Rupert Neve Designs Portico 500 Series User manual

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Serial #:
Operations Manual
Portico 511
500 Series Mic Pre with Silk

2
PORTICO 511 MIC PRE WITH SILK
Thank you for your purchase of the 511: 500 Series Mic Pre with Silk. Everyone at
Rupert Neve Designs hope you enjoy using this tool as much as we have enjoyed
designing and building it. Please take note of the following list of safety concerns
and power requirements before the use of this or any Portico Series product.
SAFETY
It’s usual to provide a list of “do’s and don’ts” under this heading but mostly these
amount to common sense issues. However here are some reminders:
Don’t operate your Portico™ module in or around water! Electronic equipment and
liquids are not good friends. If any liquid is spilled such as soda, coffee, alcoholic
or other drink, the sugars and acids will have a very detrimental effect. Sugar
crystals act like little rectiers and can produce noise (crackles, etc.). SWITCH OFF
IMMEDIATELY because once current starts to ow, the mixture hardens, can get
very hot (burnt toffee!) and cause permanent and costly damage. Please contact
support as soon as possible at [email protected] for resolution.
1) Read these instructions.
2) Keep these instructions.
3) Heed all warnings.
4) Follow all instructions.
5) Do not use this apparatus near water.
6) Clean only with dry cloth.
7) Do not block any ventilation openings. Install in accordance with the
manufacturer’s instructions.
8) Do not install near any heat source such as radiators, heat registers, stoves, or
other apparatus (including ampliers) that produce heat.
9) Refer all servicing to qualied service personnel. Servicing is required when the
apparatus has been damaged in any way, such as when power-supply cord or plug
is damaged, liquid has been spilled or objects have fallen into the apparatus, the
apparatus has been exposed to rain or moisture, does not operate normally, or has
been dropped.
10) Do not expose this apparatus to rain or moisture.
511 DESCRIPTION
With a truly legendary microphone preamplier and the exibility of variable Silk/
Texture, Rupert Neve designed the 511 to provide classic sonic performance with
500-series value. Incorporating the pristine preamp circuitry from the 517, the
universally useful sweepable high pass lter from the 5012, and the thickening
power of a variable silk circuit derived from our agship Portico II Channel, the 511
is a Rupert Neve-designed workhorse for all your most important tracks.

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PORTICO 511: BLOCK DIAGRAM
PORTICO 511: FRONT PANEL
0 - 66dB
-IN
OUTPUT STAGE
OUT PUT TRANS F ORME R
OUT PUT
20Hz - 250Hz
HPF
+/-6dB
TR IM
48V
PHASE
SILK
R ED
TEXTUR E
Level Meter
+IN
HPF ENGAGE
+INP UT
-INP UT
STEPPED GAIN
CONTINUOUS TR IM
+48VDC
36
30
24
18
12
60dB 66
60
54
48
42
20Hz 250Hz
100
MIN MAX
TEXTURE
0dB
-6 +6
TRIM
GAIN
POWER
SILK
48V
HPF
HPF
Rupert Neve
Designs 511
MIC PRE
+ SILK
22
20
18
14
10
4
-2
-10
LEVEL
Trim
+/-6dBLevelControl
Gain
66dBGainin6dBSteps
PolarityReverse
Reversesthepolarityof
themicpresignal
Texture
Determinestheamountof
theSilkeffect
PowerLED
Indicatespowerfrom500SeriesRack
HPF
CountinouslyVariableHPFfrom20-250Hz
engagedbyHPFbutton
48V
Engagesthe48VPhantomPower
LevelMeter
8-segmentpeakLEDmeterforthe
micpreoutput(preSilk)
SilkRed
EngagestheredSilkmodecontroledbythe
textureknob

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DESIGN NOTES FROM MR. RUPERT NEVE
From Rupert Neve: In former years, before the introduction of solid state ampliers,
transformers were necessary to step down from the very high input impedance
of tubes, and to provide a balanced input for the microphone line. An input
impedance of 1,000 or 1,200 ohms became established for microphones having a
source impedance of 150 or 200 ohms, with connection being made on a twisted
twin screened cable (This type of cable, while excellent for low impedance work,
has high capacitance between its conductors and between each conductor and
screen. Resultant high frequency losses are excessive with high impedance sources
like piezo pickups and may cause resonances with magnetic pickups.). Condenser
microphones worked off high voltage supplies (250V!) on the studio oor which
polarized the diaphragms and powered a built-in pre-amplier.
More and more microphones were needed as “Pop” music gained ground and
this led to the popular and efcient method of 48-volt “Phantom” powering that
was built into the multi-channel recording console – in place of numerous bulky
supplies littering the studio, a miniature pre-amplier now being tted inside the
microphone casing.
The 48-volt supply was fed to the microphone through balancing resistors so it
was impossible for all of this voltage to actually reach the microphone, resulting in
low polarizing volts to the microphone capsule and virtual starvation of the little
pre-amp inside the microphone. Nevertheless amazingly good microphones were
designed and made, becoming the familiar product we use today.
If a low value resistive load is connected to the output of an amplier, that amplier
has to produce power in order to maintain a voltage across that load. Obviously
if we want more voltage (output from the microphone) we need to provide a
larger supply for the amplier or design ampliers with a higher input impedance,
and therefore a lighter load. A microphone is a voltage generator, not a power
amplier. Most microphones give their most accurate performance when they are
not loaded by the input impedance of a traditional preamplier. If the microphone
uses an electronic circuit (transformerless) output, a low value of load impedance
can possibly stress the little microphone pre-amplier, causing decreased slew rate
and compression at high levels.
On the other hand, a high value of load impedance allows the microphone to
“breathe” and give of its best, this being particularly advantageous with very high
level percussive sounds. If the microphone has an inductive source (such as would
be the case if it has a transformer output) a low value of load impedance causes the
high frequencies to roll off due to leakage inductance in the transformer in addition
to the above amplier distortion (This can be an advantage with some condenser
microphones!).
For this reason we have provided a high value of input impedance that will load
microphones to the smallest possible extent and makes the best possible use of that
limited “Phantom” 48-volts supply.

5
DYNAMIC RANGE
Traditionally, high quality microphones such as ribbons, had very low source
impedances – as low as 30 ohms at the output of a ribbon matching transformer.
Moving coil microphones were higher impedance, but had not been standardized
as they are today. Condenser microphones, before the days of semiconductors,
used tube pre-ampliers that were coupled to the outgoing line with an impedance
matching transformer. Microphone ampliers, such as in a mixing console, also
used tubes, which typically have a high input impedance.
Microphones are voltage generators, not power generators. At the low operating
level of a microphone, it is always desirable to deliver the maximum possible
signal voltage into the amplier. It was traditional to provide an amplier
input impedance of about 1,000 or 1,200 ohms; about 5 or 6 times the source
impedance of the microphone. This provided relatively low loading on the
microphone – whatever its type – and went a long way to avoid voltage loss.
In the early 1960’s when the “Pop” music scene was exploding and sound levels
in the Studio became very high, there was concern that the capsule ampliers in
condenser microphones would overload if the console input impedance was too
low. In the early days of consoles I was asked to provide higher input impedance
than the normal 1,000 ohms. Because the microphone preampliers in the early
recording consoles used transformer gain in the input stage , this resulted in less
“step-up” in the console input transformer and there were then fears that we would
lose out at the other end of the scale; noise. The fact that microphones were less
heavily loaded allowed an increased microphone signal. The reduced loading also
resulted in less deviation of frequency response due to variation of microphone
impedance and consequently less distortion at high levels.
The Portico 511 microphone amplier provides an input impedance of 10,000
ohms which means that variations in microphone source impedance with
frequency, have only a very small effect on the sonic quality. This high input
impedance has minimal effect on microphone output and loading which results
in mic distortion which is very low, adding up to a noticeable improvement in
“transparency”.
A NOTE ON DISTORTION
The human hearing system is a remarkably complex mechanism and we
seem to be learning more details about its workings all the time. For example,
Oohashi demonstrated that arbitrarily ltering out ultrasonic information that
is generally considered above our hearing range had a measurable effect on
listener’s electroencephalo-grams. Kunchur describes several demonstrations
that have shown that our hearing is capable of approximately twice the timing
resolution than a limit of 20 kHz might imply (F=1/T or T=1/F). His peer reviewed
papers demonstrated that we can hear timing resolution at approximately with 5
microsecond resolution (20 kHz implies a 9 microsecond temporal resolution,
while a CD at 44.1k sample rate has a best-case temporal resolution of 23
microseconds).
It is also well understood that we can perceive steady tones even when buried

6
under 20 to 30 dB of noise. And we know that most gain stages exhibit rising
distortion at higher frequencies, including more IM distortion. One common IM
test is to mix 19 kHz and 20 kHz sine waves, send them through a device and then
measure how much 1 kHz is generated (20-19=1). All this hints at the importance
of maintaining a sufcient bandwidth with minimal phase shift, while at the
same time minimizing high frequency artifacts and distortions. All of the above
and our experience listening and designing suggest that there are many subtle
aspects to hearing that are beyond the realm of simple traditional measurement
characterizations.
The way in which an analog amplier handles very small signals is as important
as the way it behaves at high levels. For low distortion, an analog amplier must
have a linear transfer characteristic, in other words, the output signal must be an
exact replica of the input signal, differing only in magnitude. The magnitude can be
controlled by a gain control or fader (consisting of a high quality variable resistor
that, by denition, has a linear transfer characteristic.) A dynamics controller - i.e.
a compressor, limiter or expander - is a gain control that can adjust gain of the
amplier very rapidly in response to the uctuating audio signal, ideally without
introducing signicant distortion, i.e. it must have a linear transfer characteristic.
But, by denition, rapidly changing gain means that a signal “starting out” to be
linear and, therefore without distortion, gets changed on the way to produce a
different amplitude.
Inevitably our data bank of “natural” sound is built up on the basis of our personal
experience and this must surely emphasize the importance of listening to “natural”
sound, and high quality musical instruments within acoustic environments that
is subjectively pleasing so as to develop keen awareness that will contribute to a
reliable data bank. Humans who have not experienced enough “natural” sound
may well have a awed data bank! Quality recording equipment should be capable
of retaining “natural” sound and this is indeed the traditional measuring stick. And
“creative” musical equipment should provide the tools to manipulate the sound
to enhance the emotional appeal of the music without destroying it. Memory
and knowledge of real acoustic and musical events may be the biggest tool and
advantage any recording engineer may possess.
One needs to be very careful when one hears traces of distortion prior to recording
because some avors of distortion that might seem acceptable (or even stylish)
initially, may later prove to cause irreparable damage to parts of the sound (for
example, “warm lows” but “harsh sibilance”) or in louder or quieter sections of
the recording. Experience shows that mic preamps and basic console routing paths
should offer supreme delity otherwise the engineer has little control or choice of
recorded “color” and little recourse to undo after the fact. Devices or circuits that
can easily be bypassed are usually better choices when “color” is a consideration
and this particularly is an area where one might consider comparing several such
devices. Beware that usually deviations from linearity carry at least as much long-
term penalty as initial appeal, and that one should always be listening critically
when recording and generally “playing it safe” when introducing effects that cannot
be removed.

7
1. Tsutomu Oohashi, Emi Nishina, Norie Kawai, Yoshitaka Fuwamoto, and Hishi Imai.
National
Institute of Multimedia Education, Tokyo. “High Frequency Sound Above the Audible
Range,Affects Brain Electric Activity and Sound Perception” Paper read at 91st. Convention of
the A.E.S.October 1991. Section 7. (1), Conclusion.
2. Miland Kunchur,Depart of Physics and Astronomy, University of South Carolina. “Temporal
resolution of hearing probed by bandwidth restriction”, M. N. Kunchur, Acta Acustica united
with Acustica 94, 594–603 (2008) (http://www.physics.sc.edu/kunchur/Acoustics-papers.
htm)
3. Miland Kunchur,Depart of Physics and Astronomy, University of South Carolina.Probing the
temporal resolution and bandwidth of human hearing , M. N. Kunchur, Proc. of Meetings on
Acoustics (POMA) 2, 050006 (2008)
511 FEATURES
MICROPHONE INPUT
The microphone input is balanced but not oating, being a variant of an instrumen-
tation amplier. Our well-proven “Transformer-Like-Amplier” (T.L.A.) congura-
tion is used, which includes an accurate toroidal Common Mode Low Pass Filter
that rejects Common Mode signals and excludes frequencies above 150 kHz.
(There are high powered broadcast transmitters at and above this frequency in
several continents and, even if you can’t hear them, any vestigial intermodulation
products must be excluded!)
When the Mic Gain switch is set to Unity (0 dB), the Portico 511 microphone
pre-amplier can handle a balanced input signal of more than +20 dBu without an
input attenuator pad! This is a unique feature that enables this input to double as a
line input.
THE LINE OUTPUTS
The main output signal comes from the output transformer secondary which is
balanced and ground free. A ground free connection guarantees freedom from
hum and radio frequency interference when connected to a balanced destination
such as the input to another Portico module or a high quality ADC. However
the transformer may be used with one leg grounded without any change in
performance. It is not necessary to “ground” one leg at the Portico output. It
would normally get a ground connection when fed to equipment that is not
balanced. Maximum output level is more than +20 dBu, which provides a large
margin over and above the likely maximum requirement of any destination
equipment to which the 511 is connected.
MIC GAIN
A 12-way precision rotary switch controls gain from 0 to 66 dB in 6 dB steps.
TRIM
Continuously variable +/-6 dB level control.

8
+48V
Engages phantom power on the microphone input, as supplied by the 500 series
rack.
POLARITY
Push button inverts the polarity of the signal path, and illuminates when engaged.
The symbol “Ø” is often used to denote opposite polarity.
HIGH PASS FILTER
The high pass lter is continuously variable from 20-250Hz and engaged by the
HPF switch, which illuminates when engaged. It is a valuable aid in any signal
chain, but particularly so in a microphone preamplier. Signals below the selected
frequency are attenuated at a rate of 12db / octave, getting rid of proximity effect,
building rumble, air handling, motor hum, etc.
SILK / TEXTURE
Pushing the Silk button engages the red Silk circuit, which reduces the negative
feedback on the output transformer, adding harmonic content as the texture is
increased. Red Silk accentuates the saturation in the mid and high frequencies,
similar to that of the red silk mode on the Portico II Channel. By manipulating
the Texture control, the amount of Silk can be changed from essentially absent,
to roughly 10 times the amount of coloration / distortion found in Silk from the
original Portico Series. With Silk / Texture engaged, the distortion characteristic
and harmonic content of the unit are very reminiscent of many of Rupert’s class-A
vintage designs. The Silk button illuminates red when engaged.
LEVEL METER
An Eight-segment LED bar-graph meter displays output level (pre-Silk). The color
range proceeds from green for lower level signals, yellow for intermediate signals,
and red for high levels. When the 511 is clipped, the highest red LED will hold
longer depending on how far above the clip threshold the signal was.
SPECIFICATIONS
NOISE:
Measured at Main Output, un-weighted, 22Hz-22kHz, source impedance 150
Ohms balanced. Noise performance can vary depending on the 500 series and / or
interference from stray magnetic elds.
Unity Gain Better than -103dBV
With Gain @ +66dB Better than -60dBV
Equivalent Input Noise -125dB
FREQUENCY RESPONSE
Main output, no load
Main Output +/- 0.1dBu from 10Hz to
31.5kHz
-2.6dB @ 120kHz

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MAXIMUM OUTPUT LEVEL +23dBu
TOTAL HARMONIC DISTORTION AND NOISE
@ 1kHz, +20dBu output level, no load. Better than 0.0025%
@ 20Hz, +20dBu output level, no load. 0.025% Typical (2nd and
3rd harmonic)
TOTAL HARMONIC DISTORTION AND NOISE WITH SILK ENGAGED
TEXTURE @ min
@ 100Hz, +20dBu input level, no load 0.015%, mostly 3rd
harmonic (typical)
TEXTURE @ max
@ 100Hz, +20dBu input level, no load 2%, mostly 2rd harmonic
(typical)
GAIN
Unity up to +66dB in 6dB steps.
Trim continuously adjustable from -6dB to +6dB.
PHANTOM POWER
Supplied by the 500 series rack power supply. Switch selectable on
faceplate.
HIGH PASS FILTER
Continuously variable swept frequency from 20Hz to 250Hz.
Slope: 12dB/Octave
POWER REQUIREMENTS
@ +/-16VDC 100mA

PRODUCT WARRANTY
Rupert Neve Designs warrants this product to be free from defects in materials and workmanship for a period of three
(3) years from date of purchase, and agrees to remedy any defect identied within such three year period by, at our
option, repairing or replacing the product.
LIMITATIONS AND EXCLUSIONS
This warranty, and any other express or implied warranty, does not apply to any product which has been improperly
installed, subjected to usage for which the product was not designed, misused or abused, damaged during shipping,
damaged by any dry cell battery, or which has been altered or modied in any way. This warranty is extended to the
original end user purchaser only. A purchase receipt or other satisfactory proof of date of original purchase is required
before any warranty service will be performed.THIS EXPRESS, LIMITED WARRANTY IS IN LIEU OF ALL OTHERWARRANTIES,
EXPRESS OR IMPLIED, TO THE EXTEND ALLOWED UNDER APPLICABLE STATE LAW. IN NO EVENT SHALL RUPERT NEVE
DESIGNS BE LIABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES RESULTING FROM THE USE OF THIS
PRODUCT. Some states do not allow the exclusion or limitation of consequential damages or limitations on how long
an implied warranty lasts, so this exclusion may not apply to you.
WARRANTY SERVICE
If you suspect a defect in this product, please call us at 512-847-3013 or contact our support sta (service@rupertneve.
com) for troubleshooting. If it is determined that the device is malfunctioning, we will issue a Return Material
Authorization and provide instructions for shipping the device to our service department.
Rupert Neve Designs
PO Box 1969
Wimberley TX 78676
www.rupertneve.com
tel: [phone]
fax: [phone]
775-00017 Rev B