tubes and analog

The big advantage tubes have over solid state is that they are *far* more linear. Their gain characteristic is many times better than a transistor or integrated circuit. They also overload in a much more sonically benign fashion, tending towards compression rather than clipping.

Most solid state amplification employs feedback (and lots of it) to cure the nonlinear gain ills. The closest you can get to a tube is by using JFETs open loop. They're pretty good, but still not in the same league as tubes.

On the other hand, most tube circuits require coupling caps. There is, as several of you have pointed out, no perfect design, and they all exhibit artful compromise.

But as Atmasphere points out, the micro details and very small signal information is better recovered via tubes. This is not just opinion, but a technical limitation of topology. The exception would be an open-loop class A gain stage using a reasonably linear active device such as a JFET.

jh

>>we develop a totally new mathematics theorem to make the transistor full linear<<

What kind of fluff is that? I'm not familiar with any of your designs, but coming up with some new equations on paper does not change the laws of physics. Active devices follow certain behaviors and have been well established. On one end of the scale is the triode, the most inherently linear amplification device used in audio. At the other end is the bipolar transistor (ok, maybe an IGBT is worse). In the middle are JFETs, pentodes, MOSFETs.

The bipolar transistor has a nearly perfect logarithmic transconductance. Hard to beat in that respect. But exponential is not proportional (linear). No theorem is going to change that.

If you have, however, invented some new circuit topology that does what you claim, then I suggest you patent it immediately. Silicon Valley is going to pound your door down.

>>more SS designs come with NON feedback design<<

Well, I think this is a little exaggerated. Most SS designs on the market employ opamps. Only a handful use open loop discrete gain stages. Perhaps this number is growing, but I hardly think it is dominant.

>>It is untrue that there is a technical limitation topology<<

What I didn't make clear here was the basic difference between class A and class B stages. As far as I know virtually all opamps run class AB. The output signal is driven in one direction by one device (transistor), and in the other direction by a second device. They keep handing off the signal. Only during a small crossover window do they both conduct. Making this window larger can help. Making the window full scale turns the amplifier back into class A. No device ever turns off.

In contrast, a class A stage is driven by a single device. It is always on. There is no cross over or handoff. This is the difference between a 2A3 SET and your typical SS amplifier. Why is it people will live with a flea-powered 2A3 when they can have 50 watts out of an LM3875 power opamp? Because of the micro detail. The SET is running full bore at idle. It excels at small signals and the distortion becomes vanishingly small. By comparison, the class AB amplifier excels at large signals. But it's distortion rises as the signal gets smaller. Exactly the opposite of the 2A3. That is an example of topology.

There are a lot of other topologies I can get into, but that example illustrates the point well.

>>tubes are harmonic generators<<

Yes. So is feedback. And the harmonics generated by feedback are far more insidious. They might be quite small in relative amplitude, but multiply with each pass through the amplifier, generating a lot of non-integer harmonics. That leads to the cold, sterile, and sometimes fatiguing sound of many high feedback amplifier stages.

SS stages that do not use feedback are also harmonic generators. Heck, every amplifier is to some degree. The question is, what sort of harmonics do you want to live with? I'll take a triode any day.

jh

>>I'm glad Hagtech pulled out just in time<<

Oh, sorry, I've been really busy.

>>very old myths<<

My apologies for leaving out some crucial details in my earlier posts. I jumped onto this thread in defense of tubes, but was speaking from a device standpoint. That is, I was not arguing which type of amplifier was best, tube or transistor, but rather from a device standpoint. And with that in mind, my very offensive "blanket statement" that triodes are inherently more linear than transistors as devices still rings true. I'm sorry if that bothers anyone, but it's a matter of physics. And I can't change that. Neither can you.

Now which sounds better? Well, that's up to the listener. Each device and topology has advantages and disadvantages. We just do our best in each design given these certain limitations. In that respect, I can speak with a smidgen of authority as I have designed phonostages with triodes, opamps, and JFETs, in both balanced and single-ended configurations.

Having said that, the inherent linearity advantage of triodes merely allows a higher potential for sonics in an amplifier. Basically, they have a head start.

>>Tube problems my dear Raul are a consequence of bad design<<

I have to agree with both of you here. However, from a device and physics viewpoint, Raul stands on higher ground. Solid state electronics do indeed have a potential* reliability advantage.

(*This does not apply to missile defense radars or radio station transmitters).

jh