Manley ENHANCED PULTEC EQP1-A EQUALIZER - Manual (Page 3)

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!
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