User guide

INTRODUCTION

THANK YOU!...

for purchasing the Manley Laboratories Enhanced Pultec Mid Frequency Equalizer. The all-tube Mid

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 improve speech quality in a typical telephone system. This may help to explain the choice

of curves and frequencies. 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 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- 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.

Third - 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 another classic PULTEC that is optimized for voice - but not only

voice. They get used daily in mastering and seems to be the right tool for a huge numer of applications. Beyond

the improvements in pure fidelity, we added extra 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!