A tubes vs. Solid State question.

When driven too hard tube amps do not clip much to the ear, but are out of steam, well done solid state which in my opinion will always use Bi-polar or Jfet type transistors can do this just about as well, and still have Slam factor to wake the dead keeping characteristics of non-fatiging music and highs, of course backed by digital or analog capable of this in the first place. Mosfet has never seemed to work for this in my experiance so I stay away, whoever said that mosfet is more tubelike is wrong in my opinion, however Mosfet used in a Hybrid amplifier design with the inputs rounded off by tubes in the first place can work well. So for me Hybrid systems are the best, Via Tube Preamp, with excellent solid state amps, or using a hybrid Amp or Intergrated could have similar results. Tube amps in the end for me are too much hassel, too costly, to much to re-tube, and too much heat for things that in fact can be very closley matched with tube solid state combo's that will get you 99% of the way there with reliability on top of that.

Matrix, do you think that Mosfets are compromising Pass designs?

I have had a couple thresholds, Not all are as bad, but honestly I think the Thresholds I had were Bi-polar or Fet, or IGBT type anyway, no mosfet... the newer ones I am not sure, I did have a CODA which is also by developers of original thresholds it was excellent, Coda to this day uses a FET input with bipolar out, and yes I think they are for the world of expense in the mark levinson, pass labs the better of them. but have not heard all of it, I have heard some Krell which I don't know what they use and really don't want to know to be honest, they never impressed me for the money especially.

Now that being said, call boulder, Dartzeel and the likes of these guys, they are in fact some of the highest praised and closest sounding to tube and pure musical solid state devices on the planet, guess what all exclusivly use Bi-polar devices, they state way better sound, smoother responce, and much higher reliability than any mosfet can provide. I have always heard the difference and reality is many of the newer mosfets of Rotel, or whoever are normally in cheaper amps, and another fact that most hiend manufactures will verify if you call them is many have even moved away from mosfet based designs and gone to bi-polar the older and more musical stable technology, what does it mean, Nothing accept what your ear hears, back to the pass designs I don't know the answer, but I think he just went back to his low power hi quality amps again called "first Watt" and this is an un-altered Quote right from his own page, remember designers sometimes build with the current fad, and Mosfet was a 90's fad to some extent, so I guess to answer your question Pass found his own design comprimised.

"from first Watt, mr. Pass, heres the link and quote...
http://www.firstwatt.com/products/f3.htm

First off, for comparable devices at a given bias current, we see that the power JFET has much less distortion. The original F3 circuit was designed with a MOSFET, and comparing “apples to apples”, the power JFET operated with one-fifth the distortion of the MOSFET.

That’s only the beginning. The JFET has much less distortion operated as if it were a MOSFET, but it’s not a MOSFET, and it has characteristics which allow for even better performance.

When we look at the anode (or tube plate) voltage curves for devices we see what I would call the “triode character” and the “pentode character”.

In recent years, advances have been made in vertical JFET design which makes them more competitive in switching applications, and as a result power JFETs have been re-introduced after a thirty-year absence. Earlier this year I published the “Zen Variations #8 – the Power JFET Amplifier” and now First Watt is introducing the model F3, at this time the world’s only commercially available amplifier using power JFETs.

And to the best possible solid state on the planet for less than a pair of Krell mono's or whatever , it aint cheap though is the Dartzeel, heres a quote and link as well...

"darTZeel chose bipolar transistors -- ultra linear and fast -- for a straightforward signal path:"

http://www.6moons.com/audioreviews/dartzeel/108.html

Here is the un-varnished truth: At the very high-end of audio, a vacuum tube, properly implemented, is an inherently superior and more natural sounding amplification device than a transistor (for many of the reasons already stated and more).

Unfortunately there are enough highly colored, high distortion, poor quality tube designs to make any blanket statements about "tube amplifier" superiority meaningful. It is the tube itself that can be described as having more potential than a semi-conductor.

Most of the people who fight the good fight for solid-state are correct in noticing how good the sound of some transistor circuits have gotten. They really are very good. But when cost, maintenance, heat, size, and anything other than sound quality are not factors, the best yet achieved has still been through a vacuum tube.

Some in the solid state camp have never experienced the sound of a state-of-the-art modern tube amplifier or system. Some just aren't as picky about sound or just don't hear subtlety very well. Others are swayed by things other than their ears (watts per channel ratings, THD ratings, etc...).

Very few if any in the vacuum tube camp are guilty of not having spent time with comparable transistor amplifiers or being swayed by anything other than what their ears tell them.