16 February, 2018

Altec A7, Bell, Grommes, WE 285L, Langevin 402B, Ortofon MC-5000, T-20



Click pic to enlarge. Bottom Row, Bell Amps; Middle Row, C-J PV5 to the left and Premier 3 to the right; Top: from R, C-J PV-75, Grommes Amps, Sun Audio 2A3.
Two 6V6 Amps: Bell 2122 and Grommes Little Jewel LJ5
Ortofon MC-5000 Cartridge (vs Ortofon hot-rodded 2M Red)
Three Step-Up Transformers: Ortofon T-20, WE 285L, Langevin 402B
More Horns Without Pain: Altec A7
Letter from NYC (77) 2018 (3): The Amazing 6V6

After hearing the A5, barely a day had passed when Andy and I visited Kevin to hear the A7 (previous visit here.) Equipment had changed a bit. Through a mutual friend, he acquired an Ortofon MC-5000 which had previously belonged to me! Before I left for HK last time, I had also lent him my Bell 2122 and Grommes Little Jewel LJ5. For this round I also brought with me the WE 285L and Langevin 402B SUT's for fun. Equipment:

Analog: VPI Prime; Arm 1 with Ortofon 2M Red hot-rodded (MM); Arm 2 with Ortofon MC5000 (MC)
MC Step Up's: Ortofon T-20, WE 285L, Langevin 402B
Phonoamp: Conrad-Johnson Premier 3 (using Tape Out)
Preamp: none for Bell 2122; C-J Premier 3 for Grommes LJ5
Amps: Bell 2122 and Grommes LJ5
Loudspeakers: Altec A7 augmented by JBL 075 as supertweeters and an old subwoofer

Here I shall detour to write briefly on what I know of 6V6 tube and amps. As power rube, the 6V6 is famously still used in guitar amps, but now rarely in hifi. I probably know and have heard more than most audio tube aficionados, as the 6V6 tube's low power precludes useful applications with conventional loudspeakers, which won't do it justice like an efficient horn would. And that's a shame, as it is one of the most wonderful tubes!

Overview: 6V6 Tube and Amps

  • 6V6 Tube Astonishingly, the 6V6, like the 6L6, has been in continuous use since its inception in 1936 and, if I am lucky, will get to witness its centenary less than twenty years from now! For a surprisingly good history, read this wikipedia entry. Sonics The intrinsic sound of the 6V6 can be described as possessing uncommon clarity and lucidity (that other tetrodes/pentodes struggle to equal, let alone surpass). In fact, some knowledgeable old timers in HK regard this tube as 琴王, meaning "king", nonpareil in the portrayal of the violin (or other stringed instruments). On the other hand, perhaps due to its low power, it often sounds a little lean in the bass. Like the 45, there are a huge number of different old stock 6V6s out there, and almost all brands and constructions sound very good. 6V6G vs 6V6GT As usual for G vs GT, the earlier and larger G (ST type) has a warmer sound than the smaller GT type. However, to me (and I just found out, to Kevin), the 6V6G lags quite a bit behind 6V6GT in resolution and speed, which doesn't stop it from being favored by the "older is better" vintage crowd (prevalent in Asia; I know many of them and imho they don't know what high fidelity is). Big Family The 6V6 is but one member of a large family, with siblings and cousins like 6F6 (used in a lot of radios, and said by some to be closest to WE349A), 6Y6, 6W6, 6K6, etc. Perhaps the most famous "cousin" is the WE349A, whose price was driven up insanely partly because of people who use it as substitute for the 6V6, a dubious application in an attempt to get the "WE sound on the cheap". Durability The 6V6 is known to have a good life and survive beyond its ratings. However, I don't feel this to be true of Russian and Chinese tubes - I had quite a few die (same for Russian 6SN7/6SL7) when I first fired up my old Audio Note Kit 4, but that was a long time ago (perhaps current ones are better; I sure hope so).
  • 6V6 Usage Amps For a while, from the forties to the fifties, the 6V6, like the 6L6, was ubiquitous in home use amps (loudspeakers of the day were efficient). Therefore, there were innumerable models, even from the same company, though, in terms of sheer number, they were outnumbered by the higher powered 6L6, which survived for much longer after the emergence of stereo and lower efficiency loudspeakers. Topology As for the era, most 6V6 amps were mono Push-Pull and had classic, simple designs. Most were mass market Integrated Amps with a Phono Section (usually employing 6SC7). There were fewer Power Amps, which usually employed larger irons and were built to a higher standards (like Radiocraftsman C-400 and RC-2, McIntosh 15W-1/20W-2, WE made by Dukane KS-16617-L1), though some were integrated with loudspeakers in consoles or guitar amps (like Ampex), and some were for professional use (like Langevin, descended from WE; one may also count the WE 133, which employed the 349A). In terms of Circuit, they can be roughly divided into two eras: the earlier ones were driven by an Octal Tube (typically 6SL7, like the Bell 2122 here), which were later replaced by the smaller Noval Tube (typically 12AX7, like the Grommes LJ5 here), an evolution exemplified by the various iterations of the Bell 2122 and Grommes LJ amps over their life spans. In Our Times 6V6 is little used. Classic push-pull operation were few and far in-between, some examples being the Audio Note Kit 4 of yore and, more recently, an amp module from Swiss hi-end Swissonor. The 6V6 is sometimes used in DIY amps by horn or fullrange driver users, mostly in Single-Ended configuration (like the Sun Audio 6V6 amp). It should be known that there were a few vintage SE 6V6 amps (like the one auditioned here in this blog). The 6V6 is also known as a good Driver Tube, used in many DIY applications, with or without interstage (as well as in commercial products, one example being the Audio Note Jinro; the related 6Y6 is also used as driver in Wavac SET 811 and 300B amps).
  • Bell 2122 I acquired this pair (an "A") from an old hand, whose Altec A5 was amongst the best horn sound I have heard. He had restored it meticulously and proof was in the listening. Here are notes from a previous 6V6 listening session more than seven years ago! The History of Bell can be found hereBell 2122 The site claims the 2122 was rolled out in the late 40's, but  some 2122's for sale that I have seen claim those were manufactured in the 50's, so the model could have had a long life. Some also had a sticker proclaiming "licensed by Western Electric" (what is not?). We do know that the later 2122C replaced the 6SL7 driver with the smaller 12AX7, and by 1957 Bell had rolled out their completely different looking slimline models.
  • Grommes Little Jewel LJ5 Grommes has survived today as Grommes Precision, whose webiste has a History Page. Its cached Past Product Guide did not have the LJ5, but one can see that, as in Bell products, by the time of LJ5 (circa 1957) the noval 12AX7 had replaced the 6SL7 used in its predecessor LJ2. There is more info on LJ5 in radiomuseum. By 1959 their amps had become slim-line like Bell.
Info: Ortofon MC-5000 Cartridge; Ortofon T-20, WE 285L, Langevin 402B SUT

  • Ortofon MC-5000 This is second from the top in Ortofon's '000 series (Official Info) and employs the famous Replicant Stylus diamond which continues on successors like the Winfield, A90/A95 and Anna. The MC-5000's internal impedance is 6 ohm and output is 0.14 mV. This is one of my reference cartridges and my experience is briefly documented here
  • Ortofon T-20 (Official Info) This was originally designed for the MC200 cartridge which has an output of 0.09 mV and internal impedance of 3 ohm, both even lower than the MC-5000, which however should still be an excellent match.
  • WE 285L Western Electric 285L, the input transformer for the 124-B Amp, has a secondary of 75k ohms (pins 5 and 6) and two primaries. The 600 ohm primary (pins 1 and 4) was used for microphone/professional inputs (in conjunction with the 170B) and the 124-B is configured as such. But it also has a 30 ohm input (pins 2 and 3) which makes it suitable for use as a step-up transformer for certain cartridges, and the MC-5000 should be one of them.  
  • Langevin 402B This is reputed to be internally identical to the WE 618A. Like the WE 285L, it also has a 30 ohm primary (in addition to 120 ohm). Secondary is 50k. The figures seem perfect for a SUT and suitable for the MC-5000.
Sonic Impressions

  • General The Altec A7 turned in another fine performance. In this incarnation it seemed quite a bit smoother than the A5 we heard at R's. Although this might be partly be the intrinsic character, I think there could have been more transient information and attack. Sound with 6V6 furthered the promise shown last time with the Sun Audio (the C-J MV-75 need not apply).
  • Bell 2122 After amplification by the phono section of the C-J Premier 3, line level signal via Tape Out was fed directly into the Bell. The sound exhibited all the lucidity the 6V6 is famous for, with superb microdynamics, articulation, rhythm and pace, save for bass which was a little lean. It should be mentioned that this pair has the phono section disengaged. A brief mention here that Andy also has a pair with the phono section intact and less luxuriously restored. He thinks it doesn't sound as good, so restoration is a trial and error thing and demands patience.
  • Grommes LJ5 Unlike the above, this was not directly driven, rather controlled through the Premier 3's line section. Despite addition of a preamp and regardless of where the volume knob was set on the Grommes, the sound was softer than the Bell 2122, with less microdynamic nuance. However, the smoothness was eminently suitable for classical replay. It should be noted that the phono section is intact in this pair and we surmised that the ceramic coupling capacitors were compromising the sound.
  • Ortofon MC-5000 and 2M Red With classicals the MC-5000 turned in a performance much as I remembered it - very neutral and detailed, with excellent rendition of microdynamics. The Ortofon T-20 initially sounded quite coarse but became quite decent when proper VTA was dialed in. However, it was thoroughly outclassed by the WE 285L, which turned in the best performance that I have heard from it (better than in my setups), with that je ne sais quoi subtlety and finesse that is WE, where every phrase becomes distinct, with nonpareil rhythmic pointing and flow. The Langevin 402B did not fare as well in this setting. However, jazz and pop were quite bland and here the hot-rodded and peaky 2M Red gave good performances. This puzzled me as I don't recall such preference when I used the MC-5000.
Comments

  • 6V6 Amps With high efficiency horns, 6V6 should be seriously considered. Aside from the most famous models they are very reasonably priced, especially the integrated amps covered here. However, our experience poses questions: one wonders why the outwardly similar Bell and Grommes sound so different (even why two pairs of Bell sound different): is it due to the difference between driver tubes, restoration methods (like removal of unused stages) or component use (particularly caps)? There is no quick answer, and I promise you shall hear more of it. However, one thing is certain, particularly with more complicated integrated's - it would be highly desirable if you have some electronic knowledge and soldering skills to tackle the vagaries of restoration (the most important asset though is a good ear). Integrated vs Power Amps The ubiquitous integrated's tend to be more mass-market. Compared to the more famous power amps, they have much smaller output transformers, but, as heard, they sound just as good in their own ways. I have heard most of the famous big power amp brothers with big transformers, like the Radiocraftsman RC-2 and C-400 and the Dukane KS-16617-L1, and I don't think they sound as nimble as they less "endowed" brothers (I had better impressions of Ampex and McIntosh). When it comes to output transformers, size matters and it may not always be "the bigger the better".
  • The SUT's Those considered here are theoretically all suitable for low cartridges with low internal impedances, and so they proved. But it is amazing how different they sounded, and the spec's really are meaningless. The Ortofon T-20 is good value for money. But, for a lot more money, the WE 285L was remarkably much more enticing, though the Langevin 402B sounds better in my own setup (with 3 ohm Air Tight PC-1 and Shindo Monbrisson MM). The cartridge and the cable (I went through 8 cables to find the right one for my Langevin) make a huge difference - synergy is the word. My own thinking is, like arms and cartridges, you cannot have too many SUT's.
  • The Perfect Complement What is audio without good friends and good food? I thank Kevin for painstakingly making every one of his house specialty, Shanghai Style Wonton. The stir-fried cauliflower with cured pork (home made by Stephen's relative) was equally inspiring. All washed down with two excellent wines from Andy! Thank you all, if all audio meets were so fulfilling for the ears and tastebuds!
  • Spec's and Rules For a hobby that relies so utterly on our senses, it is amazing how many audiophiles choose to believe less in their ears than in spec's and rules. So many newcomers on the internet seek opinions, so many more trolls offer opinion based solely on spec's and rules rather than experience! I do think while one should have some technical grounding, proof in the pudding is in listening. Early in this session, I found the sound of the MC-5000 a bit unnerving. I discovered that the tail of the tonearm was way down, and so raised it by almost 1 cm! Sound smoothed out quite a bit, while theoretically it should perhaps have gone the other way. Andy surmised perhaps it was because of the profile of the Replicant Stylus. Who knows! Our rooms and equipment do not function in an anechoic chamber, and there are always local anomalies. If we spend a lot of time positioning loudspeakers (and one should) we should equally spend time matching equipment and cables. Spec's and Rules are not at all everything! In hifi, think SET amps, Non-Oversampling, even active preamps (which many think are unnecessary) and cables (which many laughably think all sound the same). Well, in the picture below are some closely spec'ed craft beers, and they all taste dramatically different. Incidentally, if you ask me, American Craft Beers are now the best in the world. Thumbs up for choice!

4 comments:

  1. I enjoy your food & wine pics as much as the audio gear! Please keep including them in your yumcha visits. It reminds me of another HK blogger who would blog about good food and wine in addition to his admiration of 47labs gear, NOS dacs & Jordan single driver full range speakers.

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  2. Interesting info and I learnt a lot.

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  3. Doctor John, do you have any experience or exposure (from audio shows or word of mouth) of Arte Forma tube amps based out of Taiwan? I'm particularly interested in their push-pull EL34 25 watt integrated amp.

    http://www.arteformaaudio.com.tw/

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    1. Sorry I have no experience of Arte Forma, but I shall make it a point to listen to them when I am next in Taipei. How much is the EL34PP?

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