PrimaLuna Dialogue Premium Preamplifier. DESTROYS SPEAKERS!!

When TWO pre amps, bought 6 weeks apart, FAIL, IN EXACTLY the same way, this points to a much deeper problem.

I agree, but the question is what is the deeper problem?

This preamp has been around a while without any reason to think there was a reliability problem. Yet two failed in the same installation. From a purely logical viewpoint, this points to something in the installation that is playing a role.

I don't think its wall paper...

The amp is equipped with 68uf input couping caps. This will prevent the amp from conducting any DC applied to its inputs. But the problem is not that the amp failed- the **power supplies** in the speakers failed- and not the matching transformers of the speaker. So we know its not DC that did the damage.

Its my opinion that the extreme power of the amplifier, coupled with a slight low frequency instability in the preamp is actually what caused the damage. When the LF instability showed up, in my theory the AC line voltage sagged, which then exacerbated the problem in the preamp, causing the amp to make the line voltage sag more, until finally the speaker couldn't take it any more.

Change any of the several variables here and its likely that there would have been no problem. For example, the amp draws a bit of power so it probably should be on its own 20Amp circuit. If its on the same circuit as the preamp, I think many preamps could have gotten into this trouble.

If the preamp had AC line conditioning, the additional time constant of the presence of the conditioner might have prevented this as well.

I personally don't think that the preamp had a severe failure. I suspect that in most systems there would have been no adverse effects at all.

IOW we would know if if there were 20 or 30 of the same preamp having the same part fail in a wide number of systems. But we don't see that- the preamp seems to be holding up just fine. We just have this rather weired occurrence in this **one** system! That's a red flag that its something in the system.

So the bottom line here is I don't think Kevin Deal has to do anything further in regards to the other preamps in the field.

Oh dear. Another failure might begin to suggest a possible design fault. 

This thread got me interested in the build quality and I have watched online videos showing how the inside is built. I would call it scary. Sorry but I don't much like the way it is built.

Greetings atmasphere,

Hey man, thanks for your post and analysis, well written and well thought out.
Perhaps you are right, perhaps this would not have happened in another system.
However, manufacturers of preamps/amps should know that their equipment will be mated and matched, with other equipment, in every possible combination.
If, primaLuna is not a good match for electrostatics, and problems can arise, then BUYERS SHOULD BE WARNED, prominently written, in the owners manual.

By the way, another post just mentioned that a Harbeth speaker was blown up, USING a PrimaLuna preamp!

I just don't know what to think, but it sure requires investigation/monitoring.

Thanks again for the post,  GOOD STUFF!

Willemj 9-25-2017
I have just found back a letter from another user who reported that a failed capacitor in his PrimaLuna Dialogue preamplifier destroyed a Harbeth SHL5+ speaker....

PrimaLuna talked this man into buying a PrimaLuna power amp as well. That is all I know.

If you are saying that the PrimaLuna amp and preamp were being used together when the problem occurred, I’m not sure how a medium powered tube amp whose output transformers are incapable of passing DC, or even passing frequencies of several Hz or more without attenuating them significantly, could have "destroyed" the speaker. At most I would think a tweeter might have been damaged as a result of severe clipping. Especially if the clipping were allowed to continue for a significant amount of time, for example if the system was running unattended.

In any event, it certainly sounds like a different situation than the OP’s, at least if the PL amp and preamp were being used together when the problem occurred.

Regards,
-- Al

P.S: Ralph (Atmasphere), thanks! I of course agree with everything in your post, which refines and elaborates on some of the things I was getting at in my earlier posts.

The original amplifier used with the PrimaLuna pre amp was a Pass XA-30.8. The PrimaLuna had a leaking capacitor that passed DC to the power amp, with sad results.