PrimaLuna Dialogue Premium Preamplifier. DESTROYS SPEAKERS!!

Lest Porsche be given a bad name, hifiman5, I regret to say that the Porsche of recent years seems to have no resemblance to the company as it appears to have existed in 2000, based on Bruce's description of it as "bad" at that time.

My experience purchasing two such vehicles in the past four years (a 2014 Cayman S and a 2017 Macan S) has been nothing short of amazingly good in every conceivable respect.  And in recent years Porsche has ranked at or very near the top among all manufacturers in J. D. Power surveys of initial quality and longer term customer satisfaction.

Sorry!  Regards,

-- Al
 

Nycjlee, methinks the post by Linnlingo was a clever mixture of sarcasm and humor, considering that The Great Wall of China has lasted for many hundreds of years, and I believe in some places for thousands of years. :-)

Regards,
-- Al

That’s interesting, Aniwolfe. It reminds me of this thread from a couple of years ago in which a member reported that his PL Prologue integrated amp had a "motorboating" problem when playing at high volume levels with his Golden Ear Triton Two speakers. Like many Martin Logan speakers the Triton Two incorporates a powered woofer and has an impedance that rises to high values at low frequencies. Ultimately the issue was resolved by a suggestion I made of connecting appropriately chosen resistors to the amp's output terminals, so that the amp wouldn’t see such a high impedance at low frequencies. Perhaps the "filters" you saw were actually resistors?

That problem did not involve damage to anything, though, and did not involve a PL preamp. Although during the course of the thread a different member reported that his PL Dialogue Premium preamp had experienced a capacitor failure at one point, which in turn took out a resistor in the preamp, and resulted in what was described as a similar "motorboating" sound. The member reported that Kevin arranged for the preamp to be repaired locally and at no cost.

Regards,
-- Al

Willemj, the Thorloki statement quoted in your post just above was in his original post, of course. Subsequent posts by me and by Atmasphere, as well as a subsequent reference by Mr. Deal to his tech’s suspicion of an oscillation, all add up to it being a near certainty that the issue with Thorloki’s preamp had nothing to do with it outputting DC. In contrast to the other case that you have cited.

Regards,
-- Al

Willemj, thank you for the clarification.  But nevertheless that sounds like the preamp had a different problem than the OP's.  As I and Atmasphere have said, and as Kevin Deal suggested (when he mentioned that an oscillation was suspected), DC does not appear to have been responsible for the OP's problem.  And in contrast to the OP's amp, the XA30.8 has no capacitors in its signal path, and as far as I know may not provide any other means of DC protection.

Regards,
-- Al
 

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.

DC input protection should be de rigeur for most amps, especially one with such high current you could weld with it.

Hi Erik,

See my earlier posts in this thread. It appears more likely than not that the amp **does** have DC input protection, in the form of 68 uf capacitors in series with its inputs. However, the amp’s specified bandwidth extends down to "< 1 Hz," so there is apparently no protection against the effects of an oscillation it may receive at very low frequencies. And Mr. Deal indicated earlier that an oscillation is suspected.

Regards,
-- Al

Thorloki 9-24-2017
Mr. Deal, I ask you this, are you going to recall all the pre amps, THAT YOU HAVE ALREADY SOLD and are in customers systems?

Or, are you just going to lay low and hope that clients with blown speakers don’t make the connection to your pre amps/amps.

Can we have an answer to this question, Mr Deal, the Audiogon community is waiting for an answer, what are you going to do?

Thorloki, as someone who has participated in this forum just about daily for the past nine years I have read and participated in countless threads involving users of PrimaLuna preamps and other components. Yours is the only instance I have ever seen in which a problem in a PrimaLuna component resulted in damage to another piece of equipment.

And if you have read my previous post in this thread, you will hopefully understand that the damage to your speakers may very well have resulted from a combination of circumstances that approaches being unique.

IMO your demands of Mr. Deal are uncalled for and unreasonable, and I for one am not a member of the community who is "waiting for an answer."

Disclaimer: I do not now nor have I ever had any affiliation, association, or interaction of any kind with Mr. Deal or PrimaLuna, not even as a user, and not even as a purchaser of the tubes he sells.

Regards,
-- Al

UpscaleAudio9-23-2017
It was a small cap in the right channel, NOT the Mundorf coupling caps. We suspect an oscillation as my service tech here works for another brand that was faced with the same problem.

Kevin, thanks for providing us with the comprehensive additional background and info in your response.

An oscillation, albeit perhaps at a very low frequency, seems to me to be much more probable than the previous assertions that the preamp was outputting DC. Given what I said in my previous post about the Bryston amp likely having coupling capacitors at its inputs, and even more so if the Mundorf caps you are referring to are the preamp’s output coupling caps.

A post by Atmasphere some years ago in this thread, concerning a low frequency oscillation problem that occurred with a preamp made by a different well-regarded manufacturer, may be helpful to your tech. I’ll quote an excerpt that may be relevant. Again, this pertains to a different manufacturer’s preamp:

Atmasphere 8-3-2012
The problem is that there is a power supply instability in the preamp. The output coupling cap, when driving a 100K load, represented a frequency pole that was lower than the frequency pole in the preamp’s power supply.

The result is low frequency instability. With many amps this may not manifest with anything, especially if the amp does not have good LF bandwidth, but I think the interaction occurred due to the fact that you do have enough bandwidth in the amp and the power of the amplifier was able to mess with the AC line voltage, which in turn exacerbated the LF instability of the preamp.

So lowering the input impedance of the amplifier solved the problem by knocking off an octave of LF bandwidth.

In any event, even if that kind of phenomenon is not what has occurred in the present situation it serves to illustrate that no matter how expert and thorough the designer is there is always the possibility that relatively unique system applications can bring out a problem that wouldn’t appear in most other applications. And the uncommonly high power capability of the OP’s amp, together with its exceptionally extended low frequency bandwidth, and perhaps also the characteristics of his speakers, would seem to make his situation uncommon at best. As well as increasing the likelihood that the phenomenon Ralph (Atmasphere) described in the thread I referenced is applicable.

For all we know, in the absence of a schematic and a detailed analysis, **even if** the capacitor has failed in some other systems it might not have caused any issues, not even sonic issues.

Regards,
-- Al

Thorloki 9-22-2017
The amplifier used was the Bryston 28B SST3 1,000 watt per channel
mono blocks....

Thorloki 9-22-2017
As for Bryston amps DC protection, I personally spoke to Mr. Brian Russell, one of the owners of Bryston, and he ASSURED me, that
the 28B SST3 DOES NOT have DC output protection.

What about DC **input** protection? (See my further comments below).

Also, looking at the Bryston site it appears that the SST designation is not used for their "cubed" series amps. Did you mean 28B3, or perhaps 28B SST2?

Ralph (Atmasphere), while a schematic for the 28B3 does not appear to be available, a schematic for the 28B SST2 can be found at the Bryston site here.

Note in zones B1 and C1 on the second sheet that a 68 uf capacitor is in series with the inputs!

Personally, FWIW, I believe the OP is sincere, but I don’t know how to reconcile the reported experience with the presence of those capacitors, which would block DC. Unless the amp is a 28B3, and that design omits any such capacitors. I note, though, that the bandwidths of both designs are identically specified, down to "<1 Hz," which suggests that they may be similar in that respect.

Regards,
-- Al