PrimaLuna ProLogue Integrated - Help Needed

Al,

Thanks for your additional detailed reply! I'm eager to try your resistor idea. Are we talking about something like this AG50 resistor? http://www.ohmite.com/cat/res_audiogold.pdf

I'm disappointed to report that the PrimaLuna is still showing the same issue with the swapped-in KT-88 tubes. The problem manifests in basically the same way, but the "motorboating" effect is much less noticeable (and the blue light "throbbing" is harder to see with these tubes), so I didn't see it right away.

I'm thinking I may have to abandon either the PL or the Tritons. I'm much enamored with the PL sound, so it might be the Tritons that get the boot.

Thank you again for your help.

Rob L.

Sorry to hear the problem is still there, Rob. Yes, the Ohmite Audio Gold resistors would be fine choices for this purpose, preferably in the non-inductive version that is indicated as being available. However, I couldn't find them indicated as being available anywhere in the 50W rating I suggested, and I couldn't readily find any other similarly high powered resistors that look suitable.

As you may have already seen, PartsConnexion carries the Audio Gold resistors in a 12 watt rating, in non-inductive form. What I'd suggest is that you purchase two (one for each channel) of the 47 ohm 12 watt 1% non-inductive resistors they carry (listed as "47R/12W, Ohmite-77999"), and on each channel connect one of them between the 4 ohm and common (0 ohm) tap of the amplifier (regardless of which tap you are using for the speakers). That shouldn't result in the resistor ever having to dissipate more than about 4 watts, well within its rating, regardless of what power tubes you may ever use in the amp and even with the amp running at max power continuously.

If you do that and it doesn't help, you could then try connecting the resistor between the 8 ohm and common terminals, which would require it to dissipate about 8 watts when the amp is putting out max power. That would also be reasonable as a long term solution if it solves the problem, although the margin relative to the 12 watt rating is a bit less than I'd ideally prefer to see.

Good luck. Regards,
-- Al

Al, you're a genius!

The resistors fixed the problem, at least as far as I can tell (and that's the important part).

I find it interesting that I'm the first person to experience this issue. I guess I'll attempt to report it to someone who might care. Would be a shame to not publicize this solution.

Thank you very much for your help!

Rob

Al's the man!

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?