PrimaLuna Dialogue HP Tube Placement Question

Discussion in 'Audio Hardware' started by Guy Gadbois, May 28, 2017.

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  1. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    I'm doing some tube swapping this week and am wondering if anyone can tell me the function of the six front tubes of this amp.

    I understand the front two are mostly in control of the tone of the amp, but what do the other four tubes do?
     
  2. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    Guy,

    According to the manual the 12Au7s are grouped in (3) left channel / right channel pairs. If it follows classic tube amplifier design then the two left 12AU7s would be the preamp tubes and have the most influence on the sound quality. The center pair would be the phase inverters (second most influence on sound) and the right pair would be the power drivers (third most influence on sound).
    The important thing is that they are grouped in (3) pairs.
    You need to experiment to find out which pair has the most influence on the sound and therefore the target "pair" to flavor the overall sound of the amp.
    Take a pair of tubes you want to roll in and starting with the left pair, swap them for the stock tubes and take note of the influence on the sound.
    Do that for the center and right pairs. Determine which "pair" has the most influence on the sound and the least influence on the sound. Then you will know which positions will have the most impact and can swap in and out from there. From experience all (3) pairs will have an influence on the sound but one pair should stand out from the others.
     
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  3. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @avanti1960 The web site says the front two are the ones to change. See here:

    Tube Rolling

    You have to scroll down about 2/3 of the page to read the info

    I just want to maximize my tubes and put them in the right place
     
  4. It tells you "gain tubes - maximum effect" What more do you want to know?
     
  5. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @morinix So I could put absolute crap JJs tubes in the other four spots and it would sound exactly the same as if I used $200 Telefunken?
     
  6. If you want to, go ahead. But maybe you should read and focus on this part; "DiaLogue Premium: In addition to the the four smaller tubes referenced in the paragraph above, DiaLogue Premium has two extra smaller tubes outside and behind the front four. These two tubes are cathode followers and will not have as great an effect as the front four. Do the front tubes first. See photo below:"
    [​IMG]
     
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  7. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @morinix That's for the Premium. I have the Premium HP. For that model it's just the front two. I would really like to know the purpose of the other four
     
    Last edited: May 29, 2017
  8. The configuration of the preamp tubes is the same in both the "HP" and non-HP units.
     
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  9. jupiterboy

    jupiterboy Forum Residue

    Location:
    Buffalo, NY
    cathode follower = phase splitter?
     
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  10. ggergm

    ggergm another spring another baseball season

    Location:
    Minnesota
    @Guy Gadbois, I've done a reasonable amount of tube rolling with my Dialogue Premium HP amp and have found changing out the center two 12AU7 do make a difference, both good and bad. My two favorites have been a pair of Cifte tubes that came from Upscale Audio and a pair of GE JAN 6189W. The Mullards I also got from Upscale Audio have been uninvolving both times I've tried them. I'm not sure they are better than the stock tubes which is surprising given the reputation of NOS Mullards.

    I changed out the other four 12AU7 tubes for some miscellaneous RCAs because I had them around. I'm not sure the change made any difference in the sound. Reading this thread, I'm going to replace the other two gain tubes mentioned by @morinix with something that might be better. I'll let you know if I hear anything.
     
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  11. TONEPUB

    TONEPUB Senior Member

    Location:
    Portland, Oregon
    Anyone plugged in some KT150s? I'm really liking the sound and extra power.
     
  12. ggergm

    ggergm another spring another baseball season

    Location:
    Minnesota
    I also made the swap and have been very pleased with the result. It definitely gave the amp more kick and volume. The bass changed a bit in character but I can't tell you which is right, the EL34 or the KT150. Both are fine in the bass, just a tad different. In any case, I think the KT150s sound really good, with an excellent midrange, highs and soundstage.

    The cage no longer fits, unfortunately. I made a pair of rails for the cage to sit upon so it would clear the top of the tubes, using some scrap wood. I got scrap results, with the heat warping the rails so much they cracked. I bought a nice piece of oak for a second attempt and it sat on my furnace for the winter to dry out. This summer some time I'll make cage rails, version 2, and post the results here.

    I'd love to get 8 vintage, super-duper EL34 and swap out the two sets, summer and winter. The KT150 would be the windows open, summer tubes, with the EL34 the keep it warm, winter tubes. I suspect 8 relatively matched vintage EL34s would cost me as much or more than the KT150s.

    [​IMG]
     
  13. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @ggergm What brand of tubes are you using? I thought about going from the 34s to the 88s, but my room is small and the volume gain...3 db...isn't worth the dynamic loss...5...to me.
     
  14. ggergm

    ggergm another spring another baseball season

    Location:
    Minnesota
    Tung-Sol

    It isn't the volume, Guy, as much as the authority. Sure, my hi-fi plays louder, and that's always good, but the improvement in punch and dynamics is what I enjoy as much or more.
     
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  15. ggergm

    ggergm another spring another baseball season

    Location:
    Minnesota
    [​IMG]

    Yesterday I heard some noise out of my stereo. Intermittent, it was only in one channel and not affected by the volume control. I immediately suspected one of the KT150 tubes of my PrimaLuna Dialogue Premium HP integrated amp was beginning to fail so I replaced all eight output tubes with the factory EL34s.

    After ordering two new KT150 tubes from Upscale Audio, a replacement for the one that must be bad and a spare, I've done some serious listening to the amp. It's been a while since I've used the factory tubes. The biggest difference is in the bass. It's what I heard first. The bass of the KT150s is significantly more articulate and well defined, in addition to having more energy in the bottom two octaves. There is also an advantage to the KT150s in the extreme highs and transient response. This morning I was listening to the new Resonance Records vinyl of Another Time by Bill Evans. I happened to play that album a few days ago on the KT150s and was struck by the attack of Jack Dejohnette's cymbal work. It's one of those recordings which emphasizes the sound of the stick hitting the cymbal and then the cymbal ringing. Today I still heard that effect but it was a definitely muted. Maybe on a bright system, and right now mine is trending toward a really sweet midrange, the softer sound of the factory tubes would be more pleasing in the highs. I'll take the KT150s.

    That said, overall I was very impressed with the factory tubes. They sound wonderful. I'm not sure I heard any difference in the midrange between the two, both in tone and the soundstage. The factory tubes also plain sound right. Their sound hangs together. This is may be the most critical requirement of a piece of gear for me. Is it coherent? Does its sound work as a whole, tonally and spatially, top to bottom, left to right, front to back? I can put up with something missing, or even not done perfectly, if everything sounds like it is coming from one band, one source. This morning I asked the question, do Bill Evans' left and right hands sound like they are playing the same piano? The factory tubes passed this test spectacularly well.

    I like to tube roll. Wait 'til you see what I have coming up. But I have always had a bias against gear that had to be modified to sound good. That is not the case here. The factory EL34 tubes sound excellent.

    You know what you'll get if you never change a tube with this amp? Terrific music.
     
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  16. Guy Gadbois

    Guy Gadbois Chief Inspector Thread Starter

    @ggergm I have Gold Lion KT77 reissues in the back, NOS Mullards in the front two spots, flanked by Amperex/Mullard NOS and EH in the last two spots.

    The Lion tubes sound better to me than the stock. Naturally it's a combo of things...room, speakers, etc, that make it work.

    But for me, with what I've got and where it's located, I'm happy with the Lions.
     
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