Articles for Audiophiles by Steve Deckert
AUDIO PAPER #012
TUBES vs. TRANSISTORS
by Steve Deckert
Below is an email I got that refers to our Tube Vs. Transistor articles located in the tube section of this site. I thought is was well written and respect the position enough to say it speaks for a whole lot more people than just Larry.
Your posted articles on Tube VS. Transistor amplifier sound are interesting, but they suffer one serious flaw: YOU SHOULD NEVER EVER ALLOW A TRANSISTOR AMPLIFIER TO CLIP!! Just below clipping, a well designed transistor amplifier well have almost unmeasurable distortion. High power transistor amplifiers today are so good and so cheap, there is no excuse for them to go into clipping. The speakers will begin to distort way before the amplifier reaches near its clipping level. The modern MOS FET transistor amplifier can easily reach peak levels of over 200 watts without clipping.
The even-order distortion that tubes produce is still distortion, but some call it "euphonically correct", and, with a tube amplifier you can't turn it off, it's always there. If I want this kind of possibly desirable coloration in my music listening, I would add a tube stage that is voltage starved which will slightly exaggerate this effect (Such as the product the "Tube Head" from PAiA), and then I would have control over the degree of coloration I would like to inject--and I can turn it off, like a tone control defeat switch.
The one common trait all of you Pro-Tube folks have in common is that it is so easy to poke holes in every one of your attempted objectivist assertions (regardless whether you are a member of the prestigious Audio Engineering Society or not). If you keep your Pro-Tube arguments purely subjective, then I have no argument--each to his own.
My response follows:
Thank you for your email! You have just narrowed down what I feel to be the pro - solid state position in only 3 paragraphs which I thought was outstanding!
I think it clear that the two articles I posted regarding the differences between tubes and solid state are an attempt to shed some light on the forever ongoing debate.
I understand where you're coming from on your first position on clipping, but don't forget that using your 200 watt amplifier as an example and listening at a nominal level of 10 watts on power hungry speakers, you would need 1280 watts to reproduce a 20 dB musical peek without clipping the wave form. Granted most music today is compressed and has limiting, but I listen to master tapes whenever possible which have no limiting and more dynamic range than CD's or LP's.
I also agree that most speakers will be into some type of distortion in the above illustration.
The even order harmonic distortion of tubes can be a non factor before clipping in a good circuit. I'm not sure it is accurate to imply that the distortion is always there as a consistent coloration because it is proportional to volume level relative to amplifier power relative to loudspeaker efficiency. Most people can't detect even order harmonics until they reach 3%. In a tube based system with high efficiency speakers and say a 40 watt amplifier, your listening level would contain about 0.2% THD. See Figure 4.
So, this all leading to my personal position on tubes vs. solid state... First off I do not categorically feel tubes are superior. I think each application in unique. For example, I am a musician, and in my studio, I use solid state amplifiers for the mains and wouldn't dream of using anything else. It is just more practical. I have heard many solid state systems that sound really good.
Where the difference comes in is in the specific application of hardcore audiophile listening. By this I mean going into my listening room (where there is no TV or furniture) and getting off on the illusion of a three dimensional presentation. In this scenario I would challenge any solid state amplifier to sound more realistic than for example my Zen amp. For me the goal is to recreate the emotional responses that occur with live music because it's real, not to make damn sure the specs are perfect and then deciding the resulting presentation must also be perfect.
There are two reasons why I think tubes sound better in this application. One is that triodes (tubes) can be operated without negative feedback. The other is because a solid state circuit needs many more capacitors in the signal path than a tube circuit, hence more parts. Also those capacitors are 10 to 100 times larger in value. The combination of all the additional parts and negative feedback will ALWAYS result in LESS depth, less detail, less involvement, less pleasure in a dedicated treated listening room.
Some people think that the goal of a perfect playback system is perfect specs, and some people think the goal of a perfect playback system is one that sounds close to real. These two perspectives are what I feel is really in debate. And the only reason in my experience for the debate is that spec-o-holics have not heard a good single ended tube amp A/B'd with their ideal of a perfect amplifier.
Figure 1 shows a typical Op Amp. One or two of these can replace a small signal tube, like a 12AX7 as an example. Figure 2 shows what's inside the OpAmp. It features around 20 transistors, all direct-coupled with negative feedback. A tube on the other hand would be similar to just one transistor with 20 times the output. Figure 3 shows a Zen Triode Amplifier, the entire audio circuit. In a solid state amp, you typically start with a few Op Amps and then use those to drive larger output transistors, which are almost always paralleled to get the power up and the impedance low enough to drive a loudspeaker. There is virtually nothing to block the back EMF from the loudspeaker voice coil so the real performance of many solid state amplifiers is nowhere near what it is on paper.
There are TONS of CRAPPIE sounding tube amps out there. I would say way more than good ones. This makes it easier for the pessimist to draw a negative conclusion when comparing the two, however I will challenge anyone to the test any time you want to make the trip over here.
The most recent person to take this test owned the Cello Music System, has a treated listening room, and has spent to date over 400,000.00 on fine audio gear, and even worked with Levenson. He has his own successful company doing sound treatment for studios. After hearing GOOD tube gear at my place, he has come 180 degrees and will be the first to tell you I'm right.