Manley EQP1-A User Manual

MANLEY

LABORATORIES, INC.

OWNER'S MANUAL

ENHANCED PULTEC

EQP1-A

EQUALIZER

MANLEY LABORATORIES, INC.

13880 MAGNOLIA AVE.

CHINO, CA. 91710 USA

TEL: [phone]
FAX: [phone]

email: [e-mail]

http://www.manleylabs.com

CONTENTS

SECTION PAGE

INTRODUCTION 3

EQ HINTS 4

FRONT PANEL 5

REAR PANEL 6

MAINS CONNECTIONS 7

TECH NOTES 8

TROUBLESHOOTING 9, 10

CURVES 11, 12

WARRANTY 13

WARRANTY REGISTRATION 14

APPENDIX:
WIRING YOUR OWN CABLES ?
TEMPLATE FOR STORING SETTINGS

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INTRODUCTION

THANK YOU!...

for purchasing the Manley Laboratories Enhanced Pultec EQP-1A Equalizer. The Enhanced Pultec Equalizer
utilizes the original WESTERN ELECTRIC passive-equalization circuit found in the long-out-of-production
and justifiably famous PULTECS. According to experts, Western Electric developed the passive EQ in the 30's
to allow music to pass through a typical telephone system. This may help to explain the choice of curves and
frequencies - boost a bit of bottom, boost a bit on top and filter out the hiss. Western Electric also seem to have
brought us the balanced audio & the 600 ohm standard. Eugene Shenk of Pulse Technologies re-discovered
the EQ and added his vacuum tube gain make up amplifier. While Pultec sold a healthy number of units to
broadcast, when transistors came in, many jumped to the new technology and Pultec fell on hard times. It was
not until the mid 70's and early 80's with the big new recording studios that engineers and producers found that
nothing had the same magic low end that old Pultec tube EQs could give. Twenty years later, and they are still
favorites (along with old British console EQs) and today few understand why they sound so good. Its not "just"
the tubes.

We can offer a few good reasons. First - the EQ is passive. That means that the components involved have no
gain. A typical modern parametric EQ can use 10 to 20 op-amps, each with many, many transistors. Music
generally prefers a simple path with the fewest parts to pass a signal through. This also is one of the big
advantages to tube circuits - simplicity. The EQ uses a few capacitors, inductors and resistors (or pots). No
headroom problems, no crossover distortions, no slew induced distortions.
Second - The EQ curves tend to be wide. While not perfect for everything, wide, low-Q, low-resonance
frequency shaping is very musical and easy to use.
Third- Transformers can add a nice fat low end. That euphonic bottom was partially due to transformer
saturation. In other words the lower and louder a signal got, the more it saturated (added some extra harmonics
to the ultra lows where most speakers are deficient). It helps us percieve that there was some energy down there
without hearing the distortion as such. The older transformers suffered from wide band distortion and losses
in the highs. This is rarely wanted. Modern high quality transformers are much better in the highs and generally
much lower distortion, due to improvements in materials, but they can still saturate - the way we like.
Fourth - Op-amp circuits have limitations. They use negative feedback to control gain. Often enough, this can
cause a loss of transient accuracy and/or instability. Most op-amp EQ circuits rely on some very small signal
levels that are prone to cross-over distortions in the push-pull outputs. Older op-amps have slow PNP
transistors that began rolling off at a few hundred hertz causing crossover distortions. Headroom can be a hard
ceiling (+20 dBu) that gets nasty when significant amounts of boost are called for. All of this worsens when
driving capacitive wire or low impedances. The better solid state EQs are discrete with high voltage power
supplies for headroom. Our Langevin Pultec is that style. The Manley tube version beats it.

Manley uses an all-tube gain block with a +31 dBu capability and less than 10 dB of feedback. Four triodes
are used for "flat" class A gain stages and demonstrate the beauty of simplicity. We use a similar line amp in
our 40 dB Mic Preamps and Electro-Optical Limiters and some of our audiophile hi-fi preamps.

Our version of this classic EQ incorporates modern audiophile grade components with our proven line-amp
for absolute sonic beauty... Conductive plastic potentiometers and sealed gold-contact switches, polystyrene
and rolled film and foil capacitors, and a our own transformers combine with a regulated stiff power supply
and state-of-the-art tube circuitry to bring the PULTEC that is as good in the mids and highs as it has always
been in the lows. It is now commonly used in the best mastering suites and has become a standard (must-have)
item in studios world-wide. We added 8 frequencies and better interfacing, and it's only 1U !

Please take a few moments to read through this manual carefully as it contains information essential to proper
operation of this unit. Thank you again, and please enjoy!

3

EQ HINTS

We usually give a few hints about tricks commonly used with our products. With an

EQ of this type it is not so likely you need much help.

The most common question we get asked about our Pultecs is "Why both a boost and
a cut knob in the lows?". We don't know why it was designed that way for sure. It was designed
in the 1930's by Western Electric to improve music fed through telephone lines. We believe
it was done this way because it was the most practical in a simple passive design. This was
before op-amps and Baxandall type cut / boost circuits were common. We do know that most
engineers do use both knobs at the same time. Cutting a bit, boosting a bit, and the
combination gets the fat bottom they turn to the Pultec for. "Wouldn't they just cancel out?"
No, the shapes of the cut and boost are different and the result typically is boosted lows and
a dip in the mids but it depends on the relative settings. The slope of the low boost tends to
be steeper as well. We included a few pages of response curves to clarify this for you.

Vintage Pultecs are known for their usefulness on kick, bass, and raunchy guitars.
They are rarely used for vocals, mixes or sounds where transparent highs are important. The
Manley version, however, is often used for these purposes. It is featured in quite a few
mastering suites as one of the primary EQs. The difference is the Manley has better gain
make-up amps and fewer and better transformers. Here is the hint: for low end punch we
suggest using the XLR transformer inputs & outputs because the signal passes through two
transformers with a selected saturation characteristics. For situations where highs and fidelity
are most important you can bypass the transformers using the 1/4 inch phone jacks. You can
also use one transformer and bypass the other for something in-between. A little experimentation
when you first get the unit will go a long way in the years of use. The Manley EQs were never
intended as a clone of the original. We sought to improve them where we could. We knew
it was a good concept and, with permission, could produce this little gem.

The Bandwidth control (mid &high boost section) seems reverse to many. As one
turns the Bandwidth control clockwise the actual bandwidth increases - the "Q" is less. If one
is used to "Q" controls then it will seem reverse - but think of it as "bandwidth" not "Q". It
also boosts less dB's as bandwidth is increased but because the "area" is somewhat constant
it doesn't sound like lost boost. The bandwidth narrows slightly as frequency is increased.

Watch out boosting major amounts of low end when using most nearfield monitors.
Most don't have great response down there. One common technique is for engineers to watch
speaker excursion to get an idea how much lows they are putting on. How accurate is that?
It is not uncommon for an engineer to be surprised once they hear the tape in the car or on
a system with a sub woofer. The extreme lows and highs are the most likely part of a sound
to not "nail" because of monitors, fatigue, and the hype factor that is occasionally called for.

Best applications for this EQ? Important up-front sounds that a cheap EQ might
butcher just passing the signal. Low end sounds like kick and bass that need serious fatness
and punch & guitar amps that have lost that low thump we hear in the studio. Strong transient
sounds like shakers, tamborines, and cowbells that some solid state gear has a way of
smearing and turning into noise. Best time and place to shape the sound - before recording
and with mic technique. Then the EQ becomes a useful tool - not a needed crutch.

4

FRONT PANEL

IN

BYPASS

BOOST SELECT CUT

BANDWIDTH SELECT BOOST SELECT CUT

POWER

A B C D E F G H I J K

LOW FREQUENCY

SECTION

HIGH FREQUENCY BOOST

SECTION

A IN / BYPASS - This switch in BYPASS mode bypasses the EQ section while the amplifier remains

in circuit.

B L.F. BOOST - Shelf - Provides continuously variable BOOST from 0dB to +15dB to the selected low

frequency (control C). Check out the curves on pages 15 & 16.

C LOW FREQUENCY SELECTOR - Used for both L.F. BOOST and/or CUT. For BOOST or CUT

this frequency is almost the maximum of the curve. With maximum boost (or cut), lower frequencies
may get 3 dB more boost (or cut).

D L.F. CUT - Shel f - Provides continuously variable CUT from 0dB to +16dB to the selected low

frequency ( control C). Many use a combination of boost and cut to get an interesting shape. The typical
effect is boosed lows with a dip in the low mids or mids. Why ? Because the boost and cut are not mirror
images of each other. The cut stetches higher.

HIGH FREQ. CUT

SECTION

E BANDWIDTH - This continuously variable control affects the width of the HIGH FREQUENCY

BOOST effect. Counter-clockwise (around 1) is narrow or a high Q. Clockwise is a larger bandwidth,
wider or lower Q. The maximum boost of 20 dB occurs at narrow bandwidths and goes to 13 or 14 dB
with wider bandwidth. Because the area stays somewhat constant it does not sound like lost boost. The
bandwidth also tends to get slightly narrower with higher H.F. BOOST frequencies - normal for
passive EQs. This knob may seem reversed if one is used to modern parametrics.

F H.F. BOOST - Peaking - Provides Continuously variable BOOST from 0 to +20dB to the selected

high frequency (select control G). The maximum amount of H.F. BOOST is affected also by the
BANDWIDTH control. (see E)

G HIGH FREQUENCY BOOST SELECT - Selects at which frequency maximum operation of the H.F.

BOOST section occurs. The frequencies are marked in KiloHertz.

H HIGH FREQUENCY CUT - Shelf - Provides continuously variable CUT from 0 to -21dB of the

extreme high frequencies.

I HIGH FREQUENCY CUT SELECT - Selects at which frequency the H.F. CUT control occurs.

The frequency is about half way down the curve (max =-21dB, at selected freq = -12 dB)

J LED - When power is first turned on the LED is RED. This means that the EQ is muted until the tubes

are warmed up. It prevents thumps and pops. About 20 seconds later the LED turns GREEN and the
EQ will pass audio. This circuit is smart enough to ignore a quick black-out.

5