Pendulum Audio ES-8 Vari-MU Tube Limiter

2 reviews for Pendulum Audio ES-8 Vari-MU Tube Limiter

1. 

   Michael Cooper’s – June 19, 2017

   Michael Cooper’s review of the ES-8 in MIX

   Rather than trying to recreate vintage tube gear, Pendulum Audio designs tube processors that incorporate modern, extended-bandwidth, Class-A circuit designs. Both the MDP-1 tube preamp ($2,495) and the ES-8 tube limiter ($3,495) are 2U, dual-channel units that feature transformerless outputs, low noise and a frequency response from below 20 Hz out to 65 kHz (75 kHz for the ES-8). Classy aesthetics, impeccable front panel screening, positive-action knobs and switches, gold-plated I/O connectors, and large, illuminated ANSI VU meters suggest the rigorous attention to quality that lurks below the hood. There you’ll find gold-plated switch/relay contacts and tube sockets, polypropylene caps, metal film resistors and custom toroidal power transformers with hum-blocking shields. On both units, the chassis is ventilated through the top and side panels.

   ES-8 Variable Mu Tube Limiter

   The ES-8 is basically the same device as the Pendulum 6386 Tube Limiter, except that the ES-8 employs two 6ES8 tubes (one per channel) for gain control in lieu of 6386 tubes, which are in increasingly short supply. The dual-channel ES-8 offers the same compression curves as the Fairchild 660 and 670, but the ES-8 departs from those vintage designs in that a Class-A, solid-state makeup gain stage is used to drive its transformerless balanced outputs. Fast and Manual modes complement the six ‘Fairchild’ presets.

   Inputs are via balanced XLR and 1/4-inch TRS phone jacks, wired in parallel. Outputs are via balanced XLR and unbalanced 1/4-inch phone jacks, also wired in parallel. A sidechain insert is provided for each channel on 1/4-inch TRS jacks (tip is send, ring is return), enabling frequency-sensitive processing applications such as de-essing. A Power switch (serving a soft-start warm-up circuit) and detachable three-prong AC cord round out the unit’s rear panel.

   As one would expect from a tube limiter, the ES-8 does not offer a ratio control. The compression characteristic is soft knee, with a smooth transition from compression to limiting as you hit the device harder. The ES-8 can provide up to 12 dB of gain reduction.

   Continuously variable rotary knobs provide control over input attenuation, output gain boost/cut and threshold. The unit is optimized for +4dBu nominal levels. Maximum makeup gain is set at 12 dB at the factory, but you can adjust trims inside the chassis to increase the output control’s maximum boost to 30 dB.

   A three-way rotary switch lets you choose between three compression modes for each channel: Fast, Presets or Manual. Fast mode features fixed 0.5ms attack and 50ms release times.

   The Presets mode activates a six-position rotary switch that implements different “Fairchild” presets. The first four presets offer release times of 0.1 second, 0.3 second, 1 second and 2 seconds, respectively. Presets 5 and 6 provide program-dependent, two-stage release times ranging between 1 to 4 seconds for preset 5 and 5 to 20 seconds for preset 6. In both presets 5 and 6, an initially quick release time is followed by a longer decay back to zero gain reduction. Attack times range from 1 to 4 ms for all six Fairchild presets.

   Switching the ES-8 to Manual mode activates continuously variable attack and release rotary control knobs that are provided for each channel. Manual attack times range from 1 to 100 ms. Manual release times range between 0.1 and 2 seconds.

   Separate rotary controls for each channel switch the VU meters to show input, output or gain reduction levels. Independent hard bypass switches are also provided for each channel. The ES-8’s two channels can be operated independently or linked via a front panel switch. When linked, channel 1’s settings control thresholds, all dynamics processing (modes and attack and release times) and bypass switching for both channels. Only the input, output and meter mode controls remain independent when the channels are linked, a logical arrangement.

   My first test of the ES-8 was on arpeggiated acoustic guitar, played with a flat pick. Switched to Fast mode, the ES-8 sounded outstanding. The processed track was utterly devoid of audible amplitude modulation artifacts with 3 dB of gain reduction showing on the meters. (Peak gain reduction levels were obviously higher than what the VU meters showed.) The ES-8 produced a smoother timbre than most compressors I’ve heard in this application. Even with 7 dB of gain reduction, amplitude modulation artifacts were barely audible.

   Fast and Manual modes provided great dynamics control for lead vocals. And pushing the ES-8 hard in Manual mode, I co-axed wonderfully warm, dense and crunchy tones out of my ’62 Strat. The ES-8 also performed well on kick and snare drums, although a tube limiter is too slow to give you explosive UREI 1176LN-type snare sounds. Disappointingly, the ES-8 lent a tone to electric bass that was a little too soft–almost cottony–for my tastes.

   The program-dependent Fairchild presets worked best for stereo bus compression. The ES-8’s dynamics processing was laudably transparent. The unit lent a slightly euphonic, softer sound to the mix, while perfectly preserving spectral balance. The harder you hit the ES-8, the creamier it sounds. Purists might bark at me, but 8 to 10 dB of gain reduction on a stereo mix sounded great.

   The only big beef I have with the ES-8 is that its inputs lack headroom. Pumping +26dBu mixes into the unit from my 02R’s analog outputs, I had to lower the input levels about 8 dB down from unity to avoid audible distortion. [DESIGNER’S NOTE: This is EXACTLY what the input attenuator is for! You can, in fact use the input control to change the texture of the sound, by controlling how hard the input transformer and input tube are driven. If you routinely work with +26dBu input levels and use large amounts of gain reduction, the range of the Output level can be internally adjusted for up to +30dB of makeup gain. The output stage can drive up to +32dBu without distortion]. I should also note that the ES-8’s +4dBu gain structure does not accommodate -10dBV levels very well, as the input control is strictly an attenuator. For most pro tracking applications, these issues should not be a problem.

   The ES-8 is a clean, transparent tube limiter that performs admirably on the acid test for compressor/limiters–percussive, broadband program material. The unit is not heavily colored, lending more of a soft sound, rather than bursting with overtones. Its only weaknesses are its limited headroom at input and practical incompatibility with -10dBV systems. Boasting a plethora of features and elegant looks that more than justify the, the ES-8 is bound to find a home in many pro studios.

2. 

   Dave Martin’s – June 19, 2017

   Dave Martin’s review of the ES-8 Tube Limiter in Recording

   If you want to pick nits, a ‘tube limiter’ is a limiter that uses a tube as the gain reduction element. That means an LA-2A is not a tube limiter-it’s an electro-optical limiter. There are tube-based amplifier circuits in the input and output stages of the box, but that doesn’t make it a tube limiter. You could correctly call it a ‘tube leveling amplifier’ without error if you so choose.

   Why does this matter? Well, one important reason is that there are tube compressor/limiters, and the term is most appropriate when talking about them.

   During the 1950s, several different manufacturers began using the rather common GE-6386 tube in a variable gain configuration for their broadcast limiters. The circuit works with the bias of the dual triode tube, and therefore the output is changed by side-chain control voltages.

   Among the devices based on the 6386 were broadcast limiters by Gates, Altec, Collins… and Fairchild, who designed a stereo limiter and continued to use the 6386 tube in a variable gain circuit. The result, the Fairchild 670, was a widely used mastering limiter that later became a widely used mixing limiter.

   The 670 is long out of production and has become possibly the most expensive piece of outboard audio gear in the world, with prices well north of $25,000. In fact, the 6386 tube is no longer made and has become fairly rare (and fairly expensive if you can find them).

   The folks at Pendulum Audio decided to build a tube limiter with the same characteristics as the as the venerable Fairchild 670 – not only its time constants (attack and release times) but also the way its compression ratio increases with gain reduction. The design goal was to maintain the ‘dynamic signature’ of the 670 but come up with a more accurate and less colored signal path.

   Initially, they used the 6386 as a gain control tube, and then coupled that with class-A amplification that had an active-balanced output stage rather than the transformer output used in the original. The result is the
   Pendulum 6386 ($3995), for users who insist on the real thing where the tubes are concerned.

   Realizing that the 6386 tube is becoming much harder to find, they set out to find another tube that could duplicate the Fairchild compression curve and time constants.They found it in the 6ES8, which led to the introduction of today’s subject: the ES-8 Variable Mu Tube Limiter.

   Swinging back and forth

   The Pendulum ES-8 is a stereo/dual mono limiter. When linked for use as a stereo limiter the threshold and time constants are controlled entirely by Channel 1; in the dual mono mode each channel is completely independent.

   The solid-state side chain offers three modes of processing. Its Fast mode is self-explanatory, with attack and release times of 0.5 ms and 50 ms respectively. The Preset mode offers program settings identical to the 670 (more on the program settings in a bit), and the Manual setting gives you control over both the attack and release times to suit the application.

   Controls

   The input control is actually a passive attenuator placed before the input transformer. Its normal operating position is at it maximum unless the overall input level is overloading the input transformer or gain stage. TheThreshold control determines how much gain reduction is applied to the source material, and the Output control is for gain make-up after compression.

   Each channel also has a meter switch, allowing you to monitor the input level, output level, or gain reduction. The manual attack and release controls are active when the Mode switch is set to Manual; the attack times
   are adjustable from 1 ms to 100 ms and the release times from a tenth of a second to 2 seconds.

   One setting on the Mode switch is Presets, which accesses six settings that are identical to the time constants of the Fairchild. These Presets are labeled by their release times, though the attack times vary as well. The first four settings offer fixed attack and release times, while the last two have a quick initial release followed by a longer decay time to zero gain reduction. (Interestingly, this type of release is a characteristic of electro-optical compressors like the LA-2A.)

   The available release settings are 0.1 s, 0.3 s, 1 s, and 2 s, with 1 to 4 seconds and 0.5 to 20 seconds on the program-dependent settings. All controls, including a hard-wired bypass switch, are duplicated for the second channel. And when the two channels are linked, Channel 2 is also bypassed by the Channel 1 switch -a neat idea.

   The rear panel has the both XLR and TRS I/O (the TRS plugs can be run unbalanced), along with inserts for an equalizer into the sidechain detector circuit. There is an IEC connector for AC power, a power switch, and fuse holder.

   Observations

   The ES-8 is an interesting box. On one hand it aims to duplicate the compression characteristics (a large part of the sound) of the Fairchild 670, while avoiding the use of output transformers (also a large part of the Fairchild sound). So rather than attempting to do any sort of a comparison-which would really be hard, since I don’t happen to have the $25 grand to purchase a 670 of my own!-we’ll discuss it on its own terms. And as a high quality compressor/limiter, it works extremely well.

   When I needed to control single instruments and lead voices without noticeable compressor artifacts, the Fast setting was often just the ticket. And the program-dependent settings (especially number 5, with a 1
   to 4 second release) were great when I wanted just a bit of an optical vibe. But most of my play time was spent using the ES-8 as a stereo compressor/limiter. To my ears, that’s where its strength lies.

   When set within the typical operating parameters of the unit (that is, without going for huge amounts of added gain), the ES-8 is sonically as neutral as any compressor I’ve heard. When you wish to rein in the dynamic range of a mix without adding any coloration, this is the box to do it with. Even with dramatic amounts of gain reduction, the output maintained a remarkable transparency.

   I’m a firm believer in Bypass switches for signal processing devices, and a hardwire bypass that routes the input directly to the output (bypassing all electronics) always gets bonus points. While I usually use the bypass switch to make sure I’m not making the sound worse, with the ES-8 I kept having to check to make sure I was indeed compressing the signal!

   The flip side of that is that sometimes you want a less transparent limiter. But it would be silly to applaud a piece of equipment for meeting its design goals so well and then turn around and complain that it meets
   its design goals so well.

   Thus

   The Pendulum Audio ES-8 is an extremely high quality tube limiter that I’d recommend to anyone looking for transparent level control without the sonic artifacts typically associated with variable mu limiters. At $ three and a half grand the ES-8 could hardly be called inexpensive, but then the good stuff