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01-13-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 41
Post ID: 3489
Reply to: 3488
The tubes pins: the Lamm's dirty secrets are out.

Actually I was wondering what the hell you were talking about what you were bitching that the ML2 socket can not handle 6N6P first. Ether you changed over 10.000 tubes in there or something else was wrong because the ML2 sockets are fine (except the 6C33C) and you should not have any problems. A possibility that you got some too skinny pins might explain it. I do not know, perhaps your party are more skinny then necessary. When I used ML2 I got a box with 100 of them for $40 (1966 made) and the pins were fine, no smaller the usually. You can always slightly bend the pins in order to make them to more firm.

Perhaps the skinnier 6N6P do exist, I do not know. If I were you I would call Lamm and ask, he obviously when over many of them. BTW, he might propose to buy 6N6P from him because he takes the skinny one tine and galvanizes metal on the pins unit the pins become larger. The price of 49.99 per tube is because during this galvanization he uses invented by him unique technology to let only females elations to stick to the pins and keep male electron wad of the tube. The reasons why it is important is because when you pay $80 for 6C33C then you have output tube has only males electrons on the pins and it created a natural flow across capacitor captor. Lamm own a paten that teachers the any capacitor hates when electrons with the same sex intermingle and according to Lamm his “sexism in amplification” helps to eliminate the capacitor’s homophobia….

BTW, you will not be able to use Absorb-GEL adapters because in ML2 the sockets are board mounted and the tube are going there the holes in chassis (I like it a lot). The Absorb-GEL adapters would need to have a surface with the sole on it so they are not the solution in your case.

The caT

PS. I moved the post in this thread as I feel that it more related to ML2 then to the Shock-absorbing tube sockets.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
02-11-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,644
Joined on 10-12-2006
Post #: 42
Post ID: 3716
Reply to: 3456
Burn in, warm up, finding harmonic center
No telling anymore how good these amps can get.  Today the re-configured phono stage finally "burned in" and I used the ML2s for almost 5 hours.  Although I have read that they keep improving as you use them, I was not really ready for the steady, obvious improvement in musical "values" that the sound exhibited.  I have to say that I am getting more and more curious about Melquiades, since the well-and-truly-burned-in-and-warmed-up ML2s are so completely free of non-musical information that it is literally difficult for me to imagine anything else being much better, at least any other "FR" amp, especially given my less-than-optimal quasi-FR speakers.  Not to pick it apart, but bass is orders of magnitude better than any other amp I've heard, including big SS, with rich, deep fundamentals that do not gratuitously riccochet up the spectrum to get "fast", etc., but hang in down there like they should, with the center of power right at the source.  All notes are so well shaped and harmonically centered that the effect is uncanny.   As this area of music is perhaps most important to me as a listener, I am very gratified, indeed and I am astounded to hear this so well rendered in playback.  Timing seems abetted by the fact that there is precious little going on besides the music, and the "focus" of the event is effortlessly clear.  It is interesting how this also helps to express the theme of the music.

This has been/is a quite a learning experience for me in both hi-fi and musical terms, well worth the price of admission.

I've got some longer, more efficient "naked" ribbon tweeters on the way from Germany, and I am curious to hear how much better the ML2's already-terrific high end can get, once the HF level is better matched to the upper MF.

Best regards,
Paul S
02-25-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,644
Joined on 10-12-2006
Post #: 43
Post ID: 3817
Reply to: 3716
Listening in without losing out
I have posted about some of my recent experience with longer "naked" HF ribbons in Romy's "Water Drop" thread.  Here are some observations that relate these drivers back to the ML2s, along with some other recent ML2 trivia.

My speakers are listed back up this thread, FYI.  They are ~ 96 dB, 3-way (not counting DX4's mechanical "whizzer"), passively crossed over, pretty "flat"from 40 Hz to (with Audaphon ribbon) way on up there.  Impedance is not "bad" compared to many/most "audiophile" speakers, but there are a couple of spikes, up and down, that do present problems to most SETs, and the 15" BR drivers are not exactly a cakewalf for the amps, either.  Although the speaker's designer intended that they would be "SET friendly", it was not possible to get anywhere near optimum performance from these speakers using 2A3 monoblocks, despite those amps having A2 drive, meaning lots more juice than any garden-variety 2A3.  It was my search for amps to drive these very promising (within their limits) speakers that led me to the ML2s.

With the substitution/addition of the Audaphon ribbons (replacing Arum Cantus G2Sis) I have wound up driving the speakers from the ML2s' 16 Ohm taps.  This has resulted in the best top-to-bottom integration of this range of frequencies that I have heard in lengthy playback sessions.  Also much improved are musical bass and both "internal" and "external" dynamics, meaning that the volume and density of material available has increased very significantly, and listening levels have increased without fear, from the amps or on my part, since there are none of the usual signs of "impending collapse" at the volumes I listen, typically under 100 dB peaks (with exceptions, depending on the material.

I finally solved my phono hum problem, so I have gotten to use LPs as a reference source, and I am much more familiar with how this "should" sound.

As great an addition as the longer/more efficient/stronger ribbons have proven to be, the ML2's contribution is quite significant in this, and despite early promise I have none the less been surprised at the way the ML2s have "embraced" and helped realize the ribbons' increase of system potential.  As I mentionmed in the ribbon thread, it is no easy thing to get a HF ribbon to perform properly in a system.  That the ML2s manage this well while driving the rest of the system simply astounds me.

Back to bass, adding the ribbons shot bass performance up significantlly with respect to both quality and quantity, using the 16 Ohm tap with my speakers.  Bass "pitch" is about perfect.  My speaker's inherent LF limitations are laid bare, but bass to 30 Hz is true and musical, albeit attenuated below 40 Hz, obviously.  I might have to call this the "antithesis" of "fast bass", because the ML2s simply will not let go of bass fundamentals in order to give an "impression" of bass, so there is, as there should be, as in live, less energy up the band than other amps deliver in lieu of bass.  When the ML2s make "propulsive" bass, it is true LF-centered bass fundamentals that pack some serious LF energy.  Also, the ML2s do not get "LF depleted" with my semi-difficult speakers, meaning other frequencies are neither "bass shaded" nor are they in any way dimished by bass continuo.  This ability to "keep it up" at all frequencies on both micro and macro levels, along with spectacular harmonic and transient response at all times, makes the ML2s by far the most satisfying amps I have ever tried for larger orchestral scores.  In fact, such scores have not really figured into my hi-fi musical plans for some time, until just recently.  The ML2s have not only opened this door again but these larger scores are becoming staples.  Wholly unexpected, and very satisfying, indeed.  I really did not think these speakers could do this, at all.

MF is now much more "powerful" at given SPL and at the same time it remains lyrical and utterly nuanced.  Instrumental voicing is as good as I have ever heard, as is the "integrity" of not only the instruments and voices but the performers and performances.  The amps still have the uncanny nack of revealing any system weaknesses without letting those limitations ruin the music/experience.   However, to be honest, the limitations are decidedly less limited than I ever expected or even hoped for just a few months ago.

I have a new phono stage on the way, mostly because I want to try a Bent TAP transformer volume control (also in transit), just to hear one for myself.  Hard to think in those terms, now that I licked the phono hum problem; but I'll get back one way or the other once I think I have anything new to say.

I would certainly love to hear more from other ML2 users.

Best regards,
Paul S
03-11-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,644
Joined on 10-12-2006
Post #: 44
Post ID: 3975
Reply to: 3817
The sound of dust settling
It took some work, but I finally got a new phono stage (K&K) and a Bent TAP (transformer-based volume control) installed, along with some new cartridge clips (ugh!), and I put the "new system" through its paces Saturday and Sunday.  I am still trying to see/hear how far I can take the ML2s/how far they will take me, and I am getting more and more clear about what the ML2s themselves do in my system.

I have said that the ML2s keep to harmonic center, and this has not changed.  The K&K (which I will post about separately, along with the Bent TAP, as well) is also pitch-centric, and the Bent is neutral, as far as I can tell.  While I still would not call the ML2s exactly "neutral" they do in fact amplify clearly and cleanly what they are fed, including, apparently, everything below 40 Hz, and they do it with/through my not-so-efficient speakers (96dB) that feature big 15" woofers and passive networks.  I am no longer concerned about volume or complexity, either.  No "cringe" and no "collapse". at any volume I would listen to.  I sat transfixed through "Sketches of Spain" with peaks over 100 dB and then just for kicks I played the Mobile Fidelity D-to-D "Ride of the Valkeries" even louder!  Huge!  Simply stunning!  So it looks/sounds like the ML2 pretty much "makes the best of what it's fed", meaning it still has a [VERY] nice way of "organizing" things, at all frequencies, and any deficiencies I'd noticed in the past are solved or seem solve-able with attention to other components.  Since my bass bins fall off so fast below 40 Hz I cannot really comment on the subterranean stuff other than to say I imagine the ML2's would do it full justice under the right circumstances.  Bass > 35 Hz with the new front end is musically right, with plucked open bass string [vibrations] clearly audible as such, as they should be.  Trombones just rip.  CD is also better through the TAP.  Although CD sounds very much like LPs, apropos, it doesn't sound as "good"; but my CD player is an afterthought.

Right now I have a very "musical" system, and I am really enjoying it.  I have no doubt that the ML2's can do "audiophile", too, because I've tweaked things to make that happen, as well.  But for now I'm sticking with [loud] music that is very close indeed to my ideal.

At this pointIi think it's fair to say that if you have ML2s with "reasonably efficient" speakers then you can safely just hew to whatever works best with the ML2s and toss the rest, because in that case "the rest" is not worth keeping.

Best regards,
Paul S
03-11-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 45
Post ID: 3977
Reply to: 3975
Yes, even more....
 Paul S wrote:
At this pointIi think it's fair to say that if you have ML2s with "reasonably efficient" speakers then you can safely just hew to whatever works best with the ML2s and toss the rest, because in that case "the rest" is not worth keeping.
Actually you might not recognize now true it is.... but from a slightly different prospective as well. It is also a fun to try ML2.0 (or M1.1) with different “reasonably efficient" speakers. Those two amplifiers in many instances uncover in well-know speakers some qualities that are not commonly known belong a given speaker. It hard to explain or to believe for the people who are not deeply familiar with ML2.0 and it is know only for a few people who actually know ML2.0 well and can affords to make own mind according to actual results instead of the extraneous external conditions.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-11-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,644
Joined on 10-12-2006
Post #: 46
Post ID: 3978
Reply to: 3977
If now was the future
Don't worry, Romy, I can hear, and I've been at this for some time, so it is already abundantly clear that the ML2s would do/be that much better with true HE speakers (yes, the right horns).  And when I say this you know that I know how troublesome multi-way "HE" (horn) speakers are to drive coherently, not on paper, but with an actual amplifier in an actual room.  But it will be a while yet before I go back down that rutted road again, and there is still much to enjoy in the context of my present set-up, thanks mostly to the ML2s.  Were it not for the ML2s I likely would have run aground with the DEBZs quite a while ago.  For one thing, what other stock unit could drive a naked HF ribbon like this?  Borrowing from your observation, above, you might even say that the DEBZs are the "different reasonably-efficient speakers" you refer to, since they are hardly a match made in Heaven for any SET, including the ML2s.

I hope people understand that I am not so much encouraging them to just go out and buy ML2s for their present speakers as I am encouraging them to buy ML2s and then do what works best with them(!).  That's how much I think of these "not neutral" amps.  Lest anyone think otherwise, my present speakers are actually pretty damned good, with the ML2s driving them; in fact I have not heard better, overall, although I can already imagine better, because of my aggregate hi-fi experience to date, which now includes the ML2s, if that makes any sense.

Best regards,
Paul S
03-12-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 47
Post ID: 3983
Reply to: 3978
Paying the price...
Well, I could not agree more.

I've had a pair of ML2s connected for the past several months. I say it like that because I have not yet seriously worked with them, as I am still building the horns that they will drive.

I connected the ML2s first just as an experiment to drive a pair of Upper Mid horns, which sounded beautifully delecate but very concentrated when playing all alone.

So good that I left the experiment in place, and now have the amps driving all of what currently exists of my horn project... some horns, and some drivers without horns, (5 per channel), with simple 1st order crossovers. So basically just a left and right pile, that play while I work on the remaining horns.

Even at this stage, I seem to be growing physically dependent on what all this stuff is starting to do with sound. I am not exaggerating when I say that I have not once reconnected my previous speakers (which are quite excellent as "normal speakers" go); even though it would be a simple matter, as they are still sitting right there.

I have also noticed a shift in the music that most often stops me in my tracks, usually while working (further hampering progress on the horns)... Romy calls it "content-loaded" music... well I'm not sure if what I've been into is exactly that, but I've certainly been adding more and more complex music (I am fortunate to live above a library with a huge and very well maintained collection of recorded music)... this is stuff I used to avoid... no longer the case. And simpler music sounds... simple.

Well we do evlove with our systems... and I suppose I am evolving along with the sound as I add horns (to the system I mean), and in fact, my biggest problem is shutting down and getting to bed at a reasonable hour... Never mind the purchase price, I continue paying for these amps every morning! I also hate leaving the house. Dangerous all this.

Other than that, my only issue for the moment is the following :

While not present to the point of ruining the experience, I would love to reduce the background hiss coming from the MF and HF horns/drivers.

I don't know how much of this is normal, (I don't have much experience with really high sensitivity drivers used with SET amps). I suspect it is in part related to the age of the tubes I've currently got in the amps and the L2 preamp (no point using fresh tubes given the very unfinished state of the system). In any case, the hiss seems to diminish as things get warm. I did not have this issue when using the same amps/preamp with my previous 89db/w @ 1m speakers, but neither did the sound have anywhere near this level of life.

Any thoughts or comments would be very much appreciated.

jd*

How to short-circuit evolution: Enshrine mediocrity.
03-12-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 48
Post ID: 3984
Reply to: 3983
The 110dB sensitivity is not a joke.

 jessie.dazzle wrote:
While not present to the point of ruining the experience, I would love to reduce the background hiss coming from the MF and HF horns/drivers.
ML2 should be absolutely silent. Pretty much it you drive with ML2 a 110dB sensitive driver loaded into a horn then sticking you head into the horn you should not be able to say if amps is on or off. Sure, you have to lift ground on the ML2, that is pretty much default operation mode on any amp. So, if you have a MF or HF hiss with ML2 then it is most likely comes from your preamp. Short the ML2’s inputs and the hiss should be gone. Most of the preamps (including Lamm’s own SS preamps) are no equipped noise-wise to work with 110dB sensitive load.
 jessie.dazzle wrote:
I have also noticed a shift in the music ….. I've certainly been adding more and more complex music …. this is stuff I used to avoid... no longer the case. And simpler music sounds... simple.

I think nothing further could be said about ML2.0, this sumizes it all.

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
03-12-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 49
Post ID: 3985
Reply to: 3984
Shorting plugs
Romy,

Thanks for the advice.

Just to be clear here :

When you say

"Short the ML2’s inputs and the hiss should be gone"

I assume it is not a mistake, and that you mean short the unused input on each POWER AMP (as opposed to the PREAMP).

(I am currently using the XLR connections because I don't have RCA cables in the correct length)

Is there any advantage (or danger) in shorting the unused INPUTS on the PREAMP?

For the moment I have metal sheilding caps on all unused inputs (pre and power amps), which don't seem to make a difference.

The ground is lifted on all equipment and and attached to a water pipe. There are 5 dedicated circuits, located in a dedicated breaker box fed directly from the line that comes in from the street (that was fun!).

jd *

How to short-circuit evolution: Enshrine mediocrity.
03-12-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 50
Post ID: 3986
Reply to: 3985
Shorting Lamm ML2

 jessie.dazzle wrote:
"Short the ML2’s inputs and the hiss should be gone"

I assume it is not a mistake, and that you mean short the unused input on each POWER AMP (as opposed to the PREAMP).

(I am currently using the XLR connections because I don't have RCA cables in the correct length)

Is there any advantage (or danger) in shorting the unused INPUTS on the PREAMP?

For the moment I have metal sheilding caps on all unused inputs (pre and power amps), which don't seem to make a difference.

Nope, it was not what I meant. Do following:

1) Disconnect ML2 from preamp.
2) Disconnect any RCA or XLR from ML2.
3) Stick RCA shorting plug into ML2’s input RCA jack (not the shielding caps but shorting)
4) If you do not have a shorting plug then stick RCA male-to-male into ML2’s RCA input and then short the other side of the RCA terminator with any metal object.

What you will go is shorting the grid of the input stage to ground that will kill all externals noise. In this mode the ML2 should be absolutely silent.

Warning: Do not short anything on the preamp’s output or input. A preamp should not be on the picture at all.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-12-2007 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,644
Joined on 10-12-2006
Post #: 51
Post ID: 3988
Reply to: 3983
Shorting, etc.
Jessie, I just wanted to say that I make my own shorting jacks from the worst possible plastic Radio Shack RCA plugs and small, cheap (1/2 Watt) 100 Ohm resistors, which I solder across the +/- RCA plug connection points and then I screw the plastic covers back over the resistors.  A piece of tape applied serves as a reminder that these are shorts, so I can spot them in the junk box.

Like Romy says, healthy ML2s are  truly silent, in and of themselves; and I do mean no sound whatsoever.  Once you lift/disconnect the 3rd (ground) wire going into the amp you should have it licked, as far as the ML2s are concerned, given all tubes are OK.  OTOH, some tube rush is normal from even "good" tube pre-amps, but you might also check the L2's 6N6Ps if its been more than 10 minutes since you last replaced them ;>Wink  Didn't you just buy that Englishman's Placette Active right out from under me?  Use that and hear what happens.

As smitten as you are right now, the ML2s just get better with demanding FR use (just like a fine musical instrument...), and good tubes do improve the performance, as well, as you will confirm.

I certainly concur with your "complexity thesis" regarding listening fare (in fact I think I made the same observations/comments myself, up the thread).

Best regards,
Paul S
03-13-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 52
Post ID: 3991
Reply to: 3988
Hang on a minute...
Romy and Paul,

Thanks to both of you for the further input.

But...

If I do as suggested, and this removes the hiss, that's great; only one problem (forgive my slowness in understanding here); with the plugs in place, how do I then get a signal into the ML2s?

I am assuming that removing the shorting plugs would reintroduce the hiss... So do I leave the shorting plugs in place on the RCA inputs, and connect the XLR cable? (that sounds wrong).

As for using plugs that incorporate a small resistor : Yes this is something I was wondering about as well. A bit of research indicates that people use different values, or none at all. It seems that Lamm's shorting plugs do not have resistors.

Thanks again,

jd*

How to short-circuit evolution: Enshrine mediocrity.
03-13-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 53
Post ID: 3993
Reply to: 3991
That Englishman's Placette!
Paul S wrote :

"Didn't you just buy that Englishman's Placette Active right out from under me?  Use that and hear what happens."

Nope it was not me... My only recent acquisitions have been three very very cool industrial-strength tube testers (one Russian, and two French) and a honking-big inductance (LCR) bridge... As I gear up for construction of the Melquiades... subjects for another thread perhaps.

I would however like to experiment with a Placette unit...

I also kept my old L1, with the idea that once everything settles down I would do some direct comparison testing against the L2.

jd*

How to short-circuit evolution: Enshrine mediocrity.
03-13-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 54
Post ID: 3994
Reply to: 3991
... and this is a whole idea.
Jessie, this is a whole idea: do not get a signal into the ML2. It is NOT an operations sate but juts immediate testing. Do NOT short the ML2 input when preamp is connected to ML2 XLR inputs. By shorting the amp’s inputs you hear the inner-noise of the amps itself. The cap might dry up; the tube could pick noise and many other thighs…. BTW, if you use Lamm L1 as a preamp then be advised that it notoriously noise in context of high sensitively speakers. Lamm L1/L2 has MOSFET output stage and the have a strong MF noise. So I ma sure that even with mo shorting of ML2 but only by disconnecting L1 you will have all noise after ML2 gone.

"I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche
03-13-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 55
Post ID: 3998
Reply to: 3994
Noise test results
Ok, so I did the test (no explosions, flames, or smoke!).

Results with the shorting plugs in place :
Just like you and Paul said, only upon sticking my head (my ear really) right up inside the MF horns was I able to hear just the slightest hiss... very very minimal... absolutely nonexistent from one foot away.

So I now know the amps are fine. Too bad I can't listen to music with the plugs in place!

I should mention that with all the wonderful things it does, the L2 (preamp) definitely deserves a fresh pair of 12AX3s and a 6C19P. (I have not changed them since starting work on the horns... all tubes are exactly one year old, which with my listening habits is more like three years).

Thanks very much for the clear instructions.

jd*

How to short-circuit evolution: Enshrine mediocrity.
03-13-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 56
Post ID: 3999
Reply to: 3998
ML2, 109dB sensitivety, L2 and everything else...

 jessie.dazzle wrote:
I should mention that with all the wonderful things it does, the L2 (preamp) definitely deserves a fresh pair of 12AX3s and a 6C19P. (I have not changed them since starting work on the horns... all tubes are exactly one year old, which with my listening habits is more like three years).

Jessie, the retubing of L2 is necessary but it will not affect the noise that preamp output. The MF nose that is coming from it is the noise of MOSFER output stage and it is intrinsic with the topology of the given preamp. Well, I do not know if is it really correct but it was what Lamm was truing to convince me when I complained about the L1/L2 noise.  Still with 109dB sensitively and ~25dB gains in ML2 you might mitigate the noise and make it practically auditable. You have too much gain in your playback for 109dB sensitively. So you burn ~8-12dB in the L2 attenuators, use it at the very first clicks. However, it is the L2’s out stage the one the produces the noise and the noise is constant with change of volume (I called it “bias noise” but it was juts my name). So, what you can do it to let the L2’s output stage to run full throttle (the L2 has unity gain when attenuator points at 1PM) but kill the gain at ML2, or AFTER the preamp. So, this way you will have your ~8-12dB voltage divider at ML2’s input that will kill voltage ALONG with the noise of output stage. It means your noise will be ~8-12dB less but you will add volume of music by more opening up the L2 attenuator (not to mention the L2 sound better when it more opened).  I used ML2 with 109dB sensitively and L2 with 12.5ddB voltage divider at ML2 and I had no annoying noise at nearfiled.

Also, a very few words slightly off the subject. If you did not replace the 12AX3s and particularly the 6C19P for a year then your preamp is absolutely dead sonically. A few years ago Lamm in response to my publics criticism of extremely low lifespan of L1/L2 power supply made a note on his site recommending to change the 12AX3 and 6C19P once a year (it is after 10 year of L1 production). I still disagree with what Lamm said. The 12AX3 in L2 must be changed after 6 months and 6C19P after a month or two maximum (I would say 200-400 Hours, no more). I have personally witnessed L2 preamp where the 6C19P was dieing after 20 hours, I am not kidding. Sure, it is still regulated voltage and tested any my tester with perfect transconductance and cathode emission but it begun to sound with compressed white-noise injected of any tone… truly disgusting... So, buy a box of the 6C19P (that’s God in Russia they cost pennies) and replaced them as I did it – each time when I paid my apartment rent….

Rgs,
Romy 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
03-14-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 57
Post ID: 4009
Reply to: 3999
Deep-fried dbs
Romy,

Your approach makes sense; I will look into fitting a "12.5 db voltage divider".

As I did not have any noise issues when using the same equipment with a variety of direct radiating speakers, I can only speculate as to what other information went missing (or got rounded off) when using these less than sensitive drivers.

Regarding tube replacement :

The sound that you call the "whitish sound" has an analogy in food; Where I used to live, the "best" Chinese restaurants started off with fresh oil every evening. They would change it the following day, but as it was only now a slightly deeper amber in color, instead of throwing it out, they passed it on to the "better" Chinese restaurants, who also changed it daily, and also passed it on, until it would finally end up thick, dark, and suspending various solids, in the fryers of Chinese restaurants where you just don't sit down.... The food fried in these places always had a kind of metallic tinge, which would cote your tongue making it feel as it does when you've kept yourself going for 48 hours, having replaced sleep with too much caffeine.

This weekend I found some hour meters in a surplus store... it will be interesting to know just how much I am using this system, and how many hours I put on the "longer life" tubes (the ones that don't need changing as often as the cat litter) before the quality drops off.

As always, thanks for the input.

jd*

How to short-circuit evolution: Enshrine mediocrity.
03-14-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 58
Post ID: 4011
Reply to: 4009
uh, what I meant to say...
Ok, so that didn't come out right...

This part :

"...I can only speculate as to what other information went missing (or got rounded off) when using these less than sensitive drivers"

Actually there is no speculation involved; a lot of information WAS missing, the move to high sensitivity drivers made that obvious and quantifiable.

jd*

I'm really not anal-retentive!





How to short-circuit evolution: Enshrine mediocrity.
03-23-2007 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006
Post #: 59
Post ID: 4053
Reply to: 3999
Meow ! No more hiss !!!
Romy wrote :

"...You have too much gain in your playback for 109dB sensitivity... I used ML2 with 109dB sensitively and L2 with 12.5dB voltage divider at ML2 and I had no annoying noise at nearfiled..."

Ok so I made a couple voltage dividers for the balanced inputs on the ML2s.

And, ahhhh, nice.... Thank you Romy!

For the moment I'm using normal metal resistors, nothing exotic, no bulk metal foil etc. (and yes the elements are magnetic, but not the leads). Before spending lots for really good resistors (balanced requires 4/input), I wanted first to establish :

1) that this would cure the hissing issue, and
2) the correct values and level of attenuation.

I decided to start off with a strong reduction :
(R1=4K99Ω, R2=1K06Ω, into 41KΩ load)
If I've done my math correctly, that works out to -15.3 dB.

I seem to have got it right straight out of the box. Setting the volume pots at the 1:00 position (as Romy mentioned this is where the L2 is at unity gain) puts the level right where I would want it when seriously listening.

This very much took care of the hiss, so yes, problem solved. However, if I am really really picky, there is now a very faint buzzing... not something I can hear unless I put an ear right up into the horn.

???????????
Can anyone comment on the likelihood that the buzz might be a product of the type of resistor I am currently using (which seem to be normal metal-coated ceramic-core type resistors)
???????????

I did try substituting other resistors, but still of the same type; this yielded identical results. It should also be said that for the moment, the resistors are not soldered into place (they are held by very small clips).

The voltage divider assemblies are super well shielded, as they are housed in thick metal cases which are tied to system ground.

I did some research on low noise resistors, and of course Vishay has the answer... more than one actually. It seems from going over their data sheets that the VSRJ is probably the latest and lowest-noise offering ; quieter than the famous S102 or Z102 (correct me if I'm wrong here).

???????????
Does anyone have any experience using any of these in a fixed potential attenuator circuit
???????????

Thanks in advance for any comments,

jd*


How to short-circuit evolution: Enshrine mediocrity.
03-24-2007 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 10,131
Joined on 05-27-2004
Post #: 60
Post ID: 4055
Reply to: 4053
Stick it in the ML2 input stage.
Jessie,

I think you go overly crazzy in here. The buzzing you got is from your inaccuracy of your “small clips”. A Regular divider at input should not have ant noise, regardless the resistors were used. Do not spend a lot and do not go into the craziness of ultra low noise resistors - it is absolutely unnecessary. Get 20c-30c worth Vishey-Dale RN60(CMF60) and it will be perfectly enough. You might alternately incorporate the divider into the ML2 input stages (it has own divider and a shunt cap in there) but it would require to open up the amp.

Rgs. 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
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