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My first tube roll in a Primaluna Dialogue HP Integrated

First off, special thanks to tomy6--a fellow audiogoner who helped me identify, with specificity, the exact tube I was swapping in:  an Amperex 12AU7 tube made in the early to mid 70s; Great Britain Mullard factory. 

I swapped out stock Chinese sourced Primaluna 12AU7s--6 of them--from the preamp section. 

The process of rolling and twisting in a gentle swaying motion is really easy, yet there's an subtle art to it.  By the time I hit my 3rd or 4th tube, I got the hang of it.  In my mind's eye, I had a vignette of many folks who came before me, installing tubes.  I pictured repairmen with--what I think they had--a tube caddy, full of tubes separated by cardboard dividers like bottles of wine.  

I didn't bother to clean the somewhat oxidized-looking tube pins, which were much darker and tarnished than the 2016 Chinese Primaluna 12AU7s.  I rolled one set out, and dropped the other in. 

It was interesting to see the Amperex tubes flash up on startup.  I wondered if they were going to blow!  They flashed brightly and calmed almost as fast as they lit up.  My pessimism nearly expected the amp to signal that I had a bad tube or two.  Primaluna's autobiasing automatically kicks in and handled that--just like Mesa Boogie guitar amps.  

Things sounded just fine out of the box. I'd say no better or no worse than swapped tubes.  I've been running them now for 90 minutes.  The difference is real yet subtle. Here's what I think:

--The Amperex tubes have more top end attack.  I wouldn't call it bite. There's more detail on top....not much, but it's there. 
--The Amperex may be less warm.  The bass seems to be more defined but there's less of it. 
--The Primaluna's sounded a bit bloatier, which was kind of nice in some ways, yet in another it's making me thing and digest these differences. 
--While the soundstage of the Amperex seems to go back deeper than the Primaluna, it seems like I'm sitting a bit farther back from the performance.  I cannot tell which I prefer.

I haven't had a chance to really crank the volume and get them heated up and pumping.  

I have no strong takeways from this experiment yet and I certainly haven't decided which I prefer.  Next up is a set of 6 Ciftie military grade set of 12AU7s.  

Different indeed!  


128x128jbhiller
jbhiller's avatar
jbhiller OP
1,399 posts
 
One more thing--

The Amperex do not show as great of a sound difference when I switch between triode and ultralinear settings.  Not a good or a bad thing...just a thing.
tablejockey
3,888 posts
 
"Next up is a set of 6 ciftie military grade set of 12AU7s."

I don't have an extensive collection of different NOS, but do hear the subtle refinements of the 2 preamp(innermost). The 2 other stages don't seem to be as sensitive to rolling. I ended up changing all of them, just for the sake of continuity. Mine are a row of 50'sRCA blackplates. Now and then I switch the 2 innermost with Raytheon and the Mazda(Cifte)

I have a shoebox full of old American tubes from years of guitar amp spares.

There does seem to be audible differences with generic new tubes and NOS. 6@$50+ is a little steep for the euro fancy glass, so the RCA I purchased for $5 each work.

Once you start playing with NOS, IMO the subtleties are even greater, and don't warrant the high cost. Or likely, my hearing is just aging like the rest of me.

The Power tubes are what can be the real wallet killer. I've seen a little price discount for the KT150, but $800 is just out of my league when it comes to lavish spending.

Regardless, enjoy the roll.
lowrider57's avatar
lowrider57
5,417 posts
 
--The Amperex tubes have more top end attack.  I wouldn't call it bite. There's more detail on top....not much, but it's there.
--The Amperex may be less warm.  The bass seems to be more defined but there's less of it.
--The Primaluna's sounded a bit bloatier, which was kind of nice in some ways, yet in another it's making me thing and digest these differences.
--While the soundstage of the Amperex seems to go back deeper than the Primaluna, it seems like I'm sitting a bit farther back from the performance.  I cannot tell which I prefer.
Your observations are spot on. If these tubes are new, they will require a burn-in period.
The Amperex do indeed have more air and detail on top. They are not a warm tube, but should sound full-bodied. I have never owned the orange label Amperex, but their Holland factory tubes have deep bass extension so maybe your's need more time.
Wide, deep soundstaging is what these tubes are all about. Hopefully, you'll like their spacious presentation. If you do, in the future look for the "Bugle Boy" version which are their top of the line tubes.


jbhiller's avatar
jbhiller OP
1,399 posts
 
I'm about 2-3 hours in and bass is more prominent and they sound less bright.  The detail and soundstage is great.  I'm going to let them burn in for 15-20 hours before I critically review them.

Thanks for the background and advice.  
rotarius
431 posts
 
You are going to get a lot of recommendations for the expensive and rare tubes on Audiogon.  If you don't want to spend the big bucks, start with some American brands readily found on ebay.  I will let you in on a secret. The older Raytheon black plates were terrific.  I then swapped in Raytheon Japan short gray plates and they were as good.  In my preamp circuit, these beat out the brands with the lofty valuations.  The best part is they are easily found under the Baldwin organ label and were screened for low noise and microphonics for Baldwin.
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