Volume VII Number 2
Sunfire Classic Vacuum Tube Control Center
(AKA a tube preamp)
It has been a long time since I've had a piece of tube gear or an analog front end (turntable and phono cartridge) as part of my audio system; supposedly the two go together like love and marriage. I have listened casually to tube gear and LP's during this time (systems of fellow audiophiles) and I am sure I haven't missed anything....or have I? I keep hearing how much LP's have improved as a result of advances in analog record/playback technology. In particular, the sound resulting from the combining of LP's with vacuum tube equipment is spoken of in terms reserved for an out of body experience. Is this true or is it tripe?
The opportunity to checkout these claims and visit my audiophile "roots" presented itself in the form of the new Sunfire tube preamp. Or, to call it by its given name, the Sunfire Classic Vacuum Tube Control Center!
Bob Carver designing and selling a piece of tube gear? In the later part of the twentieth century? Yep. I'll let you in on a secret. Underneath Bob Carver's solid state exterior lies a warm and glowing vacuum tube aficionado who also loves the LP sound! Make no mistake, folks, the Sunfire Classic Vacuum Tube Control Center (AKA a tube preamp) is a limited production item that (I believe) is Bob Carver's last hurrah for the tube technology and LP world from which he came.
Wanting to do justice to what the spirit of this preamp is about and to checkout today's LP technology I requested that my review unit include the sensibly priced $350 optional phono stage. Not having any analog front end for several years (since 1993) meant I had to start from scratch in acquiring a turntable, phono cartridge, and quality LP source material. My adventures in acquiring an analog front-end and quality source LP's are not the main thrust of this review. For those interested in, "Joe acquires an analog front-end and visits LP land" I have included a sidebar article. Let it be known that the analog front-end I used for this review consisted of a Denon DP-59L turntable with integrated arm and a van den Hul MM-2 moving magnet (MM) cartridge.
The Sunfire tube preamp is an attractive unit, weighing in at 23 lbs., housed in the identical black anodized case (19"W x 9"H x 18"D) used to house the Sunfire amplifiers. Whereas the amplifier has a meter (measuring joules of energy) centered left/right and slightly closer to the top on the front panel, the preamp has an amber tinted widow pane located in this cutout. The purpose? Would you believe to be able to look into the preamp's innards and watch the glowing tubes! And to supplement the warm glow of the tubes there are three small incandescent lamps that glow with the same color and warmth of the tube filaments! Surrounding the printed circuit board, on which the tubes and incandescent lamps are located, are three mirrors (silver coated plastic). These mirrors add further to the warm glow by reflecting the light from the tube and lamps toward the front window pane. Lots and lots of warm tube glow for tube aficionados.
Before moving on I will admit that, yes, Virginia, I did remove the outer cover. A well thought-out chassis design means removing 10 sheet metal screws and the top cover/sides slides out from the chassis and front/back panels. And what to my wondering eyes should appear but one of the cleanest, neatest layouts I have seen in electronic equipment. The four printed circuit boards in particular are of a high quality and do not have even one of those ugly wire jumpers anywhere in sight. The transformer is much more substantial than those found in solid state preamps, an indication of the substantial current being drawn by the tube filaments. Speaking of tubes, I have no problem with tubes being used in a preamp where-unlike in most tube amplifiers-they are operating in what I call their "loafing" range, both voltage and heat-wise. Under these conditions tube life is not a concern.
The front panel has the following rotary controls: Volume, Balance, Input Selector, Low Trim Contour, and High Trim Contour. In addition, the front panel has the following two position toggle switches: Power, Mono/Stereo, Contour in/out, and Tape Monitor. Certainly nothing unusual here; the controls and switches are your standard preamp functions, although a brief explanation of the Contour controls and Power switch is appropriate.
The Contour controls are the equivalent to tone controls (bass and treble) but more sophisticated in their operation. Bass and treble can be boosted or attenuated gently with minimum effect on the rest of the frequency spectrum. Although I have nothing against trimming the sound via contour/tone controls it's rare when I do. If the truth be known I still am enough of a purist in wanting to keep the supposedly (!) pure source signal untouched by any signal processing, however slight.
When the Power switch is turned on there's approximately a 40 second delay before the preamp is powered and ready to go. Two LED's monitor the power-up process, a yellow one indicating Mute for approximately 40 seconds after the power switch is turned-on. This Mute light goes off when the other blue LED, indicating Power, turns on after the 40 second wait. Hey, gotta give 'em tubes time to warm-up.
The rear panel input/output connectors (all RCA jacks but one pair) are divided into three groups. The output connectors grouping is as follows: Balanced out, Main Out 1, Main Out 2, and Tape out. The line input connectors grouping is: Tape, Aux, Video, CD, and Tuner. The phono/line inputs grouping is: Two sets of phono inputs consisting of MM and Moving Coil (MC) jacks/Two sets of Inverse Phono connectors consisting of Line level in and Phono Level out. The operation of the Invervse Phono feature will be discussed later in the review. Beneath these phono/line level jacks is a two position pushbutton switch-it's "out" if a MM cartridge is used and "in" if a MC cartridge is used. All the phono jacks are the gold plated, solid-build kind. And all the jacks mount to the rear chassis panel, not to a printed circuit card impersonating a metal chassis. Three unswitched AC outlets (1,000 watts total maximum draw), a gold-plated grounding post, a 2 amp fuse, and a husky power cord round-out the remainder of the rear panel.
The tube compliment is as follows, all tubes of the miniature variety: Line Board-Three 6DJ8's, one used in the Contour amp, and two used in the Line Amp/Balance amp circuitry. Phono Board-Three 6DJ8's used in the MC amp, two 12AX7's used in the MM amp, and one 6DJ8 used in the Infrasonic filter.
The Infrasonic amp circuitry is used in the phono circuitry to attenuate everything from 10 Hz down. These low frequencies (sub-sonic energy) are produced by record warp, tonearm/cartridge resonance, and turntable motor rumble. If not filtered out they can cause (among several things, all bad) excessive cone excursions in the woofer, resulting in muddy bass, aka Intermodulation distortion.
The cover is back in place and the preamp is now ready to do its thing. My first listening session was done with the preamp in the CD input mode. I used my very recently purchased Living Stereo 24KT Gold CD's as the source material. These CD's Are: Gaite Parisienne with the Boston Pops conducted by Arthur Fiedler, Scheherazade with the Chicago Symphony conducted by Fritz Reiner, and Richard Strauss in High Fidelity with the Chicago and Reiner. Waiting in the wings was a plain old, everyday, cheap aluminum CD twin of each of the gold CD's. My first listen was to the gold CD's.
The result was absolutely wonderful sound. What else would one expect from a no-nonsense line output tube circuit with a frequency response of 5 Hz to 50 kHz, +0-3 dB. I then substituted my copies of the plain old, everyday, cheap aluminum Living Stereo CD's of the same performances. The resulting sound was also absolutely wonderful. Perhaps there were differences between the gold and aluminum CD's but I couldn't hear them. And neither could a listening panel of younger ears. The gold CD's do look better though.
Having completed my comparison of identical performances on the gold and aluminum CD's I broke-out the newly acquired serialized (!) and costly LP versions (Classic Records) of the same performances. My heart raced as I placed the Gaite Parisenne LP on the turntable, lowered the tonearm, and stood back, not knowing quite what to expect. First impressions: Excellent sound considering the obvious limitations of the LP. The highs were muted and the lows limited in depth, but not bad, in fact, much better than the LP versions I remember from the 50's. The next step was to more directly compare the LP's to the CD's.
Placing a gold CD in the player and an LP on the turntable of the same performance (Strauss's Also Sprach Zarathustra) I simultaneously depressed the "play" button of the CD player and the "start" switch of the turntable. Of course "simultaneously" is impossible but an attempt had to be made to que the CD and LP as closely as possible for comparison purposes. I moved back-and-forth between the LP and the CD sound by moving the selector control between the CD and Phono positions, adjusting the volume control for differences in level. This comparison of the LP to the CD was made time consuming by my insistence on not playing the LP more than once in a 24 hour period. There were differences. Oh boy were there differences.
Zarathustra's opening bars encompass a wide dynamic range that will test the mettle of any recording and playback technology. The LP sound is noticeably constrained compared to the CD. Very simply a recording made in March 8, 1954 shows its age much more so on the LP version than on the CD version. And the CD version of a 44 year old recording pales to a modern CD recording of the same work, although not to the same degree the LP paled to the CD!
I compared the other two LP's and CD's (Sheherazade and Gaite Parisienne) in the same manner and the result was the same. Interestingly, I no longer am very understanding in having to turn an LP over halfway through a 31 minute, 48 second performance (Also Sprach Zarathrusta)! And hearing ticks and pops on an LP (no matter how slight, these gremlins are on all LP's to some degree) is a blatant form of distortion that seems to be ignored by the LP clan. Now before you shoot the messenger be sure to read the next paragraph!
I placed a more recently recorded (circa 1992) LP on the turntable-Analog Productions, breaking silence, Janis Ian vocalist, accompanied by an assorted instrumental group of electric and acoustic guitar, harmonica, drums, piano and bass. This LP was one of several recommended to by Chad Kassem of ACOUSTIC SOUNDS, who also oversees Analog Productions. In a nutshell this is a beautiful recording of a beautiful voice of a beautiful performance. The sound is the best I have ever heard on an LP, bar none. The voice is ever so beautifully natural without the stridence or excess sibilance that makes you acutely aware that you are listening to a recording. The instruments are recorded in detail and without any exaggerated effects. Take away the clicks and pops, the inevitable degradation of the sound caused by a diamond stylus scraping vinyl, and I could easily live this LP without being at all concerned with the CD version. Something I've always suspected but can never prove is that the LP media does quite well with small ensembles and voice where the dynamic range span is much more limited than that of a large ensemble such as a symphony orchestra.
Another LP suggested by Chad Kassem and which I purchased was placed on the turntable-Analog Productions (Revival Series), The Alternate Blues, with Clark Terry, Freddie Hubbard, Dizzy Gillespie, plus Oscar Peterson, Ray Brown, Joe Pass, and Bobby Durham. I am definitely not a Blues person but musicianship like this just can't be ignored even if one is only half listening....which I wasn't! Recorded in 1980 (no date was given for its remastering) the sound isn't quite that of breaking silence but is proof that the final years of a mature technology are its best in terms of the end result.
Still lurking in the background is the "Precision Inverse RIAA Network" feature of the Sunfire preamp that begs for an analog review. This feature promises LP like sound from a CD source. We'll see if that's possible, but w ould anyone want to argue that the reverse is possible....CD sound from an LP? I think not.
Yeah, I know, what in the hell is this new creation by Bob Carver? Very simple. A CD player's analog output is fed into the input of the Inverse RIAA phono jacks. The output of the Inverse RIAA circuit is fed-via short interconnect cables-to the Moving Magnet (MM) input of the phono stage. And voila, LP sound from a CD! What follows is a short and simplified description of what's happening with the Inverse RIAA circuit.
The CD player's analog output is being treated as a signal coming directly from the recording microphones. The Inverse RIAA circuit applies the standard RIAA recording curve processing to this signal, attenuating the signal level of the lows and increasing the signal level of the highs; in the real analog LP world this "signal processing" is a necessary requirement for reasons that I will not go into here. This "processed" signal could then be fed directly to the cutting head which would "cut" the appropriate information into the surface of a lacquer-coated recording disc. The problem is that the LP's made from this lacquer disc (there are several intermediate steps involved) would also have attenuated lows and augmented highs. Therefore a phono stage has RIAA playback curve circuitry which decreases the signal level of the highs (and increases the signal level of the lows) by an amount equal but opposite to the original recording curve.
The only way for me to substantiate or unsubstantiate (!) LP like sound from a CD source is to compare the sound of the same performance recorded on a CD and an LP respectively. I could then compare the CD sound, massaged by the Inverse RIAA circuit, to the sound of the LP. No, I did not do a double-blind test (it would be just about impossible to synchronize the CD and LP), but I did do an A-B comparison.
Having copies of a performance in both CD and LP format enabled me to compare the CD impersonating an LP sound with the sound of the LP. And, of course, I could compare the CD impersonating an LP sound with the sound of the CD sans any processing. What did I hear?
If you like the sound of the typical LP with the rolled off highs and the limited lows than you're in LP heaven. All of your CD's are now magically transformed into LP's and at no charge for the conversion. Of course I'm exaggerating! The resulting sound is ever so slightly muffled and softer than the LP sound. It's a pleasant listening experience that really helps tone down the brightness of certain CD's, especially those made at the dawn of the CD age. Whether or not you use the Inverse feature or not (and how often) is a personal call. It's certainly different and a lot of fun.
Compared to normal CD sound the processed CD sound suffers from the same shortcomings as the LP. At least the LP sounding CD doesn't suffer from clicks and pops, inner grove distortion, pre and post echo, and the inevitable wear and tear as a result of handling and a diamond stylus wearing scraping off the highs after each playing!
There are two problems with the Sunfire tube preamp, one minor and one I believe to be potentially major. The minor problem is lack of a remote control for even the volume control. Okay, if you're an audiophile it's the music that's important and having to turn the volume control manually is no big deal. After all, we audiophiles are primarily concerned with music. You really don't need all those remote functions that are part of the Home Theater scene. And since the Sunfire preamp is meant to take one back to the heyday of tubes and LP's then perhaps a remote would not be in the spirit of what it's all about. Again, this is a minor quibble.
The major problem I have with the Sunfire preamp is a function selector switch which is clunky in feel and operation. It works just fine but I've been around long enough to recognize a potential source of trouble. Moving the switch from one position to another results in a scraping, tinny, feel that is indicative of operation that will eventually lead to problems with intermittent contact. Not only is the switch clunky and scraping in feel but as you move the switch from one position to another it doesn't lock into the new position as solidly as I'd like; the detent positions of the switch aren't very secure. To give further credibility to my problem with this switch is my son. He used the preamp and was high in praise of it but also commented on the selector switch being "cheesy." Perhaps my criticism is unfounded but I think not. I would highly recommend that Sunfire replace the present selector switch with one that is more robust and positive in its mechanical operation.
So what do I think about the Sunfire preamp? If tubes are your thing along with LP's and CD's then I don't think there's anything out there in its price class. It's not cheap at $1849 (including the optional phono section) but it offers a front end for all analog and digital applications, including MM and MC phono inputs Throw in the Inverse RIAA function and clean digital sound is transformed into a LP type sound, minus the worry of wear and tear, no clicks and pops, and no need to turn an LP over every 15 to 20 minutes. Whether you like the sound resulting from this feature is an individual call.
With all the emphasis on tube circuitry it's easy to forget that the Sunfire preamp is a no-nonsense design, ruggedly built, and attractive looking unit that will do as good a job as any preamp out there. The line output is proof that if tubes are used correctly there will be no coloration of the resultant sound, just a clear, pristine and amplified output of the input signal. And if I remember correctly that's what a preamp is all about. Give this preamp a try. You'll get performance, flexibility, and a wonderful sight to behold in a darkened room. Oh, it was good enough to have me make the analog front-end a permanent part of my reference system!
Web hosting for Sound Off is sponsored by
-- provider of innovative products in audio and acoustics.