I have recently acquired a pair of (2000 vintage, I think) Lamm ML2s and would like to share impressions and development strategies with other ML2 owners, including former owners, and perhaps I may learn from any pertinent experience.

In addition to changing amps, from Wright-Sound WPA3.5 2A3 SETs to the Lamms, I have just moved into a new (to me) house with 8’ ceilings instead of the sloping (10 - 20’) ceilings at my former residence. The ”new” listening room is  on a wood-framed floor while the old one was on a slab.  Also, while I had pretty much solved my grounding problems at the old place (3/4” copper rod driven just outside the system wall, for phono), I am just getting into this again here and now.  In other words, my recent audition of the ML2s was compromised, to say the least.  But, still, I got some impressions from the ML2s.

I had finally reached the point where I had done about all I could with the Wrights.  I had gotten the room pretty well pressurized, etc., but I was growing annoyed and disappointed with the limited frequency range and dynamics, and so I began looking around to see what I could find as a next step.

And so, under these clouds and with highest hopes, the Lamm ML2s entered the picture.

I am pretty sure the amps could do with new tubes, but here goes with 1st impressions, with CD source instead of my usual phono:

For one thing, the amps did everything better and better as time passed, up to the 1 hour mark, when I ended the session.  From the first the amps did not sound like the coveted straight-wire-with-gain, but rather they seem to somehow rearrange the mosh they are fed and turn it into a more realistic musical sound.  I suspect some sort of feedback is involved in this, and maybe even some mysterious form of group/phase delay, although there was no overt trace of echo effects or smearing, at all, which might cause me to suspect this.

But the thing these amps did the best during my first, compromised session was the way they create an artfully correct(ed) version of time and space, in which the musical notes and pressures assumed their correct-as-in-living-music attitudes and relationships.  There is roughness when appropriate, which is very rare, and overall sounds happen just about the way they should, neither forced nor held back by the ML2s

And the background to all the sound was not “black” but simply the part that is not music, just as one finds with live music, which effect so charms me that I am excited about hearing it again.

Something I have observed with solid state versus tubes in general, and SETs in particular, is that notes through SS amps seem to implode, while notes though tubes seem to explode.  And now that I think back, I am not sure that notes from the Lamms do either.

One sound I remember well as a reference is that of a band playing outdoors, where the sound almost seems to contradict itself if one tries to describe it, the way it is at once ragged and smooth, so immediate and vital, yet it just dies away so quickly it’s as if it went into a vacuum.  Likewise, the frequency range is all there, obviously, yet where are the “highs” or “lows” the audiophile craves?  I think I want to hear some marching band music through the ML2s.

I should also mention that the “sound stage” was plenty “deep” and “wide” from the get go, but it was oddly short in terms of height, and it “grew” in height over the one hour session.  The “space” the amps put the music in is more about music than space, which I like, but the space is “there”, and it sounded/felt as if it just went on  and on like the rest of the world; very odd.

My own sonic priorities are pitch, timbre weight and scale of acoustic instruments and voices; then dynamics; then immediacy; then sound effects (soundstage, etc.); then “details”, which I simply cannot abide out of proportion.  I actually like all these things, but if the first things are wrong, I cannot sustain interest for long.

The ML2s started out with some SS congestion but cleared up considerably by the end of my first session.  I did not get good bass or proper lower-mid weight, but this is so room/speaker dependent that I don’t think it’s worth discussing at this point.  I found myself pulling my speakers farther and farther out into the room, off the short wall, and I may eventually try them along the long wall, firing across the short axis of the living/listening room and into the dining room.  I certainly have not gotten the room pressure level right yet.

Paul,

The idea of the not threaded forum is good that it is always there is opportunity to go back to all there and update own views, or to extend them. In many moths/years when the ML2 stop be a novelty for you, you might return to this thered and fine my following post worth consideration.

So, I went today to The AA Sewers ™ and have seen you were bitching about the Lamm charging $300 for a pair of the marched 6C33C and about the price of the 6N6P. Certainly I do not question the Vladimir’s right to make money on the intimidation and misapprehending the operation need for his products. After all, the Volkswagen use to sell their cars very cheap, practically at the cost, and made quite lot of money selling the services…

Anyhow with all my quite2xtended experience with Lamm ML2 there was one experiment that I never conducted and I am sorry now that I did not as it might be very interesting.

The ML2 second stage use a Russian made dual triode 6N6P. It is very critical tube in the ML2 circuit and it is hugely responsible for the sound of this SET. (BTW, change this tube one a year). The 6N6P is very good tube, one of the very few Russian tubes that actually sound very refined… but it is Russian tube… if you know what I mean… It would be VERY interesting to use in ML2’s second stage the best of the Western equivalents. Russians ripped up their 6N6P from Western 5687 (don’t ask me why but Russians very seldom designed own tubes but mostly juts mimicked western tubes). The 5687 is very well know and it is also VERY-VERY superb tube, widely used in many designs. The specifications are nothing dramatic but it has a very serious driver sound, is anything else as important? The 5687 has slightly less gain but all together it might be used in place of 6N6P without any change of operation point. It has different pins layout but it very simple to make a non-complicated tube socket adapter to cross-map the 6N6P and 5687. Sure a good version of 5687 might cost $6 or $25 but the 6N6P you can get for $1-$2, but I still, despite the economic advantages of 6N6P would try the Western tube. At least a dozen companies made 5687: Tung-Sol, Sylvania, Philips, General Electric, Amperex, Ratheon, RCA …etc… and it is suitable to be drop replaced by 6900, 7044, 7119, E182CC) instead of the 5687 (also I do not know how they sound).

Anyhow, I would generally do not proposed such experiments but if I have a change to putt the marvelous 5687 into the game then I would defiantly try it. As I said I am sorry that I did not do it when I used ML2. I still do not feel that 5687 will be able to address the sonic kisses I had with ML2 but… who knows… A driver is very critical part of any SET….

There are no relays in the ML2 that might produce the “violent switch-on pulse… which threatens to blow your speaker”. What you have is a dead V2 tube. When 6C33C dies then it begging to produce the erratic pings. Juts replace the tube and you should be all set.

Anyhow, ML2 is won by many people nowadays but very few know what the have and how to use it. In fact it was always. People buy it just because the Media praises it but they both, the owner and the Media are clueless what and why the do what they do. I know at least 20-25 ML2 owners and 95% of them are complete Morons and have the corresponding sound from ML2….

Paul S wrote:

I got new 6C33Cs for V2s from Lamm because no one else wants to match them, let alone match them for gain…

There is no meaningful mutual conductance or bias matching for 6C33Cs (in context of ML2) besides gain matching, and to match gain of this tube is very simple with any special equipment or skills.

Paul S wrote:

but the loud thump through the speaker still happens just when one amp self-switches from warming its filaments to full-throttle operation.

Paul, I do not know if I misunderstood you or you juts mis-presented the case. As I understood you, you complained about the pulses when the amp was operations. THAT would be because the aged L2 tube. If you have pulse when the amp accepts B+ then it is totally different story.

Paul S wrote:

I don't know how this internal switching would happen without a relay or a thermistor, etc., but I'd like to find the source of the pulse and fix it before it blows a speaker.   Needless to say, I want to avoid shipping the amp from San Diego to Brooklyn and back, if possible.

I am sure it would makes sense to ask Vladimir about the possible reason but Vladimir has a tendency to do discuss problems with his circuits. In order to answer what is going on it is necessary to have the amp in hands. I do not know what kind delay it executes. As I remember it has only one relay switching and permeably it applies regulated voltage to 6C33C plate. I do not know how ML2 applies the plate voltage to the first and second stages perhaps Lamm does it the “cold” tubes at the initial start. Still if you hear an auditable pulse then you heard some voltage running across the primary of the ML2‘s output transformer. What might it be? A regulator, a 3200uF cap the transformer and then the tube…. I presume the bias is applied immediately as soon the amp is turned on. I really do not know. Perhaps that last large cap does it regulator create this  “ping”. Confirm that gas regulator holds the voltage during switching? Put a new amplifier tube in the regulator. Make sure that regulator does regulates and do not create any spike during loading itself to the plate of V2. Perhaps Vladimir was afraid to charge that 3200uF caps and has some kind of charging spreading mechanism in there that went out of the sync? Still, if you apply voltage to wormed and properly biased 6C33C then 6C33C should not generate any noise.  Hm… the ML2 uses global feedback… and perhaps something is coming from there… I remember the ML2 was very unusable when it was loosing 3-4dB of feedback…. Yet, without having it in hands it is difficult to say anything. Rehabs, some folks on this site who have some technical expertise would advise you.  Nevertheless, I do feel that Vladimir would perform an initial debugging with you over the phone… It is kind of his part of the game

As I play the old-but-new-to-me ML2s more, and as I slowly replace tubes, performance has changed a lot, and all for the better.  Understand that I am not really talking about the ML2s, but about the sound I am getting, which is so different and so much “better” that I think it warrants discussion here (or nowhere), and I envision (or sense) a possible 2nd wave of hi-fi stemming from the possibilities exposed and highlighted by this amp (and its ilk).  Although it looks like it will be a while before I digest and process the effects of the ML2s in my system, I already have plenty to think about.  Lots of lights are going on, like flying over the countryside as night falls.

Romy already disabused me of the notion that the ML2’s effects are similar to the L1/L2 “X-Factor”; yet reading and re-reading his pieces on the L1/L2 preamps I am still left with the sense that I understand some of what he’s talking about from my time with the ML2s.  Specifically, I cited earlier and I still hear some sort of active re-tooling of the signal that “puts things (back?) in their places”.  Which sounds like a “fault”, but it isn’t at all in this case, at least not taken alone.  Also, there is so far an odd quality that could easily be mistaken for compression but is not that so much as an * almost *  SS quality of keeping a handle on the signal, compared to the SET “let it rip” approach.  The SS winds up being able to “push” the signal a lot farther than the SET, although the signal is always more or less compressed, while the SET gives the signal the freedom to “be itself”, and it dissipates and gives up way too soon.  So far, with no analog and the few CDs I have, the ML2s have not obviously “limited” the signal, per se, the situation being rather more like well-educated older parents showcasing their perfectly-behaved, well-traveled, beautiful children for other older, well-educated people who are not easily impressed with this sort of nonsense.  And the generally held opinion that good genes will out is certainly vindicated here.

Meanwhile, there are two things that just get stronger, that I want to talk about.  One is space, as opposed to soundstage or “stereo”, and the other is a certain hardness that makes on-axis listening too rough (at least with CDs), but makes off-axis listening phenomenal.

Previously, with my little SETs, the best results were generally on-axis, with a voluminous soundstage that really filled my large listening room pretty well, although there was limited musical energy forward of the speakers.  Now I am experimenting with the speakers pulled well into the room, much closer, sitting almost between them, and the musical energy just charges the air/space around me in a much more lifelike manner.  I assure you that this more than just 3-D sound effects, and in any case it has not been anything I have cared much about or looked for in the past.  But it is something I plan to pursue in the context of a certain necessary hardness that may or may not wind up being viable both on and off axis with the same program.

My phono is down and out with hum since I moved, and now I am wondering more about the “X-Factor” and whether it is desirable or too-something in the context of the already-factoring ML2s.  For sure, I have for some time gone back and forth on the old “straight wire with gain” ideal.  But I have had reservations about the AI M3A since I bought it, and despite some serious modifications I am not sure it will ever be pitched right to continue here.  I know Romy eschews parts swapping, but I will try some more coupling caps and grid resistors and get the phono going before I give up on the AIM3A, since changing that requires new phono and line stage auditions, and I just don’t have the time right now.  But if the bass, at least, doesn’t get into line, then, adios.

I will close this by saying that I don’t get around like I used to, mainly because I have become so cynical about the relationship between audio and music.  So I have no idea what is “out there” that may do what the ML2s do with an audio signal.  But whatever it is, I believe it is significant in a generic sense, and for me it is a harbinger of a 2nd wave that I now await with renewed interest in hi-fi.

Paul,

I re-mapped your post to your older thread; I hope you do not mind…

Anyhow, I find absolutely nothing in the older ML2’ sound related to L1/L2 “X-Factor”. As I suggested in the second post of the flowing thread:

http://www.goodsoundclub.com/TreeItem.aspx?postID=257

the L1/L2 are most likely use pro-audio tricks of “spatial expanders”. Sonically it manifests itself in unique pattern of “phasing of sound” – very beneficial and very desirable. In my years that I spent with ML2 I did not detect any “X-Factor” coming form this amp. It is also important to understand that the “X-Factor” is not something “nameless” but the very specific and vet well-defined sonic characteristic. One again, this characteristic is not belong ML2 but belong the Lamm’s L1/L2.

The most distinctive characteristic of older ML2 for me was its absolutely unique ability to demonstrate very “odd” but valuable integrity of “blending of tones dynamically”. There are not other amps out there that did it so fascinatingly. It is ironic any of tube rolling that you are trying now is not able to affect the ML2’s “dynamic tone blending”. The tubes will change the tonal balance and many other things but not the tonal blending. Even the Super Melquiades does not demonstrate that “blending integrity” in its HF channel (in bass and MF it is tine). Howevever, the Super Melquiades has different thing: the gass-biased 6E5P “dynamic viscosity” that in many instances overrides ML2 “blending integrity”. The “blending integrity” and the “dynamic viscosity” have different effects and I spent a LOT of time thinking if the “blending integrity” of ML2 is worth to be replaced by the “dynamic viscosity” of Milq's HF. I agreed to close my eyes to many other Melquiades’ advantages over ML2 if I conclude that ML2 “blending integrity” was worth to stuck with…

I thought that the ML2’s “blending integrity” comes for the fact that Vladimir regulated the output plats voltages. In many instances it should not be a big deal, or even to be a deterrence (dynamic is got eaten with regulation) but in case of 6C33C I heard from two other none-confirmed sources that it “might” work differently. I did regulate the 6C33C in Melquiades. I did not use 6C33C as a regulator but a set of three 807 tubes. I clearly preferred the non-regulated 6C33C built the Melquiades and ML2 have PS implemented at very different levels so I figured that non-regulated 6C33C is a way to go. There were then some thought that it might be the modulations of a full-range he amps make different but in the Super Melquiades I have some “tricks” that handle it. After all I decided that the key is in the transformer.

You see, no mater how minor delta between “blending” in my older ML2 and my new amps the delta did not exist when I used a full-range Melquiades. So, I consulted that the “blending” issues might take places because I used too “fast” transformers for Super Melquiades HF channels. Sometimes I plan to try other output transformers in there, the project that always was intended

Anyhow, as you see, even after a few years, still there is something things that ML2 can teach….

Keep the driver stage, the 6N6P, as new as possible. This tube is very critical for the given amp. You might get a tube tester and measure the mutual conductance but with the low price of 6N6P I think it is hardly necessary. I would change it as often as twice a year if you use the amp a lot. The 12AX7 can live in this amps for many-many years, find a good one get an pair and it will be enough to the rest of your live. The 3C33C should be changed in this amp once a year, with very minor variation of frequency of use and your preferred plate current.  The gas reference and the regulator amplifier might less for a few years as long as the plate voltage is stable and no nose is auditable. The big regulator tube I never changes and usually used the used up V2 tubes… BTW. You might get slightly more “juice” our of older ML2 by loading your probably 8R speaker (I do not know what you have) to 16R ML2 tap. You will loose some power but gain something that you might like. The tube will be slightly less loaded and you might with to drive it with less current. By doing the current-loading balance  *even the ML2  not as sensitive to loading as some no-feedback amps) you might dial in very precise harmonic balance of sound and very precise dumping of you LF section (sure the multi-amping will defiantly help)…

What speakers are your using? The “4R at about 80 Hz before going back up their average 8 Ohms at 30 Hz” is not good for SETs.  I prefer to have 16R and do not let it to drop below 12R.  Lamm is quite fixable with loading, probably because of the feedback. I do not know how Lamm loaded the output stage. It was possible to figure out but I did not care. Generally a full 6C33C might be loaded form 500R up to 1.8K, or in some cases even higher. It all depends of many factors within amplifier and with within speakers. Usually the 800R-1200R works out well. Sure the “speed” and transient capacity of speakers is a huge factor, as different speakers would handle harmonics differently… Do not forget that the tube drops plate impedance with raise current. Lamm is less sensitive for current change but still it is with auditable for bass the change between the 280mA and 310mA. Less current higher impedance but very interesting, although very minor improvement in bass.  Sure, you loose power, so add some voltage. Balancing the amp with sufficient voltage and sufficient current for the given signal, given loading and the given load it is possible to dial in very precise bass. I usually drove my LF pair of ML2 at ~185-190V and 280-280mA.

ML2 is also making me hear my modified AI M3A pre-amp, not to mention I guess I could now benefit from all shielded cables.  All this stuff was fine with the Wright 2A3s. 

Speakers:  I built a version of Dick Olsher's 3-way Diamond Edition BassZilla (hard to find at www.blackdahlia.com), and I tricked it out considerably from his mule.  Bass is BR, 15" Audax P380MR, which is a nice semi-stiff driver, low-passed at 150 Hz.  Lowther DX4 is high-passed at 150 Hz. All drivers share a 2' X 6' front baffle, and there are tapered wings for the Lowther, which is OB.  Lowther is notch filtered at 2.4k and 8k, to tame its "spikes", but I let it run itself out up top.  An Arum Cantus G2Si phases in at 10k, since the Lowther trails off from that point.  Driver integration is seamless.

Nework is passive, which I may address to deal with the impedance wavering from 40 Ohms at ~80 Hz (this is correct; I mis-stated it above) to 4 Ohms at ~50 Hz +/-.  Otherwise, load stays near enough to 8 Ohms, where it matters.

The best I have gotten from these speakers is the best I have heard, overall, certainly better than Avante Guarde Trios, overall.  Since I am so attuned to pitch and timbre, I have not found suitable horns, and also I like the dynamics I'm getting better than the tromboning I hear from horns, despite their stronger initial "push", which is nice.

Lowthers have well-known problems, but DX4 has better potential for correct tonal/timbral balance than Alnico drivers, IMO, and addressing the "spikes" changes more for the better than some might suppose.

As you say, the speakers aren't realized without a suitable amp.  ML2 may not like this speaker, but I can tell you it handles it pretty well, and likely as well as any off-the-shelf amp could.  These speakers are way too revealing for SS, and PP was a disaster, as well.  They sound great with the 2A3s, as long as you don't feed them a lot of signal.  ML2 is another kettle of fish, handles tons of signal, no problem, as you know, and way more clarity, and so astoundingly realistic in its presentation, it's uncanny.

Since ML2 is obviously better than these speakers, it looks like I can use ML2 to develop these speakers for a while yet.

I still have some other work to do before I start in with bi-amping, although that is something I have considered since the beginning.  I have also considered subs from the start, and if/when I get to that point I could re-address the crossover points, apropos.

Again, I just stay amazed that more people have not gotten onto these amps, especially since they are now available on the re-sale market.

Best regards,
Paul

Paul S wrote:

Speakers:  I built a version of Dick Olsher's 3-way Diamond Edition BassZilla (hard to find at www.blackdahlia.com), and I tricked it out considerably from his mule.  Bass is BR, 15" Audax P380MR, which is a nice semi-stiff driver, low-passed at 150 Hz.  Lowther DX4 is high-passed at 150 Hz. All drivers share a 2' X 6' front baffle, and there are tapered wings for the Lowther, which is OB.  Lowther is notch filtered at 2.4k and 8k, to tame its "spikes", but I let it run itself out up top.  An Arum Cantus G2Si phases in at 10k, since the Lowther trails off from that point.  Driver integration is seamless. Nework is passive, which I may address to deal with the impedance wavering from 40 Ohms at ~80 Hz (this is correct; I mis-stated it above) to 4 Ohms at ~50 Hz +/-.  Otherwise, load stays near enough to 8 Ohms, where it matters. The best I have gotten from these speakers is the best I have heard, overall, certainly better than Avante Guarde Trios, overall.  Since I am so attuned to pitch and timbre, I have not found suitable horns, and also I like the dynamics I'm getting better than the tromboning I hear from horns, despite their stronger initial "push", which is nice.

Lowthers have well-known problems, but DX4 has better potential for correct tonal/timbral balance than Alnico drivers, IMO, and addressing the "spikes" changes more for the better than some might suppose.

Paul S wrote:

I still have some other work to do before I start in with bi-amping, although that is something I have considered since the beginning.  I have also considered subs from the start, and if/when I get to that point I could re-address the crossover points, apropos.

Paul S wrote:

Again, I just stay amazed that more people have not gotten onto these amps, especially since they are now available on the re-sale market.

This all brings me to a said observation that I think I have already made somewhere within my site. I recognize Lamm ML2 as a very unfortunate symbol of weakness, ridiculousness and foolishness of high-end audio. When in the end of 90s Lamm came up with ML2 the audio Morons took it almost violently. I remember it was impossible to open month mentioning ML2 because immediately a swarm of typical, “always-there” bottom-eaters ran to you, screaming with foam at this mouth that ML2 is overpriced peace of sonic crap. I remember somewhere in 2000 I was arguing with many idiots at AA about the ML2… and NONE OF THEM ACTUALLY WERE FAMILIAR with the ML2 sound. Still, any single Moron out there had a strong opinion about the ML2’s perfomance. Then the ML2 went south (I would avoid to name reasons), initially gradually and then the new revision - the ML2.1 was introduced. The ML2.1 revision has as much common sonically with original ML2 as a firecracker has in common with a ballistic missile. However, the ML2.1 receives IDENTICALLY glorifying and admiring reviews from the industry idiots as its predecessor and nowadays each second idiot who few years ago was spitting forwards Lamm has his ML2.1 sitting in his listening room. Still, the fact that the new production of Lamms sounds more like Krell amplifiers does nod bother anyone.

I think what was happening with Lamm is very-very indicative for the damn audio community generally. Most of audio Morons have no integrity, no conviction, not ability to recognize or interpret the factual results, no reference points and no familiarity with nature Sound. Nowadays the Lamms become a buzz-word for the cretins with audiogon-brains ask them “why” and they will hardly have any rational in their preferences or opinions.  Still, the “vintage” L1 (some of its aspects), the “vintage” M1.1 and the “vintage” ML2 (if they properly used) remind as some very special audio elements that, because of multiple reasons (with exception of M1.1), did not really find a deserving utilization in the world of Dominating Audio Moronity ™…

I do not have any disappointment that there was no serious public overview of ML2. I have quite low esteem to audio public generally and to the people who facilitate public overview in particularly. It has nothing to do with cynicism but rather with objective observation of the reality out there. It is kind if shame as it never happened as the ML2 is gone and the current production of ML2.1 has nothing to so with ML2 legacy. In addition Lamm, as I understand nowadays abandoned any ideas of good sound and goes to cash out the market of mid 90dB-sensitive speakers buy buttering up his prospective customer on the idea of ML3. It will be basically the "new ML2 type Sound" approach only with the unnecessary 40W, based upon high-voltage-compromised, more powerful output tube.

Regard the rest. You might discover eventually that despite of beneficial contribution of some exotically performing audio-elements and despised that some of them are able to inflict long term listening consequences to listening culture but the only thing that counts is not the capacity of the audio installation but the way in which that capacity is used but the system owner. From this perspective all those audio toys are quite irrelevant…

I’m glad that you are in your way to discover the vintage ML2 – it well worth it. Spend a couple years with those amps – you will observe and learn quite a few interesting things. In 2001 I have written somewhere at AA that ML2 is able to demonstrate it’s sonic advantage even when it is not powered on. I remember that all Morons out there informed me that I was an idiot.  They are fortunate that they did not know how it really felt about their competence on the subject or about their primitive understanding what the subject really was.

Paul S wrote:

I heard back from Lamms about the relay pulses.  They suggested I bias the amps again and then Lamms went silent when that didn't work.  But the problem disappeared when I got around to replacing the 12AX7s that came with the amps.  I happened to use some NOS ribbed-plate Telefunkens.  These not only cured the pulsing but resulted in astounding improvements to the sound.

Yep, it happens. Tubes could go bizarre sometimes, even such a reliable as 12AX7. After walking over more then 40 different 12AX7s with ML2 I have seen some very strange 12AX7 behavior. The ribbed-plate Telefunkens are fine, I use them on my LF amplifiers that drove my line arrays. I find them too rough for MF use. Still, all Telefunkens are very different and they sound differently batch from batch. I have some (genuine) Telefunkens that sounded like “nothing special” and I have some that did phenomenal job. Interesting that with “better” input tubes ML2 might sound “better” in Hi-Fi sense, I call it “tactical” change in sound. However, with change of the input tine the ML2’s “strategic” sound is not affected. BTW, the driver stage more affects the strategic then the input stage. The driver stage is VERY important in SET.

Paul S wrote:

6N6Ps are next, if I can find some good ones, since I have no way of testing the "bulk" stuff generally offered.  Of course, Lamm remains an option, and I am pleased with the V2 tubes he sent me; expensive, but at least they are as advertised.

There is no “good 6N6P” at least I was not able to find them. Get juts new 6N6P, with full cathode emission and it all that will need. The wearing of 6N6P very nicely shows on a tube tester but with their negligible price juts change them twice a year and it will be enough. I remember Lamm told me that the 6N6P are good for over 5 years… God luck with it… BTW, I did some experiments trying to found of if the early production of the 6N6P from 60s sounded better then the later production from 80s. I was not able to detect any difference.

Paul S wrote:

Any ideas for sources for 6AK5 and 5651A?  Seems like most of the ML2 tubes are "hard to find" from local sources.

I do not know why you say it. Both 6AK5 and 5651 are very common and very inexpensive tubes. The 6AK5 are penthode and dozens and manufactures made them. I had few or them, perhaps a half dozen of different brands, and I did not detect any huge differences in their sound. As I understand Lamm uses it as aerial amplifier in his B+ regulator to drive with 6AK5’s plate the grid of the 6C33C regulator. It is HF penthode and it is fast, nothing more requires from this tube, so it is no surprise that it did not affect sound tangibly. I ended up to catch a party of Western Electric 6AK5. Honestly they did not sound better or worth then anything else and I used them juts because the sexy yellow Western Electric letter across the tube.  I think I paid for them a few bucks per tube…

5651 is also is very common tubes. It is actual not a tube but a low current gas regulator on 80-90V. You can use in there absolutely any type of gas voltage reference diode that could regulate near 85V and can handle under 3.5mA. There are many substitutions for 5651 and many different manufacturers made them. I also did not detect any big difference in Sound in those tubes.

Do not confuse the Gas tubes that Lamm used in his regulator and the gas tubes that Melquiades uses.  If you read the thread from my bookmarks:

http://www.goodsoundclub.com/TreeItem.aspx?PageIndex=2&postID=2792#2792

They you might be under impression that gas tubes do affect sound, however Milq and ML2 use them differently. In ML2 the gas tubes are juts the voltage reference for stabilizer but in Milq the gas tubes supply bias, driving the grid of driver stage. Evan it took place via a large resistor but still it is way more mending duty. If I had ML2 I would change one resistor and would try a 35mA gas regulator instead of 3.5mA. In Milq the 35mA-type were better but it not necessary would means that they might be better in ML2. Those gas tubes are also a couple to few dollars per tube and they are good for years. The good part about the 3.5mA-type gas tube that there are practically not fake tubes among them…

The cat

Paul I slightly surprised about your comments. The regulating aerial amplifier tube affected sound very mildly, if ever, at least it was my experience. I had a few different 6AK5 but changing them was not a highly notable effect. I still have left a dozen of so of Philips Miniowat 5654SQ “Special Quietly” tubes, if you wish I might send them to you, as I have no use for them. BTW, be advise the all this tubes need to be burned in and they will change sound after then…

About the input impedance  - I do not remember the values now. I have the calculation sheets for my crossover somewhere and I might look for it… if I did not trash it… It has a voltage divider with I think slightly under one 1K in series and the shunt resistor that makes it 41K… Anyhow, why are you planning to drive the ML2 input to higher impedance? Your preamp can’t handle R41K? I usually peruse opposite and try to drive input impedance as low as possible with objective to load cables with current. I love drive cables with current, even with active bias current. If it were up to me then I would run 1A of DC though all system interconnects…. In fact I will do it sometimes…