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Tuesday, September 19, 2017

WARM AUDIO EQP-WA vs KLARK TEKNIK EQP-KT, PULTEC-STYLE TUBE EQ SHOOTOUT

by Mark King for proworkshop.com


We've been using the Warm Audio EQP-WA since they first hit the market, as early adopters we purchased two from the very first batch, we've since added a second pair because we liked the first pair so much.

Several months after the release of the Warm Audio EQP, British designer Klark Teknik announced they were also going to release an EQP-KT model for the same price as the Warm Audio product.

The KT model made an uneventful entry in the market place and after a very short time Klark Teknik reduced the price, first to $499 and then to the unbelievable price of $299 each. This low price combined with encouraging threads on various audio forums like Gearslutz caused a run on these units. Almost overnight dealers went from some on the shelves to triple digit backorders of the unit.

User reports about the EQP-KT have been very positive so we ordered a pair for the Proworkshop studio in July, 2017. They finally arrived September 16. Were they worth the wait?
This review is going to be a quick comparison of the two low priced EQP-style equalizers because lots of people are wanting to know which performs better, which is more usable, which is built better and more.

EQP EXPLANATION
Recreation of vintage 3U Pultec EQ by modern Pulse Techniques Company
The vintage Pultec EQP equalizer which has gained a cult status following was a two band shelving type equalizer. These are hardware implementations of passive shelving equalizer circuits invented by Western Electric in the 1930's for use in the telephone industry. They utilize tube amplifiers to restore gain and level from the loss encountered in their lossy passive circuits of capacitors, resistors and inductors. The input and output are both individually transformer coupled.
Another Pultec recreation by the modern Pulse Techniques Company
Both the Warm Audio and Klark Teknik share these basic characteristics in common. If you compare the controls on these low priced EQP-style units to the original Pultec you'll find that the newer designed units feature more frequency points than the originals.

Some folks have complained that the circuits in these reproductions are not true to the original because neither includes the interstage coupling transformer which connects the passive eq portion of the circuit to the tube makeup gain which ultimately drives the output transformer. Given that modern tube Pultec equalizers wearing the company logo are 9-10 times the price of the EQP-KT it's easy for me to say I'd rather have a lower price and receive the performance these inexpensive versions deliver.

The Pultec style EQ is not a surgical device, it spreads its magic out in very broad strokes and it takes careful listening to learn how to harness the power of this special equalizer. These are all "two band" equalizers, basically divided into low and high frequency ranges that get affected depending on the front panel settings. The knobs on a Pultec style EQ generally present boost and cut signal shaping functions that are not found on any other equalizer (except for other Pultec style circuits).

Why is the Pultec-style equalizer so magic? Why is it so coveted?
In the right hands they are capable of making the bass and treble ranges of your stereo mixes sound better in a way you can't achieve with other tone controls. They can add weight and size to a bass track like no other EQ. You can push the highs to incredible brightness levels without the mix sounding brittle. These are over-simplifications but they form the essence of why these special equalizers are so desirable to seasoned engineers.

EQP IN USE

The most popular application for a pair of these equalizers is in the stereo bus on the way to a master recorder. This allows the engineer to inject some very broad curves of bass and treble boost. In addition "Cut" controls allow certain frequencies to be reduced.
Bass section on EQP-KT, note only one frequency selection available
In the bass range there is only one frequency select knob which affects the performance of both the Cut and Boost knobs. Both boost and cut rotary controls may be used at the same time in varying degrees to add some low end to a recording in a way that no other equalizer type can match. This is because the boost and cut circuits have different curves and gain potentials, they don't perfectly cancel each other out. Instead using judicious amounts of both boost and cut can result in pushed bass and a dip in the mid-range frequencies.
Treble section of EQP-KT, note separate frequency selections for boost and cut
In the treble range you have separate frequency selectors for high frequency boost and cut. The boost control can add "air and high frequency sheen" to a mix. The cut control is useful on individual microphones that have excessive high frequency content. As a tracking tool the EQP can help by rolling off the highs of overly bright microphones, it's easy to give a vintage vibe to a mic that would otherwise be too piercing above 10K.

The bandwidth control has a subtle effect, the KT manual states the bandwidth control rotary switch varies the width and shape of the high frequency boost curve from relatively sharp to broad. If you are using it on a specific instrument then the sharp position might help you get what you need.

MASTERING

When I first bought a pair of EQP-WA I just wanted to get an idea of what all the fuss about Pultec EQ was about, I could never afford $10,000 to $15,000 for a working pair of the originals. I've worked on A LOT of old broadcast equipment and hate doing repairs and maintenance constantly, this is another reason I'm not a good fit for originals.

I tried the first pair of EQP-WA on a number of different signals, the first day was spent listening to familiar tracks through it. After a lot of experimentation the pair of EQP got inserted on the mastering loop of our Neve mixer and there they stayed. I had to build a pair of precision attenuators to adjust the level of the EQP-WA for unity in mastering but the sound enhancement they provided on stereo masters was very compelling.

I bought a second pair of EQP-WA for use channel patched during tracking of vocals and instruments.  Word to the wise, if you're already using these in your mastering loop and boosting at 10K you won't want to use them on individual channels at 10K because you'll end up with too much at that frequency when you mix it down.

Hardware: WA vs KT

Both units have:
Same frequency selection points and same number of selections
Same boost and cut knob functions
Same bypass function
Same on-off control on front panel

Differences:
LED power indicator on the Warm Audio EQP
Large jeweled power indicator on the KT EQP
LED power light on EQP-WA
Large Jeweled indicator on EQP-KT
Mini toggle switches on the Warm Audio for bypass and power
Big toggle switches on the KT for bypass and power
Mini bypass toggle switch on EQP-WA
Large bypass toggle switch on EQP-KT
Both units have detented potentiometers,
the KT detents have a slightly finer and more precision feel
the WA detents feel larger, more chunky and less precise
the pots feel solid and don't wiggle on either unit

Both units are two-rack space packages.
Both have parallel pairs of XLR and TRS input-output connectors

The WA model uses American Made input and output transformers by Cinemag.
The KT model uses Chinese made transformers designed by Midas in England.

Both WA and KT EQP units are modern designs, built without trying to mimic the original quirky broadcast style packaging of the vintage Pultec's which utilize external metal-cans on the rear of the unit for shielding the tubes and transformers.

EQP-WA has an additional gain level trimmer-knob on the back for matching the level between multiple units.
The EQP-KT has no level matching adjustment controls.

SOUND COMPARISON
I listened to both EQP models in the mastering loop of our Neve 8816/8804 using stereo content I was very familiar with.

BASS
The WA-EQP seemed to have a broader and less specific bass boost.
The KT-EQP seemed to have a more precise bass sound, tighter and more focused.

It was easier to hear the boost provided by the KT than the WA, overall the KT seemed more active than the WA in the bass region. In the mastering loop we were more attracted to the timbre of the WA, it's more subtle, not so in your face. The bass performance on the WA seemed broad and sounded huge, the KT sounded less broad, more focused and smaller.

Overall the EQP-WA feels like it has more headroom than the KT model. Warm Audio does not specify the maximum input and output levels for their EQP.

The KT specs show +21 dBu maximum input and output levels for their EQP. These levels are consistent with other Music-Group products by Behringer and Midas.

TREBLE
The WA-EQP high frequencies sounded smoother, less specific, less precise, broader and more airy.

The KT-EQP high frequencies sounded tighter, more specific, more precise, less airy. It was easier to get too much high frequency boost with the KT than the WA. The KT high frequency boost knob achieved more by the 12 o'clock position than the WA did. The WA seemed to spread its high frequency effect out over more of the knobs rotational range.

No analyzers, scopes or signal generators were used in creating these performance impressions, all comments are based on playing music through the respective products and listening on the Proworkshop Meyer HD-1 monitors.

WHICH IS BETTER?

Only time and hands-on use can really answer the question of which is better. Both pieces have reasonable noise floors, transformer coupled input-output, good packaging and built in power supplies. They both can achieve varying degrees of classic Pultec tonal magic. The fact they sound a bit different from each other is a good thing because each has its own personality in spite of similar feature sets.

Your overall signal will receive a larger boost by just passing through the EQP-WA than going through the KT model. This can be a problem in some applications because the WA is capable of a pretty hefty signal level increase just by being in the circuit. As previously stated I had to fabricate a pair of precision attenuators to tame the output level from the EQP-WA in our mastering loop.

The KT models have much less level-boost as a result of simply passing signal through them.

The sound from the WA feels like it has more headroom and generally sounds bigger than the KT.

The EQP-WA has a great effect on bass-heavy tracks such as the MiniMoog, it can bring the highs to the front and make the bass region sound absolutely gargantuan without destroying the integrity of other bass instruments in the mix.

WHAT NEXT?
Right now the two Warm Audio EQP-WA are staying in our mastering loop. They add a nice broad bass enhancement to the lows and an airy high frequency clarity like no other processor I've used. The EQP-WA are working in this application and I could hear no compelling reason for changing to the KT right now.

On the other hand I'm anxious to use the EQP-KT models during tracking and mixing on individual tracks. I've found by using the EQP-WA in this application that it does not take a big treble boost to bring a dark sounding track to the front of a mix, it's more subtle than the EQ in my Soundcraft console.

I've also found the EQP-WA to be useful channel-patched on the bass guitar track when mixing, I run this into an LA2a compressor which levels it out nicely and makes the bass sit very naturally in a mix.

I've used the EQP-WA to tame the highs on a vocal microphone track that was way too bright, this was my most unique use for the high-frequency cut control on the EQP and it added a wonderful vintage tone.

WHICH TO BUY?
Well certainly the price of the EQP-KT is going to be a big selling point, right now you can buy two KT for the price of one Warm Audio model. That is going to mean a lot of tiny home studios are going to grab a pair of the KT for stereo bus applications because of the cost difference.

Is the WA model worth twice as much as the KT? That all depends on your own opinion and applications. My EQP-WA are not going anywhere, I like the tone and sounds they produce. I can honestly say the same about the EQP-KT, I like the way they sound and I'm looking forward to using them on a variety of sound sources.

I've spent countless hours in the last couple of years listening to the EQP-WA and right now my ears are more attracted to its sound but that could easily change because the KT is so new and I just don't have as much experience with it. The WA feels like a comfortable pair of shoes, by contrast the KT feels like a brand new pair of jogging shoes laced up tight. They are both good but different and each has its own personality.

We'll post a more complete review of the EQP-KT by itself after we have time to gain some hands-on recording experience with it.

Good music to all!