Lamm LL2.1 Deluxe "DC Offset"?

Charles1dad and P59teitel,

Thanks for your support.

An interesting comment and I wish I could have that luxury of choosing among 1) getting a proper repair, 2) a replacement with new unit, or 3) a full refund. I share same understanding with you on how this mechanism supposed to be well implemented in that manner.

The problem is, the manufacturer will not even respond to my email, you may see it in their email dated 14 June when they finally shift the issue to the dealer and that’s it (I will share it afterward). You also may learn that they don’t even have sincerity in trying to find the real problem, they rather playing the game when the manufacturer shifting the problem to dealer and then the dealer ridiculously asked me to talk directly to their technician, funny.

I can envisage that finally they will leave me alone in the jungle. When I talked to their technician, the result is absurdly unbelievable and you will be amazed when compare it to the explanation made by the manufacturer, it’s totally contradictive statement and conclusion.

Below are my communications/correspondences with the technician and Lamm:

1) Dealer’s Technician Explanation (by phone call on Monday, 8 July 2013):

The Lamm’s, particularly in the power supply system topology, is designed to be simple without (AC) regulator inside, therefore it is sort of common that the fluctuation of AC voltage will “directly and totally” reflected to the DC (offset) in the preamp output, as it is. In other words, to my understanding, a fluctuation of +-200 milliVolt DC offset is the consequence of such typical Lamm design, (so it is common to Lamm?). If I may interpret further, it is typical Lamm design to be a very sensitive unit, even to the AC swing/fluctuation as little as 0.3-0.5V, it will directly generating high DC offset fluctuation to the preamp output. Therefore, the technician stated, the unit no need any repair.

The challenge is then, to find a matching power amplifier for Lamm which can manage high fluctuated DC Offset which generated by Lamm Preamp as affected by even low AC swing. (This actually funny and doesn’t make any sense to my humble logic thinking. How long that so called “matching” amplifier can handle such continuous high fluctuated DC Offset assault that generated by the preamp before it finally get broken or blew up?).

2) The Lamm e-mail (dated 14 June 2013, no further reply to my email afterward):

"Your measurements of voltage fluctuations at the LL2.1’s output are puzzling to us because we’ve been producing this model since 2001 and have not come across the effect you describe. It’s hard to explain.

On extremely rare occasions it may happen that the output capacitor C111 and/or C112 exhibit slight leakage which does not manifest itself at the time when we are burning-in the assembled units at our factory. But even in cases like this the voltage at the preamp’s output never exceeds 50-100 mV. Therefore, we view your measured result of about 1V as not quite reflective of the objective reality (this may have to do with possible low quality of measurement device, method of measurement, etc.)

Since the beginning of production of this preamp, we’ve had three cases that were somewhat similar to yours. In two cases it turned that the owners used relatively inexpensive but quite powerful solid-state amps with DC input and output; these amps were incompatible with LL2/LL2.1. When these people were able to replace their amps with different ones, all problems went away, indicating that the preamp was not at fault.

In one case the problem had to do with leaking capacitors, and the issue was easily solved once the replacement capacitors were installed.

In your case it is difficult to judge what’s going on in reality. If you wish, we can send the replacement capacitors to your dealer. Let us know if you decide to do that. Perhaps, you will have an opportunity to try different amps in your system.

We would like to ask you to abstain from making irresponsible statements about quality control at our facility. Lamm Industries is known for excellent service and unsurpassed quality control. The page with measurements that was sent to you is part of a comprehensive “production report” where we record every step in rigorous testing and assembly processes. This is a confirmation of our statement because each single product that we produce is accompanied by its own production report, which is not the case with many manufacturers.

For your information, we do not usually deal directly with customer – this is the job of our dealers/distributors. Our main function is manufacturing. Therefore, it would be healthier if all questions came to us through your dealer….”

So, that was the strange of comments made by manufacturer and dealer technician.

I agree with P59teitel that I finally have to share this case with any audio forums I can find to wake the manufacturer and dealer ignorance. It may also worth to share it with some High End audio magazine, particularly to those that put Lamm Industries products in their recommended component list. But still, I hope I can manage my frustration and get their sincere attention before I finally come to that ultimate position.

I think I also need Syntax help and confirmation, since is very difficult to get from either manufacturer or dealer about what is really the design of the Lamm LL2.1, whether this true that the Lamm is designed that way.

Any other thought from folks of this forum would be highly appreciated.

Lamm suggested that it could be a leaking capacitor. I'd accept the offer to have your dealer install them and see if this solves the problem.
Regards,

Hi Charles1dad,

Following that Lamm suggestion, about ten days ago I dropped the unit to the dealer for observation and necesary repair by their technician.

Amazingly, what they did and feed back me after having their own observation are as follows:

1). There is no repair or parts replacement required to the Lamm. They said this is new unit and no need any repair, only small tightening by reinforcing some solder has been made in and to the power supply area (I am not sure whether this is necessary)

2). The DC Offset fluctuation on the preamp that caused by AC voltage swing is naturally common in Lamm as this is the natural design of Lamm. In other words, the Lamm design will allow such AC swing, even as small as 0.3-0.5v AC, and pass it through the circuitry, to generates high DC milliVolt.

3). They suggesting me to use another power amp that may compatible with the Lamm. They also suggesting me to use stabilizer.

Learning from the above:

1)Should I push the dealer and technician to change the capacitors while they are very confidence that there is nothing wrong with the unit?

2) To my understanding, installing stabilizer and using other power amp is not the right way in solving the root of the problem, it's only curing the symptom while the real problem still exist, beneath. This only creating a time bomb.

I urged the dealer to contact Lamm about this, but they asked me to bring back the unit isntead. They very confidence the unit will be just fine. I can imagine, once the unit back to my system the problem will still exist, and do know what should be the next thing to do except to sell it

Gr-gin,
Well,it appears that the Lamm has this inherent design issue and will require a more compatible power amplifier. Or keep your amplifier and sell the Lamm, as there's no repair for this situation(design choice).

Charles1dad,

Welll, that actually a statement coming from the dealer free-lancer technician and His statement is contradictory with Lamm statement.

if we learn from the Lamm email, as a manufacturer who design and pruduce the unit, it's clear that this not their natural design. They said that the measurement of AC fluctuation causing high DC fluctuation was PUZLING them and they never had that experince on such case. They also said that even if there is a leakage on the caps, it will never exceed 50-100 DC milliVolt. So, there are two big questions that they themselves dont have the answer.

I believe they can find the answer, only if they deeply and sincerely and honesty listen, learn and dedicated their time to observe the unit. Further, if I were them, I will have myself to look back and learn the design and then have one or two comparison units put in the bench to be tested. And I believe those unit will perform well, contrary to mine.

If that is the design, does a highly fluctuated +-200 milliVolt DC offset common and acceptable to the industry? Secondly, does the small swing of 0.3-0.5 AC voltage that generates a fluctuated hundreeds DC Offset also aceptable to the industry?. If that the case, then Lamm will have extreem difficulty in finding a matching power amp in the market. They can only be paired with Lamm power amp, which is notbthe case.

There is also the fact that for the first 4 weeks the Lamm work well with my entire system, we did have microphonics problem in one of the tubes but we replaced it by new one and things back to normal.

There is also the fact that before I bought the unit, I firstly contact Lamm whether their preamp will be matching with my system, their answer is: the Lamm LL2.1 will work well with any power amp as long as the input impedance is 10k-ohm or more.

Again, the answer is depend on how serious the dealer, technician and Lamm trying to solve the problem. Not shifting the issue or blamming other products.