Jessie, current is mentioned repeatedly because in the case of DC, and in this situation, the current is actually what one wants to meter out.  Lamm just gave us a simple way to take a reasonably stable, real-time "measure of current" at this point, which would otherwise be +/- impossible to do.  No slights were (or are) intended or implied regarding any of these (or any other) "test procedures", since the actual circumstances are, to my feeble mind, far more arcane than we have touched on herein.  I went for years assuming that all calculated values could always be measured and "verified" for working voltage and current, inductance, capacitance, etc., and I was amazed and remain quite confused to find that, for all intents and purposes, math is as close as one actually gets to "knowing" the actual operating "values" one cranks with figures throughout a given circuit.  Basically, it's Heisenberg, all over again.  Few people have the depth of understanding necessary to conduct meaningful electrical forensics or really design in audio circuits, and IMO fewer (far fewer...) can go from there to get "good" working results in hi-fi.  I consider myself to be looking up at the bottom rung of the electrical knowledge ladder, and to tell the truth I see myself as not much farther "up the ladder" with respect to hi-fi, either, with much to learn and little to "teach".  And I am not being modest here.  The past year has been particularly "enlightening" with respect to exposing to me my own incalculable ignorance.

Re, 185V V2:  I always, eventually, get around to fiddling with operating points in all my active gain circuitry, since this is such an important tool for shaping sound, including the character of the sound.  This gets back to Romy's facination with "plate loading", a rich field of inquiry, indeed, for those at a certain level of comprehension, and the certain road to ruin for the unprepared.  In the case of the ML2s, I am aiming for a sonic matrix that is - in my system - "the best" compromise between harmonics, harmonic integrity and a sort of general sense of FR "continuity" that the ML2s either are or should be particularly famous for, since they are head and shoulders above anything else (I have heard) in this regard.  I have dutifully recorded my findings, which attempt to speak to what is possible, conditioned by my own system's special requirements and its (and my own) limitations.  I will air a personal suspicion, however, that Lamm's "factory settings" are aimed at the people he (correctly) deemed most likely to buy his amps.

Best regards,
Paul S

To crack the small-pin tubes by jerking them in tube-sockets?  I do not believe in it but you are at your full right to feel that you did it. If you cracked 6AK5 then it will very fast (a few hours) loose the getter on the top of the tube (dark-silverfish residue). If you cracked 5651 tube then you have no Neon (or Krypton or whatever they use) in the tube and it will have ability stabilize voltage.  I guess it will bring some noise as well. Also, I think that if you did somehow cracked the tube by rocking tubes “GENTLY” in their sockets then you realty need to review your definition of gentleness.

Now, and I am not kidding. After this “gentleness” you certainly need to trash the current sockets as you have destroyed them. Initially, when you just felt a need to rock the tubes in the socket you needed to clear the socket and do not do any tubes jerking.

Does anyone know the voltage the big couping caps actually see?  Yes, I should measure it, but I would rather avoid the drill of opening the amps, propping them up somehow and measuring if someone already knows the answer. Of course, I'm asking in order to get new caps in the correct rating.

Thanks,
Paul S

Paul S wrote:

Does anyone know the voltage the big couping caps actually see?  Yes, I should measure it, but I would rather avoid the drill of opening the amps, propping them up somehow and measuring if someone already knows the answer. Of course, I'm asking in order to get new caps in the correct rating.

There are some very interesting moments with the not-so-expensive Sonicap Gen I caps, which I have described in the K&K thread. I will replace the 935s with these.  I am willing to take the chance that the little .033 uF 1000V 950s in my unit are just overrated bypass caps, and I will replace those, too, with the Sonicap Platinum teflons, since I now know this combination from the K&K.

Yes, yes, I know we're not supposed to use the same caps everywhere.  But I am presently thinking that the Sonicaps are simply more "correct" from an electrical standpoint, and I am willing to take a flier on them based on this (as heard, of course).

Good point about the potential for overheating/de-soldering the old cap lead stubs at the thru-holes; I will try to be careful when the time comes.  I have little heat sink clips that I use to divert heat from where it's unwanted.  I was actually thinking I could use my de-soldering gun to simply remove the old cap leads cleanly, but I would indeed be very pissed if I messed this up and wound up having to take the board out to make it right.

Like I confessed a while back, Duelund definitely had me at one point. I was totally hypnotized, ripe for the picking; but insufficient funds curtailed the madness.

Best regards,
Paul S

You have this behavior with the tube that you run for 6 month? That is strange. The behavior you described (with this amps) is typical for a very fresh new tube but after 20-50 hours  the amplitude of the current raise shall be minimum and and after 100 hours it I pretty much negligible.

http://www.romythecat.com/Forums/ShowPost.aspx?postID=6140#6140

I did not see a tube that behave as fresh as the new one and I did not see a tube that need 2 hours to stabilize current. It does not mean the do not exist and you might get one. If I were you then I would get a gamma probe and would try to test the tube for radioactivity….

I usually suggest to set your new 6C33C tube for operation of 250mA-270mA, use it for a while and only then set 300mA
The Cat

jessie.dazzle wrote:

I just poked around on eBay and it seems the 6c33C-B tubes are not so easy to find. There are however plenty of the model 6S33S-V. My understanding is that this is supposed to be a more durable version, intended to better resist vibration... Any opinions as to whether there is a difference in sound?

Jessie, 6C33C-B and 6S33S-V are identical, in fact the very same tubes. The 6C33C-B is Cyrillic writing and 6S33S-V is just Western transcript of the very same tube. It is like feeling that “cat” and “chat” are different animals...

http://www.shinjo.info/frank/vs.html

That's good news.

ТХАНКС !

jd*

One ironic thing about the ML2s is the contrast between the fantastic workmanship and the mostly average parts. Of course, the sockets are plain crappy, and I suffered plenty with them until I started using the dielectric grease. I have been too lazy to replace the sockets or the caps in mine, which are obviously the originals. And anyone looking at anything I ever put in there will be able to tell immediately that my work is not the original...

The absence of a schematic makes even the prospect of working on this thing scary. That big oiler in there looks downright dangerous!

I've said it before and I'll say it again, I'd love to have the ML2 schematic.

Best regards,
Paul S

Paul S wrote:

One ironic thing about the ML2s is the contrast between the fantastic workmanship and the mostly average parts.