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08-11-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 101
Post ID: 8011
Reply to: 7192
New cause/cure for switch-on pulse
Just wanted to report that less-than clean 12AX7 pins can cause a switch-on pulse through the speakers just like bad 12AX7s can do.  I think it's been about 18 months since I cleaned these, when I first installed them, and I just was not ready to believe that NOS Tele 12AX7s went bad after only 18 months.  This happened yesterday.

Today, I was getting a faint "crumpling plastic wrap" noise from the right speaker.  I was able to exacerbate it by SLIGHTLY moving the (new/clean!) 6N6P (don't try this at home!!!).

I turned off the amp and waited for the caps to drain, then I pulled the 6N6Ps, straightend the pins and carefuly reinserted them. It worked fine, with great music all day, until the electricity went south, around 7 PM.
 
Reminder to self:  Keep all tube pins/sockets and other connections clean, including long-lived tubes, which should probably be cleaned once a month or so, or more often in ocean front and/or humid environments.

It's hard enough to get good sound from a properly-operating system.  It's impossible with bad connections.

Paul S
08-14-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 102
Post ID: 8034
Reply to: 8011
Weird tag-team tube failure (with no consequences?)

I tried listening for a while this morning, figured the electricity was not good enough.  When I went to switch off the amps, I immediately noticed that BOTH 5651s had failed spectacularly, with cracked bases and "white-out" on the tops of both tubes, IOW, no vacuum.  Weird, and weirder that it did not make it sound any worse than bad electricity.

I'd first suspect modern "value engineering" at its finest, but these are not modern tubes.

I would also suppose that other tubes got fried, too, for want of voltage regulation; but wouldn't that tell more noticably in the sound (which was not good, but it has been worse with good tubes and worse electricity)?

???

Paul S

08-14-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 103
Post ID: 8035
Reply to: 8034
Paul, are you insane?
I am serious, Paul. Reading your tail of straggling with ML2’s tubes and tubes’ sockets I suspect that something is very fishy doing on with you. There is absolutely NOTHING might be with ML2 tubes sockets. You reported that the second stage of ML2 has burned sockets – I never have seen or heard it and I hardly believe that 650mA of the 6N6P can do a damage. Then it was the 5651. This is cold running gas regulator – how the hell it could be “failed spectacularly, with cracked bases and "white-out" on the tops of both tubes”. BTW, there is no vacuum in those tubes – they are gas-filed. The only thing that I suspect is going on in your hour is you wife what you are not home smash the amp with hammer. I am not kidding – something is very wrong with the way how you amp work. Is it you first tube amp? Is it possible that you do something very fundamentally wrong with those tubes?

Rgs, Romy

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-14-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 104
Post ID: 8036
Reply to: 8035
Arguably insane; the hand that rocked the cradle
Read again, Romy.  No burned sockets, and none reported; just dirty pins and then failed 5156s, as reported.

While I do have two busy and curious granddaughters one might at first suspect, I now believe that I cracked both 5651s MYSELF when I "rocked" them gently in their sockets (with the amps off) as part of the pin/socket cleaning ritual.  This theory would account for both tubes having cracked bases and both failing at once - from the cracks.  And since there is no vacuum in this case, "white out" was the result when regulating gas escaped out cracks.  Many tube amps; many tube cleanings; first cracked-by-me tube bases.  Live and learn...

Again, I did noit notice (or hear, for that matter) any other damage, so that seems to concur with your sniffing at 650mA as no problem for the 6N6Ps.

Best regards,
Paul S
08-14-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 105
Post ID: 8037
Reply to: 8036
Very improbable.
Paul, the dirty pins are the pins that become dirty because of corona burns the pins. It is unless you marinade tubes in A1 souse before you place the tubes into the amp. I would hardly belie that it is possible to cracked 5651 no meter how rough you handle them. To have two tubes cracked on different amps at the same time – very very improbable.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-14-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 106
Post ID: 8040
Reply to: 8037
Cracked, all right
Well, most metals in air simply corrode over time; we all know that.  And running a little current through it can hasten the process.  To pick an extreme example, I lived at the beach for nearly 30 years, and ALL connections were constantly going bad there, a real PITA.  I figured I would not have problems like that here, ~ 20 miles inland, and indeed, it's been nothing like that.  Rather, it's just as I've said.

Sauce?  I ONCE tried "Pro Gold" on tube pins, several years ago.  Never again!  No, these were cleaned the usual way, with Q tips, little plastic dental tools and LPS "no-residue" contact cleaner, using magnification.

Here I am, looking again.  Both 5651s have cracked bases, and both cracked in exactly the same area, along the pins  And, yes, it does seem very unlikely, if only because I am very careful and painstaking with the gear, and I was not at all "rough" with these tubes, which are NOS RCA 5651WA, supposedly "mil spec", installed in April of this year.  Also, as I said, this is the first time this has ever happened to me, with ANY tube.

I post here just to share my experience and because it's the only place I know to get intelligent feedback on the ML2, despite the fact that there are supposed to be so many "out there".

BTW, lots of the NOS tubes I get have pins that are "mottled", like they were brought up to a high temperature and air cooled, and I always assumed this is due to the glass manufacturing process versus the pin metal.  I have never noticed any further "burning" of pins that I have recognized as such, however, including with these amps.

But I suppose it wouldn't hurt to replace the tube sockets, if that's what you are recommending.

Best regards,
Paul S
08-14-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 107
Post ID: 8041
Reply to: 8040
Ah, it is the cracked tube’s bases not the tubes.
Well, I never seen it happens but who know – that might be if some use “violence” on tubes. The sad part is that to replace these sockets is difficult. I have replaced in ML2 the 6C33C sockets in ML2 - it was easy but the 5651 are PC board-mounted and to replace them need to the amp board taken out. I did take the ML2’s PC board out – just a few screws and 20-30 connectors. The connectors are well-colored and shell not be confided. So, take a good phonograph of the connectors and then you will not confuse them. In worse case you will have the other amp for color references (Lamm build then identically). Alternatively the 5651 uses just two contacts – anode and cathode it has 7 pins and 3 pairs of contacts the do the same. So, if your tube base cracked and some of the pins got loose then you might find an adopter with fat pins that you might permanently place atop of the damaged socket, bridging it.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
08-14-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 108
Post ID: 8043
Reply to: 8041
Cracked glass at tube's "base"
where the pins go through the tube glass

Thanks for the tips, Romy.  But I am not sure from your response if you now get that it IS the glass at the bottom of the tubes themselves that cracked.  The cracks did not "run" up/break the tube envelope but stayed across the bottom/base.  The tubes remained "whole" when I took them out of their sockets, and they did not break further when I tossed them onto the empty bottom of the waste basket from a standing position.  "Clunk", but no more breakage.  Go figure.

I might replace the sockets to stop micro-arcing, if I thought that was a serious problem and I could solve it that way.

Although I would not choose the stock sockets Lamm provided, neither would I venture to replace them at all based on these two tubes cracking or even because of that much corrosion over 18 months; it would have to get worse.

Uncommon and unlikely as it may be, and in the absense of a better explanation, I still think I cracked the tubes myself, as I described it.  These tubes came in a "sleeve" of 5, so they may be from the same, fragile lot; although I had no problems with the first pair that I think I treated the same way.

I guess if you live long enough...

Best regards,
Paul S
08-30-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 109
Post ID: 8125
Reply to: 8043
So much for "10,000 hours"...
I have been fighting the electricity and getting off-track enough to find it wearying, not to mention the silliness with the tubes.  The other day I happened to drop a double album and it hit dead flat on the carpeted floor. The mute was off and I distinctly heard the album hit the floor through the right speaker.

Lightly tapping the amps in turn, I was very annoyed to find that my specially-selected "10,000 hour" NOS Telefunken "ribbies" have gotten microphonic, and further checking revealed that they have also gotten noisy, as well, after about 1 1/2 years of weekend listening!

I checked my tube stash and found some substitutes. The back-up pair of ribbies was not nearly as good as the first pair, so I am presently using some culled GE 5751s while I wait for some more that are supposed to be better.  These tubes are not especially good; but they aren't bad, either.

I did enjoy the quiet from the new tubes, listened to the Mercury Rigoletto straight through, like a nice, calming shot of morphine.

I draw no conclusions from any of this, except that I have to stay conscious of the way the tubes behave; I can't just plug them in and forget them; not even "10,000 hour" tubes.

Paul S
09-10-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 110
Post ID: 8213
Reply to: 8125
How Better Tubes "Saved My Cartridge"
The "better" 5751s got here and I took advantage of wifey's absence to listen at night.  It was cool and the electricity was pretty good, just a little "dry", but no "cotton".  Lazy boy, I still haven't fixed my DAC, so I have had only vinyl for months now, serving +/- as "its own reference".

Well, I guess I got lucky. The amps were in fine fettle, to the extent that bass depth and power, along with overall  clarity, were the best I've gotten from the system to date.  Mid/upper bass "tie-in" was also better, with more power.  Harmonics were still developing when I shut down, but the quiet-other-than music was also as good as it's ever been, providing a nice sense of the recording sessions with no loss of the music.  Very little or no microphonics or self-noise now, and it is now obvious that I have been putting up with at least some of this for some time, since well before it became obvious that the tubes were a source of trouble.

A bonus, like the header proclaims, is that I no longer think I need to replace my cartridge, and when I do, I'll get another just like it, if I can still find one, because it turns out it was better all along than I ever realized (for that matter, so are my speakers).  These tubes do not seem to suffer overload (yet...), which I had been attributing to cartrridge mistracking or saturation.  Apparently, the cartridge also tracks more and better than I thought, and the tubes do not seem at all flapped by any noise, etc. the cartridge is putting out along with the music, so the results are musical.

Live and learn.

I still want to experiment with IC, but within the fixed limitations of the system, if it stays like this I will be pretty stoked.

Paul S
09-10-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 111
Post ID: 8216
Reply to: 8213
The Lamm ML2 and feedback.

Be careful with those 5751. ML2 became unstable with 6db more or less (I do not remember already) global feedback. Lamm told me a long and big story how critical for ML2 to have the global feedback of exact amount and how “properly” the feedback is implemented in this amp. At that time I was ignorant and was listening what Vladimir told me gullibly? Stressing the exactness amount of global feedback in his design Lamm however endorsed to use the 5751 in input stage.  Later on what I get some understanding of the process I was laughing on Lamm’s self-pomposity.

The ML2 has global feedback that covers all 3 states and 12AX7 in the first stage. If you put the 5751 in the first stage then the gain of the first stage gets reduced by ~25% that would make the gain of open loop reduced. The closed loop is still that same that would make the amps in a whole to change the amount of the global feedback that is being used. I did not detect any problem to use the 5751 but I found that it was very funny that Vladimir insisted that the feedback resistor mast not be changed because it will be “bad for feedback sound” but the change of the gain in the open loop is permitted - like it would not affect the close loop.

I am sure that for 3 easy payments of $699 Lamm would promise to reset the laws of physics in his amp….

The caT

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-10-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 112
Post ID: 8217
Reply to: 8216
Just one of the sheep
I have to say, I never gave it much thought, since, as you say, The Book says 5751s are an OK sub for 12AX7.  I did realize that the gain was lower, but I obviously had a brain cramp in not interpolating the lower gain to "redistributed" global feedback.  Of course, similar/the same applies to the choice of output taps...   What, me worry?

No doubt the applicable resistors are safely sandwiched between two boards, or something, so replacing them is like doing a valve job on a vintage Bugatti.

Well, whatever, the sound is good enough now that unless I detect smoke or ocillation I will keep these tubes in there.

These amps are very nice indeed for my lazy-ass approach, and they at least sound much better with these particular tubes.  However, naturally, I will be QUITE pissed if they melt.

BTW, did anyone besides Stereophile figure out that Lamm had "discontinued" the ML2.1?  I guess a couple pair of "bespoke" ML3 "Signature" amps a year keep him in endangered species shoes and coats.

Best regards,
Paul S
09-21-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 113
Post ID: 8354
Reply to: 8217
If a Tree Falls in the Forest...
I've been keeping this ML2 log for myself, of course, but also for anyone else who wants to chime in.  It has been my intention (and practice, I think) to report not just "sucesses" but also whatever happens, +/- as it happens, with no regard to how it "makes me look" when I do stupid things, jump the gun, etc.

So, now I feel bound to say that I have not been able to repeat the sound quality I got that prompted the original "enthusiastic" post about the "better" 5751s.  While sound has been pretty good a couple of times since, the combination of qualities that especially distinguished that session have not come together like that since, either.  The overload-proof clarity has remained, but harmonics with these tubes have not yet gotten as good as they were with the "special" ribbies, and bass has not been nearly so strong or integrated again.  Closely mic'd bass instruments sound strong, but bass ambience and overall harmonic balance from orchestra or ensembles are nothing all that special.

It looks like the last word, every session, is still from the electricity.

Paul S
09-22-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 114
Post ID: 8357
Reply to: 8354
It would be like a déjà vu feeling…
I do not know Paul; I feel that you have a lot strange fantasies about ML2…. BTW, this week, because some odd courses, I will have a pair of ML2 in my room. It would be like a déjà vu feeling. If I found myself in the mood then I might look if ML2 uses the demagnetizing coils in it’s output transformer.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-22-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 115
Post ID: 8361
Reply to: 8357
Tripping the Life Fantastic
I wish I had other sources for reference, since it's obvious (even to me) that the amps will only sound as good as what they are fed (and what they feed).  I think I still have my old CD player around, somewhere, while I wait for my iDAT...

Basically, I feel simultaneously encouraged by the best I've heard and discouraged by the the fact that the best is not obtainable at will.

Although I always recognize good electricity, I am slow to recognize the bad electricity as such on occasion, given the myriad choices of parts that can and do go out of sync, or just out.

Sure, the ML2s are about as "plug and play" as it gets; but I am a long way from a switch on and press buttons system, for better and for worse, even though this has been something I've tried to improve on over the last couple of years.

As for the fantasies, I have given people credit for being able to take what I say for just what it is and use or not any information that comes out of this ML2 journal.  Your input/information has been invaluable, and I have willingly taken some lumps to get it.

Funny you just won't believe that the 5651s cracked, etc., but I tell it like it happens to me and try to learn from the feedback.

I don't know what you mean by "the demagnetizing coils in its output transformer".  What does this mean?

Are you planning to actually use the ML2s a little?  Which speakers?

Best regards,
Paul S
09-23-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 116
Post ID: 8363
Reply to: 8361
The demagnetizing coils in ML2 – a false alert.

 Paul S wrote:
I don't know what you mean by "the demagnetizing coils in its output transformer".  What does this mean?

I do not have any plans about ML2. A friend of my asked me to help him with his ML2. So, I did end up the amps sitting in my room. Since I opened them last time (in 2001) I learned a lot and begin to understand a few things that I did not understand then. I have written (I think it was in David Bearing thread) some that there is a technique of dynamic demagnetization the transformer core with injected could to prevent the core from early LF clipping.  I remember Lamm said in his ML2 design “the special measures were taken to prevent the ML2’s output transformer from saturation” - so I fell that it would be worth to see how it is done. Upon looking at the ML2 circuit it does not look like Vladimir used any demagnetizing coils in his OPT. The primaries go to plate of output tube and to the grid of the regulator. The secondarys go the binding posts. Everything else is pretty straight forward…  So, it look like that there is no dynamic demagnetizing in ML2. It is said in a way, as it the ML2 did use it then the depth of the demagnetizing would be VERY interning parameter to measure.

The Cat

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-25-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 117
Post ID: 8377
Reply to: 3488
The Lamm ML2 bites…

Reading at my site Paul’s narrative about his fight with ML2’s tube and the ML2’s tube sockets I need to confess that I always was suspecting that he is some kind of odd wacko with bizarre and sick approach to the subject of amplifier tubing. Too much of what he said just did not make sense to me. Well, until the last night…

Disclaimer: (wherever I say ML2 I imply the Lamm ML2.0 version not the ML2.1, about which I do not case)

I own two pairs of ML2 that I bought new and used them dally since then. I know dozens of ML2 heavy users who never had any problem with those amps. In fact ML2 were very stable and very secure in operation amps. The Lamm’s ML1, the preamps were with operational “issues” but M1.1 and ML2 were very stable.

Anyhow, I have this week a local friend of my brought to me a pair of ML2 and he need a help with inner-amp filter. The amps he brought were not used for a while and were sitting in storage for 5 years. I did the necessary things with filtration and desired to listen them. I have no way to drive Macondo full-range but I have my MiniMe prototype…

The plate currant on both of amps was too high. The further inspection showed that ML2 regulators stopped working. The B+ was not eaten by regulator tube and ML2 had 230V at .6A on plate – it is over 130W anode dissipation – bye-bye the 6C33C… Actually, I was rung the 6C33C like this for a whale, when I was searching the problem, the tube did not failed. The ML2 regulator is too simple and cannot work without a load. 

Anyhow, chasing the problem in the ML2 belly I was wondering why the regulator was down… on BOTH AMPS. The das tune was on, the error pentode was on the regulator tube was on. The design was very simple and very straight forward… I measured and confirmed that the right voltage was given to all tubes but it looks like the error amps did not corrected the voltage. I test the error amp’s pentode it was perfect. I went to my storage and brought my own WE 6AK5 – the same result. What the hell I was wondering…. I pulled my dummy loads to substitute the output tubes as it was glowing with 130 on plate like crazy and then the regulator … kicked in!!!

OK, guess what was the problem? The problem was the fucking frugality of Mr. Vladimir Lamm. This guy makes 30.000 worth amps with none-treated steel tube sockets. It was juts ridicules – the tube sockets on 6AK5 were rusted to the point of no contact with cathodes. The sockets were cleaned and the amps were working flawlessly… I wonder if Lamm would use not $.15 tube sockets but $1.15 then would it lead to extra $10.000 of the retail price… Anyhow, the idiotic economy on such a mall things in a flagman amp that cost $30.000 (the amp was made in end of the 90s with serial number in 40s) appears to me… to idiotic. It is not something that saves money to Vladimir and it is not something that Vladimir do because of his ignorance (his is a brilliant technologist). Those things that he does are because his attitude and he learned that his customers and his revisers are deaf idiots and he can go away with it. if not then how can in such case one explain that in early prod action of ML2 Lamm used Cube 950 caps for inner-stage coupling – the phenomenal-sounding Polypropylene foil caps. In the amp that I was fighting with regulator all coupling was made by bypassed Cube 935 that are Metallized Polypropylene and with very different, less sophisticated sound. It was $7.35 for Cube 950 vs. $5.11 for Cube 935 – I am sure it was well worth it… I was wondering how much Lamm “saved” in more important thing – on output transformer for instance. I wonder how far Lamm electronics sound off from the level as it MIGHT sound if the electronics was made with respect. I remember a few years ago Lars Fredell let me to listen his M1.1 that Lamm custom-made (just with better parts) for him. It was WAY more interning then the production M1.1. Well, I presume that if Lamm wish to kiss somebody else ass with sound then his is perfectly able to get better sound of his design. I wonder why it shell be a condition? Does Lamm’s series production is just the Lamm’s attempt to eagerly spit on somebody ass? Well, if you understand what I mean then you understand what motivated me to design Melquiades and do not be subordinate of that “subordination”.

Anyhow, the Paul’s suffering with tube sockets was understood now, at least…

The caT

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
09-25-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 118
Post ID: 8381
Reply to: 8377
Designing with a Pencil
We should always remember that VL designs by design, rather than with his ears.  While I would guess it's OK to sub 950s for 935s, at the same time I'll bet VL has taken into account ESR and other parameters that the average capacitor-swapper might overlook.  The short-ish lifespan of a cap means that some of us should be thinking about replacements, and I really don't see myself sending my amps back to the "factory" for an overhaul...

As near as I can tell, there is no reason/excuse for the el-cheapo tube sockets throughout, although I don't know what else was available for the 6C33C when VL first built the ML2.  What does BATman use?  One day I will pop the bottom off to try to figure out how hard it would be to swap out those sockets.

Meanwhile, we all know the story of those "cheap plastic binding posts"...

I can't listen to the ML2 and regard it as an "accident", since it sounds like anything but that.  But it seems pretty clear by now that VL will stick to his desiderata regardless of what we think or do.

Paul S
10-03-2008 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,672
Joined on 10-12-2006
Post #: 119
Post ID: 8434
Reply to: 8381
Curiosity (and bad AC) prompts discovery
Finally looking under the hood, for the first time, my immediate observations are similar to those expressed by Romy and others who've checked and reported earlier: Top-Flight construction; "more than adequate" (but not "premium") parts.  My amps (#s 57 and 58) have .033 uF 1000V Electrocube 950s, and the larger 10 uF, 400V Electrocubes are 935s.  I have made no attempt to trace the circuit(s) yet, but the layout looks very simple compared to my former pre/phono amp, the AI M3A (which I modified extensively).

Regarding the 935s, 10uF seems pretty big for a coupler, but at this point I would guess that is their function.  Based on Romy's observations it seems like an obvious swap to make the 935s become 950s, and the clean, open layout makes it look like it should be easy to do this (with the board in place).  In fact, now that I've seen it I am almost overcome with the urge to swap those 935s for something else, even though the plastic caps are probably all still working fine, electrically.

I did not see any ID/factory info on the BIG cap, which I presume is an oiler.  I wonder if it is still working to spec.  If it's a mil-spec poly, then probably, yes.  I don't have a dedicated cap meter, nor do I have an ESR meter, for in-circuit checking.  One thing for sure: I would not want to get zapped by a full charge from that puppy!

These amps have lots of decent electrolytic caps.  I think of typical electrolytics as lasting 3 - 5 years, although some seem to "function" for over 10 years.  Swapping electrolytic caps would mean pulling the board, which, as Romy has said, looks easy IF proper protocol is followed.  I can't even guess if it would be worth the effort to do other than a straight new-for-old swap of the PS "lytics", but I have gotten sonic benefits from using especially swell 'lytics in cathode RCs.

At this point I caution myself to at least match or beat Electrocube's ESR and ripple with any prospective substitutes.

At this point, I admit that it is probably weeks of terrible electricity that are causing my itch.

I am also thinking of putting in an "audiophile" fuse (and not mentioning it here).

A great listening session would probably put the wood to my "curiousity".

Paul S
10-03-2008 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,183
Joined on 05-28-2004
Post #: 120
Post ID: 8438
Reply to: 8434
Only if you have specific complains…
It does not sound right to me. If I am not mistaken then it has 2 X2uF caps. What 10uF coupling cap can do there and what 1000V cap does in ML2. The 1000V cap is almost $6 more expensive – Lamm would kill himself but would never allow such a waste of capital! The PS of ML2 even with delay develop such a high voltage and it shell be used smaller voltage copping caps. Let see, the first stage has on plate probably 150V with second stage has on grid a few volts – 400V cap will do there perfectly fine. The second stage has I think 150V-200V on plate and the last stage has up to minus 100V on grid. The 400-600V cap will do there just fine, if the stages are capacitance coupled. Then the caps. The selection of 935 is kind of strange. The 935 are Metallized Polypropylene. They have higher volume and inferior sound. The Polypropylene Foil 950 are way better but at this voltage they have max nominal of 2uF (it is what Lamm used before. I do not know what he changed. He might change the loading impedance of the first stage that forced him to go for higher coupling capacitance. It is not difficult to trace and to measure it and to circulate the filter that the cap will form. Stay with 5Hz or lower. I would stay with Electrocube 950, Multicap RTX or those new Teflon V-caps. I do not like to bypass them if a good cap used to begin with (Multicaps are self-bypassed). If I were you then I nether would worry about ESR of the electrolytics nor about anything else in ML2. Whatever is made in there is sufficient enough to leave it alone. Still, I would touch anything only if you have the specific complains to the way how the amps sounds.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
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