2. amps-preamps
  3. 152875-3731

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
newbee
4,767 posts
 
As you might suspect (or not) the choice of tubes in any amp or pre-amp can easily affect the sound you get. Just 'cause some one else liked, and some one else recommended, any particular tube really means nothing other than that they like them (in preference to what?). Add to that that the tubes are now 5 years old, and presumably tired from use, adds to the difficulty in assessing the benefits of using a (this) tubed pre-amp. If that isn't enough already, integration of the source with the pre-amp and the pre-amp with the speakers amp adds more to the equation.

Now if I had to guess what a likely problem may be for you is the interface of your pre-amp with your amp. The pre-amp has a fairly high output impedence and would only work best with an amp with a high input impedence (like X10 of the pre-amps output impedence).

Put your research hat on or wait for a good techie like Almarg to sign in.
lowrider57's avatar
lowrider57
5,417 posts
 
I think your first move should be to roll in some new tubes. The current tube selection may not be to your taste or they need to be replaced; they are five years old with unknown history.

I don’t know the different tube stages of your amp, but you don’t need to use the same tubes in all positions.
I love the CV4003’s, but they are laid-back and you may need to add more dynamic and engaging tubes. NOS Amperex, Telefunken, Sylvania all have more detail, are very open, yet still retain the timbre of tubes. NOS tubes have more realistic sonics than new production and are worth the extra money. There are so many NOS you can try that are less expensive than those mentioned.

A good source of information..
http://www.audiotubes.com/12au7.htm

The rectifier tubes may also need replacing. And it's possible that a different brand may be more engaging, although Philips makes  excellent tubes.

highstream OP
207 posts
 
Thanks for the replies. The preamp is non-demanding on tubes, so five years should be well within their range, although admittedly I don't know how the previous owner handled it (tubes were not why the previous owner sold it). In describing the Mullards, I found that many people use some version of warm, sweet, lush, liquid, smooth to, so that’s what I was expecting. I haven’t found this set of tubes laid back or lacking in dynamics. In anticipation of the PrimaLuna, I’ve started watching for good deals on Brimar CV4003’s and have just now rolled in an NOS pair. There’s also a pair of Brimar 13D5’s (CV4003) on the way. These four will cover the most important spots on the front end. The Brimars seem to be considered a bit warmer and more extended on top and bottom than the Mullards, but as you all say it’s in the mix (and taste).

Output impedance of the PL preamp is 256 ohms. Input impedance of the ATC SCM19As is 10K. I hadn’t considered that, although in a discussion with Don Sachs, he mentioned his preamp would need a 3uF cap to handle impedance that low (don’t know the output impedance of his).

P.S. Not sure why "follow" isn’t alerting me for this thread.
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