Tubes Asylum: REVIEW: Supratek Triode Cortese Preamplifier (Tube) by Todd Krieger

Model:	Cortese
Category:	Preamplifier (Tube)
Suggested Retail Price:	US$5000
Description:	Full Function Tube Preamplifier
Manufacturer URL:	Supratek Triode
Model Picture:	View

Review by Todd Krieger ( A ) on September 16, 2002 at 02:52:21
IP Address: 208.176.171.209

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The Australian Supratek Cortese preamplifier is designer Mick Maloney's new flagship model, incorporating some new features, most-notably a "parafeed" output design instead of the standard transformer-coupled implementation in the original Syrah preamplifier. (The newer Syrah is also parafeed.) This hand-made preamplifier (by Mick himself), like the Syrah, is a marvel to look at. The preamp uses a separate power supply, with a 5Z4/5AR4/GZ33/GZ37 rectifier and two 5881 power tubes for regulation. A "Kimber Kable" like umbilical cord ties the power supply to the main preamp unit, which consists of a parallel-triode 6SN7 for each channel (dual 6J5's are also an option, but the choices in such tubes are limited relative to the 6SN7) as a single stage (non-cathode follower) driving the parafeed transformer output. The phono stage consists of 6H30 and 6C45 tubes. The main drawback with these two particular tubes is there is only one manufacturer (Sovtek) and no equivalent. So I'd suggest stocking up spares of these phono tubes if you get this preamp. (The unit pictured is the 6J5 version with two extra 5881 regulators on the power supply. The 6SN7 version has just the outer "6J5" sockets for the 6SN7s, and the standard power supply unit has the just the "rear" regulators, arranged in a straight line with the rectifier in the middle.)
The Cortese, like all Supretek electronics, is available in a variety of woods and metal finishes. My particular unit is the standard "Jarrah" wood with the "copper" finish. (I just love that copper finish- Gives the unit a unique "one-of-a-kind" look.) The metal finish is lacquer-coated to prevent oxidation.
Like all tube equipment, I have "tube-rolled" the rectifier and regulators on the power supply, and the 6SN7 tubes in the line stage. (As I mentioned, the phono tubes are not "rollable.") I ended up settling on the Mullard CV1988 for the 6SN7 (the Raytheon VT231 and stock Sovtek 6N8P work well too), with the Mullard GZ37 rectifier tube (The GZ33 and stock 5Z4 also work well. The GZ32 arced on me- use it at your own risk.). And the famous Tung Sol 5881. (The stock Sovtek 5881/6L6WGC makes the pre sound somewhat "analytical.")
Two other comments about this preamp. One is the power supply unit runs *extremely* hot. But Mick Maloney assured this is perfectly normal. It seems to be affected by which 6SN7 is used. It runs almost unbearably hot to the touch with '40's Ken-Rad VT231s. It does run cooler with others, including the Mullard CV1988 mentioned earlier. The other thing is the preamp has a very long "break-in" period. You will initially hear the "mechanical" sonic character of the output transformers when first played, and the sound will waver between dark and bright. The sound does open up after about a month, and is continuing to do so.
Now to the sound. My pet peeve with preamps has been the lack of linearity at the bottom end of the spectrum. It seems to plague tube pres in particular. (And aside from the Hegeman Hapi/Hapi2 and Hafler 915 preamps, I've never heard a solid-state preamp that didn't sound overly like solid-state.) I have gone through *lots* of preamps before settling on the Cortese. (I probably would not have traded up had my Syrah not been damaged in shipment.) I think this lack of bass linearity often provides a characteristic "tube sound" from tube pres, but the bass becomes congested with complex orchestral and especially organ passages. Making most tube pres sound "bloated" at the loud end of the dynamic spectrum. (Most people don't realize this problem exists, until they maybe try a solid-state pre.) The Supratek Syrah and Cortese are the first tube preamps I've heard that are mostly *devoid* of this bass-linearity flaw. So when you turn up a rock tune, for example, you hear the warmth of the guitar amps and "tzzssszzzsszzz" sound of the high-hat cymbal in its full and acoustic glory. Or the sparkle of the triangle at the very end of the Mahler One, often lost in the complex orchestral activity with most tube pres. What this linearity does for the rest of the spectrum is make everything in complex passages easier to pick out. As one could normally do with small-scale acoustic music, but rarely with complex music. And in a way, if one is used to the "blasting" of a loud audio system, this preamp might sound "unspectacular," but totally consistent with what he would hear with live unamplified music. Everything is merely "there." (Such a piece of electronics will make one play the system louder than he normally would- the lack of dynamic distortion makes the system seem "less loud.")
The phono stage, in spite of the lack of the flexibility to "tube-roll," is also examplary. It is the first phono stage I've tried that I do not prefer the BRB 20 preamp phono stage over it outright. The phono stage sounds very similar to the BRB, with the extraction of every last bit of detail off the record grooves, where lesser stages will "blend" these fine details, often making the cartridge sound "brighter" than it really is. The Cortese phono may have a slight edge over the BRB in microdynamics, where the BRB has a slight edge in extension at the frequency extremes and in absolute dynamics. The latter only noticeable when playing those pre-CD-era Telarc LPs, which I say are maybe the most-dynamic recordings ever made. But still, the Cortese's phono stage, with a good source, will make the search for a digital rig to match its performance potentially an eternal one. Where the BRB's phono may be slightly on the analytical side of neutral, the Cortese's phono is slightly warm, and possibly more-forgiving.
Now the weaknesses. Not to be picky, but I think the Cortese is ever-so-slightly "soft" at the extreme top end. (Although my opinion here could be due to the tweeters on the Von Schweikert VR-4.5 Mod 5, which I have a similar complaint.) The pre is otherwise very neutral. The Syrah is a little warmer. The stepped ladder attenuator has gradations that will occasionally make one wish they were a tad finer- I've occasionally run into instances where the best volume setting is between two gradations. The "blend" switch (which is called a "mono" switch in the user documentation) is useless. It should be left in normal mode. The "blend" setting, which mixes a little of a one channel's signal into the other channel (and vice versa) to make some early stereo recordings "less disconcerting," actually makes this pre sound a little "slow." Even though the Cortese is a tube preamp, its neutral character will *not* tame sources that are either "hot" or "forward," nor will it "smooth-out" the "rough edges" of most solid-state amplifiers. (The Syrah, which is more-forgiving, will actually complement such electronics a little better.) But put clean associated equipment around the Supratek Cortese, and you will get an extremely-clear window to the music.
At five grand, the Supratek Cortese is not for everyone. But for a preamp that walks that fine line between the details/linearity/dynamics/staging/neutrality to satisfy the "audiophile" and the emotion of the performance/event to satisfy the "music lover," one would be hard-pressed to find a better preamplifier, at any price, than the Supretek Cortese.

Product Weakness: Expensive. Top end could be ever-so-slightly soft. Tube-matching is a must for absolute performance. Phono-tubes not "rollable" with different types/brands. Very long "break-in" period. Power supply module runs *very* hot. "Blend" switch setting affects top-end "speed." Volume gradations may be large in certain situations.
Product Strengths: Combines the linearity of the best solid-state with the musicality of the best tubes. Exceptional bass linearity for a tube preamp, making it devoid of the "congestion" during complex passages that plagues most other tube preamps.

Associated Equipment for this Review:
Amplifier:	Symfonia Opus 10, Marsh A200S
Preamplifier (or None if Integrated):	Review unit
Sources (CDP/Turntable):	JVC XLZ1050 transport/Prism DA-1 DAC, Teres/Redpoint hybrid turntable/Sumiko MMT arm/AT OC9ML cartridge
Speakers:	Von Schweikert Audio VR-4.5 Mod VR-5
Cables/Interconnects:	Silverline Audio speaker cables. Belden 88281 interconnects. Bocchino, WBT, and Vampire terminations. WireWorld Supernova III+ Glass Toslink digital cable
Music Used (Genre/Selections):	Everything
Room Size (LxWxH):	19 x 16 x Vaulted
Room Comments/Treatments:	Carpeting on floor
Time Period/Length of Audition:	3 months
Other (Power Conditioner etc.):	Brickwall surge protectors, TrippLite regulator, Shunyata Hydra for power amp, Bybee conditioner for electronics. Crescendo and ESP Essence power cords.
Type of Audition/Review:	Product Owner

Product Weakness:	Expensive. Top end could be ever-so-slightly soft. Tube-matching is a must for absolute performance. Phono-tubes not "rollable" with different types/brands. Very long "break-in" period. Power supply module runs very hot. "Blend" switch setting affects top-end "speed." Volume gradations may be large in certain situations.
Product Strengths:	Combines the linearity of the best solid-state with the musicality of the best tubes. Exceptional bass linearity for a tube preamp, making it devoid of the "congestion" during complex passages that plagues most other tube preamps.