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PrimaLuna ProLogue Integrated - Help Needed

Hi everyone. I recently made a big upgrade (for me); I traded in all my aging mediocre equipment and purchased a pair of GoldenEar Triton Twos and a PrimaLuna Prologue integrated amp. I'm using Nordost Purple flare speaker cables. No power conditioning at this point.

The problem is this: when I turn up the volume past a certain point (about 95 dB sustained), the amp begins to produce a low-frequency "throb". The throb is of moderate volume, very audible during quiet passages. The throb is about two beats per second, I'd say. It manifests both audibly and visually (in the form of a pulsing blue light from the left channel power tubes).

I've done a lot of work to try to diagnose the issue, but would like your opinion. Has anyone heard of a problem like this? I've had all sorts of suggestions from the dealer and PrimaLuna, from microphonic feedback to bad power. I don't think it's feedback, as I've isolated the amp in a separate room from the speakers and still experience the problem.

I'll shut up and just link a video I made. If you use headphones, you can hear the throb pretty clearly.

https://www.youtube.com/watch?v=Juk1ILtarS8

Thanks for any help!
roblinx
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mofimadness
5,117 posts
 
Al's the man!
iclickjohn
26 posts
 
Same amp, considering same speakers. How do you connect the resistor between the 8 ohm and common terminals? Are you saying on the back where the speaker terminals are, run an Audio Gold 12 watt? And in one sense it said between the 4 ohm and then it suggested the 8 ohm. Which of those worked and was this where it was attached?
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almarg
9,670 posts
 
Same amp, considering same speakers. How do you connect the resistor between the 8 ohm and common terminals? Are you saying on the back where the speaker terminals are, run an Audio Gold 12 watt? And in one sense it said between the 4 ohm and then it suggested the 8 ohm. Which of those worked and was this where it was attached?
For each channel, the resistor would preferably be connected between the 4 ohm and common terminals. I had suggested trying the resistor between the 8 ohm terminal and the common terminal only if connecting it between the 4 ohm terminal and the common terminal didn’t resolve the problem. Rob didn’t mention which pair of terminals he ended up using, but I suspect it was the 4 ohm and common terminals.

As I mentioned, using the 4 ohm terminal rather than the 8 ohm terminal is preferable, assuming it resolves the problem, because it would provide greater margin between the amount of power the resistor would be called upon to handle and the maximum amount of power it is rated to be able to handle. Although using the 8 ohm terminal should be ok in that respect as well.

And yes, you would connect the resistors to the binding posts on the rear of the amp, in addition to connecting the speaker cables to those terminals. Although the speaker cables needn’t necessarily be connected to the same terminal (4 or 8 ohm) as the resistor.
... run an Audio Gold 12 watt?
Yes, but be sure to also note the other characteristics I indicated for the resistors, especially the 47 ohm resistance.

Good luck. Regards,
-- Al

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