Tubed Power Amplifiers. Are the disadvantages too great ?

The bottom line is that tube gear is going to cost more money to operate over time than SS gear. Tubes have a finite life and will have to be replaced periodically. People who aren’t willing to deal with tubes shouldn’t.
 
mep said:
You are correct about reliability being an objective measurement. The hard data is in the hands of the OEMs who repair their gear and track their failure modes. Audiophiles don’t have access to that data which leads to old guys swapping war stories.
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I'm too young of an old guy to be an old guy. :rolleyes:
 
Joseph R. said:
Just simple ones, like tube degradation, low power, limited ability to handle less than 8 ohm loads, bass overhang, rolled off high frequencies, quality tube availability, high cost of power tubes, need for a vacuum tube tester, tube biasing, tube matching, sound variability dependent on tube brand or date of manufacture, total tube failure, high heat and overall reliability.

I understand that all of these rarely apply. But every one can be a possibility and therefore a trade off. Oh, and I forgot that sometimes the tubes needed go out of production. The stock pile of NOS is not going to last forever.
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If you don't mind me debunking this at this late point in the thread:
Tubes do degrade, but if you stick to triodes the degradation is much slower.
Yes, tubes make less power, but that really isn't a problem as we shall see.

Its pretty fair to say that no amplifier really handles less than 8 ohms all that well. The problem here is that as load impedance is reduced, the distortion of any amplifier goes up. You might think it 'negligible' but its not; that increased distortion is almost entirely IM and higher ordered harmonics, both to which the ear is keenly sensitive. So the result is less detailed, harsher sound. Put another way, if high quality reproduction is your goal, your amplifier investment dollar will be best served by a loudspeaker that is 8 ohms or more, all other things being equal. A simple way to make any solid state design sound smoother and more detailed (due to less distortion) is to simply increase the load impedance. What I'm talking about here is the difference between a good hifi and something that sounds like real music.

There is no reason high frequencies have to be rolled off. The H/K Citation 2 had bandwidth to well over 60KHz; our amps go up to 200KHz (with full power to 1 Hz). It might be though that you hear less energy up high for a different reason- the ear converts distortion into tonality; higher ordered harmonics are perceived as brightness. If they are masked as they often are in a tube amp, the result is a perception of less energy even though the bandwidth might be the same. IOW the brighter sound you hear from solid state is often just distortion that isn't masked.

Bass overhang isn't a thing if the design is at all competent.

We get our power tubes from Russia; they cost tested at retail about $28.00 each. That's really not crazy money. We don't need a tester to test them; they can be tested visually- just by looking at them you can tell if they are good (and how they behave in our amps). BTW this is true of a lot of power tubes. Our bias and that of many other amps is automatic. We don't match the tubes- we've found no need but this is an issue in many other designs. We don't find a lot of variance between the Russian and Chinese variants; the American tubes sound a little better but are often less reliable (counter to how that sort of thing usually works with tube amps).

One thing you might want to keep in mind is that quite often these days its easier to find a replacement tube than it is to find a replacement semiconductor. There are millions of different semiconductors in production and that have been produced; of the latter many are obsolete and no longer available. We had a Classe amp in for repair some years back; what stymied the repair was that the output devices weren't available even from Classe. But that particular amp was made in the early 1990s and while almost any tube amp made in that time you can still find the replacement tubes, this decades on after tubes were declared 'obsolete'.

Reliability is an engineering issue. You can design for a given tube and depending on how you do it, the tube may or may not last. This is true of semiconductors as well, but since tubes are bit more forgiving (if you overheat one but let it cool off properly it might still be OK; don't do that with a transistor...) you can often get away with quite a lot. At audio shows I often short out the outputs of our amps, pull tubes while the amp is playing and the amp acts like nothing happened. Don't do that with a solid state amp!
 
atmasphere said:
IOW the brighter sound you hear from solid state is often just distortion that isn't masked.
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Or expectation, sighted, etc, etc bias.
So of course never demonstrable under "trust ears"/"just listen" conditions. Totally ad hoc, sure!
 
Kingrex said:
So it sounds like there may be to many disadvantages to SS amps to use them.
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I'm not sure I would agree. The problem isn't that the engineering talent to make a musical solid state amp does not exist. There are some pretty good examples out there right now, but as far as the industry is concerned, they 'measure poorly'. IMO/IME this has to do with the simple fact that we simply don't measure the right things; not much has changed since the head engineer at HH Scott pointed this out decades ago. IMO one thing that would help a lot is a weighting system on the harmonic spectra created by the amplifier; with heavier weighting on higher ordered harmonics and very low weighting on lower orders.

The problem with this of course is the resulting spec sheet would tell you how the amplifier sounds- you wouldn't have to audition it to know it would work in your system. The industry as a whole probably could not imagine a worse outcome! So don't hold your breath on that one.

But there are a few mavericks out there that push the state of the art. One is pretty well known- Nelson Pass. And now that class D has been around a while, there appear to be a few players that are making amps that are better than the usual tripe- that have musical qualities. Nelson is applying engineering to make the amp work according to what we know about human hearing perceptual rules rather than designing the stuff to look good on paper. As a result he makes some of the more musical solid state amps around. IMO we need more of that.
 
Kingrex said:
So it sounds like there may be to many disadvantages to SS amps to use them.
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Yep, that's why all audiophiles worldwide have tube amps and Mike/Suncoast refuses to sell SS. Especially for Bluegrass music.
Yeah must be it.
 
Atmasphere, I was beind somewhat facetious. But my personal experience has gravitated me to tubes.

I want to find a musical SS amp but the ones I see praised are $20k. I am stunned at what I'm hearing from my $4,400 pentode 60 watt kt88 amps. I do see a pair of your monoblock used for $6k. If I was not so happy with mine, I would buy they. I'm personally wondering about SS and can I find something as musical as mine for less than $6 used. I do wonder about the T+A amp 8. Randy likes his. That or a Luxman M600 or 800. Or a Pass XA 60.5. I'm just not at all confident any would be as magical on Classical or Jazz as what I have now.

AJ, I though Mike had Luxman and Gryphon as well as Pass Labs?
 
A GREAT tube amp/amps,advantages significantly out weigh any disadvantage.....IMO....Would not trade my SETs for ANY SS amp...at any cost...The sound is that good...!!!
 
But there are a few mavericks out there that push the state of the art. One is pretty well known- Nelson Pass. And now that class D has been around a while, there appear to be a few players that are making amps that are better than the usual tripe- that have musical qualities. Nelson is applying engineering to make the amp work according to what we know about human hearing perceptual rules rather than designing the stuff to look good on paper. As a result he makes some of the more musical solid state amps around. IMO we need more of that.[/QUOTE]

Atmasphere, Why Class D? I am sort of interested in class D. I bought that super inexpensive Allo Volt +D amp. It's dead quiet in my system. Not a sound from it or my speakers. Every other Tube or class AB SS amp I have had hums on my rack and through my speakers. I am suspect its an issue with the output transformers picking up something and amplifying it. My little class D amp seems to have no transformers in it.

Do your amps have an input transformer. I know they don't have output transformers. Are your amps more resistant to humming issues?
 
Not sure anymore where this thread is heading...or maybe there's actually no longer any direction. :skeptical:

Regardless, I think it's accurate to say that we have really excellent tube and SS amps today that can meet a wide set of customer's requirements for performance and create engaging musical experiences.
 
Kingrex said:
Atmasphere, Why Class D? I am sort of interested in class D. I bought that super inexpensive Allo Volt +D amp. It's dead quiet in my system. Not a sound from it or my speakers. Every other Tube or class AB SS amp I have had hums on my rack and through my speakers. I am suspect its an issue with the output transformers picking up something and amplifying it. My little class D amp seems to have no transformers in it.
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The hum is probably due to poor grounding schemes in the prior designs. That sort of thing is very common in high end audio. We have direct-coupled inputs. Occasionally we also run into hum issues- but in dealing with them we often find that something in the system was defeating the grounding scheme. We support the balanced line standard- AES48, which is pretty specific about grounding.

As to class D, initially it seemed about lower power consumption which it why its very practical in smartphones. But it can also be about quality if the designer recognizes what is important in the final design. The criteria are different, since class D lacks many of the traditional issues and instead has issues associated with switching. But if they are dealt with correctly the result can be quite musical.
 
Although I have a slight preference for SS, sonics are the bottom line for me. If it sounds good, it is good. Doesn't matter whether it's tubes or SS. In January I'll be taking delivery of a Gryphon Diablo D300 for my downstairs primary listening room. But I also had the opportunity to audition a VAC 170i all tube integrated amp that I would be perfectly satisfied with. Outstanding amp. Beautifully built. I can easily see why some might prefer it to the D300. But my personal preference and the sound my ears liked most was the D300. Doesn't mean it was better than the VAC, just different. I'm just not sure I want to mess with tubes. But that's me and my particular application. YMMV.

However, I definitely could see where I might want the VAC for a secondary system (my upstairs living room) and for a different sound. I might not be going through tubes as much since it would be a secondary listening room and not used as much as my primary listening room. My 2 cents.
 
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