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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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almarg
9,670 posts
 
07-29-15: Roblinx
Thanks Almarg... I actually meant the link in your second post, that went to the PrimaLuna site.
That was the "Adaptive AutoBias" link which appears about 1/4 of the way down on this page: http://www.primaluna-usa.com/product-main/prologue-premium/prem-int.

The link itself is: http://www.primaluna-usa.com/home/tech-briefs/aabb?tmpl=component&print=1&page=.

(The apparently incomplete "page=" reference at the end of that link is accurately copied from what is there. The link works for me, btw, in both Firefox and Internet Explorer, running in Windows 7).

Good luck once again. Best regards,
-- Al
timrhu
2,779 posts
 
The amp is new, right? Why not take it back for another? Why accept it at all?

This seems to be a common scenario; someone buys a defective piece of gear and attempts to right it instead of returning it for a perfect piece. If I was in your situation I would never be happy with an amp that was defective from the get-go.
dsper
663 posts
 
Roblinx,

Sounds like a bad capacitor based on a similar sound I experienced with a PrimaLuna Dialogue Premium preamp.

Talked with Kevin Deal who set me up with a local tech who diagnosed and fixed the problem.

In my case one of the French capacitors was bad, which also took out a resister.

Back in business now with no problems and no cost - just the inconvenience of not having the preamp for a couple of weeks.

My preramp had a couple of hundred hours on it and makes me wonder about PL quality?
roblinx OP
5 posts
 
This is a followup for everyone: the working theory is that this is some sort of distortion-based feedback loop that happens apparently exclusively with the GoldenEar Triton speakers.

I took my PrimaLuna to a friend's house and tested with his B&W 80somethings. No matter how hard I pushed it, the pulsing issue did not occur.

I took the PrimaLuna to the dealer today and tried it with their floor model Triton Twos. I was able to reproduce the problem just as at home.

We hooked the amp up to some higher-end speakers (can't recall the model now) and could not reproduce the problem.

At this point the tech commented that I was simply pushing the amp too hard, and the Tritons were causing some sort of electronic or microphonic feedback. I don't entirely buy this explanation, but it does seem to be specific to the Tritons.

He then had the idea to replace the stock EL-34s with some KT-88s that he had on the floor.

Presto, problem solved. Problem no longer happens with the Tritons.

Again, I don't pretend to understand the issue, but apparently the EL-34s were freaked out about playing loud with the Triton Twos.

Thanks to everyone for their suggestions!
mofimadness's avatar
mofimadness
4,984 posts
 
Thanks for the update. Glad you solved the problem.
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