Tube amplifiers: distortion & coloration or transparency & realism?

There is a distinct kind of tactile handling of timbre that tube amps seem to do particularly well that solid state amps sometimes don't do as well, which maybe has to do with the distortion profile of tubes v. solid state, but I wonder, say if we're using ultralinear tube amps with solid state like distortion profiles for THD and IMD that are sufficiently powerful for the speakers they're being asked to drive, with speakers that present a relatively easy-to-drive load, how much the distortion is really responsible for the differences. Are we really driving those amps into audible levels of distortion regularly? Or is it something else that's responsible for any characteristic differences we hear? Single-ended triode amps and other sorts of tube amps might be much more characteristically tubey with higher levels of distortion present.

 

But the inherant differences still remain, and the god's in the detail as such?

Sounds sensbile, assuming their aiming for the same 'ideal', if such a thing exists?

I've heard so much difference and variation in just the few SS amps I've had or tried out (all else being equal) that it makes it even more interesting to think what else sits in the parallel world of tubes, especially as some people seem to sit so firmly in one camp or t'other...

 

I think it relates to how much negative feedback the designer uses in the circuit. Some tube amps allow you to select how much negative feedback you want.

 

Very compellingly put, thanks.

 

Yup. That's exactly how I felt the first time I directly compared solid state to tubes. I can't ever imagine going back and losing that realism- that illusion of the musicians in the room with me.

 

I didn’t know a tube from a doorknob, but I knew I could spend what a decent “rack system” cost, and hopefully get something that was better made and sounded better. I spent more than two years driving around to shops, and heard some better, more expensive systems. In my price, nearly every shop had a Marantz integrated with some Japanese disc spinner, usually Rotel, and some Advent speakers. That combo sounded pretty meh, nothing special. I drove over a city to a shop and listened to a tube hybrid (30 Watt) that used EL43s and SS mono on the bass frequencies. That and the Vandy 1Bs and a Rotel disc spinner were right around $2,000. I was immediately excited. Grabbed my wife and we drove over and put in The Mission soundtrack. She was squirting tears within 5 minutes, and I KNEW we had it figured out. Coming up on our 25th anniversary, and we have run that gear into the ground, but the hours spent together listening can not be valued.

 

There is no shame in using modern technology to avoid having to be a walking dictionary.

In the specific case of audio amplifiers, damping factor is the ratio of system impedance (the impedance the speaker is nominally rated for) to source impedance in the amplifier output/conductor/load loop.

http://en.wikipedia.org/wiki/Damping_factor

In this loop, a tube amplifier includes the secondary of its output transformer. In addition, on the primary side, the tube amplifier has a high voltage low current power supply to begin with. Tube amplifiers tend to be current limited and have high source impedance as a consequence.

It is important to have an intuitive understanding of voltage, current and resistance and also the resistive and reactive components of impedance. It takes no math beyond the eighth grade level to understand this. You do not need to be an electrical engineer. (It might be better not to now that the EE curriculum is being transformed more and more into a CAD workstation operator vo tech program!)

Solid state amplifiers having high current low voltage supplies and direct output to the load tend to have far lower source impedances and therefore higher damping factors.

When amplifiers are quoted for damping factor, this is taken at the output terminals. Working loop DF in a stereo installation is going to include the resistance and reactances of the speaker cables and that reduces practical damping factor a lot in most cases.

It's important to understand that when amplifiers are designed, particularly high current high end type solid state ones there is a certain inevitable external DF (read: cable resistance) assumed. That's why when in the eighties the really heavy cables were introduced-at prices now seeming reasonable-certain amps blew up. It's also important to know, if you are into vintage speakers that many of these were also designed to be driven by higher source impedance sources (read : old tube amps or 70/100 volt lines with local matching transformers) than are common now. The stock Klassic Klipsch line work a lot better when driven by modern big amps if a padding series or shunt (or both; a pad) resistor is used to bring the damping factor down on purpose. Their crossovers were deliberately designed for small low output amps and in fact the ONLY amplifier PWK ever endorsed was a specially modified Brook push pull triode unit-specially modified for lower damping factor in fact.

In the very late 50s there was a craze for "Variable Damping" and McIntosh and several others offered variable damping as a factory option.

Steve Lampen of Belden wrote several good articles on this topic but they do not appear to be available online at this time.

 

The vast majority of musicians I've hung out with, played at playing music with, and worked on their amps, guitars, stompboxes, etc. as well as the classical types I've met socially are basically not interested in home reproduction equipment-at all-beyond they can hear the record well enough to learn licks off it or get the general idea of how it's supposed to sound. Typical musician setup for years, the vinyl and early CD years was a Japanese direct drive table and a solid state receiver and Radio Shack speakers....or a boom box.....and now they use their computer's CD drive, iTunes or Winamp or whatever, and cheap active computer speakers. If they do home recording they have a Mac Mini or iMac and a pair of moderately priced active monitors from Guitar Center.

The exceptions certainly do exist but, on average they are even less interested in "serious" or "high end" audio than the average person in their economic stratum. It isn't they can't hear the difference in a really good system....it's that, being still not a really live experience, they just don't think the delta in results is worth the delta in effort and expense. (Music is calculus, they just don't know it, see?)

High end saloons have found this out over and over again when they sponsor acoustic jazz or classical or whatever kinds of music performances in their space. The true music lovers pack the joint, are appreciative and cool....but they don't buy a thing and if they do it's the cheapest pair of two way speakers in the place.

The exceptions are exceptional.....because the norm is different and a lot more common.

 

Tubes have a way of seducing the ear. I fell for the EL34 sound of a CJ MV55. Loved it for 5 years. But did notice the sound was not consistent over the years, the sound changed every time I retubed, sometimes by a lot. It was when I directly compared in my system better solid state gear to tubes that I became aware of the shortcomings in the treble and bass of the tube amp, which admitadly are easy to overlook, because the midrange timbre is just unbeatable. Class A solid state has a very nice midrange too, plus a less distorted treble and better bass. I could live with either but these days live with neither lol. I got out of the kitchen, as the saying goes.

 

Don't want to derail this too far off, but isn't there something special about the design of either the Mac 25's and/or 30's over the other higher watt Mac lineup that a lot of people really like in comparison?

 

Steve's giant solid state amp was possibly a Crown or similar
A PA powerhouse
These plus JBLs were used to' impress the client' rather than monitor the track imho
Musicians in studio may be playing at silly levels
The control rooms wanted more subtle rendering and transferability
Big soffits gave way to nearfields for monitoring/mixing

 

Any possibility the MC 275 needed servicing and had not been performing up to snuff?

FWIW - For every model McIntosh tube amplifier manufactured prior to 1972, each model has a group of individuals who champion it above all the others.

Whether MC 225, 240, 275; MC 30, 40, 60, 75 - any one of them is somebody's favorite.

 

I used be just like you guys. Just lately my tube world is being challenged and is crumbling. The best systems I have heard lately have all been solid state. AND one of them was a PWM amp. In a nutshell they are Kevin Gray's mastering room, On A Higher Note at THE Show 2014, MBL demo just yesterday at The Source AV in Torrence CA. I'm going through a paradigm shift!

Don't mind this turncoat continue on!

 

I'm a definite newcomer to valves (unabashed tube noob), but I'm hoping that by starting my journey with new Audio Note gear I'm avoiding some of the pitfalls that older, used tube amps could present to someone unfamiliar with kit that requires manual biasing, etc.

 

Manual biasing is simple, as long as you can read a multi meter, which is also simple.

 

Not to worry - at least as far as McIntosh is concerned.

Ie: From the MC 240 Owners Manual:

The excellent performance that is inherent
in all Mclntosh amplifiers does not
depend on the critical adjustment of bias or
balance controls in the output circuit. The
patented Mclntosh circuit delivers its advertised
specifications without any need for
these controls and is not dependent on carefully
balanced tubes for its performance.

 

I have heard some amazing SS gear, but they have all been mega-buck systems. TAD and MBL come to mind.

 

They all have identical signal circuits....except the 75/275 has an additional primary filar winding brought out to the driver and the 225, using high gain later output tubes does away with the cathode followers.

Schematics for all these are downloadable all over the net and I urge the skeptical reader to look for himself.

What differs is the power supply section and the output transformer and output tubes.

My favorite is the 40/240 although I would much rather be able to buy a new set of Mc 100 percent compatible and correct opt's and build one for myself. Maybe using EL34s.

There isn't a bad one in the bunch AFAIK. Any are good units that last a long time, are easy on tubes and sound like a high fidelity amp is supposed to sound, e.g., they are accurate. Mc never built a bad amp to be honest.

 

The 30s use tube rectifiers with definite current limiting and sag. Put one on a dummy load and run it up and watch the B+ drop if you can. The 225 uses a truncated driver circuit and high gain tubey tubes.

If you like tubey they are the best, but there are a lot more tubey amps than any Mac. I don't want tubey I want fidelity. If the musicians wanted the record to be tubey they would have tubied it up themselves. In the wrong place tubeyness can be repellent and nauseating.

That said you have to run a 30 or 225 pretty hard to be tubey and I would not kick either one out of bed if you know what I mean..........but given the choice I'd take a 240 or an ORIGINAL 275 over any other Mc's.

 

Well I appreciate both your and Steve's vote of confidence in the MC 240 which was the model I chose for my vintage system. (Steve's for the endorsement of 6L6GC)

I also think it's the prettiest of the MC 225/240/275 trio.

 

You are absolutely correct about the $$$$. The MBL system I heard was the cost of a house.