Lamm LL2.1 Deluxe "DC Offset"?


Hi there,

Is there anybody who has a deep experiences with high fluctuated "DC offset" in Lamm LL2.1 Deluxe PreAmp?.

My Lamm LL2.1 Deluxe Preamp shows a highly fluctuated DC reading that reaching +-200mV even more. Last night measurement showed a flucuated reading and reached +-300mV.

A three weeks continuous observation shows that the preamp DC fluctuation seems higly affected by the swing/fluctuation of AC Volatage,day time and night time. I can see that even as small as 0.3V AC voltage abrupt swing will directly generate significant DC offset in the LL2.1.

Your sharing experience and advices are higly appreciated.
gr-gin
Gr- It sounds like the bottleneck is the dealer- I agree that you should not ship the unit to Lamm without a return authorization and some idea of turnaround time. It seems odd to me that the dealer wouldn't handle this, or at least arrange it for you.
Can you tell me what city/country you are in? (I don't necessarily want you to name the dealer here, but perhaps I can help). You can send me a PM or email if you like.
Whart,

I dont thing the probelm is in the dealer alone. The tone of manufacturer's email responses was unbelievable. I can say that, both of them, in the way they responding to my case is similar. They are very defensive and tried to shift the issue to somebody else fault.

Iam not realy sure, but I guess something strange on the way they build and arrange the business which refrain the dealer to conduct intensive and frank communication with the manufacturer.

I live in Jakarta, Indonesia.

What reason does your dealer give for declining to replace the capacitors that Lamm offered to supply?
Jtimothya

I am not sure why.

Perhaps, the Lamm statement itself did not really confincing about the real problem that cause when they said "But even in cases like this the voltage at the preamp’s output never exceeds 50-100 mV."

I can understand if the dealer and thier technician in doubt to change the Caps. Based on my personal observations, the question should be addressed to the power supply system. Why an abrupt small AC swing (as small as 0.3-0.5v) can generate highly fluctuated DC output? shouldn't it be a tollerance range? says +-2v before this kind of AC swing hits the circuitry and manifested into high preamp DC output?

In this case a full technical support and detail instruction from Lamm is definetly required, they are the only one that really know about the design and topology/circuitry, so that it will not drive dealer and technician to perform a trial and error repair.
Lamm gave you a diagnosis and offered to supply the parts to your dealer to address the issue. Your dealer has a Lamm qualified technician.

This situation is either very simple or there is some information missing. Seems like it is up to you and your dealer to effect the factory recommendation and it appears odd that this has not happened and equally odd that you do not know why.

Work things out with your dealer to make happen the factory suggested change. Regardless of what you think or who you think should do what, until that happens there's little else to be done. If Lamm's advice is ignored or otherwise not taken, that moves them outside the resolution loop. Speculating about a design or conjecturing about motives on an internet forum will not change things. Fwiw, the LL2.1D is an excellent preamp that yields further enjoyment with NOS tubes. Good luck.