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Tubes Do It -- Transistors Don't.

I never thought transistor amps could hold a candle to tube amps. They just never seem to get the "wholeness of the sound of an instrument" quite right. SS doesn't allow an instrument (brass, especially) to "bloom" out in the air, forming a real body of an instrument. Rather, it sounds like a facsimile; a somewhat truncated, stripped version of the real thing. Kind of like taking 3D down to 2-1/2D.

I also hear differences in the actual space the instruments are playing in. With tubes, the space appears continuous, with each instrument occupying a believable part in that space. With SS, the space seems segmented, darker, and less continuous, with instruments somewhat disconnected from each other, almost as if they were panned in with a mixer. I won't claim this to be an accurate description, but I find it hard to describe these phenomena.

There is also the issue of interest -- SS doesn't excite me or maintain my interest. It sounds boring. Something is missing.

Yet, a tube friend of mine recently heard a Pass X-350 amp and thought it sounded great, and better in many ways than his Mac MC-2000 on his Nautilus 800 Signatures. I was shocked to hear this from him. I wasn't present for this comparison, and the Pass is now back at the dealer.

Tubes vs. SS is an endless debate, as has been seen in these forums. I haven't had any of the top solid state choices in my system, so I can't say how they fare compared to tubes. The best SS amp I had was a McCormack DNA-1 Rev. A, but it still didn't sound like my tube amps, VT-100 Mk II & Cary V-12.

Have any of you have tried SS amps that provided these qualities I describe in tubes? Or, did you also find that you couldn't get these qualities from a SS amp?
kevziek
karls
332 posts
 
I've been very curious about the Berning but never tried it. Do you have any experience with driving lower-impedance speakers with it? My speakers are a ruler-flat 3.5 Ohms with near-zero phase throughout the entire audio band, except for a single closed-box peak in the bass, so what do you think? I've talked with one zh270 owner who felt that this would be pushing it a little too much, that the amp probably couldn't handle that kind of load. But if you have any comments, I'd love to hear them.

I appreciate the Atmasphere approach, but I can't bring myself to burn that much juice or to think about the retubing costs!
twl
3,251 posts
 
Karl, I think that it could do it, with the feedback selector switch in the 2 ohm position. My experience with the low impedance on the Bernings is some of the "life" goes out of the music. I think that this limits the dynamic headroom capability of the amp. I did not notice any problems with reproducing the low frequencies with a 4 ohm impedance load. It was most noticeable to me in the midrange vocals, where some "life" left the sound. 6 ohms was just as "happy" as 8, so anything above 6 ohm nominal should not be noticeable. I found this when I was doing some speaker designing for my MicroZOTL which is a push-pull design much like the ZH270 except no feedback. By using some non-inductive load resistors in a series-parallel network across the speaker terminals, I could determine the sonic behavior of the amp at different loads during play. I could determine where it would "harden up", if you will. Now the ZH270 has some limited feedback switching which provides better behavior under some difficult conditions than my no-feedback design. But my output impedance was 1.8 ohms, which is the same as the 2 ohm setting on the ZH270, so I think it would be similar. So I expect it would sound good, but not as good as a 6 or 8 ohm load.
wellfed's avatar
wellfed
690 posts
 
I concur with Fatparrot on the Atma-Sphere assessment. I have heard the Plinius 102's in Jadem6's system and am impressed with the sound he is getting from these amps.

Karls, If I remember correctly, Atma-Sphere states that their amps consume only 10% more power than a similarly spec'ed Class A SS amp. Also, the Atma-Sphere amps do not have to be retubed very often and use low priced tubes to boot.
tubegroover
2,279 posts
 
Karls-I haven't tried the zh270 into a load that dips low or in your case ruler flat at 3.5 ohms but have read and heard many conflicting comments on its performance at the frequency extremes into such loads that I don't know what to think. How about you Twl? Nah you're definitely the wrong guy to ask :)

I sure am curious myself and anyone in the Central Florida area that has such speakers I will gladly bring over this amp to find out first hand. Everyone I know has medium to high efficiency speakers and the amp sounds great on all of them. The high frequency impedance converter adjusts for impedance dips unlike traditional OTL amps which just run out of current unless there are enough output tubes to provide enough. Transformer coupled amps also do the brute force gig which is why they don't fare well into such loads, especially in the bass and why ss is a better choice for across the board performance.

Regardless, my guess is that the tonal balance especially at the frequency extremes may be affected with certain loads. With my speakers the amp is well balanced and extended across the frequency spectrum. The high frequency performance is also right up there with an absolute crystaline clarity with air and space to match. I really can't hear any problems anywhere but I'm still looking. You know something is on the ball when you start critically listening and find yourself just enjoying in spite of yourself, it happens all the time :)
twl
3,251 posts
 
Tubegroover, see my last post above for my experiences at lower impedances with the Berning.
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