Heritage Audio HERCHILD 670 User manual

USER MANUAL
April/2022)Rev.)1.0.)
DUAL CHANNEL TUBE COMPRESSOR
AMERICAN HERITAGE
MODEL 670

INTRODUCTION
CONTENTS
DESCRIPTION
GETTING STARTED
DC THRESHOLD SETTINGS
TIME CONSTANT SETTINGS
APPLICATIONS!
SPECIFICATIONS!
SIGNAL FLOW!
TROUBLE SHOOTING
REGISTRATION
WARRANTY STATEMENT!
RECALL SHEETS
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TABLE OF CONTENTS
Thank you for choosing the HERCHILD Model 670. 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.
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HERCHILD 670
AC POWER CORD EU & US

DESCRIPTION
The HERCHILD model 670 is our newest release and one of the products we are proudest of. A tube-based audio
compressor with a striking resemblance to one of the most famous compressors of all time, the Fairchild 670. After years of
research, development and new designs we are finally ready to release this beast to the public. While making sure to
capture all the lush sound and mystique of the original we were able to improve on several aspects and offer a more
reliable, more durable, modern version that will last you for decades to come. The HERCHILD Model 670 contains nothing
less that 22 valves and 9transformers to achieve that indistinguishable, classic, triumphant sound that we all know and
love. The original intention of the his historical compressor was to be used in the cutting of lacquer masters for vinyl
albums, but it soon became an industry standard for getting that all enveloping sound that takes us to another level. The
Fairchild Model 670 is found on almost all of the classic releases in the 60´s and 70´s, defining the sound of a generation…
or two.
The grandaddy of all tube-based compressors had a relatively limited amount produced, somewhere between 500 and
1,000 units. Therefore, some 60 years later there are only a small amount that remain today. There are even fewer that are
totally usable as years have gone by since it´s late 1950´s introduction so many units aren´t exactly as they once were.
Maintenance is obligatory on a high-end piece like this and unfortunately, too many of them have simply been neglected
and aren´t up to their optimal specifications. This means an alternative is needed. And this is where the HERCHILD Model
670 comes in, to once again offer that magic that only this compressor design can.
Our HERCHILD Model 670 offers a couple of new and ever so helpful features. The user now has immediate access to the
all important DC THRESHOLD. This control basically combines adjustments to the progressively developing curved RATIO
and the KNEE simultaneously through 4 different settings varying from a gentle slope to a more pronounced and aggressive
slope. This control really does put sound manipulation right at your finger tips as opposed to the original´s out of reach and
inconvenient screw adjuster. The other main addition is something no modern day studio can be without, a side chain filter.
With the SC FILTER on the HERCHILD Model 670 you have 4 different frequencies to choose from: 50, 100, 200 and
350Hz. Using this feature you now have lots more control over just how much compression will be applied as you can
make it less sensitive to the lower frequencies therefore allowing more compression where you need it and for the track to
stay powerful.
The HERCHILD Model 670 also has the AGC section to determine which mode it will work in. There are 4 modes of
operation to choose from: IND, LINK, LAT VERT &LAT VERT LINK. The IND & LINK modes are for normal stereo
operation. IND give you independent control for each channel while LINK, obviously, links the two channels operation
together so both channels are controlled by (the LEFT-LAT channel´s settings.) taking the average from the two channel´s
settings to determine what the overall stereo control will be. The LAT VERT mode is originally from the days of using a
cutting lathe to prepare vinyl records. It was crucial to carefully decide the depth and the width of the grooves, so you had
precise control over both aspects in this mode. Nowadays, people have discovered the advantages of mixing and
mastering with MID/SIDE processing as it allows you creative control over the center and side signals of a stereo track
separately. LAT VERT is the equivalent to MID/SIDE and when used properly it really gives you the control to make your
songs sound wider, deeper and more focused. And the last option is LAT VERT LINK and is again for MID/SIDE processing
but this time with the two channels linked together and controlled by taking the average from the two channel´s settings to
determine what the overall control will be.
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GETTING STARTED
4
FRONT
1-METER ADJUSTMENT SCREW: This is not meant to be user adjustable. We recommend not adjusting this and to
contact an official repair service.
2-POWER SWITCH: Turns the unit on or off.
3-RED JEWEL INDICATOR LIGHT: Simply indicates that the equipment is ´On´.
4-VU METER: Indicates GAIN REDUCTION.
5-ZERO ADJUSTMENT SCREW: Use this screw to set the meters to 0dB on the VU meter when there is no
compression happening. It is normal for this setting to drift for the first 30 minutes of operation.
6-METERING: Knob to choose the readout of the VU meter, either for adjusting the balance of the valves or the gain
reduction being applied.
7-BALANCE ADJUSTMENT SCREW: Use this screw to balance the circuit for optimum performance based on the
particular set of tubes installed.
8- INPUT GAIN CONTROL: This knob is used to control the amount of input gain applied. This is actually an attenuator
that reduces the the input by up to -20dB.
9- AC THRESHOLD: The threshold knob determines when the compression begins. It’s used to decide when and how
much gain reduction takes place. When in the fully counter-clockwise position, the HERCHILD Model 670 will not
compress at all. As the threshold control is turned clockwise, the amount of compression will progressively increase.
10- DC THRESHOLD: Here you decide what kind of curve will be applied to the compression. It is similar to a knee and
ratio effect combined. So at the most counter-clockwise position the HERCHILD Model 670 responds like a limiter with
immediate and aggressive action happening as soon as the AC THRESHOLD is passed. While as you turn it clockwise
more of gradual, progressive effect occurs until you have a very slight compression happening at all times.
11-SC FILTER: This is a side chain filter applied only to the control signal to decide if and where the HERCHILD Model
670 will be less sensitive to certain frequencies. There are 5 choices available: 50, 100, 200, 350Hz and OFF.
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4
1
5
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5
REAR
All XLRs are:
Pin 1: GND!
Pin 2: Hot!
Pin 3: Cold
1
2
3
3
2
1
GND!
Hot (+)!
Cold (-)
MALE XLR
FEMALE XLR
1-LINE INPUTS (x2): Female Gold Plated XLR Connector.
2-LINE OUTPUT (x2): Male Gold Plated XLR Connector.
3-VALVES: (22) User changeable valves with easy access.
4-POWER INPUT: IEC standard power input connector.
5-VOLTAGE SELECTOR: Here you can select the correct voltage input according to the country you are in.
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3
1
2
5
12-TIME CONST: Here you have 6 options for the attack and release timings giving you combinations for fast and slow
timings. (Please see the TIME CONSTANT Section for exact timings.)
13-AGC - Here you choose between 4 different modes of operation for the HERCHILD Model 670.
•The first being ´IND´ and refers to each channel being individual with it´s own independent control.
•The next, ´LINK´ will tie the channels together and base the compression applied on whichever channel is producing
the most compression to be used for both channels. This is used for stereo operation.
•The ´LAT VERT´ takes us way back to the vinyl cutting days and refers to the lateral and vertical adjustments when
cutting grooves onto vinyl records. This is similar to what we refer today as Mid & Side. A very effective way of
widening a stereo image and improving and strengthening the center image. Here the upper channel of the
HERCHILD Model 670 controls the ´Side´ information and the lower channel controls the middle or ´Mid´ information.
•´LAT VERT LINK´ is the same but with the controls linked together, once again deriving the overall compression
from whichever channel is producing the most at any given moment.

DC THRESHOLD
SETTINGS
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MEDIUM KNEE & PROGRESSIVE
HIGHER RATIO
.3 Seconds for individual peaks
10 Seconds for multiple peaks
25 Seconds for consistently high program level
RELEASE
.2 ms
.2 ms
.4 ms
.4 ms
.4 ms
.2 ms
2 Seconds for individual peaks
10 Seconds for multiple peaks
5 Seconds
2 Seconds
.8 Seconds
.3 Seconds
ATTACK
1
2
3
4
5
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TIME CONSTANT
SETTINGS
MEDIUM KNEE & PROGRESSIVE
LOWER RATIO
HARD KNEE
HIGH RATIO (LIMITING)
SOFT KNEE & VERY PROGRESSIVE
MEDIUM RATIO
The HERCHILD
Model 670, just like
the original, uses a
progressively
developing ratio
curve so it is not
possible to describe
the ratio as 2:1, 10:1
or anything so exact.

VOICE
TRACK INSERT
APPLICATIONS
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MONITOR
SPEAKERS
THUNDERBOLT
COMPUTER
LEAD VOCAL
CHANNEL 1
BACKGROUND VOCAL
CHANNEL 2
BACKGROUND VOCAL
OUTPUT 2
LEAD VOCAL
OUTPUT 1
PROCESSED LEAD VOCAL
LINE INPUT 1
AUDIO
INTERFACE
PROCESSED BACKGROUND VOCAL
LINE INPUT 2
INDIVIDUAL OPERATION

INSTRUMENT
RECORDING
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MONITOR
SPEAKERS
THUNDERBOLT
COMPUTER
BASS GUITAR
CHANNEL 1
ELECTRIC GUITAR
CHANNEL 2
PROCESSED BASS GUITAR
LINE INPUT 1
AUDIO
INTERFACE
PROCESSED ELECTRIC GUITAR
LINE INPUT 2
BASS
D.I. INPUT - CH 1
GUITAR FX PEDAL
BASS
OUTPUT - CH 1
GUITAR
OUTPUT - CH 2
INDIVIDUAL OPERATION

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MIX
STEREO BUSS
INSERT
MONITOR
SPEAKERS
THUNDERBOLT
COMPUTER
MIX LEFT
CHANNEL 1
MIX RIGHT
OUTPUT 2
MIX LEFT
OUTPUT 1
PROCESSED MIX LEFT
LINE INPUT 1
AUDIO
INTERFACE
PROCESSED MIX RIGHT
LINE INPUT 2
MIX RIGHT
CHANNEL 2
TWO POSSIBLE OPTIONS
- LINKED STEREO
- LINKED MID/SIDE

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MASTERING
MONITOR
SPEAKERS
THUNDERBOLT
COMPUTER
AUDIO
INTERFACE
As recommended, a blank panel
is used to allow proper spacing
for the unit to ventilate correctly.
SUCCESSOR
LEFT & RIGHT
LINE OUTPUTS
LEFT & RIGHT
LINE INPUTS
MASTERED MIX
STEREO MIX DAW
LEFT & RIGHT
LINE OUTPUTS
MOTORCITY EQ
LEFT & RIGHT
LINE OUTPUTS
HERCHILD 670
LEFT & RIGHT
LINE OUTPUTS
HERCHILD 670
LEFT & RIGHT
LINE INPUTS
TWO POSSIBLE OPTIONS
- LINKED STEREO
- LINKED MID/SIDE
EQUALIZER
LIMITER

BASS GUITAR COMPRESSION
TRIGGERED FROM
BASS DRUM
MONITOR
SPEAKERS
THUNDERBOLT
COMPUTER
BASS GUITAR
CHANNEL 1
BASS DRUM
CHANNEL 2
PROCESSED BASS GUITAR
DAW LINE INPUT 1
AUDIO
INTERFACE
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BASS GUITAR
D.I. INPUT - CH 1
BASS DRUM
MIC INPUT - CH 2
LINKED OPERATION NECESSARY
BASS DRUM
DAW LINE INPUT 2
BASS DRUM
CONTROL SIGNAL
INPUT R - HERCHILD 670
AUDIO SPLITTER

SPECIFICATIONS
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SIGNAL FLOW
LINE INPUT
LINE OUTPUT
CLASS A !
VALVE AMPLIFIER
INPUT
TRANSFORMER
OUTPUT
TRANSFORMER
•Input Impedance: 2K Ω
•Output Impedance: 600 Ω
•Output Level: +4 or +8 VU (+30dBu clipping point)
•Frequency Response: 40Hz to 15kHz +/- 1db
•Self Noise: Less than -82dBu
•Harmonic Distortion: Less than 1% at any level up to +18dBu output (no limiting)
• Dimensions (W x H x L): 482mm x 265mm (6 Rack units) x 200mm
•Weight: 13.3 Kg
LINE INPUT
LINE OUTPUT
CLASS A !
VALVE AMPLIFIER
INPUT
TRANSFORMER
OUTPUT
TRANSFORMER
LEFT-LAT
RIGHT-VERT

TROUBLE SHOOTING
PROBLEMS
SOLUTIONS
There is almost no sound coming from the HERCHILD
Model 670.
Make sure you have raised the INPUT GAIN to a sufficient
level.
There doesn´t seem to be any compression taking place.
Make sure you have adjusted the AC THRESHOLD level
to a reasonable setting.
I´m getting way too much compression for what I need.
Try lowering the AC THRESHOLD.
I´m still getting way too much compression for what I
need.
Try adjusting the SC FILTER to make the HERCHILD
Model 670 less sensitive to the lower frequencies.
The HERCHILD Model 670 does not seem to be reacting
as it should.
Have you allowed the recommend 30 minutes for the unit
to warm up?
The readings on the VU meter don´t seem to correspond
with what is actually happening.
Sounds like it´s time for some calibrating.
The compression I am getting is altogether too aggressive
for what I am looking for.
Try a different setting on the DC THRESHOLD to alter the
Ratio/Knee.
The compression I am getting is still altogether too
aggressive for what I am looking for.
Try a different setting on the TIME CONST selector to
ease the attack and release controls. (See Time Constant
Settings for exact timings).
The compressor isn´t responding the way it should.
Double check to make sure you have selected the desired
mode of operation in the AGC section.
The compressor seems to be heating up excessively.
Have you installed a blank rack panel above and below
the unit to assure proper ventilation?
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* For any further doubts or questions please get in contact with us at: [email protected]!

LIMITED 2 YEAR WARRANTY
Heritage Audio HERCHILD Model 670 is warranted by Heritage Audio SL to be free from defects in materials and
workmanship for the period of 2 years to the original purchaser. In the event of such defects, the product will be repaired
without charge or, at our option, replaced with a new one if delivered to Heritage Audio prepaid, together with a copy of
the sales slip or other proof of purchase date. The warranty excludes problems due to normal wear, abuse, shipping
damage or failure to use the product in accordance with the specifications.
Heritage Audio shall not be liable for damages based upon inconvenience, loss of use of the product, loss of time,
interrupted operation or commercial loss or any other damages, whether incidental, consequential or otherwise.
This warranty is not transferable.
Heritage Audio and the Heritage Audio “H” logos are registered Trademarks owned and/or licensed by Heritage Audio.
REGISTRATION
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Please visit our website:
WARRANTY STATEMENT
https://heritageaudio.net/registration/

RECALL SHEETS
12
Session / Title: Track: Connected Equipment: !
Date: Instrument: Notes:

www.heritageaudio.com
HERITAGE AUDIO. C/ Alfonso Gómez, 38, 3C. 28037 Madrid – Spain. Tel: [phone]
[email protected]