Horns + tube amps: can they handle LOUD like SS?


I was inspired by the SET thread currently running, but
wanted to take the thread in a different direction without
disrupting the original.

FYI, my history is all SS... but do I run 2 sets of high-
efficiency Klipsch speakers: La Scalas (104db, 8ohm) +
Forte II's (99db, 8ohm).

That said, I've read countless statements that SET/horns
are just the milk and honey. Sam Tellig for one raves
about small-wattage (any given day he probably mentions
something from 3.5 to 8 watts) SET amps and horns in
glorious harmony.

I haven't heard that combo myself - but I always notice
the caveat that even with high-efficiency speakers, there
is something missing about ability to play loud (there is
always the hedge that "subjective sound is louder"... ok,
sure... but what about the real, honest limits to the
power output?)

I've heard clipping from 100w SS amps into an easy 104db
8ohm load during heavy passages... (no, I'm still not
deaf) - this could be an effect of the particular impedance
curve of the speakers, but that's irrelevent - if 100w
of SS can't muscle it, how can a 3.5-8w SET amp?

Some of us (metalheads, not Patricia Barberheads), listen
to horns for their unmatchable ability to present a live
and engaging experience, with transient response that's
faster than a steel trap. Others love the lush, effortless
nature of the midrange and sweet highs when paired with
tubes... the later seem to be the majority.

I currently run a 200w MOSFET CJ amp into my Klipsch
La Scalas, and am more than happy... they can both sing
and bruise as called for. Can a SET/horn combo deliver
the same? Do other tube amp designs make more sense?
What about push/pull, pentode, etc...

How did Ritchie Blackmore, Leslie West, Tony Iommi
et al. rip the doors off in the 70's? Probably not
on SET guitar amps!

I've been eager to try some tubes with these horns, but
even with the efficiency, it's taking me more than 100w
of SS power to deliver the experience I want with the
proper control. What tube designs/philosophies can
go there?

Obviously, I am no tube pro. Any primer fodder that
you offer won't offend. I've seen a little, but not
enough.

Thanks for your thoughts!
mwilson
You might be interested to know that the amps used by those guitar rockers were more than likely tube amps like Fenders and Marshalls. Their power rating was probably not as high as you think. Most guitar players know that a 25 watt tube head will play louder and better than a 100 watt SS rig. Some people wonder how that can be. It just is. It is a similar case with home audio. It would not surprise me if a 50 to 75 watt tube amp would play louder than your 200 watt SS amp. Also, if and when distortion is reached, the tube amp produces even order distortion which is easier on the ear than the irritating odd order disortion off SS. So the clip is softened with tubes. However, you can't expect a 3 watt 2A3 amp to produce stadium level sound. If you want loud and clear, I would suggest a Berning ZH270 ZOTL tube amp. This design has 70 powerful watts of very clean, fast, and pure sound that will drive your Klipsch speakers to very loud levels and sound very clean while doing it. It is a push/pull amp, but a very good one with the speed, weight, and authority in the bass that one expects from big SS rigs, but the clarity and sweetness of OTL tube amps. Of course, if you can afford more money the Tenor 75 watt OTL's will also do a great job on the Klipsch. They will also play plenty loud and clean. The big AtmaSphere amps will do a great job as well. These are some of the finest amps made today. The little amps under 8 watts are made for a different purpose, which is to provide the ultimate purity of sound at a more reasonable SPL. Every thing has its trade offs. Nothing is perfect. You just have to do system matching with the gear that suits your listening tastes and budget.
Simple and clear:
Transistors have a very small region of linear operation in their output characteristics(Volt-Ampere characteristics)and have to operate at less-than-half of their rated output power.
Tubes have 90% of linear region and can be basically driven to almost clipping. Thus, the tube amp 50W/ch can easily overscream SS with 100W/ch since SS will "choke" much earlier.
I would HIGHLY recommend reading the "white papers" on the Sunfire amps to see how most SS designs operate. This will give you a better understanding of why they sound "grainy & gritty" when being pushed. Bob Carver puts it into words that are quite easy to understand. He also looks at things from a slightly different angle than most others, so it is both refreshing and eye opening ( in my opinion ).

As to the SS vs Tube power ratio, i would say that a good tube design of 30 - 50 wpc would be equivalent to a "typical" SS design of 100 wpc in terms of "clean music power". This has to do with the differences in transfer function between tubes and transistors and the ways that they "saturate" or "clip". SS clipping is much harsher sounding ( in most cases ) and is typically pretty easy to detect. Tubes can be driven into occasional clipping and you may never notice.

As to TWL's comments about guitar amps, the main reason that guitar players prefer tubes are for the very reasons that i just mentioned: clipping and saturation characteristics. I don't think that it has much to do with volume capacity at all. Tubes simply produce FAR more "pleasant" overdrive, harmonics and sustain characteristics than SS amps are capable of. Besides that, they just sound "richer" with added emphasis to the "warmth" region and don't sound as "screechy" on the top end. As such, many rock / metal guitar players actually prefer a smaller ( 50 watt ) head to a larger ( 100 watt ) tube head because it is easier to push into clipping and keep there. The fact that this chews the hell out of the tubes is of little concern to them so long as they can get that "chunky" sound that they are after.

For the record, i've got a set of La Scala's and Heresy's and have used them with several different BIG power amps many times over. I am currently running them with a "vintage" 30 wpc tube amp and it sounds very nice. While it will not "deafen" you with slam and impact by any means, they do mate quite nicely together.

If you've read some of my posts pertaining to spl and power levels, you will know that I am of the opinion that increased headroom in a system ( both speakers and amp ) are a big benefit. So, if you want to rock and use tubes, look for something that is a little stouter than what i have. This will give you the reserve capacity that i mention without having to push the amp or tubes to get the volume levels that you want.

I would look for a 70-100 wpc tube amp. That should give you everything that you are looking for i.e. volume and reliability. A smaller amp is just not suitable for "headbanging levels" in my experience. Others may disagree, but that's what i've found to work.

By the way, Patricia Barber and Diana Krall sound quite good on this type of system. You may find that the better your system is, the more versatile it becomes and your tastes may begin to broaden slightly. In case you're wondering, i'm speaking from experience : ) Sean
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