Dynaco PAS 3 Mods

Click pic to enlarge. L: Slightly modified PAS 3.

Dynaco PAS 3, Part II
Letter from NYC (84) 2018 (10)

Revised Mar 11, 2018.

PAS 3, Part I saw the stock Dynaco PAS 3 run for may hours. The sound then was remarkably detailed at low volume, but stressed when pushed harder. While mods were definitely on the agenda, as is my wont I decided to go against the fashion of sea change (replacing everything) and start with a minimalist approach. First, I researched on the internet, but found the documentation of sonic changes to be quite lacking, even contradictory (as opposed to electrical changes, for which most would agree on). I ordered just a few caps and resolved to do one mod at a time to hear the individual impact each has on the sound. Yes, I heard enough potential to think my efforts would be repaid. They were, amply.

Tone Control Mod Dilemma
Most people bypass the tone controls, which is not hard to do. One popularly discussed method is the Curcio Tone Control Bypass. It seems, however, this increases the DC present at the PAS 3 Output, which can be resolved by adding a 0.1 Output Cap, as done at audioregenesis. As I did not have the requisite caps, for the moment I decided to leave the tone controls in the circuit.

Now the Mods I have done this time, numbered in order and rated in efficacy from * to ***:

1. The Amazing $0.25 Non-Electrical Mod (***)
While waiting for the caps to arrive, I thought about how to improve the preamp. Staring at the innards, I saw both PC Boards (PC-5 and PC-6) were affixed to the chassis by 4 screws, bolts and washers. Since the chassis also has the transformer directly bolted on it, the idea of providing some measure of isolation against vibrations came to me. This did not come out of nowhere. Similar tweaks can be found in some modern manufacturers, but also in vintage equipment (e.g. the Marantz 7 has some isolation for the tube socket mounting plate.) As I did not have rubber washers around and as I was working on some Gotham DGS-1 cables, I slotted in small cross sections of the springy PVC jacket between each screw and the PC board, and between the chassis and transformer. The length was not enough to completely encircle some screws, particularly the ones fixing down the transformer, but that would have to do for the moment. I figure, proper rubber washers would cost you less than 25 cents. With just this done, I sat down to listen. !Oh My! The difference was unbelievable! Not only did the sound smooth out a bit, I now could play significantly louder before the sound tightened up. No, it did not completely cure this particular ill, but it went quite a way towards ameliorating it. Even if you have already done all your mods, I can still confidently recommend this easy and reversible step. Do keep in mind that the PC Boards are a little looser than before and a little more care should be exercised when swapping tubes, particularly during insertion (use gentle wiggles).

2. Output Cable Change (*1/2)
The stock hook up cables are tinned solid cores. As I usually prefer stranded cables in interconnects, I decided to first change the high level cable from the output tube to the main out. I swapped in a run of Gotham 2-conductor GAC-2, one of my reference interconnect cables (center run in pic). The copper shield was not connected at either end. Compared to the above, the result was a small (but audible) improvement in the same qualities.

3. $3 Capacitor Change (***)
I replaced the two 0.22 Output Coupling Caps (the green globs seen in the Part 1 pic) with German Audyn (Parts Express, bright red ones in pic). I wanted to also replace the two 0.02 caps that couple the two sections of the 12AX7, but that would have to wait as I don't have the parts, and the original Black Cats are not bad in my previous experiences. The Sonic Improvement was Dramatic, on par with the isolation measures above. Considering that there were only two cap changes, the degree in improvement is quite amazing! As the tone control circuits, which employ all Black Cats, are still in-circuit, this strengthens my belief that they are not as nearly as bad as they are often made out to be.

4. Line Input Cable Change (*1/2)
Emboldened, I then re-cabled with GAC-2 one of the Line Inputs ("Spare") and the same small incremental improvement was audible. Note that I only replaced the segment immediately leading out from the Input Sockets (the longest, see pic). The Selector has three gangs, and it would be a major task to replace all wires going to the PC Boards and Switches (it would be simpler to install a new selector).

5. Phono Input Cable Change (**)
I then made the same cable change to the Phono Input, though this time I used the shield, which was tied at the Input End only (not in the pic, as this was done after). The sonic difference was more substantial than cable change in the line section, resulting in a smoother sound and quieter background. However, I did notice a very subtle drop in the presence factor, but that did not worry me as the PAS 3 is super strong in this department.

Impressions

• Chez Moi As reported in Part I, the PAS 3 always had excellent transient speed and great presence. The challenge was to get it to smooth out, and it was immensely gratifying to hear it do exactly that as the mods progressed. After the Cap and Line Input Cable Change I went through the CDs I used in the last visit to R (here). I knew my job in the line section was complete when I tried out Masekela's Stimela; yes, that crescendo was perfect; the train imitations were strongly rhythmic; and the loud cries were heard without strain. After the Phono Input Cable Change I listened to cuts from Tchaikovsky's Swan Lake (Ozawa/BSO, DG), which had previously sounded strained, and all was well. Finally, it was time for the real litmus test - the two LPs I heard last time at Andy's (here) that so impressed me. Moravec's Beethoven (Connoisseur Society LP) showed considerable dynamic range, and the inner voices were clear and vital, the atmosphere charged. The PDQ Bach LP (Vanguard) was very lively; though occasionally the recording still appeared a little hot, it was quite listenable and never strident. The PAS 3 now joins my Reference System II, which has just been completely revamped (sidebar)!

• Chez Andy As with most of my projects, I took it to Andy's for a final assessment. Kevin was also present for the excellent lunch of rack of lamb. In his system the PAS 3 sounded slightly brighter than usual but with less grain than the Citation I even when pushed hard. Throughout the afternoon, we played many records and everything sounded very good. Yes, replay of the PDQ Bach and Beethoven were just as beautiful as before, but it was the album below that deserved the limelight. Project Accomplished!

• Radka Toneff Transformed Most amazingly, Andy played his original pressing of her mostly digitally recorded Fairy Tales (Odin, LP). Her rendition of The Moon is a Harsh Mistress needs no introduction to audiophiles, but although I have probably heard it close to a hundred times in the past two decades, I have never taken to it, or understood what the fuss was all about. This time, however, the fine modulations of her voice were more impressive and I actually managed to hear several other tracks. Most importantly, I finally heard at least some emotion and charged atmosphere, which were devoid from all the CDs and 2015 re-issue LP I have heard in other systems in HK. Incidentally, a new re-issue is just available and the April Stereophile (not online yet) has a story on it by Atkinson. Apparently, the 2015 issue was flawed technically (see this google translated link). I note too that I had also heard the original LPs in quite a few very expensive systems in HK, but never to this effect, attesting that the horn reigns supreme.

• PAS 3 Then and Now The transformation of the Dynaco PAS 3 was utterly amazing. Indeed I had to ask the same question that I asked after I brought my Citation I back from obscurity: Why had I not appreciated it before? Likewise, there is no easy answer. Horns perhaps just show everything in a new light. For more musings on this subject, see here.

• Thought on PAS 3 Mod As you have read, my mods are minimal, cost almost nothing and can be accomplished in little time. I believe the isolation work is very effective. Also, before you decide to embark on a wholesale mod, ponder this: as I had changed only two caps, I believe the original Black Cats are no at all as bad as they have often been made out to be. For the moment, I do not have that great a desire to do further mods. It is already an excellent preamp and can fully stand alongside the Citation I.

Wunderbar!

Lucy Dacus

Letter from NYC (83) 2018 (9): Good Indie Singer

Just heard Lucy Dacus on CBS TV singing selections from her sophomore album and it was great. I have never heard of her before and the album (CD and vinyl) may be difficult to find in stores (easier to download, if you do that kind of stuff).

https://store.matadorrecords.com/historian

https://youtu.be/0WDZdT04ls4

 

SMSL SA-36A Pro, Citation I, Conrad Johnson Premier 2 and 3, Cary CAD 211

For all pics, click to enlarge. L: Note the weighted down SMSL on top of HT center loudspeaker, behind which is the subwoofer. On the flanks are the Cary 211 monoblocks. Marantz 8B and Jadis JA-80's in front.

Review: SMSL SA-36A Pro
SMSL vs Cary CAD-211
Conrad Johnson Premier 2/3 vs Harman Kardon Citation I
Cary CAD-211 vs Jadis JA-80 vs Marantz 8B
JBL L20T, Part II
Letter from NYC (82) 2018 (8): Smorgasbord

R's Altec A5 saga continues. After the last report, we made two more visits and exhaustively tested numerous combinations. This article summarizes the two visits. But first, a little diversion.

SMSL SA-36A Pro (TDA7492PE) 

• T-Amps Though I firmly believe in the superiority of tubes, for some fun at low cost I occasionally do dabble in T-amps (expensive implementations are ridiculous). My first one was the (discontinued) Lepai LP-2020A+, which employed the well-regarded Tripath TPA2020 chip. I was delighted by its performance (as an amp in a humble system here and even more as a power amp in a hi-end system here). I also bought one of its successors, the Lepai LP-2024A+ (employing TPA2024) which was almost as good, though a shade cooler in sonics (no report yet). As the TPA2020 chip had long been unavailable (Tripath had gone bankrupt), my curiosity for a better built one with a better power supply had me turn elsewhere.

• General Info This model from the interestingly named (in Chinese, 雙木三林) company (official info) has been in production for a long time and had gone through many iterations. The earliest used the Tripath TPA2020 chip, but it was replaced soon by the Texas Instrument TPA3118 chip and all of these garnered a good reputation. However, after the company switched to the current TI TPA7492PE chip, there were quite a bit of noise and confusion on the net (read the incredible fuss made over something under $50), and that is the version I have just bought. There are variations, and mine is the more common 12V version.

• Ergonomics The build quality is very good, though for the bare wire user (me) the small speaker binding posts are no more convenient than the cheap posts on the Lepai. What really bothers me is the lack of an indicator lamp, so be mindful of the on/off status.

• Round 1/Chez Moi/JBL L20T I tested these on my JBL L20T (Part I here). Direct-In First I fed the output of my reference Aurorasound Vida phonoamp directly into it, and the sound was very good. As Power Amp Next, I used it with my reference System III (last described in detail here) driving the JBL L20T's. The sound was surely even better. Compared to my bookshelf reference Almarro M1A (reported here; a tall order indeed), the L20T's were just a little more weighted towards the midrange, less pure in the treble (which may be the amp too) and smaller in soundstage. It should be known that my relatively near-field and way-in-room placement minimizes the room effect and difference between loudspeakers. Although the JBL's likely would like even more power to pump out more bass, the SMSL did an excellent job driving them. The 

• Round 2/Chez Kevin/Altec A7 It was briefly tested at the same session reported here (note in the R pic the SMSL perched atop the Dynaco PAS 3). Suffice to say the the SMSL stood up to the Conrad Johnson MV-75 amp very well.

• Round 3/Chez R/Altec A5 The result was astonishing, as detailed in the section below.

Home Visit 1: Sometimes I think of the squad as the coaching team, trying to coalesce the players (the equipment) into a winning whole. Andy is the mild-tempered and democratic head coach, myself a temperamental assistant; R of course is the owner of the franchise - demanding at times, but not quite a Steinbrenner. On this occasion, Kevin was the fourth man, and we tried out numerous plays. The lunch (L pic) as usual was wonderful, an overstuffed omelette washed down with a brut sparkling.

• My Agenda During the previous visit to R's smaller room, I thought that although the Altec A5 sounded quite nice, the leading edge/attack was slower than what I am accustomed to hearing from Altec (e.g. Andy's) and other well implemented horns. Remembering that none of the amps were quite satisfactory, I decided to take along my SMSL for "diagnostics". Since I also thought R's turntables in this small room had anomalies, I wanted to use digital playback as a reference. The California Audio Labs Delta Transport/Sigma Tubed DAC were dusted off and pressed into action. I brought several of my own test CD's. Equipment used were somewhat different from last time (see link above). The CJ Premier 2 served as full function preamp in lieu of the previous Jadis DPL2, its phono section also replacing the Lamm. This section described mostly the results obtained using digital playback, which was very instructive.

• CJ Premier 2 + Cary CAD-211 We didn't hear the Cary's last time, as they had only just recently returned from electrolytic cap replacement (the big blue cans, which R had listened to for several days and heard them opening up). This long running model has had multiple iterations - these are from way back (no bias meters). The 211 designation is a misnomer, as these use a pair of 845's in each channel. Used with the CJ Premier 2, the sound was powerful but overly warm and woolly, somewhat rounded off and slow in the leading edge. These were touted for their "life sized" images, which unfortunately were rather fuzzy through the horns. Substitution of the RFT EL34's for the Russian fat bottle 6CA7 brought a significant improvement - more believable outlines.

• CJ Premier 2 + Cary CAD-211 (vs SMSL SA-36A Pro) Using the same CJ Premier 2, the very humble SMSL showed off the glaring weakness of the Cary. Aside from a warmer tone and more power, there was nothing favorable. On Masekela's Hope, the audiophile fave stimela (Track 12) best illustrates this: the big crescendo was perfectly gauged and proportioned through the SMSL, but ill-shaped and prematurely saturated through the Cary's; the rhythmic imitations of the train were incandescent through the SMSL but sorrily flaccid through the Cary's. The trombone and double bass in the vivo movement of Stravinsky's Pulcinella (ASMF/Marriner, Argo/Decca) commanded their own lines and were perfectly integrated as a duo though the SMSL, but through the Cary's they were just plain mushy. Even worse was the Bach Double Violin Concerto (Kuijken/La Petite Bande, Pro Arte) - through the SMSL, the lines were perfectly clear, and one could feel the up- and down-bow's, all hopelessly lost through the Cary's. The playback of a jazz CD, Shirley Horn's You Won't Forget Me (Verve) was similarly excellent and, imho, much better balanced than the analog rigs.

• CJ Premier 2 vs 3 vs Citation I We used the two turntables mostly. As there were two full function preamps with both phono sections and tape out, we went  through quite a few permutations that we had to go through. Suffice to say as a whole: CJ 2 vs 3 The CJ Premier 3 is very similar to 2, but solid state rectified, and they sounded more similar than different to my ears. Citation I As expected, the Citation I was obviously more neutral and did not unduly soften the leading edge, making it a much better match for the lugubrious Cary. Not only that, as we had fed the CJ (can't remember whether it was the 2 or 3) phono section into the Citation line stage, I can conclude that the Citation I phono section is superior. Just before we left, we played the Masekela track, and it was a lot better than before, but the crescendo was still not quite shapely.

Home Visit 2: On this occasion almost the full gang showed up. We were also joined by R's friend Louis. This occasion was marked by the arrival of an Audio Research Reference 2 preamp, which we compared to the Jadis JPS2 in the main Wilson rig. Then we tried out more combos in the A5 room. Lunch was R's wonderful home-made sausages and, for novelty, venison burger, all washed down with an excellent Chilean Shiraz and  California Red.

• Reference 2 vs Jadis JPS2 We used the Rockport Sirius turntable, now fitted with 100 ohm loaded Ortofon 2M Black (Andy said this eliminates the unpleasant peak). We first used the Lamm LP2 phonoamp, which did not woo us, and so we replaced it by the sweeter phono section of the CJ Premier 2. We unanimously agreed that the venerable ARC (with completely stock tubes) had much better focus and control than the Jadis JPS2. In this room this is of great importance as the ARC obviously consolidated the center stage, which has a tendency to be less filled up. Naturally, with the all-Russian tubes, sound was not quite as sweet, but it is a trade-off I personally would gladly take. Interestingly, although this setup was targeted to play classical music, jazz sounded even better. On Ellington - The Pianist (Fantasy LP) Ellington's piano sounded smart (as it must) while Sam Woodyard's brushwork was breathtaking on (side 2, track 1) Tap Dancer's Blues. Sony Stitt also was very much his golden-toned, comforting self in one of his late outings, Sonny Stitt meets Sadik Hakim (Progressive, LP).

• Cary CAD-211 vs Jadis JA-80 vs Marantz 8B based on the session reported above, we stayed with the Harman Citation I as preamp. The Cary was just as I remembered it, but the Jadis JA-80 fared not one whit better. Then we swapped the Marantz 8B in. Previously, we had heard it with the CJ Premier 2 and its slow speed bothered me. Not this time: partnered with the Citation I, the Marantz 8B showed a clean pair of heels to the Cary and Jadis. The leading edge was faster and cleaner; Masekela's Stimela almost edged up to the SMSL amp. The tonal qualities too were way superior to the Cary's and Jadis'. I was quite satisfied and would personally stay with this combo in this room.

• Jazz vs Classical? Although the results were satisfying enough, I still think on this day, in this room, supposedly the jazz room, the jazz playback was not as as good as in the living room, supposedly the classical room. Similarly, the classical (digital) playback through the A5's sounded to me as good as the big rig. For myself, there is no such division, and indeed may write more on this in a coming article. I do think now that there is much competition between the two setups, we can expect improvements in both in due time (they are already quite wonderful).

Assessment

• SMSL SA-36A Pro This is a wonderful little amp. The sound is excellent, particularly with efficient loudspeakers. It is more robust than my Lepai  LP-2020A+, and I have yet to hear it clip with my less efficient JBL L20T. Mine is the current version, which uses the TI TPA7492PE; I think if it can pass muster with me, there is little point in struggling to compare it with past iterations. The treble is generally good (witness how it renders violin and massed strings) though not as pure as tube, but there is a little grain at the very top which becomes noticeable at high volume. I think a little mod or a better power supply could take the amp to a higher level, though I shall stop at here for the moment. Horn users should have one of these amps on hand to compare with the tube amps (and preamps) they are using - they may be pleasantly, or unpleasantly, surprised. Its neutrality and simplicity reveals most of the music, which is more than can be said about severely flawed lesser tube gear (and this from a tube lover).

• Conrad Johnson Premier 2/3 To my ears, the 2 and 3 are more similar than different. They share similar sonic characteristics - a big, bold sound that many like. However, their weaknesses - lack of dynamic and rhythmic exactitude, not to mention refinements - preclude my endorsement. In many ways, I think the Premier 2 and 3 are just beefed up PV-5's (substitute your favorite numerals) and may be even the worse for it. This is true of the line stage for sure. Although we had tested it less, I do also think the phono sections are too colored for me (much prefer the Citation I).

• Jadis JPS2 Much the same can also be said about the Jadis. There is some measure of opulence, a la creme, but where is the finesse?

• Harman Kardon Citation I The Citation I continues to impress. The phono section is superior to those in the Premier 2 and 3 and, if you ask me, likely the Lamm LP2. I also much prefer the line section over the sluggish CJ Premier 2/3 and Jadis JPS2, all cathode follower designs (Stu Hegeman was definitely onto something). Yes, the line section gets stressed a little when playing loud but this is largely ameliorated by partnering with a more forgiving amp, like the Marantz 8B.

• Cary CAD-211 and Jadis JA-80 Not my cup of tea, as you must know by now. They were decidedly bettered by the Marantz 8B, not to mention the tiny SMSL. I actually think these have no place in a horn system but would probably do better with conventional dynamic speakers of good to moderate efficiencies and a fast modern preamp.

• Marantz 8B Like I said before in my last report quoted above, it is hard to go wrong with this amp; the more you work with the 8B, the better it is - it repays your efforts.

• Altec A5 Absolutely marvelous! R's pair surprise me by how well they play classical material (via CD though). I am not sure why the analog rigs are not quite performing as well - I'd venture to guess the very revealing A5's just reveal every anomaly in the chain. Personally I think, factoring in the difference in partnering gear and room, the A5 renders classical music (again CD only) at least as well as the big Wilson's; in fact, in dynamic gradation and presence they are unquestionably superior. If placed in the big living room I am confident they will easily trounce the Wilson's. Remember, the good sounding living room rescued the Wilson's, and it would do wonders with other loudspeakers too. Also, further improvement in A5 playback can likely be obtained by substituting a better subwoofer (e.g. my cheapo but over-achieving Pioneer SW-8, reported here) for the subpar (home theater) Focal. 

• Audio Research Reference 2 This definitely has potential. I await the results of some tube rolling. I have heard this many times before in HK, and it has aways turned in reliable, if not often exciting, performances.

• California Audio Lab Delta/Sigma This is a combo that has stood the test of time; I have heard it many times in HK, always to good effect. Although I am a fan of true multi-bit players, this is nonetheless a very good implementation of Delta-Sigma. A classic.

• JBL L20T Impression here is the same as in Part I. Typical JBL quality that needs no further touting.