CV4003 NOS Mullard at Upscale Audio.
Primaluna dialogue premium HP tube rolling suggestions to reduce brightness
I have had the dialogue premium hp for about 6 months now, using naim preamp and proac tablette anniversary speakers. I have been noticing some brightness in the high end, and am wondering is I might be able to switch out the tubes to cool it down a bit.
I am running the stock el34 and 12au7. As this is the hp with 8 power tubes, I would rather not switch the el34 for financial reasons, so does anyone have recommendation to change the 12au7 tubes.
I also think the the proacs are contributing to the brightness, but would rather not go speaker shopping again, but have not eliminated that option if you have some ideas
I am running the stock el34 and 12au7. As this is the hp with 8 power tubes, I would rather not switch the el34 for financial reasons, so does anyone have recommendation to change the 12au7 tubes.
I also think the the proacs are contributing to the brightness, but would rather not go speaker shopping again, but have not eliminated that option if you have some ideas
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- 31 posts total
I don’t believe output tube rolling is the answer to the OP’s problem, as the below will still be there and explain. One must remember speaker and the speaker wire introduce not only a resistive load to the amp but a capacitive one as well. ESL’s even more so capacitive, so all amps theoretically should be unconditionally stable, eg no ringing whatever the load on bench square wave tests. In Ultra linear mode this amp is a little unstable into 10khz 8ohm pure resistive loading, even without any speaker/wire capacitive loading which would exaggerate this ringing even more which may cause the brightness heard. http://www.stereophile.com/images/214PLDPfig03.jpg But in triode mode it seems to be a bit more stable, and should not sound as bright, but still we don’t get to see it with some capacitive loading just 8ohm pure resistive. http://www.stereophile.com/images/214PLDPfig04.jpg Even JA "Stereophile) who did the above measurements said this " PrimaLuna DiaLogue Premium performs at its best with tubes operated in Triode mode." One can clearly see in ultralinear mode the sharp rising frequency response after 20k this is the rigging seen on the 10khz square waves. "It a bit like an uncontrolled resonance peak of some metal dome tweeters" "brightness???" http://www.stereophile.com/images/214PLDPfig01.jpg It seems to me that in Ultralinear mode they’ve gone for too much bandwidth (70khz) at the sacrifice of stability. But in triode mode all is far better behaved, with no peak after 20k. http://www.stereophile.com/images/214PLDPfig02.jpg If I owned this amp I would only use it in triode mode, and if that didn’t have enough power, I’d get another amp that was. Cheers George |
The stock Primaluna Preamp tubes in the 2 middle slots were way too bright for me. So if you want to go with new production tubes. I would suggest the reissue Mullard 12au7's. If you want to experiment with old American tubes. You might want to seek some Baldwin or Conn organ pulls for less than $30 a pair. Triode mode will help as suggested. |
- 31 posts total