PrimaLuna Dialogue Preamp = emotionless?


After years of running a PS Audio Direcstream dac directly into ATC active floorstanders, I decided to take everyone’s advice and add a preamp into the mix. I picked up a used PrimaLuna Dialogue with highly regarded Mullard CV4003’s and Phillips 5R4GYS’s, the tubes purchased by the original owner five years ago from Upscale Audio, a terrific source. My correspondents were correct about adding a good preamp: it transforms everything in a very big way. That’s the good news -- and bad. The latter is the reason for posting.

Before the preamp, this was a modestly warm system, for which the Directstream is known. It was one in which it was not hard to find myself drawn into the music and performance. Since adding the PrimaLuna however, I find myself watching -- or listening to -- emotion but not feeling a thing. That is, beyond marveling at the other characteristics of the presentation. After that, I’m left perfectly cold - 100%. This is not at all what I expected -- or desire.

So what to do... Is there anything I should look at with the preamp? What about other preamps, preferably tube ones? The skinny these days is that tube gear developers are trying to imitate the "neutrality" of solid state, the so-called modern tube sound some call it. With the PrimaLuna, I was expecting to find a point in between the classic tube sound and the common solid state one, but what I’m hearing is more than a little distant from that.

(Other than adding the PrimaLuna and not having Ultimate beeswax fuses in the DS and PL currently for other reasons, nothing else in my system has changed: modified Oppo 203 w/ digital output only, PS Audio P15 Regenerator and AC-12 power cords, and MG Audio Design AG2 ICs,)
highstream
15 or so years ago I sold my Preamp and bought a BAT VK5i SE it came with new production RCA 6922's and couldn't enjoy the preamp. The amp took 8 6922's. I knew it was the tubes so I bought 8 bugle boys it was better but the music didn't grab me. Was advised to buy nos power supply tubes so I did. Music just wasn't as fun listening to music anymore. I figured I needed to warm things up so I bought some nice nos Valvo's and then Mullards, everybody said BAT was so nice. I sold the amp. Funny thing was while I was chasing tubes to fix the BAT I listened to my 10 pound Don Allen Preamp that came with some kind of oddball $15 tubes he chose for building the preamp that was a complete joy to listen to big tight bass wonderful detail reteaveal but main thing it was very musical. I saw a video of Kevin Deal talking what makes the prima Luna so great was how much it weighed and how many parts are in it and a bad sounding preamps are light with not many parts in it. I don't know if I agree with that one. Problem is with all the things involved in a system a few things can through it off. You don't know if you can fix it unless you try but it can be expensive and agrivating road just to listen to music.
I’m not a PL owner but have owned many tube preamps. I highly recommend NOS Tung Sol rectifiers for a deep bottom end.

For a dynamic, lively presentation 1950s Amperex Holland Bugle Boys are an affordable alternative to the 7316 tube.


@paulcreed
I had a BAT BAT VK5i a long time ago, with a similar experience - based on reputation I thought I was in for an amazing preamp listening experience, but it definitely was NOT a joy to listen to. Tried tube rolling, including Tung-Sol 5881, etc. At best, maintaining all those tubes and keeping noise low was a nightmare. That said, my system was a mess back then with a lot of problems - but I certainly wouldn’t ever give the VK5i another try.

But all else being equal (and it never is), I do believe weight (meaningful weight) and parts quality are at least somewhat correlated to sound quality. I definitely don’t see anything wrong with Kevin’s PrimaLuna pitch on that front.
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Highstream 12-5-2019
... failing improvement there, take a photo of the bottom insides to see if any modification had been made.

It would probably be a good idea to take a look at the underside of the unit in any case, especially to verify that the two output coupling capacitors are the same as the two white objects that are shown closest to the output jacks in this photo, which appears on PL’s website page for the Dialogue Premium preamp as currently produced.

Those objects appear to be 10 uF (ten microfarad) Mundorf capacitors. But it seems possible that in the 5+ years since your unit was produced the output coupling capacitors that are being used have been changed. If those are what is in your unit, though, and assuming the rest of the design of the output stage is the same as in the currently produced version of the Dialogue Premium (with a nominal output impedance of 256 ohms), the output impedance of your unit at the worst case audible frequency (20 Hz) will be about 836 ohms, which means it should be suitable for driving the 10K input impedance of the active speakers.

@newbee, thanks for the mention early in the thread. I just noticed the thread now.

The point @kalali made earlier, that ...

The published 256 ohm output impedance is most probably measured at 1KHz and can be (and most likely is) much higher as the frequency response varies during actual music playback.

... is absolutely correct, especially in the case of many tube-based preamps. With the highest output impedance within the audible range usually being at 20 Hz.

Regards,
-- Al