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  »  New  A quest for a better SET...  Still, there is something in it....  Melquiades Amplifier  Forum     3  44667  02-05-2005
  »  New  The Silence of the Lamms!..  Well, Lamms are not exactly fun anymore. ...  Audio Discussions  Forum     7  53586  06-12-2005
  »  New  Romy, how does the original ML2 sound in regards to acc..  Modification of Lamm’s SET...  Audio Discussions  Forum     5  45865  06-20-2005
  »  New  Lamm Industries: a special interview with a special com..  I do not think so but I migh be wrong....  Audio News Forum     94  948020  09-18-2005
  »  New  Lamm hybrids: M1.2 vs. Lamm M1.1..  Lamm hybrids: M1.2 vs. Lamm M1.1...  Audio Discussions  Forum     0  21482  12-12-2007
  »  New  The short "6C33C Survival Guide"...  Ac filament.....  Melquiades Amplifier  Forum     20  251737  12-18-2007
  »  New  Amplification and Consciousness...  Freedom of expression vs. something to say...  Playback Listening  Forum     15  75388  01-07-2008
  »  New  Relief from micro-arcing tube pins?..  Still Going......  Audio Discussions  Forum     6  35716  09-28-2008
06-22-2010 Post does not mapped to Knowledge Tree
skushino
Seattle, WA
Posts 93
Joined on 07-07-2004

Post #: 181
Post ID: 13816
Reply to: 13814
6c33c socket repair
fiogf49gjkf0d
Jessie-

There are the current japanese teflon sockets, and vintage american manufactured sockets - I think either should be fine.   The pin springs on the OEM pair I replaced had no grip or spring characteristics.  When the pin holders are bent, they stay bent and don't return.  On the replacement sockets, the pin springs return to a tight-grip position.  The replacements are clearly superior to the OEM parts.

'I too have fluctuating V2 plate current, forcing me to run the tubes at around 250mA in order to ensure that it doesn't creep above the recommended max of .31;'

I was operating my amp around 275mA for the same reason as you, to have a margin before V2 runs off the cliff.  It happened to me once before.  In addition to the fluctuating V2 readings, I was noticing audible 'noise' coming from the speakers when the probes were inserted and removed from the test points on the deck of the ML2.  Since the test points are closely connected to the 6c33c sockets, the noise seemed to be consistent with trouble around the sockets.  With the amp open, it was easy to see the sockets were already replaced at least once.  The solder work was very sloppy and some of the wires were very loosely connected - these connections were clearly suspect.  The exposed wire was brittle and dull.  I simply cut the ends back until 'good' wire was exposed and then re-connected everything. 

'One "advantage" of the cheap sockets used throughout Lamm gear is that they can be easily, purposely broken (carefully crushed with pliers), thereby facilitating their removal from the board; once broken, it is no longer necessary to simultaneously heat several soldered points.'

If I understand you correctly you are referring to crushing / breaking the old sockets for removal?  I think it's easier to simply remove the wires and four screws, then removing the old socket is straightforward and simple, without having to destroy it and having to remove debris.

'While the amps are open, it would seem logical to replace all the sockets (those for the smaller tubes as well).'

The other (non-6c33c) tube sockets might be more 'interesting' to replace - at least it looked more difficult to me.  These sockets are attached directly to the board, without direct access. 

'I am hoping new tube sockets will solve this issue.'

Me too!  Will post here if the problem doesn't go away.

Scott
06-22-2010 Post does not mapped to Knowledge Tree
skushino
Seattle, WA
Posts 93
Joined on 07-07-2004

Post #: 182
Post ID: 13817
Reply to: 13815
ML2 cap functions
fiogf49gjkf0d
Paul-

Again the disclaimer - I don't have a schematic nor is the circuit board fully visible, so these are solely my speculations and I could be wrong.

'What is the MKP's value, and why do you think it's "the" coupler, while the 'Cubes are else?'

I forgot the exact value (~.47uf?), but it was smaller and more consistent with a coupling cap, especially compared to the huge 10uf cube 935.

'What do you think the 'Cubes filter?'

Not sure - maybe the power to the input or driver.  In which case the 935 bypassed with the 950 should be more than adequate.

'Mightn't there be several couplers in a 3-stage amp?'

Maybe.  There may be another coupler I missed or maybe the other stages are direct coupled.

My goal wasn't to reverse engineer Lamm's design, just to understand whether or not there was a benefit to replacing the cube 935s.  I admit to obsessing about them...  since the ml2 is single ended, mono, it seemed odd for the cubes to be side by side.  plus the value seemed too large for a coupler.  I just need to connect everything and verify the amp with new sockets is stable and solves my operating point issues.

Scott

06-22-2010 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 183
Post ID: 13819
Reply to: 13817
Coupler Values
fiogf49gjkf0d
Yes, 10 uF is rather large for a coupler, alright, but not unheard of. Conversely, .47uF would be on the small side for a "powerful" amp using the 6C33C out (4.7 uF might be more like it...). My own phono stage uses 5 uF film couplers. One would suppose that anything out of the signal path or correction circuits could be electrolytic, or possibly something like the large oiler. What other sort of "input" would one filter with a 450V, 10 uF film cap?

Did you measure the rails and check against the MKP V rating?

Since I still feel "fuzzy" on the subject, I have waited to do anything but talk; the "replacement" caps are actually in a drawer; I'll get to it eventually...


Best regards,
Paul S
06-22-2010 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 184
Post ID: 13821
Reply to: 13816
Socket removal etc.
fiogf49gjkf0d
skushino wrote:

"...I was operating my amp around 275mA for the same reason as you, to have a margin before V2 runs off the cliff..."

About that cliff... As a result of not fully backing off the plate current trim pots (thinking a few turns would suffice) when swapping out V1/V2 tubes, I once accidentally allowed an old V2 tube to be driven to 900mA for a very short time (the phone rang while the amps were nearing the end of their soft start phase). When I returned, one half of one of the tubes had become a very bright orange; but surprisingly did not fail. Lesson? Backing off a couple or even a few turns is not always enough; best to be safe and back the plate current all the way off when changing these tubes.

"...If I understand you correctly you are referring to crushing / breaking the old sockets for removal?..." 

Correct.

"...I think it's easier to simply remove the wires and four screws, then removing the old socket is straightforward and simple, without having to destroy it and having to remove debris..."

Yes, for the 6C33C sockets.

"...The other (non-6c33c) tube sockets might be more 'interesting' to replace - at least it looked more difficult to me.  These sockets are attached directly to the board, without direct access..."

I have not been inside the ML2 amps, but you are not the first to mention limited access, but in replacing the sockets on an L2 pre-amp for example, I see this crushing as the best technique. I would say the same holds true for any board-mounted component having multiple "legs"; if it is not possible to crush the component, its legs can sometimes simply be cut before unsoldering. I guess I have a fetish for neat solder work.

"...Will post here if the problem doesn't go away..."

I'd be interested in knowing your results in either case.

jd*




How to short-circuit evolution: Enshrine mediocrity.
06-25-2010 Post does not mapped to Knowledge Tree
skushino
Seattle, WA
Posts 93
Joined on 07-07-2004

Post #: 185
Post ID: 13838
Reply to: 13821
Problem solved
fiogf49gjkf0d
Today I had a chance to connect everything back together - I had been using a spare amp while the ML2 was out of service.  After replacing the tube sockets, the problem amp's behavior is stable.  Not sure if the cause of the problem was the loose pin connections in the socket, or the poor soldering and loose wire connections, or both.  Regardless, the operating points are stable and not fluctuating anymore, and there is no noise when using probes in the test points.  I decided to increase plate current from .275 to .285.  Plate voltage remains unchanged at 174.4v.  Based on these results, I'll proceed with replacing the sockets on the second amp as preventative maintenance.  There are currently no issues on this amp, but I'll sleep soundly knowing the OEM sockets are gone on both amps.
06-25-2010 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 186
Post ID: 13840
Reply to: 13838
Which, Again?
fiogf49gjkf0d
Scott, since you mention only the 6C33C operating points, I assume you replaced just the big sockets. If you did or do all the sockets, I hope you will chronicle the procedure.

Anyway, that's got to be a relief!

The stock soldering is so perfect that I would love to see it done.

Best regards,
Paul S
06-25-2010 Post does not mapped to Knowledge Tree
skushino
Seattle, WA
Posts 93
Joined on 07-07-2004

Post #: 187
Post ID: 13843
Reply to: 13840
Scope of work
fiogf49gjkf0d
Paul-

I only replaced the big 7 pin 6c33c sockets.  If there was an easy way to access the small tube sockets I might consider doing the work while the amp is open.  But my motivation is low - they haven't been a problem.

that's got to be a relief!

Yes it is!

Scott
11-19-2010 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 188
Post ID: 14993
Reply to: 13843
Plug and Play, After All
fiogf49gjkf0d
What is it, 4 years gone now since I got the ML2s?  After all my groaning about tube sockets, cheap caps and Russian tubes, I have to say these amps have gotten downright comfortable!  Over time I have even come to take these amps for granted, which I mean as the highest audio compliment.

Recently I have refined my DEBZ speakers to the point that they are indicating posibilities yet farther "down the line".  Still, I can only imagine "better" amp performance very much in the context of very SPECIFIC drivers/systems.  This is to say, I still know of no way to "beat" the ML2s as "generic" HE speaker amps.  With good power and dialed in speakers today, I was once again, for the 1,000th time, forced to re-evaluate and upgrade my opinion of these amps.  If they come up wanting in any area, yet they are at the least totally "acceptable", and, take it all around, they are remarkably durable and even fairly ignore-able as everyday, workhorse amps to power even "dream" speaker systems to advantage.  Looking back, the ML2s have been no more "trouble" than any other tube gear I have ever owned, and they appear poised to continue doing their job without complaints, indefinitely.

So, how is this for a change of pace from my usual, constant bitching about the ML2s?

Paul S

01-02-2011 Post does not mapped to Knowledge Tree
Lx_
France
Posts 32
Joined on 12-06-2009

Post #: 189
Post ID: 15347
Reply to: 14993
Socket replacement
fiogf49gjkf0d
Hello,

After buying replacement sockets for the 6C33Cs and keeping them stored for months, I finally fitted them. I had been having the signs of tubes dying for several weeks: thumps in the bass drivers when warming up, after about 15/30 minutes -- the workaround is to simply turn off the amp and then back on. Only one amp did this (the same that had failures before). So I decided it was time to give a shot to the new sockets.

I thought the original sockets were cheap plastic ones. That is what I have read several times here, and they looked like plastic. I was quite surprised after unsoldering the wires and taking the socket away to discover that they were actually ceramic. Two of them bear the Reflector logo (rhombus), so I assume them to be Russian (not too surprising). It looks like they had not been replaced (stock sockets), and looked pretty good to me. BTW, mine is a ML2.1, so maybe Lamm changed the sockets he used for that (or maybe it was just luck).

Anyway, the new sockets are in. I still had some thumps while burning in new V2 tubes with the same V1s as before, so it was definitely a problem with a V1. I switched the old V1s for the old V2s and haven't had a thump yet. I though maybe there was a problem with the sockets (arcing) but it now looks like this wasn't the case.

Happy new year to all of you, with plenty of listening pleasure!
Cheers


01-02-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 190
Post ID: 15348
Reply to: 15347
The discipline with tubes.
fiogf49gjkf0d
Lamm uses Russian ceramic sockets, at least use to use them 10 yeas back. What he uses not I have no idea. The material of sockets is not as important – the profile of contact is the key. Unfortunately Russian sockets use triangular contact that makes the actual contact with tube pin in single point, thus inclined to arcing.

The thumps effects that you descried indeed have absolutely nothing to do with arcing. Read my 6C33C Survival Guide (link thread). The thumps while heating up (and later on) are unmistakable signs that the tube is dying. It is very important as soon you find out what tube it is to replace it and immediately to trash the dying tube. I can not stress it hard enough – the thumping tune must do to garbage can. I know that it is fine looking nice tube and I know that you have sentiments to use if for “something else”. Trust me, I have many amps with 6C33C and use them foe long time: no matter how good you mark this tube and put it in a “special peace” with the bad tubes -  this tube will find it’s own way to the pull of good tube and you will be forces to fish it out again. So, as soon you heard the very first thump, find the tube that do it and toss it to garbage. Do not forget that the cost of the tube is equal to the cost of a sandwich you eat during your lunch.

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
01-29-2011 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 191
Post ID: 15488
Reply to: 15348
Daisy chaining ML2s & New sockets for 6C33Cs
fiogf49gjkf0d
Daisy chaining ML2s:

Over in the thread about CES 2011
http://www.goodsoundclub.com/Forums/ShowPost.aspx?postID=15482#15482

Romy posted a link to photos taken by Mike, the owner of Audio Federation
http://www.audiofederation.com/blog/

Scrolling down to the images of the Lamm ML2.2, I see something that intrigues me...

Lamm ML2.2 Connection 01.jpg

Four ML2.2s are used to bi-amp the Verity Audio speakers; I didn't know they could be daisy chained by using both the XLR and RCA inputs of one pair of ML2.2s (front pair in this case) to output an unamplified signal to a second pair.

Also, I'm curious about that black thing that looks like a tube shield...

New sockets for 6C33Cs:

I finally received and installed the new tube sockets for the 6C33Cs. Results: NICE!!!! Rock-steady plate current and voltage. The sockets I used have a solid machined Teflon base with receptacles that each have multiple contacts for the pins.

Before changing the sockets the sound had gradually picked up some glare (old sockets were probably micro-arcing like hell); the new sockets fixed that and, in the time I've owned them these amps have never sounded better (I'm the second owner). The sound now is now generally more relaxed and natural. I do not attribute the improvement so much to the Teflon, but rather to the pin receptacles and of course to finally being able to properly set the bias; for the past six months (prior to socket replacement) I had been running it at about half the recommended settings in order to keep things from going overboard during drift. With the new sockets, I have not tried listening with the bias turned down to half the recommended setting, but I should, as it would give me a feel for how much this factor alone might be contributing; however, in the past, varying operating points never seemed to make a difference of this magnitude.

The sockets did require some serious modification work before they could be installed; I took some close up photos showing the process; I'll post them if anyone is interested (I might not get to it instantly, as I'm neck deep in other stuff).

jd*




How to short-circuit evolution: Enshrine mediocrity.
01-29-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 192
Post ID: 15490
Reply to: 15488
Mo' Betta
fiogf49gjkf0d
Jessie, congrats on the new *TEFLON* sockets.  Did you do the cap shuffle, too, while you were at it?  And what's this you say; you had to mill the sockets (or the chassis) to get them to fit?  Tres droll!

Now that your operating points are stable you can really begin to explore...  operating points, the effects that various controlled current and voltage levels have on the sound you hear (right along with output impedance...).

And OF COURSE I am interested to see the full extent of your suffering, so do post the link to the You Tube version of the socket R&R ASAP, SVP!

Were you planning to "daisy chain" your ML2s with your 1.1s??  How would of this "daisy chain" configuration be an advantage over separate feeds from a buffered pre-amp?  Not that I presently own a buffered pre-amp...

In any case, would "doubling up" the amps jack with the load seen by the pre-amp?

I wait with baited breath.

Best regards,
Paul
01-29-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 193
Post ID: 15491
Reply to: 15488
Daisy chaining, unfortunately
fiogf49gjkf0d

 jessie.dazzle wrote:
Scrolling down to the images of the Lamm ML2.2, I see something that intrigues me...

Four ML2.2s are used to bi-amp the Verity Audio speakers; I didn't know they could be daisy chained by using both the XLR and RCA inputs of one pair of ML2.2s (front pair in this case) to output an unamplified signal to a second pair.

I am not sure what makes you intrigued. This is very typical unfortunate/fortunate configuration for Lamm ML2 bi-amping. The XLR and RCA jacks in ML2 are parallel and they run like built-in Y-adaptor. If you have amp very far from your preamp and do not want to run another long ran cable then you might source your frequency section right from LM2’s input. The unfortunate part is that if you still intend to run a dedicated cable to your let say LF section and if you use Lamm preamp then you can’t/ This is one of the most Moronic thing Lamm did. I did pointed it out to him even what we were close but his discarded presuming that his users are anyhow idiots who does not mater do not understand what they do. He was right about it BTW. So, the Moronic think was that his preamps (L1 and L2, I do not know how about L3 but I think it will have it as well) have single ended and XLR outputs and fully balance topology. So, when you flip the absolute phase on Lamm preamp then your XLR output and RCA out become in opposite phase. Pretend how fun it become to bi-amping but as Vladimir very acutetly noted his customers are to idiotic to understand it. Go read all reviews ever were written about L1 and L2 and see if any of those Morons ever noted it.

 jessie.dazzle wrote:
Also, I'm curious about that black thing that looks like a tube shield...

This is not tube shield but a capacitor installed trough the amp chassis, similar to what I did in the earlsy version of Super Melquiades

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=1207

What is interesting is that to use this “trough chassis” configuration was absolutely not necessary. There is plenty space at the bottom of the amp to locate a larger snap in cap and there are wide and short configuration of any large caps if the high become a problems. There is certainly nothing wrong in making this trough chassis connection but I think Lamm just wanted to emphasize that his new amp is different from his old versions. I think there is no “claimed” change in input stage in there but most likely the B+ for input stage has a local cap to shunt B+ right next to the 12AX7 anode - the way how it shall be. If that is the” great Lamm improvement” then Lamm is of course is very “unique” engineer.  BTW, I do not have doubts that in context of this compromised PC board assembly of ML2 the move of PS cap closer to load shall be beneficial.

I finally received and installed the new tube sockets for the 6C33Cs. Results: NICE!!!! Rock-steady plate current and voltage. The sockets I used have a solid machined Teflon base with receptacles that each have multiple contacts for the pins.

 jessie.dazzle wrote:
Before changing the sockets the sound had gradually picked up some glare (old sockets were probably micro-arcing like hell); the new sockets fixed that and, in the time I've owned them these amps have never sounded better (I'm the second owner). The sound now is now generally more relaxed and natural. I do not attribute the improvement so much to the Teflon, but rather to the pin receptacles and of course to finally being able to properly set the bias; for the past six months (prior to socket replacement) I had been running it at about half the recommended settings in order to keep things from going overboard during drift. With the new sockets, I have not tried listening with the bias turned down to half the recommended setting, but I should, as it would give me a feel for how much this factor alone might be contributing; however, in the past, varying operating points never seemed to make a difference of this magnitude.

The sockets did require some serious modification work before they could be installed; I took some close up photos showing the process; I'll post them if anyone is interested (I might not get to it instantly, as I'm neck deep in other stuff).

I did not use those sockets for 6C33C. I use Johnson sockets, love them and never had any problem with them for 6 years as I started to use them. I use the expensive Teflon sockets for my driver tuber and they are very good. Interesting is the material of sockets is very much irrelevant; the configuration of the pin grabbing contacts is the key. I do not know how the contacts are made in the Teflon sockets. For the small currents Teflon is very good as it stress the contacts to be very tight. For the tubes like 6C33C the Teflon that would push the contact to be tight is not good idea as the coals run much hotter and if they are surrounded with Teflon then they would not be ventilated well. Still, I did not play with them and do not know how they made. BTW, there is gay out there who looks like do not like them

http://www.troelsgravesen.dk/AudioMirror-6C33.htm

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
01-30-2011 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 194
Post ID: 15499
Reply to: 15491
Bi-amping (L2) & Images of new sockets (ML2)
fiogf49gjkf0d
Regarding L1 and L2 outputs and bi-amping:

Romy wrote:
"...The unfortunate part is that if you still intend to run a dedicated cable to your let say LF section and if you use Lamm preamp then you can’t... his preamps (L1 and L2, I do not know how about L3 but I think it will have it as well) have single ended and XLR outputs and fully balance topology... So, when you flip the absolute phase on Lamm preamp then your XLR output and RCA out become in opposite phase..."

This is true.

"...Go read all reviews ever were written about L1 and L2 and see if any of those Morons ever noted it..."

One did; in reviewing the L2 preamp, John Atkinson (Stereophile) wrote:
"...The absolute polarity was preserved from both sets of outputs with the front-panel switch set to "0 degrees," confirming that the XLR jacks are wired with pin 2 hot. Setting the polarity switch to "180 degrees" inverted the unbalanced output but not the balanced output..."

From the manufacturing point of view there may be a good reason why this is the case, but from the consumer's point of view, it is not ideal.

In a bi-amped system running an L1 or L2 preamp, if one of the pairs of power amps happens to be Lamm M1.1s (and the later versions of this amp), it is possible to reverse the phase of the entire system, as the M1.1 offers the possibility to invert phase (and therefore bring it into phase with the other pair of amps) via a shorting plug. This is how I get around it; obviously, inverting phase is not something I do often.

Back to the ML2; since the XLR and RCA inputs on the ML2 power amps are wired in parallel, the XLR inputs are in fact not balanced, and this is stated in the operator's manual.

Regarding the Teflon sockets:

Romy wrote:

"...I do not know how the contacts are made in the Teflon sockets..."

The part that grips the pin is made of several tiny contacts. I don't think they are gold-plated; in any case, gold would likely not fare too well in the presence of the heat generated by the 6C33C.

Pin Receptacles Internal Close Crop Light 01.jpg

"...For the small currents Teflon is very good as it stress the contacts to be very tight. For the tubes like 6C33C the Teflon that would push the contact to be tight is not good idea as the coals run much hotter and if they are surrounded with Teflon then they would not be ventilated well. Still, I did not play with them and do not know how they made..."

Image below: In the case of the Teflon sockets for the 6C33C, the Teflon plays no roll in clamping the pin; there is in fact a generous gap around the pin receptacle and all clamping force comes from the springiness of the metal contacts, which are confined by a hollow cylinder.

Sockets Installed Top Close Crop Light 01.jpg

Next two images: The pin receptacles are composed of threaded parts, which, in my opinion, should be soldered as one to improve both electrical and thermal conductivity between the individual parts, as well as keeping them from coming loose over time.

Pin Receptacles Small Exploded Close Crop Light 01.jpg

Pin Receptacles Exterior Close Crop Light 01.jpg

Image below: Here is the problem with these sockets... The threads of the large pin are not long enough (not enough of them protrude through the Teflon base) to allow proper threading of the securing nut. Threads on the smaller pins are longer and the smaller assemblies can be adjusted to compensate, but as this is not an option with the large pin; thickness of the Teflon base must therefore be reduced by at least 1.5mm.

Pin Receptacles Large Pin Exploded Close Crop Light 01.jpg

Image below: Showing material that needs to be removed to allow for short threads of large pin.

Socket Base Thickness Close Crop Light 01.jpg

Image below: Fully assembled after Teflon base has been reduced by 1.5mm; note, even after reduction in thickness of base, there are still no excess threads protruding past the securing nuts. In the case of the ML2, the four chassis mounting holes in the Teflon base must also be enlarged.

Pin Receptacles In Socket Close Crop Light 01.jpg

Image below: New sockets have pin receptacles closer to the center of the socket... Lamm rightly leaves no excess length, so getting the original wires to reach the pin receptacles is tricky.

Socket Installed Bottom Close Crop Light 01.jpg

In spite of the work necessary to correct the thickness issue, I'm very happy with the results and would in fact recommend these sockets. I do nevertheless have to admit, considering the price paid (something like $38 each plus shipping and customs), that it is reasonable to expect a finished product. I assume these are among the first that the manufacturer has produced for the 6C33C, as the thickness issue could be easily corrected during future production.

About the "guy out there" who does not like the Teflon sockets; look at the reasons he gave; "difficulty in desoldering" and "darkening of the metal". This is silly; solder typically melts below 400 °C (752 °F); the type of metal used for pin recepticals will not chang that. About the darkening of the metal; if you want to see darkened contacts, take a look at those of the original sockets (image rotated 90° counter clockwise relative to image above):

V2 tube socket 01 for mail.jpg

jd*



How to short-circuit evolution: Enshrine mediocrity.
01-30-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 195
Post ID: 15501
Reply to: 15499
Lamm L2 jacks and ML2 pins.
fiogf49gjkf0d

 jessie.dazzle wrote:

One did; in reviewing the L2 preamp, John Atkinson (Stereophile) wrote:
"...The absolute polarity was preserved from both sets of outputs with the front-panel switch set to "0 degrees," confirming that the XLR jacks are wired with pin 2 hot. Setting the polarity switch to "180 degrees" inverted the unbalanced output but not the balanced output..."


From the manufacturing point of view there may be a good reason why this is the case, but from the consumer's point of view, it is not ideal.

Good one. I do not remember it. Still from the Atkinson language I see that it was written by Atkinson in his technical summary not in the review itself. In his technical measurement summary he just report data but not interprets data. So, users of L2 do not understand what it means. At the time when I used L2 I spoke with many L2 owner including with a few people who bi-amp. No one let me say again: NO ONE, including those who consider themselves the heavy L2 users realized that XLR jacks do not reverse phase. This type of setting is absolutely not permitted in a balanced preamplifier. Mind you that inverting phase is one of the main functions of this preamp as it is made with fully balanced topology; this is why is double all parts of the signal circuit.

 jessie.dazzle wrote:

The part that grips the pin is made of several tiny contacts. I don't think they are gold-plated; in any case, gold would likely not fare too well in the presence of the heat generated by the 6C33C.

Image below: In the case of the Teflon sockets for the 6C33C, the Teflon plays no roll in clamping the pin; there is in fact a generous gap around the pin receptacle and all clamping force comes from the springiness of the metal contacts, which are confined by a hollow cylinder.

Next two images: The pin receptacles are composed of threaded parts, which, in my opinion, should be soldered as one to improve both electrical and thermal conductivity between the individual parts, as well as keeping them from coming loose over time.

Image below: Here is the problem with these sockets... The threads of the large pin are not long enough (not enough of them protrude through the Teflon base) to allow proper threading of the securing nut. Threads on the smaller pins are longer and the smaller assemblies can be adjusted to compensate, but as this is not an option with the large pin; thickness of the Teflon base must therefore be reduced by at least 1.5mm.

Image below: Showing material that needs to be removed to allow for short threads of large pin.

Image below: Fully assembled after Teflon base has been reduced by 1.5mm; note, even after reduction in thickness of base, there are still no excess threads protruding past the securing nuts. In the case of the ML2, the four chassis mounting holes in the Teflon base must also be enlarged.

Image below: New sockets have pin receptacles closer to the center of the socket... Lamm rightly leaves no excess length, so getting the original wires to reach the pin receptacles is tricky.

In spite of the work necessary to correct the thickness issue, I'm very happy with the results and would in fact recommend these sockets. I do nevertheless have to admit, considering the price paid (something like $38 each plus shipping and customs), that it is reasonable to expect a finished product. I assume these are among the first that the manufacturer has produced for the 6C33C, as the thickness issue could be easily corrected during future production.

Very good job with the sockets. I did not see this type of the sockets you use. The only one Teflon sockets for this tube that I seen were $100 sockets by a Japanese guy, I think it was Yamamoto or something phonetically similar. They were a bit different; I like your better as they have better pin ventilation. Ideally I would like to have more air exposure to the 6C33C pins and the pin on this tube run very hot. I would like to have a micro heat sink on the pins to let them to be cool down. Two words of warning: make sure that you wind the wire around the pins and then fill it with plumbum. The old sockets had whole where the wires were able to be inserted and tighten before soldered. Another thing: do not use the low temperature soldering metal. Many of contemporary soldering metals have silver in them that lower the melting temperature. If you solder with this easy to use soldering metal then the temperature of the socket pit will eventually melt the join. I had a few times until I learn how it needs to be done properly.

 I have one question to ask. From what I see you changed the wire that goes to filament. Lamm has Brown-Brown/White cable but you have has White-Brown/White. Was any reason why you changed the wire?

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
01-31-2011 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 196
Post ID: 15507
Reply to: 15501
Comments on sockets
fiogf49gjkf0d
Romy wrote:

"...I would like to have a micro heat sink on the pins to let them to be cool down..."

Had I thought of it before installing the sockets, it would be fairly simple to do, however, these pin receptacles already have more mass than those of the original sockets.

"...Two words of warning: make sure that you wind the wire around the pins and then fill it with plumbum. The old sockets had whole where the wires were able to be inserted and tighten before soldered..."

Yes, though it doesn't really look like it in the photo, they are all wrapped at least one full turn before soldering, and in reality the soldering work looks better than in the out-of-focus photo.

"...Another thing: do not use the low temperature soldering metal. Many of contemporary soldering metals have silver in them that lower the melting temperature. If you solder with this easy to use soldering metal then the temperature of the socket pit will eventually melt the join. I had a few times until I learn how it needs to be done properly..."

The solder I used dates from about 1990; I think its pretty old-school stuff, but I'll double check.

"...I have one question to ask. From what I see you changed the wire that goes to filament. Lamm has Brown-Brown/White cable but you have has White-Brown/White. Was any reason why you changed the wire?..."

No, I did not change the wires, just took the photo of the old socket from a different angle (off 90°); you need to mentally rotate the image.


How to short-circuit evolution: Enshrine mediocrity.
01-31-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 197
Post ID: 15509
Reply to: 15507
The mental rotattion....
fiogf49gjkf0d
 jessie.dazzle wrote:
No, I did not change the wires, just took the photo of the old socket from a different angle (off 90°); you need to mentally rotate the image.
I did mentally rotate it. The very first wire on right from the bridge between the filaments is brown on the old socket and white on your new socket.

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
01-31-2011 Post does not mapped to Knowledge Tree
jessie.dazzle


Paris, France
Posts 456
Joined on 04-23-2006

Post #: 198
Post ID: 15512
Reply to: 15509
Toasty-brown insulation
fiogf49gjkf0d
Romy wrote:
"...The very first wire on right from the bridge between the filaments is brown on the old socket and white on your new socket..."

Yes, in a way you are correct; the wire is white but over time became sort of brown toward the socket; this is either from the metal contacts of the socket having oxidized in close proximity to the insulation, or simply from the light colored insulation having been close to the heat... I cleaned the insulation using acetone, which restored the white color.

jd*


How to short-circuit evolution: Enshrine mediocrity.
01-31-2011 Post does not mapped to Knowledge Tree
Romy the Cat


Boston, MA
Posts 9,543
Joined on 05-28-2004

Post #: 199
Post ID: 15513
Reply to: 15512
The in-wire auto-cooler.
fiogf49gjkf0d
 jessie.dazzle wrote:
Yes, in a way you are correct; the wire is white but over time became sort of brown toward the socket; this is either from the metal contacts of the socket having oxidized in close proximity to the insulation, or simply from the light colored insulation having been close to the heat... I cleaned the insulation using acetone, which restored the white color.
I see, it was dirt, I got it. The reason I asked is because in ML2 the 6C33socks is well isolated and it does makes sense and it is possible to do the in-line wire cooling. I thought that you’ve experimented with something like this. The idea is to have an extra foot of wire. You take the isolation off and then wind the wire around a pencil of something like this. What you remove the pencil you have a very mild choke of 3-4” long but the inductance of the thing is relevant. What is relevant is that the spiral of this think 10 ga wire hangs in air and dispatches hit very nicely. Since the spiral is solder to the pin holder than it presumably will suck out hit from the 6C33C pins.

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
09-30-2011 Post does not mapped to Knowledge Tree
Paul S
San Diego, California, USA
Posts 2,156
Joined on 10-12-2006

Post #: 200
Post ID: 17107
Reply to: 15513
If Interested to Buy ML2s
fiogf49gjkf0d
Price is 13.5k.  Please contact me privately; do NOT respond here. There are no "issues" with the amps. This is not a "must sell" situation; it is logistical rather than strategic, as I expand to  5 channels, 19 rather inefficient drivers.

Probably a stupid idea I'll regret...

Paul S
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