| Home | Audio mag. | Stereo Review mag. | High Fidelity mag. | AE/AA mag. |
Have you EVER considered building one of the preamps discussed in TAA over the years? If so, your next thought was probably “Which one has the best sound? ” The purpose of this article is to answer that question. For the past several years, James E. Boak (JEB), Patrick J. Amer (PJA) and I have conducted an irregular series of listening sessions in which we have tried to determine how various pieces of hardware can help us approximate the sound of live music in our homes. As part of this process, we decided to listen to as many of the preamps appearing in TAA as we could find and try to determine which has the best sound. Since this project was conducted in our spare time, it was impossible for all of us to get together at one place and time for listening sessions. I have listened to all the preamps on my system (with the exception of the DH-110) and on PJA's system (see the sidebar on p. 23 for a description of both systems). JEB has listened to all of them (with the exception of the SP-8 and PV-5) on PJA's system and to several of them on mine. Equipment Reviewed The preamps under consideration are listed in Table 1. These include most of the preamps that have been discussed in TAA since 1979. We could not find samples of the Marsh pre amp (TAA 3/80, p. 18) and the Jung/Hollander modified Marantz 7C (TAA 1/81, p. 20). The PV-3, A-502, DH-110 and P-10 are commercially available kits whose construction and sound has been described in TAA. The units we auditioned were those previously reviewed by PJA. Patrick. Amer has reviewed many preamps for TAA and is a member of the Cleveland Orchestra Chorus. James E. Boak is a contributing editor of TAA, an engineer with a musical ear and a rich source of technical knowledge. William L.R. Cruce is a neuro-biologist who loves music and electronic tinkering. All were in “stock ” kit form except for the use of OFHC wire wrap for some internal wiring. The Lampton Zukauckas (L-Z) unit we used is the prototype built for the article describing it (TAA 1/79, p. 5). The WJ-1A (TAA 3/79, p. 24) and the Last PAS (TAA 4/82, p. 24; 5/82, p. 28) are construction projects that began earlier in TAA as the quite different WJ-1 (TAA 1/78, p. 7) and PAS mod (TAA 1/74, p. 4; 2/76, p. 21). The WJ-1 had numerous modifications (see references 4, 9, 14, 15, 16, 21, 22, 23, 25, 27 and 40) until the major modification known as the W]J-1A was published. Both the WJ 1A and the Last PAS have been subject to several modifications, as cited in Table 1. We looked at a representative version of each of these pre amps, but neither unit embodied all the modifications suggested. The SP-6b has served for several years as our reference for what is sonically available in higher-priced preamps (although it no longer qualifies as state-of-the-art). It has been the subject of two TAA articles by Brian Clark (TAA 4/80, p. 42; 1/81, p. 7), but these dealt only with the modification of its RIAA active equalization circuit. I tried those modifications (which were based on sound theory), but found that they interacted with the phono stage regulator (which in the SP-6b verges on instability) in an undesirable way. My modification of the SP-6b, which I call the SP-6x, is basically an application of POOGE techniques (TAA 1/81, p. 20; 4/81, p. 7), many of which were suggested to me by the instruction sheet in a capacitor modification kit from Two Jeffreys Audio of Phoenix, Arizona. Those modifications not previously published are described in the sidebar on p. 27. We selected the Conrad-Johnson PV-5 as a “close-to-state-of-the-art ” reference preamp. Its current list price of $1,485 is about four or five times that of the other kits and projects we tested (except the SP-6x, which is available used for about $600 to $700 and has about $200 worth of new parts in it). But since the PV-5's little sibling, the PV-3 kit ($299), performed so well in our comparisons, I just had to see how a more all-out approach might sound. We chose the SP-8 as another “close-to-state-of-the-art ” reference preamp because it is the successor to my own SP-6x (for a mere $850, Audio Research will upgrade the SP 6b to an SP-8 by total replacement of circuit boards). At a list price of about $1,900, the SP-8 is the most expensive preamp to which we listened. The PV-5 and the SP-8 have siblings that cost twice as much, but I did not feel it would be fair to consider them. The PV-5 and SP-8 were loaned to me by The Golden Gramophone of Akron, Ohio. Listening Methods A scientific study does not require the reporting of numbers to be “objective. ” Indeed, many scientific papers in fields as diverse as botany and neuroanatomy are simply careful descriptions of visual observations. What is required is that the conditions of the observations be reported in sufficient detail that another trained observer can repeat them. The report gains credibility if several observers are included. It is in this spirit that we have made our observations of the sonic differences in preamps. I have in the past used blind and double-blind comparisons to evaluate audio equipment. In those days, I had to satisfy my scientific self that I could really hear differences between electronic components. The procedure is tiring and tends to detract from my ability to make detailed observations of the music. I have subsequently found that it sometimes takes extended listening before my ears “lock in ” on a particular sonic feature of a component. Once detected, I can usually recognize the feature in a double-blind test. Other listeners may detect sonic differences much more quickly than I (PJA and JEB, for example), but if I can hear it after they call my attention to it, then the feature is much easier to detect repeatedly. We listened to the preamps in clusters of two or three per evening, off and on, over a period of three months in the summer of 1984. Room temperature was mostly in the 70s and 80s, while humidity typically exceeded 50 percent. We gave the tube preamps at least a three-hour warm-up and left the solid-state units on continuously. We usually matched preamp gain levels to with in +1dB at 1kHz by measurement. Sometimes we adjusted the gains to match by ear. This was sufficient, since we were not doing rapid A/B switching. The components of the reference systems are described in the sidebar on p. 23. The recordings used in the evaluations are listed in Table 2. Hafler DH-110 While this preamp (Photo 1) was not available for review in the current round of listening, I heard it earlier on PJA’s system, where it demonstrated a harsh edge on high-frequency sounds and transients that was unpleasant and tiring. As PJA states in his review of the unit (TAA 3/83, p. 48), it makes violins sound as though the artist is 'sawing on wires.' In my opinion, this unpleasant quality represents the worst aspect of 'transistor sound.’ JEB and I concur with PJA's other assessments and feel that the DH-110 does not merit any further discussion. It is on a different planet from the rest of the preamps under consideration. Phoenix P-10 It was difficult for me to spend much time listening to this preamp (Photo 2). Its sound is uninteresting, the stereo image is flattened, and small tonal and transient details are lost. This is best heard on DAFOS, where the airy sound of the flute is distorted, the slapping sound of the flute keys is lost, and the sound of the light drum tapping has no tone (which it does on the other preamps). PJA also reviewed this preamp in TAA 3/83 (p. 48), and since JEB and I are in complete agreement with his evaluation, I will quote from that review. PJA noted that the P-10 produces clean, quick, clear sound. Transient attacks and percussion sounds are accurate, but the sound is dry and for ward, with little sense of the sound space in which the music was re corded. The P-10 does not reproduce music with the warmth and resonance of the Jung PAT-5 (WJ-1A) or the Vorhis PAS, and in extended listening sessions the dryness becomes fatiguing. Strings, in particular, sound dry and wiry. Wood winds and bass are reproduced accurately, if a shade on the dry side. In the lower midrange, cellos and trombones seem thin. The soundstage has good lateral spread but insufficient depth. The P-10 might be a good preamp for $150, but the Conrad-Johnson PV-3 is available for $299 and the Fuji A-502 for $349 (all three are kits). Why settle for crawling on the earth when you can soar with the eagles? Lampton-Zukauckas Preamp This preamp (Photo 3) is characterized by a dry sound that might be described as white, bleached and sometimes analytical when com pared to the colorful tones transmit ted by the better units. In the I Ching terms suggested by Harry Pearson of The Absolute Sound, the L-Z's brighter highs might be characterized as “Yang, ” as compared to the “Yin ” (fuller/warmer) sound of the SP-6x, PV-3 and A-502. Photo 1
---------------- 24 TABLE 1 Audio Research SP-6x (POOGed SP-6b) Audio Research SP-8 (Audio Research, 6801 Shingle Creek Pkwy., Minneapolis, MN 55430) Conrad-Johnson PV-5 TAA 4/80, p. 42 TAA 1/81, p.7 (Conrad-Johnson Design Inc., 1474 Pathfinder Lane, McLean, VA 22101) Conrad-Johnson PV-3 Fujitech A-502 TAA 5/84, p. 44 TAA 4/83, p. 36 (Monarchy Engineering, Box 5517, S. San Francisco, CA 94080) Hafler DH-110 (The David Hafler Co., 5910 Crescent Blvd., Pennsauken, NJ 08109) Jung PAT-5/WJ-1A Lampton-Zukauckas (L-2) Phoenix P-10 TAA 3/83, p. 48 TAA 1/83, p. 51 TAA 3/79, p. 24; also references 6, 7, 17-20, 24, 31, 33-36 TAA1/79,p.5 also references 5, 26, 30 TAA 3/83, p. 48 (Phoenix Systems, 91 Elm St., Manchester, CT 06040) Vorhis Last PAS TAA 4/82, p. 24 TAA 5/82, p. 28 also references 37, 38, 39
---------------- On the Bach harpsichord and Tafelmusik records, it lacks fullness of bass and distinctive differences in tone (overtones?) among the various instruments. The clarinet on the Schuman disk sounds nasal and metallic, whereas with the SP-6x it sounds full, rich and woody. Violins on the Tafelmusik disk sound steely and dry compared to the warmth and richness of the SP-6x and the A-502. On the recording of Norman Blake and friends, the analytical quality of the L-Z displays itself in a positive way: the “pluck ” and low “thump ” of the string bass sound cohesive (as one string), exactly as they do on the PAS, A-502 and PV-5. On the PV-3, SP-6x and SP-8, the pluck and thump sound like two different strings, with the thump having a distinctly tubby quality to it. The L-Z's stereo image is flat. Sound tends to be clustered in the center and inside each speaker whether on orchestral pieces such as the Gliere or small bluegrass performances such as that of Norman Blake. The images of the A-502, the SP-6x and especially the PV-3 have far greater width, depth and detail of instrumental spatial separation. The L-Z does not seem to add anything unpleasant to the sound (some people might prefer its steely character), so in that sense it is not fatiguing. But it does omit many of the details that bring pleasure to critical listening. For example, on DAFOS, small musical sounds in the background are not very clear, and the flute “air ” is incorrect. Looking back at Vorhis' review of the unit (TAA 1/79, p. 15), I find that we are in substantial agreement about the sound of the L-Z preamp, even though we compared it to different reference units. I should also note that the bass and treble controls did not give a flat response at their center settings and had to be adjusted with pink noise and a spectrum analyzer. The balance also varied considerably at different volume control settings. The major virtue of this preamp is that it is absolutely quiet, even at full gain (and that was one of the designers' main goals). Still, it is not in the same class as the better preamps in our survey. PHOTO 2: The Phoenix P-10 produces a flattened stereo image, and small tonal and transient details are lost. Its sound has a dryness that becomes tiring in extended listening sessions. PHOTO 3: The Lampton-Zukauckas preamp lacks the full bass and distinctive difference in instrumental overtone of the better units. Vorhis Last PAS This preamp (Photo 4) is several steps above the previous three, and in some respects, it surpasses the SP 6x. On DAFOS, for example, it recovers much of the detail of the flute “air ” and key slaps. In addition, the drum tone is clear, and the drum slaps are sharp and clean. Although the Last PAS is better than the SP-6x on these sounds, it does not quite equal the PV-3. On the Last PAS, castanets have a harsh, unpleasant sound, and tubular bells do not have the round, whole tone that they do on the SP-6x. In the mid and low bass on DAFOS, the PAS and PV-3 seem to be weaker than the SP-6x. Yet in a test of bass transient capability (the string bass on Norman Blake and friends), the PAS is tightly controlled in a way matched only by the A-502 and PV-5. Here the PV-3, SP-6x and SP-8 do not seem to render the pluck and thump as the sound of one string. A major weakness of the PAS is that hiss levels are slightly higher than on the SP-6x when used with a moving-coil cartridge without a step up device. The PAS also has considerable trouble with hum, which can, however, be reduced by careful placement of the preamp and leads to it. The PAS was not, however, designed to handle such low-level in put signals. It also lacks a cathode follower output. This became clear when I tried to run it into a biamp crossover consisting of a passive high-pass network and an active low pass, and it suffered considerable high-frequency loss. Compared to the SP-6x, it has slightly more mid bass warmth and transient roll-off, which used to be considered characteristic of tube preamps. Overall, however, the SP-6x is superior, although the PAS is the sonic equal of the unmodified SP-6b. I do not think it is sonically equal to the PV-3, but PJA disagrees with me on this. Jung PAT-5/W}-1A This preamp has a more neutral tonal sound and a more accurate rendition of harmonic detail than the original SP-6b or the PAS, but the SP-6x modification obscures this distinction. The WJ-1A's handling of bass and treble transients is slightly better than the PAS's and about equal to the SP-6x's. Compared to the SP-6x, the WJ-1A has less depth and width of stereo image, such as on the Beethoven/Rasoumovsky piece, and the exact placement of the instruments on the stage is much less distinct with the WJ-1A. The greatest weaknesses of the WIJ-1A are its high hiss level and low gain. The rest of the preamps under review are able to take my Talisman S moving-coil cartridge directly into their phono inputs and amplify its sound without excessive noise. The WJ-1A cannot. The WJ-1A still represents an attractive choice for the listener who will be using only moving-magnet cartridges. It might be attractive for someone using moving coils who already has a step-up device and can accept the sonic com promises the step-up will introduce. A good step-up purchased new will, however, cost more than the cost of building this preamp (around $300), and the cost of a step-up and the WJ 1A would exceed the cost of many of the better preamps in our survey. High noise and low gain are uncommon for a transistor preamp, but at the time the WJ-1A was designed and built (1977-1979), these were not considered important criteria. Now they are. Since many of the design principles (e.g., power-supply regulation, layout and wiring) em bodied in the WJ-1A are still valid, one modification might be the use of low-noise, high-gain op amps in the phono stage. Audio Research SP-6x Physically, the SP-6x is almost as rugged as an old tube-type Tektronix oscilloscope. In spite of the confidence that its 'built of bricks’ look may convey, the SP-6x has very unstable power supply regulation, which tends to go into low-frequency (DC) oscillation from large, low-frequency inputs, such as inserting an interconnect cable into a phono socket. The phono section power supply was also driven into high-frequency oscillation when I tried to modify the RIAA circuitry. Fortunately, an elaborate autosensing circuit quickly mutes the preamp's output. Other tube preamps such as the SP-8, PV-3, PAS and PV-5 do not seem to have this power supply stability problem. The SP-6x's overall sonic character is Yin in nature. Individual instruments have warmth and a life of their own. On the Bach Musical Offering, the flute has a breathiness that has always pleased me. This pleasing warmth is especially evident on chamber music recordings such as Tafelmusik. At first I thought I was hearing the harmonic complexity of real instruments. This is a subtle effect, which you can check by listening to the playback of a recording that you heard being made. Since we were unable to do this, we had to check the SP-6x sound against other preamps. We found that the richness clouds details that are present in the PV-5, the A-502 and even the little PV-3. I now suspect that the SP-6x adds this harmonic richness instead of transmitting it from the record. Although this might be “inaccurate, ” it makes playback more pleasing in a natural way. This is tube coloration at its most seductive. In the low bass, the SP-6x has tremendous impact. For example, on the Sheffield Drum Record or the “African Ensemble ” cut of Professor Johnson's Astounding Sound Show, it delivers a solid, impressive drum sound. On the “String Quartet ” cut of Professor Johnson's record, the bass string sound is solid and forceful. This bass sound seems much Photo 4
-------------------- TABLE 2 RECORDS USED IN LISTENING TESTS Gliere, “llya Murometz, ” Bach, Harpsichord Concertos (BWV 1052), Archive R 215351. Bach, Musical Offering, SEON ABCL-67007. Beethoven, “Hammerklavier ” Piano Sonata, DG 2530-869. Beethoven, “Rasoumovsky No. 1 ” String Quartet, Denon 0X7168-ND. Cantate Domino (Side 1, Band 2), Proprius 7762. DAFOS (Side 1, Band 1), Reference Recordings RR-12. Melodya ( Columbia) MG 3383. Growing Up in Hollywood Town ( “The Rose ”), Sheffield LAB-13. Haydn, Die Schopfung (The Creation), Accent ACC 822829. . Jazz at the Pawnshop ( “Lady Be Good ”), Proprius 7778-79. . Norman Blake and friends (Side 1, Band 2), HDS 701. . North Park Elementary Choir ( “Tom Sawyer ”), Fulton ARC 4185-S. . Professor Johnson's Astounding Sound Show ( “African Ensemble ” and “String Quartet ”), . Rachmaninoff, Symphony #3, EMI ASD 3369. . The Scholars: When Winds Breath Soft, L'Oiseau Lyre DSL033. . Schumann, R., Fantasiestucke Op. 73, Aulos FSM 53546. . Sheffield Drum Record (Ron Tutt's side), Sheffield LAB-14. . Tafelmusik (Side 1, Bands 1 & 2), Reference Recordings, RR-13. . Weavers Reunion at Carnegie Hall ( “Wimoweh ”), Vanguard VSD 2150. -------------------- more controlled than the boomy bass of an earlier generation of tube preamps, but it falls apart on a real test of bass transients-the plucked string bass at the beginning of the reference cut on the Norman Blake recording. Here it sounds as though the SP-6x is delivering a fuller, more live bass string sound as compared to the PV-5, the A-502, the PAS and even the L-Z. Careful listening reveals that the SP-6x delivers two distinct tonal qualities-one associated with the pluck of the string and the other with the thump that follows. This dual-string sound is also characteristic of the SP-8 and, to a lesser extent, of the PV-3. I had always thought the SP-6x had good transient response because it was the equal of the PAS and the WJ-1A. But in comparison to the best of the current crop, it does not fare so well. The PV-3 and PV-5 outclass it. Wire brush and cymbal sounds on the Sheffield Drum Record and Jazz at the Pawnshop sound slightly blurred and hashy. Toward the end of the “Lady Be Good ” cut on Jazz at the Pawnshop, the saxophone sibilants are also slightly blurred, and the same is true for the vocal sibilants of the solo female on Cantate Domino. A major strength of the SP-6x has always been its ability to render a wide and deep stereo image on recordings such as the Gliere and The Weavers disks. Aside from its higher gain and lower noise, this is its major advantage over the WJ-1A. On Tafelmusik and the Sheffield Drum Record, it is able to put the individual instruments into a distinct “place ” in space. When compared to the PV-3 and PV-5, however, it seems to have a wandering and blurry image of that space. This is still a magnificent preamp. --------------------- Ref Listening Systems My system, where all the preamps were auditioned, has at its front end an Oracle Alexandria turntable with a Prelude arm. The turntable is powered by a Lambda LM C24 regulated DC power supply set at 27V DC, instead of the original wall-mounted trans former. My reference cartridge is a Talisman S connected to the preamps with a 1 meter length of Neglex 2534 cable. I used no step-up device because nearly all the preamps tested had sufficient gain and low enough noise with the Talisman cartridge fed directly into their 47k input loads. During each listening session, I monitored the AC line voltage and periodically adjusted it with a Variac to keep it in the 117 to 120V range. Fulton 47-inch interconnects fed the preamps' output to an Audiovisual Systems PB-289G patch bay and then to a Snell solid-state active crossover (6dB high, with low pass around 380Hz), which had been POOGed by replacing the wiring with 4P24 OFHC Tefzel wire-wrap and by adding 0.22 uF polypropylene caps to bypass the power-supply electrolytics. The crossover’s low-pass output went via short (18-inch) Sound Connectors cables to a pair of Kenwood LMO7 mono amps, while its high-pass out put went to an Audio Research D-90 (6550 version) with its input gain pots disabled. Monster power-line cable (10 feet) connected each amp to Snell type A speakers jumpered in the biamped mode. I placed the speakers at one end of a listening room (15.5 by 30 by 8.8 feet WLH) in which the floor is covered with thick carpet and the windows with lightweight curtains. Sofas and chairs in the listening end of the room provided considerable sound absorbency, while bookcases on the walls to the side of each speaker pro vided moderate absorbency. The speaker end of the room was more “live ” than the listening end. The speakers were placed about 3 feet from the side walls and 6 feet from the end walls, slightly toed in toward the listener. PJA's system, on which most of the preamps were auditioned, consists of a Dynavector 23R cartridge, an SME 3009 II arm, a Kenwood KD-500 turn table, a Dynavector 6Z step-up trans former (when needed), a Fuji A-502 preamp, a Jung crossover network (references 10-13) crossing over at 375Hz, a Fuji A-501 amplifier? in class A operation driving the midrange and tweeters, and a POOGed Hafler DH-500 driving the woofers in IMF TLS 50 II speakers. All his interconnects (including speaker cables) are constructed of OFHC wire-wrap.
--------------------- It has the natural balance of a good musical instrument, and although it is not the best at anything, it does everything well. That showing is good enough to put it ahead of the PAS and WJ-1A. Conrad-johnson PV-3 Physically, this preamp (Photo 5) is the total opposite of the SP-6x. It looks like something you might pick up late in the afternoon at a hamfest. It hums like a power line unless you place it just right in relation to your other equipment. If you touch the volume control, you get hum. (PJA describes the difficulty in mounting that control in his review in TAA 5/84, p. 44.) It has no cathode follower buffering after the phono or output stages, so attached cables must be short, and the next stage's impedance must be high. Still, the PV-3 has low hiss comparable to the SP-6x at all but the highest gain set tings, and it has gain enough to play my Talisman S cartridge quietly. I was quite taken with this little preamp. It made me fuss with all kinds of trivia just to be sure I was hearing things correctly, and it made me re-tube my SP-6x to make sure the competition was fair. I took it apart to see what kind of black module or IC Conrad-Johnson had snuck inside. Its insides are uninteresting. The electrolytics are Sprague Atoms and CDE cardboard-wrap. The largest (1uF) film caps look too small to be polypropylene, and I noted a generous supply of Sprague 418P “Orange Drop ” polyester film caps in the smaller sizes. The company used silver micas rather than polystyrenes in the picofarad range. Most of the resistors are Corning metal films. As PJA mentions in his review, the power supply and heaters are regulated, but minimally. Although the parts are not what we POOGEs are used to, they are not from the bargain basement either. In fact, I do not know how Conrad-Johnson could af ford to use even these parts for the $299 kit price. More to the point, I do not understand why the PV-3 sounds so good. The only modification included in the test unit was PJA's use of OFHC wire wrap from the phono input to the board and from the board to the output sockets. The PV-3 is a very Yang-sounding preamp. It delivers pure tones in contrast to the harmonic richness of the SP-6x. At first listen, these seem steely and hard-etched, but they are precise. Unlike the SP-6x, they do not enhance the sound of the record. On the Bach Musical Offering, I can distinguish the tonal differences be tween the two violins, and the flute is pure and clean. This preamp presents a detailed view of three-dimensional space, which is evident on Tafelmusik, where some instruments are located to the outer sides of the speakers. It has the spatial width and depth usually associated with tube equipment, which was well demonstrated on the Gliere recording. In combination with its harmonic detailing, its imaging abilities allowed me to pick out individual instruments and musical sounds by spatial and tonal cues, even in the rich tapestry of sound presented by DAFOS. The unit also has superb transient reproduction. Wire brush and cymbals, as found on the Sheffield Drum Record and Jazz at the Pawnshop, are rendered with exceptional clarity, seemingly etched in musical space. Other good preamps such as the SP 6x seem slightly blurry by contrast. Sibilants, as in the female voice on Cantate Domino and in the saxophone on Jazz at the Pawnshop, are clear and clean. In its crisp handling of transients, the PV-3 resembles the better transistor preamps, such as the A-502, and another “un-tubey ” tube preamp, the PV-5. It outclasses the PAS and SP-6x in its transient cleanness, and it beats the PAS, SP 6x and WJ-1A in its reproduction of subtle background musical sounds. One major sonic fault is a lack of impact in the bass. This is often evident as a simple absence of bass, compared to the SP-6x. In addition, with bass transients such as the string bass on Norman Blake, the PV-3 lacks the control characteristic of the PAS, L-Z, A-502 and PV-5. In this way, it resembles the SP-6x and the SP-8: the pluck and thump of the string bass are rendered tonally different, as though they come from two strings. An additional weakness of the PV-3 is its handling of the human voice. Depending on the record, my impressions of its simulation of the real thing varied. Amanda McBroom's voice on Growing Up in Hollywood Town sounds rich and full in comparison to the SP-6x, yet the solo female voice on Cantate Domino sounds slightly drier on the PV-3 than on the SP-6x. The Weavers' voices sound hard and almost glassy on the PV-3, but very natural on the SP-6x. On the North Park Elementary Choir record, the clusters of voices are easier to separate on the SP-6x than on the PV-3. PJA de scribes this problem with vocals more precisely in his review, attributing it to an emphasis on the up per midrange and treble ranges and a de-emphasis of the lower midrange and bass. As a member of a chorus, he is more sensitive to this than I am. PJA and I are in substantial agreement regarding the PV-3's crispness of transients and lack of bass impact. PHOTO 5: Physically, the Conrad-Johnson PV-3 is the total opposite of the SP-6/8 series. It represents an excellent compromise between good tube (deep and transparent) and good transistor (crisp and accurate) sound, which ranks it between the SP-6x and the SP-8. PHOTO 6 Overall, he feels it is in the same league as the PAS, WJ-1A, SP-6x and A-502, but it is his last choice in this group. I feel it is in the same league, too, but I prefer it to the PAS and WJ 1A and possibly to the SP-6x, and I consider it second only to the A-502 in this group. JEB admires the PV-3's elegant design, which shows a thorough understanding of each component and exactly what it is doing in the circuit. He would not rank either the PV-3 or the A-502 at the top of the group, but he is more comfortable with the sound of the PV-3 than with that of the A-502. He feels the PV-3 represents an excellent compromise between good tube and good transistor sound, having some of the depth and transparency of tubes and some of the crisp accuracy of transistors. Audio Research SP-8 Because of the short time I had it, I was able to compare this preamp (Photo 6) with only the SP-6x, PV-5 and A-502. I felt it was important to include this near-state-of-the-art descendant of the SP-6 series to see how the TAA preamps compared to it. The SP-8 had about the same level of hiss with the Talisman S as the SP 6x and PV-5. It had a little more gain than the SP-6x and not quite as much as the PV-5, and it was more micro phonic than either unit. Like the PV-5, but unlike the SP-6x, its regulator circuits seemed quite stable in response to plugging in interconnect cables. In every sonic respect, the SP-8 is slightly improved over the SP-6x. For example, on Tafelmusik, the highs are a little crisper, spatial localization is a little tighter, and you can hear some subtle instrumental goings-on in the background that are not evident on the SP-6x. This attention to detail is also evident on the Sheffield Drum Record, where the wire brush is more carefully etched than with the SP-6x. While it sounds better than the SP-6x in its high-frequency detail, the SP-8 has its limits. Com pared to the A-502 and the PV-5, I noted a smooth roundness to the edges of the voices on The Scholars recording, a little blurring of the notes on the Beethoven “Hammerklavier ” and a softening of quiet transients in the drum tapping and flute sounds on DAFOS. The mid-low bass, as evidenced by the solid drum sound on the Sheffield Drum Record, is more prominent than with either the SP-6x or the PV-5. Like the SP-6x (and the PV-3), bass transients seem poorly controlled. The pluck and thump of the string bass on Norman Blake seem separated into sounds from two strings, a condition not heard on the PV-5 and the A-502. In addition, the thump has a tubby quality rather than a string sound. The slight tendency to mid-bass looseness is evident in the voices on The Scholars recording and on the Beethoven “Hammerklavier. ” Fujitech A-502 This preamp has already been reviewed at length by PJA in TAA 4/83 (p. 36). It is a kit builder's dream or nightmare, depending on your perspective. It contains more than 800 components and 245 terminal posts to be stuffed into the boards. PJA estimates it would take an experienced builder 60 to 80 hours to build the kit. What you get for $349 and your time, however, is a DC-coupled, solid-state preamp with all the buttons, bells, whistles and controls you could ever want, as well as a switch to bypass all this for the phono circuit. And it includes a separate high-gain, moving-coil phono circuit, with a selectable input impedance of 10 or 10 ohm.
------------------- Pooging in the SP-6b When devising the SP-6x, I used the stock SP-6b circuit, replacing the resistors with metal film devices (Corning where available) and bypassing the electrolytics with polypropylene and polystyrene capacitors. I also replaced the film caps with polypropylene and polystyrene caps in the parallel “sandwich ” configuration (see Jung's articles in TAA 1/81, p. 20, and 4/81, p. 7). I used Reliable Capacitor Wonder Caps because they were the most readily available polypropylene caps at the time. I added 2,200uF of electrolytic capacitance to the tube heater supply below the circuit board and bypassed it with a film sandwich. Although Vorhis recommends adding as much as 40,000 to 70,000uF to heater supplies (see TAA 4/82, p. 24, and 2/83, p. 56), this would have required an external capacitor box, which I wanted to avoid. I replaced all the RCA phono connectors with the large, gold-plated, rear-mount type supplied by Old Colony. I also replaced the short, un shielded wiring on the main circuit board and from the main board to the front panel board with four strands of 24-gauge (4P24) solid OFHC Tefzel insulated wire-wrap. I used the same wire-wrap for the short wiring from the phono input sockets to the main board, but ran it through small ferrite beads to suppress radio-frequency interference. I replaced the long wiring from the main board to the output sockets with 4P24 wire-wrap surrounded by a shield connected at the board end only. When replacing other long pieces of wiring that had to be shielded (e.g., from the input sockets to the front panel board and from the tape/source switch to the boards and sockets), I used Neglex #2534 OFHC quad microphone cable (available from Old Colony). I connected these in the manner described by Bill Ruck, with the ground side connected to one pair of wires, the hot side to the other pair and the shield at the input end only. I disconnected the switch for changing gain in the line stages and fixed the gain in the high (60dB) position by short 4P24 wire-wrap straps on the board. I replaced tubes (12AX7) V1, V2, V4 and V5 with selected Telefunkens (both sides matched for equal and high transconductance) and substituted selected Radio Shack “Hungarian ” tubes (believed to be Tungsram) for V3 and V6 (cathode followers). After my modifications, the SP-6x exhibited increased clarity of subtle harmonic details (e.g., the ability to distinguish the tonal differences of two violins in a quartet), faster transient attacks, a more neutral tonal character, and a wider and deeper stereo image. Its tonal character was more like that of a good transistor preamp (the WJ-1A) and less like that of a good tube preamp (the PAS), and it surpassed them both in presentation of stereo image. I used the Old Colony inverse RIAA network to measure the frequency response from phono input to main output. The POOGed SP-6b now has a slightly flatter frequency response than before the modification. It retains the high-end rise to +0.20dB in the 10 to 20kHz range, but the bass at 20Hz is now -0.08dB, an improvement over the original -0.20dB (see TAA 4/80, p. 42). Although I did not measure the noise level, I think it decreased audibly, and now I rarely find it necessary to use an accessory step-up device for my moving-coil cartridge.
------------------------- Surely, you say, we can't have all this and good sound, too? Yes, unbelievably, it beats all the preamps we have been able to sling at it, save for the magical PV-5 from the wizards Conrad and Johnson. To quote from PJA's review, it is very clean...correctly reproducing the characteristic timbre and color of each instrument and voice. Transients and percussive sounds are faultless.... Depth of image is adequate, and spread of image is very good. The preamp captures hall resonance and the subtle decay of instrumental sounds with delicacy and realism. Most welcome is the absence of the metallic dryness characteristic of so many transistor preamps. The sound has the warmth and color of live music. On the Beethoven Hammerklavier recording, you can hear the separate attack of the hammer and the note that follows. The A-502 re produces this sound with greater clarity than the SP-8, but not as cleanly and distinctly as the PV-5. The A-502 is tonally neutral, showing none of the mid-bass “tubbiness ” of the SP-8. On the Norman Blake record, the A-502 delivers the coherent string sound of the plucked string bass, but not with quite the realism of the PV-5. The only weakness I found in the A-502 is in reproduction of vocal sibilants. On The Scholars or Haydn's The Creation, the A-502 seems to exaggerate the sibilants slightly, giving them a harsh, shimmery edge. Although this might be the recording microphones, what ever the source, the sound is so loaded in high-frequency energy that I think it is causing a little distortion in the preamp. The SP-6x and SP-8 tend to ‘round off' this sound and create a pleasing effect. The PV-5 seems to have a proper balance, delivering a clear but not harsh sibilant edge to the voices. Whether or not it is an accurate reproduction of the recordings, what the PV-5 delivers is pleasant, and what the A-502 delivers is not. PJA, who sings in a chorus, says that live vocal sibilants are pretty striking with the A-502, but he also admits that the PV-5 reproduction of these is slightly more realistic. JEB is less enamored of the A-502 than PJA and I. He does not think it has quite the transparency of the PV-3 or SP-6x. He finds it over meticulous, delivering a hard edge to vocal sibilants and to crashing crescendos of orchestral sound. He is unsure whether to assign this to a problem in the recordings or to the transistors in the A-502, but he tends to favor the sound of the PV-3. JEB describes the circuit as brilliant, if incredibly complex. The preamp contains a lot of active cir cuitry with many contacts in the signal path. It looks as though a committee designed it because of the Byzantine methods used to clobber each problem. It is a miracle that it works at all. Conrad-Johnson PV-5 After hearing the PV-3 make sonic mincemeat of my carefully POOGed and tweaked SP-6x, I decided Conrad and Johnson must be onto some thing. I recalled some recent favor able reviews of the PV-5 (references 3, 8 and 29) and an equally rave review of the $850 PV-6.28 That did it! I just had to see what the PV-5 (Photo 7) could do. Besides, we had nothing better than the A-502 yet. I wanted to be able to place it in the proper perspective. As you will see, the PV-5 became our reference preamp, our own version of “state of-the-art. ” The PV-5 is more ruggedly constructed than the PV-3 (not difficult to do), but it is not built out of brick like the Audio Research SP series. It is, however, built solidly enough to produce the sounds we want with out wasting hundreds of dollars on sheet metal. It has high enough gain and low enough noise to reproduce most records through my Talisman S cartridge without any intrusion of 'tube rush. ” Its sound is flat from sea to sea and the most neutral of any preamp I have heard. On The Scholars recording, the highs are not harsh (particularly the sibilants with which the A-502 has trouble) but extremely clear. Al though its tonality resembles that of solid-state, it is a tube preamp. On the Beethoven “Hammerklavier ” disk, the PV-5 renders the cleanest separation of individual notes and hammer strikes; the dynamics are excellent; transients are clean; and the tones are mellow and rounded. It gives a detailed yet coherent clarity to the sound of the plucked string bass on Norman Blake's record. On Haydn's The Creation and The Scholars, the voices are precisely separated tonally and in space-one of the more difficult tasks for any electronics. The depth and width of the image on The Creation and The Scholars is superb, which I have found characteristic of tube pre amps. The three-dimensional quality of the stereo image that the PV-5 creates is most dramatically revealed on the Rachmaninoff record. It is more alive and has greater dynamic range, better stage and better delineation of details in real space than I have ever heard on this record. When PJA and I listened to this pre amp, we kept remarking on how realistic things sounded. It reproduces the tonality, harmonics and sense of space around the voices and instruments with a clarity we have never heard over any high-fidelity electronic sound-reproducing system. Shootout Wrap-up As you may have gathered from PJA's and JEB's comments, we are in agreement about the individual sound of the preamps, but not about exactly how we would rank them. We all found the DH-110 and P-10 to be decidedly inferior to the others; the L-Z, while somewhat better, would still fall in this bottom group. We would group the PAS, WJ-1A, SP 6x, PV-3 and SP-8 together, while the PV-5 is a step ahead of them all. I have discussed the preamps in the approximate order in which I would rank them. I have tried to present you with enough information so that you can decide for yourself which preamp would suit you best. If you are trying to select a preamp from this group, you should consider some other factors in addition to those already mentioned. The first is cost. Only the PAS, WJ-1A, PV-3 and A-502 are reasonably priced (under $400). Second is ease of construction. Only the PV-3 and A-502 are commercial kits (all parts and instructions are in one package), with the PV-3 being relatively easy to build and the A-502 incredibly complex. The third consideration is potential for modification. The PAS and WIJ-1A are very personal projects. So many modifications have been suggested in TAA that your preamp will probably never be exactly like any one else's. The WJ-1A has great potential for improvement simply in the selection of newer, quieter op amps. The PV-3 kit also has the potential for modification. For in stance, you might upgrade some of the components, grounding and shielding. Finally, you should consider each preamp's special features. The A-502 is the only unit with a full array of filters, tone controls and switches. The rest are minimalist preamps. In selecting a preamp, JEB points out that you must also consider the system with which you will be mating it. If your amplifier (or midrange high amp if you are biamping) is a tube amp with a soft character, the A-502 might make an excellent partner. But if your amp has a more analytical sound, like the Hafler DH-200 or DH-500 after POOGing, you might be happier with a slightly softer-sounding preamp such as the PAS, WJ-1A or PV-3. The differences among the pre amps in our middle group are subtle. PHOTO 7: The Conrad-Johnson PV-5 became Mr. Amer's and Mr. Cruce's own version of “state-of-the-art. ” It reproduces tonality, harmonics and a sense of sonic space with a clarity approaching “reality. ”
If you listen to them casually, you will probably detect no differences; if you listen to them for extended periods of time, none will tire you. All are pleasing. What we were striving for was perfection-a preamps) that reproduces sound most like the real thing. If you decide to build one of the TAA kits or projects from our middle group, you can be sure that it will do as good a job of approaching the sound of real music as some very expensive commercial preamps that are widely recognized for their sound reproduction. a “The Hafler DH-110 2. Birchall, S., “The Fujitech A501 Amplifier, ” TAA 3/83, p. 50. 3. Cordesman, A.H., “Conrad-Johnson PV-5 Preamp, ” Audio, August 1984, p. 68. 4. Curl, J., “Inversion, RIAA and TIM, ” TAA 1/79, p. 49. 5. Dragan, M., “Lampton-Zukauckas Preamp Modification, ” TAA 2/84, p. 56. 6. Greenhill, L.L., 'A Subjective Listening Test of the PAT-5/WJ-1A, ” TAA 1/80, p. 42. 7. Greenhill, L.L. and R. Blumenthal, “Lipshitz/Jung Forum Listening Tests, ” TAA 2/80, p. 50. 8. Holt, ].G., “The Conrad-Johnson PV-5 Preamplifier, ” Stereophile (Volume 7, Number 3), p. 15. 9. Jakowczyk, T., 'PAT-5 Power, ” TAA 2/78, p. 49. 10. Jung, W., 'Op Amps for Audio: Active Filters, Part 1, ” TAA 1/75, p. 22. 11. Jung, W., 'Op Amps for Audio: Active Filters, Part II, ” TAA 2/75, p. 28. 12. Jung, W., “A L.F. Garbage Filter, ” TAA 4/75, p. 14. 13. Jung, W., “Op Amps for Audio: Active Filters, Part III, ” TAA 2/76, p. 33. 14. Jung, W., 'PAT-5/W]-1 Modifications and Improvements, ” TAA 1/79, p. 49. 15. Jung, W., “PAT-5/WJ-1: Department of Error and Amplification, ” TAA 2/78, p. 49. 16. Jung, W., “More PAT-5 Errors, ” TAA 3/78, p. 50. 17. Jung, W., “PAT-5/WJ-1A Notes and Up dates, ” TAA 4/79, p. 58. 18. Jung, W., “Jung-White PAT-5/WJ-1A, ” TAA 1/80, p. 56. 19. Jung, W., “Updates for the Jung-White PAT-5/WJ-1A, ”“ TAA 1/80, p. 56. 20. Jung, W., “ PAT-5/W]J-1A Servo Improvement, ” TAA 2/80, p. 54. 21. Jung, W. and S. Lipshitz, “PAT-5 Inver sion and Equalization, ” TAA 3/78, p. 48. 22. Jung, W. and V.S. Mogavero, “PAT-5 Redo, ” TAA 1/79, p. 51. 23. Jung, W. and D. White, “A PAT-5 Modification, ” TAA 1/78, p. 7. 24. Jung, W. and D. White, Jung and White on Greenhill's Tests, TAA 2/80, p. 51. 25. Jung, W., D. White and J.P. Moncrief, 'A Forum on the Lipshitz, Vanderkooy, Young Letter, ” TAA 3/79, p. 5. 26. Lampton, M., “Lampton-Zukauckas Follow-Up,' TAA 3/79, p. 59. 27. Lipshitz, S.P., }J. Vanderkooy and P. Young, “PAT-5 Listening Tests-An Alter native View, ” TAA 2/79, p. 52. 28. Miiller, T.O., “The Conrad-Johnson PV-6 Preamplifier, ” The Absolute Sound (Volume 8, Number 32), p. 110. 29. Miiller, T.O. and W.T. Semple, 'The Conrad-Johnson PV-5 Preamplifier, ” The Ab solute Sound (Volume 8, Number 32), p. 100. 30. Nojkovic, B., “Lampton-Zukauckas Preamp Modification, ” TAA 3/82, p. 52. 31. Repka, C.P. and W. Jung, “Lipshitz/ Jung Forum,' TAA 4/79, p. 59. 32. Ruck, B., “Current Thoughts on Wire, ” TAA 4/82, p. 22. 33. Spangler, D., “Spangler to Jung: PAT 5/WJ-1A, ” TAA 2/80, p. 53. 34. Spangler, D., 'Spangler on Servo, ” TAA 2/80, p. 55. 35. Sulzer, M., 'Servos, Slew, and Equalization, ” TAA 4/79, p. 60. 36. Vorhis, D., 'Listening Tests on the Jung-White PAT-5/W]J-1A, ” TAA 4/79, p. 48. 37. Vorhis, D., 'Correction: Cut Off at the PAS, ” TAA 2/83, p. 58. 38. Vorhis, D. and J. Adelsbach, 'Last PAS Revisited, ”“ TAA 2/83, p. 54. 39. Vorhis, D., and R.H. Plumb, “Vorhis on Voltage, ” TAA 2/83, p. 56. 40. White, D., “White to Lipshitz,' TAA 4/78, p. 55.
------------------- Also see:
|
Prev. | Next |