Tube Preamps...I'm sold

Hi Bart, I don't agree with you. Although our preamps are clearly affected by the tube choice, it is also evident that the preamp performs in a certain way- for example I can state with no qualms that our preamp plays the bottom octave better than other tube preamps on account of its direct-coupled output. It is also capable of greater detail since there is no output coupling capacitor to affect that detail.

That's not a thing affected by the tube choice. Additionally, tube preamps in fact do have coupling caps- (ours does, just not at the output). The choice of these caps has a serious effect on the sound of the preamp, again, not affected by the tube choice. Some preamps employ an output transformer, like the Shindo, they will have a sound peculiar to the operation of the transformer, again, not affected by the tubes.

Although tube choice can definitely have a big effect on the sound of a preamp, by no means are they the deciding factor on all preamps, though I don't doubt that there are preamps out there that simply don't shine until you get the right tubes.

Hi Atmasphere,

Thanks for the post. Point taken. My experience has been with extesive tube rolling in three different tube preamps.
The CAT Ult MK2, VTL Ultimate and Ming DA 2A3. I have read many threads (particularly on the CAT) describing the
sound. Many were using the stock tubes and described the sound as leaning toward analytical with great dynamics and frequency extension. I an agreeing with you here. Regardless of the tubes rolled the CAT will maintain those two characteristics (dynamics and extension). But the analytical character can be modified to overly lush depending on tube selection. I now select amps and preamps primarily by the tubes they use(12ax7's, at's, au's etc.).
I like products that use several (three or four) different tube families (not any tube families as some are better than others). This allows the greatest range of tuning.
The tube choices are not arbitrary. The Chinese pre I am using currently uses 2A3's (rectification), 6922's (input),
6SN7's (output I think), EL34 (voltage regulation I think).
I have an idea of the quality of some tube families and regard all four of these as top shelf. My point is that the selection of these tubes will allow this pre to out perform a pre that uses all 12AX7's for instance (not universally, generally). I am meandering a bit here but to get back on point, we are essentially in agreement.
The design and the tube selection contribute to the outcome. I think you feel that the design factors have more weight while I believe the tube selection, generally,
is more determinant of the outcome. The point I am trying to make to the posters on this thread is that when talking about the "sound" of a tubed product to remeber that the vast majority of these are chameleon like in that they change character based on tube selection. The SS product on the other hand is a constant. Comparing the same tubed product with different tubesets will produce very different results.

Bart

Got it!

I know Albert, who posts a lot here, will agree. He might spend days sorting out the right tube for each position in his preamps.

Certain things are not going to change though, for example, what a preamp is doing if it is designed with feedback as opposed to one that isn't, how well grounded it is, the quality of power supply regulation and the like. They all affect the sound.

But *your* point is taken too- just because you heard a tube preamp sound a certain way, does not mean you have heard what that preamp can really do if the tubes are not up to it. I have seen a reviewer install junkbox, outright defective tubes in a preamp, and then trash it in print when it didn't perform! Later the magazine announced that it would not publish a review if the tubes had been rolled.

One thing that is tricky for a manufacturer is the fact that modern tubes are often not up the quality of tubes from 40 years ago. Manufacturers have to buy tubes in large quantities, whereas an individual need only find enough tubes to populate his preamp. So- should the preamp be judged on how it sounds from the manufacturer or how it sounds if you can find the right tubes? In the words of Deep Thought- 'Tricky!'

On the subject of tube rolling, I recently changed out my stock tubes in my CAT signature with NOS GE Smooth plates and Russian Rocket tubes in the line section...BIG improvement. The pre-amp was no slouch before, but took on a new life with the swap-out. Far more realistic dynamics, more extension of both ends of the spectrum and less haze.
So, I am wandering how many people have actually heard what is possible with their pre-amp, certainly brings up the question of whether a reviewer has heard what a piece of tube equip under review can do.

Atmasphere, I sure hope you are talking about the MP1 when you mention the bottom octave, because the MP3 up against a BAT 31SE a couple years ago was severely lacking extension at both frequency extremes. Perhaps it was ill but it was a Mpls Atmasphere dealer demo. And the comparison was made at the Mpls BAT dealer and later on, my home. Upon switching from the 31SE to the MP3, the BAT dealer and I just looked at each other with total surprise as we never could have imagined the MP3 to have such issues.

Bart really nails it here on the significant improvements that are possible if the owner is willing to put forth the effort to investigate tube options. With some starting points as advised by Albert, I have taken the Aesthetix Io/Callisto and CAT UII and JL-3's to levels that transform these products far beyond their showroom performance.