September 2005

Pacific Creek Separo SE300I Integrated Power Amplifier
An Appealing Approach, But Can It Deliver The Goods?
Review By Dick Olsher
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  Pacific Creek — the company — is the new kid on the block, in business only since October 2003. You cannot say that, however, about its founder and chief designer, Jerry Wang. He has been actively building tube amplifiers for over 30 years, having built his first tube project when he was only 13 years old. With a technical background in radio circuit and system design, and digital signal processing, the transition to high-end audio combines Jerry's engineering skills with his passion for tube sound. The Separo SE300I represents Pacific Creek's inaugural product, a 10 watt per channel integrated stereo amplifier — a single-ended triode design featuring the ever-popular 300B power triode. The gold-anodized front panel and elegance of finish in general suggest a lofty retail price. Its actual retail price ($1899) should turn more than a few heads, and is only possible because the Separo, while designed in the US, is being manufactured in China.

The Technology
The power switch, volume pot, and an input selector that controls four line-level inputs adorn the front panel. In line with other classic 300B designs, the philosophy here is simpler is better. There are only three active stages. After negotiating the input selector and volume pot, the signal arrives at a 12AU7 based Series Regulated Push-Pull (SRPP) input stage.  The SRPP, also known as a Mu Follower, has proven to be an extremely popular circuit over the past 15 years, and for good reasons, as it offers substantial gain with low output impedance. The SRPP feeds the driver stage, a triode-connected 6L6. This choice was based on the desire for a low-gain stage with a large peak-to-peak voltage swing. Actually, instead of a New Old Stock (NOS) 6L6, the Separo uses a Russian 6P3 (6L6 equivalent).

The output stage consists of a Chinese 300B-98, self-biased for long-term stability. The output transformers are said to be oversized and capable of handling nearly 20 watts in single-ended operation. The primary's impedance is 3,500 Ohm, which is on the high side of the optimal load for a 300B, but was chosen to provide a damping factor of about 6. Secondary winding taps are provided for 4 and 8 Ohm loads. No global or local negative feedback is used. The power supply is vintage-tube in conception with a modern touch thrown in: tube rectification using a 5Z3P (a Chinese 5U4G equivalent), a choke input filter, and a DC supply for the 300B filaments.

The Sound
Right out of the box, the SE300I required a long break-in period - emphasis on long. Initially, harmonic textures sounded dry and grainy to the extent that would have required chaining me down to my listening seat in order to continue serious listening. A 300B SET amplifier's calling card is typically a sweet and mellow harmonic spectrum, rich in consonant second order distortion products — a high-fat Atkins Diet, if you will, for your matching speakers. Being so far off target was definitely worrisome. Fortunately, after days of break in, the gap narrowed between expectation and reality, but not sufficiently to satisfy my musical palette. The next step in the process was tube rolling, the time-honored practice of spicing up the sound using tube substitutions.

I did experiment with substitutions for the Chinese 12AU7 and 300B output tubes, but I did not touch the Russian 6P3. The most transforming tube roll-in turned out to be the KR Audio 300B Balloon. Image focus and stage depth perspective improved, textures became sweeter and more luxurious — just what a old tube romantic needed! The moral of the story is that the Chinese 300B-98 does not appear to work well in this context. And there is no reason for prospective customers to be forced to purchase this tube. A more customer-friendly policy would be to provide for either 300B alternatives or optionally sell the amplifier without output tubes.

It was now time to take stock of the situation. The soundstage was reasonably well reproduced, with convincing width and depth, but lacked adequate projection into the room. Image focus was very sensitive to absolute signal polarity. With the "correct" polarity setting, however, instrumental outlines snapped into focus resulting in good spatial resolution. Bass lines were not reproduced with the tightness and control of solid-state amplification, but certainly the Separo was no better or worse in this regard than many other SET amplifiers. Treble extension was very credible for a SET design. I am certainly not a fan of an overly liquid and dark presentation, which is symptomatic of a severely restricted power bandwidth. The Separo managed to project a "sunny" disposition with good treble detail. For example, Ernestine Anderson's rendition of "What a Diff'rence a Day Made" [Never Make Your Move Too Soon Concord Jazz CJ-147] came through with crystalline enunciation. However, the tonal balance was not entirely to my liking, being a bit recessed in the midrange.

So far pretty good. But storm clouds were gathering on the horizon. It has been said that a life is not measured by the number of breaths you take but rather by the number of moments that cause you to hold your breath. It became clear that with the SE300I in the chain, those moments were precious few; the music's tension and drama were being substantially siphoned off. Imagine a taut balloon that is suddenly pricked by a pin. The explosive pop and subsequent startle reaction are due to the sudden release of pressure. It was as though the Separo was allowing the air to leak slowly out of the balloon. Hair-raising performances were turned pretty mundane. A couple of examples are in order. A young Joan Baez gives a deeply haunting performance of "House of the Rising Sun" [Joan Baez Vanguard VSD-2077], a ballad of a girl gone wrong. Instead of being riveted to my seat, I was fiddling with the volume control trying to coax more drama out of the music. The lack of dynamic scale was also painfully apparent during Walton's Belshazzar's Feast [EMI AN-324]. André Previn whips up the massive forces of the London Symphony orchestra and chorus to imposing levels of dramatic intensity. The Separo simply failed to negotiate the transition from loud to very loud. It could not shift gears fast enough to keep up with the action. There are imperfections I can forgive in reproduced music, but this is not one of them. Take away the emotional underpinning of the music, and what's left of reproduced music is nothing but a canned, uninspiring copy of the real thing.

Conclusion
Despite its good intentions, I found the sound of the Separo SE300I to be ultimately disappointing. This is all the more frustrating in view of the design effort and parts quality inherent to this product. Matched with a premium pair of 300B tubes, such as the KR Audio Balloon, soundstage dimensions, image outlines and harmonic textures are certainly competitive with the performance benchmark set by similarly priced 300B based SET amplifiers. However, its Achilles heel is lack of dynamic conviction. Dramatic tension is the life force that energizes reproduced music. It starts with the reproduction of dynamic nuances, the subtle details that help convey urgency and emotion, and finishes with the uncompressed ascent of loud passages. In the case of the SE300I, its performance in these areas is on "life-support." For the record, I do find the Separo's design approach appealing and I hope that Pacific Creek manages to implement the requisite modifications to resolve what I consider to be an obvious and critical sonic problem.

Manufacturer's Reply
It was a shock and disbelief when we first saw Dick Olsher's review, as we received nothing but praises from existing customers so far. We raced to do a thorough check of the returned sample as soon as we received it, but could not find anything wrong with it. We could not help thinking, what's wrong with Dick?

The mystery began to unfold one day, when we tried to burn in an E34I (our entry level EL34 amp) and did a quick side by side comparison to the returned sample. The humble E34I clearly outperformed the returned SE300I sample. This kept us busy for a while and we finally realized that the sample we sent to Dick had excessive bias which in turn caused core saturation in the output transformers. The "thorough" test (we thought it was) simply could not catch the failure that Dick was able to detect with his ears.

We are sending a replacement unit to Dick and hope he has time for a follow up review. Needless to say we are also adding steps to prevent the same failure from happening in the field again.

Jerry Wang
Pacific Creek, Inc.

Specifications
Type: Integrated tubed stereo preamplifier / amplifier

Power Output: 10 Watts rms per channel

Total Harmonic Distortion:: <1% at 6 Watts; <2 % at 8 Watts; <5% at 10 Watts (@ 1kHz, 8 Ohm)

Frequency Response: 17Hz to 27kHz (-3 dB); 30Hz to 17kHz (-1dB)

Background Noise Level: <3.5 mV rms. at 8 Ohms

Tube Complement: 
   Two 300B-98
   Two6P3 (Russian 6L6)
   Two 12AU7
   One 5Z3P

Input Impedance: 47 KOhm

Dimension: 17 x 15 x 8 (WxDxH in inches)

Weight: 68 lbs.

Price: $1899

Company Information
Pacific Creek, Inc.
P. O. Box 992
Issaquah, WA 98029

Voice: (425) 961-0136
Fax: (425) 557-0700
Website: www.pacificcreek.com