PrimaLuna Dialogue Premium Preamplifier. DESTROYS SPEAKERS!!

Dear fsonicsmith,

Here is what you said,

"I bet you are not the original owner of those ML's and paid a mere fraction of the $30K you kept spouting about."

I guess, it must be in your nature, to make STUPID assumptions!
I bought the speakers NEW, I am the ORIGINAL owner!
That is why they were repaired by Martin Logan at no charge, Martin Logan warranties are Not transferable.

Too bad you are not mature enough to deal with the issue, trying to discredit me reflects very badly on your level of intelligence.

+1   Only Sonic has a magic formula to proper resource allocation.  GMAB!

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

Time to give it a rest and move on. Good luck though.

Primaluna Prologue 5..beautifully built..zero issues..bought used..can recommend Primaluna 100%.I liked Mr Deals response...contacted the customer while on vacation in Eurpoe.That seems like he does care..maybe they can post a statement on site warning of possible issues?

Still, it's all better than when the fighter jets crash and we are not told the truth. At least 50% of cases its something like bad capacitor,sometimes Chinese. Yeah, let's move on.