -125 dBu EIN all over the gain positions.
•Use the readily available ±16 V power from the 500 Series protocol. By doing this, the magic distortion of a 73 amp is
compromised.#The 73 JR II uses a true 24volt on board power supply for identical performance and distortion point.
•Use of surface mount technology. Although there is no actual drawback in using SMD components, it should be
reflected in the price, not merely to enlarge the manufacturer´s profit. No 500 Series 73 mic pre using SMD should
cost more than $500.#The 73 JR II uses only discrete, through hole traditional components and hand labor for that
great 70s vibe.
THE 73JR II TRANSFORMERS:
No 73 preamp is such without the correct transformers. For the 73 JR II (and its predecessor the 73 JR), Heritage Audio
went a step further then the competition. The output transformer, the same used all along the Heritage´s line of
products, is a Carnhill gapped one made exclusively for us in the St Ives factory. The input transformer, again exclusive
to our company, is made in Carnhill´s Oxford factory, and has a big impact on the extra mojo of the unit. It is the same
one found in our higher end 80 Series modules and sets one of the main sonically differences in between the 73 JR II
and the competitors.
When looking for an exclusive sound, do not settle for non-exclusive transformers.
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GETTING STARTED
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D.I. INPUT
High Impedance Class A JFET
MIC PAD
20 dB Reduction Ahead of
Input Transformer
PHANTOM POWER
Activates 48 V
HIGH PASS FILTER ON
SWITCH
-3 dB at 82 Hz, Discrete Class
A
OUTPUT ATTENUATOR
Attenuates from 0 to Infinity
FRONT
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INPUT GAIN SWITCH
5dB Steps From 30 to 80
MIC INPUT IMPEDANCE
1200 Ωor 300 Ωwhen pressed
LINE
Switches from MIC/D.I. to Line
PHASE
Flips phase 180º
HIGH PASS FILTER FREQ
-3 dB at 82 Hz, Discrete Class
A
REAR
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SLOT CONNECTOR
Gold Plated
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1
500 SERIES CONNECTOR
+!
OUTPUT + (4 LEVEL)
OUTPUT - (4 LEVEL)
INPUT - (4 LEVEL)
INPUT + (4 LEVEL)
GND

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MIC
APPLICATIONS
CONDENSER MIC
USB - COMPUTER
LINE INPUT - AUDIO INTERFACE
D.I.
USB - COMPUTER
LINE INPUT - AUDIO INTERFACE
OUTPUT 1
73 JR II
SLOT 1
D.I. INPUT
ACTIVATE LINE/D.I. SWITCH
ACTIVATE +48V FOR CONDENSER MIC
OUTPUT 1
INPUT 1
73 JR II
SLOT 1