Reviewing the Manley Pultec EQP-1A - by George Shilling
Taking the classic Pultec equaliser circuitry of Eugene Shenk, Manley has produced the updated EQP1-A EQ. George Shilling checks the price of progress.
MANLEY HAS OFFERED a mono Pultec EQ replica for some time. Now, due to customer requests, the company has started producing a stereo unit, the EQP1-A. The unit uses the Western Electric passive EQ circuit found in the original Pultecs (made by PULse TEChnology Labs) and it is a measure of Manley's diligence, that of the many copyists, it remains the only manufacturer to have taken the trouble to track down the original designer Eugene Shenk and sought permission to use his circuitry. However, the Manley Pultec is not an exact copy--the new model includes extra switchable frequencies, a Manley-designed make-up gain amplifier and power supply. And of course, modern electronic components which are made to closer tolerances than originals.
The construction of the unit is in the Manley house style: the front panel is thick and sturdy, with beautiful legending clearly etched into black anodised panels and small, deep knobs with a loose feel, due to the Bournes conductive plastic pots that Manley insist sound best and are most reliable. Alternatively, you can order the mastering version with Grayhill 24-position gold contact rotary switches, similar to the frequency selectors on this unit, but this will cost considerably more. The top and bottom panels are very thin and rattly metal meshes which might vibrate, but in a rack these are probably not a problem, and enable proper ventilation of the valves and power supply.
The rear includes inputs and outputs at +4dB on jacks and XLRs. A 3-position toggle for each input selects 0(infinity), 180(infinity) (phase reverse) or Direct In: the high impedance unbalanced jack input, which bypasses the transformer. Interestingly, original Pultecs had three transformers in the signal path. With the ability to run this model completely transformerless, this unit is much cleaner and quieter than an original, with little discernible or measurable difference whether the transformer is in circuit or not. Anyone hoping to 'tubeify' their mix might be disappointed--this modern valve circuit adds no coloration that I could discern, and boasts exceptionally low distortion figures.
All the controls will be familiar to anyone who has ever used a Pultec or any copy. The low-frequency band features both cut and boost knobs. Like the original EQP1-A3, shelving-only frequencies are supplied at 20Hz, 30Hz and 60Hz, but instead of 100Hz there are 90Hz and 120Hz. And like the original, these shelves are gently curvaceous, so for example with a full boost at 20Hz there is a 2dB gain at 100Hz, 7dB at 50Hz and 13dB at 20Hz. The low cut interacts with the low boost so that when both are turned up there is a dip in the frequency response above the pivot frequency, the boost occurring lower down the frequency spectrum.
The High Boost section is a quasi-parametric bell-curve boost: there are 11 selectable frequencies--the original EQP1-A3 had only seven. The continuous bandwidth control interacts with the boost knob: when the bandwidth is narrow the boost is greater, with up to 20dB of gain available on all frequency settings. With frequencies available from 1kHz to 16kHz this section is extremely flexible and powerful.
The High Cut shelf has five frequency settings (as opposed to the original's three), which are useful for removing unwanted nasty highs, smoothing harshness, or reducing noise on bass guitar, for example.
With many Pultecs, the Boost-Cut knobs seem to have little effect until somewhere past the halfway point; then, somewhere around 6 or 7, there is a huge sudden change. Not so with the Manley. EQ boosts and cuts have a natural progression which feels more even, making this unit seem more powerful at milder settings. Distortion is very low for a valve unit, and I found no discernible difference whether or not the input transformers were in circuit. The frequency response easily reaches the quoted 70kHz.
However, I am duty bound to report that during use Channel A stopped passing signal, even in Bypass. Ridge Farm Studios' chief technician traced the problem to several signal wires which were pinched and almost sliced between the edge of one of the circuit boards and the case, which was surprising to find in a unit from a manufacturer with a reputation for diligence. Perhaps this early example is not representative of subsequent production models.
[Manufacturer's note: we could not figure out how this could have happened as there is no routing of cables in this manner. It's a mystery to us.]
In conclusion, I found the unit to be quite unlike any Pultec: it is precise, clean and powerful. I quite missed the coloration and distortion of a real Pultec, but the EQP1-A exactly achieves its design objectives and despite lacking fully-parametric controls is a surprisingly flexible tool.