New Prima Luna Amp In Distress / Me Too


Prologue II 40WPC Integrated – (4) KT-88s (2) 12AX7s (2) 12AU7s. The amp arrived new six weeks ago and has maybe a bit over 200 hours operation. Today, sequences of double popping began coming over the speakers. About a second between each pop then after a minute or so another double pop. There was no input signal at the time.
I switched the input selector from phono over to CD and the popping continued.
I then played a CD and noticed a gain and fidelity increase in the middle of the pops (the short sequence). I then noticed that the blue glow from one of the KT88s increased within these short bursts of fidelity/gain that were bracketed by the pops as well.
I shut off the amp and let it cool before swapping tubes to see if the problem followed the tube or was dedicated to that socket. When the amp was powered back up, the popping was gone but both middle output tubes (the ones that were swapped) did not come up to full blue glow and a good part of the bass section has fallen through a trap door in the soundstage – and remains that way. It is now off line. I’m ready to box it up and send it back for warranty work. One note – this amp has a proprietary on-the-fly auto biasing circuit.
Anyone who can explain what’s going on will have praises sung by me until my dying day. I’m heartbroken!
mario_b
Have you replace the rectifier tubes ?
I beleve that the Prima Luna has solidstate rectification.
Just got my PL2 on wednesday and rolled in 4 jj E34L and voila what a difference! With auto biasing on this amp you can try many combinations. So far the hype is for real.
hi,,I currently am intersted in the prima luna amp..I saw your thread on audioggon,,do you sttill have it and are you still happy with it,,this week i heard the prima 2 and one i found the one to be warmer,,maybe it was because of the kt88 tubes,,so was it warmer when switching the output tubes,,i could use the little more power that the 2 has over the one ...
Hi Vm8444,

Yes, I still have my Luna II and am extremely happy with it. Currently it is running with 3 Kt88s and one OS 6550. Thanks to its autobiasing board you can run unmatched and even different compatible tube types and it adjusts and brings everything onto a balanced output. After a long troubleshoot, I was able to determine that one of the power tubes had an intermittant short. I resoldered the pins but the problem kept cropping up. A Hickock tester finally revealed an intermittant short to the cathode screen. A warrantied replacement tube is on the way from Upscale.
The Prima Luna II really puts out tube power. I've got medium sensitive floorstanders @ 93db in an 11'X14' room and I've never had the volume knob past the 10:00 position. If you like bass slam, the KT-88s really bring it home. And if you're into vinyl, I'd recommend getting the modestly priced phono board installed. This phono stage took a full 200 hours to burn in, but once it did, it made its very musical, full-range presence known. Hope this helps.
- Mario