"Warning! Long Wild Bill techie post!"
Coustfan'01 said:
Contrary to what a lot of people will say , solid state is not necesserely bad . I love my vetta 2 , and I've never seen a more versatile amp...It's as expensive as almost any tube amp though .
And about wattage , like the other guy said , it's because the amps are rated in watt at a certain (low) thd . Past that , either the ss amp has all controls at 10 ( crates are rated that way ) or either it will clip ( which sounds really bad ) , while a tube amp will start having a hearable power amp distortion , which is pleasing to the ear . So you may have a 100 watts clean or almost clean , and 150-175 watt with a lot of distortion , while on a ss amp you have 100 watt on distortion , and equal or less clean .
There is a phenomenon called "psychoacoustics", referring to how due to the peculiarities of the human ear we perceive sound in a different manner than one would expect from common sense.
To us a sound needs to be 4 times louder to be perceived as twice as loud. This means 1 watt, 4 watts, 16, 64 and so on. This is why a 5 watt Champ into a 4-12 cab sounds pretty loud. It's not as many steps as you'd think below a 50 watt Plexi! Audio volume controls are tapered inside to change NOT at a 1,2,3 linear rate like with a motor speed control but rather at the 1,4,16 rate to match the human ear. This is called a "log" for logarithmic or more commonly an "audio" taper.
Amp voicing is also a psychoacoustic property. Bright amps sound louder for the same watts. That's why a VOX AC 30 at 30 watts will often cut through and over a 50 watt Bassman. It's why many amps have "bright" switches to leak more highs into the signal at lower volume settings. Our ears need more treble power at lower volumes to sound the same as at high volumes.
Our ears do indeed need much more power from a solid state amp to sound the same as an equivalent tube unit. As has been already said, we usually measure amp power before clipping. Solid state devices tend to stay clean until they are maxed out and then break into a harsh distortion. Tube amps have a long ramp on the distortion curve, where they just start to get warmer and "thicker". There's a long way past clipping before the distortion gets to be too much for most tastes.
Because of this the rule of thumb over the years for power difference between a tube and a solid state amp is actually 2-3 times! Remember, we're not talking about techie measurement differences here but rather the perception of our ears. So a 50 watt tube Plexi will honk nicely over a 100 watt ValveState. You'd need the 200 watt model to be sure of sounding louder and maybe not even then, depending on how bright a tone you dialed in.
You can google up a lot of techie papers on psychoacoustics that explain this better than I have but suffice to say, it's true! Techs first began to understand the differences between tubes and transistors when transistor mixing boards first started appearing in studios. The engineers immediately found they had to pad the hell outta the inputs when miking a source with high peaks and dynamics, like a singer who belts it out or a snappy snare drum. What was happening was that although transistors do a better and cheaper job with clean signals when you drive them hard they stay clean until they "lose it" and snap into harsh sounding clipping. The transistor inputs just couldn't handle the same peaks coming in as when using tubes.
This is why so many artists prefer tube studios and pay big bucks on Ebay for old tube Altec studio gear. It's not really that the tubes stay clean but that transistors would give a touch of harsh clipping on those peaks where the tubes masked the clipping. The clipping might still be there but the tube didn't hard clip but rather compressed and rounded off the "peak" so that the note sounded "warmer" instead of harsh. For years no one had really noticed or complained about this soft and warm clipping but with transistors the clipping was more painfully obvious.
You don't need a completely tube studio to appreciate the warmth of tube recording. All of these clipping differences occur in the 1st amplifying stage. A good tube preamp is all you need. Once the signal is amplified up to line levels in the board it doesn't matter if it's tube, IC or transistor.
Psychoacoustics is a classic case of where usually engineers just don't get what musicians are telling them. Engineers are schooled to think that a good amplifier is supposed to be as clean and "hifi" as possible. They jumped on transistors for audio like a fat lady on a doughnut!
Yet the first transistor amps tended to go over like a lead balloon, except for bass guitar units. The reason was that unlike with bass guitar where you usually want an amp to be loud, clean and "snappy" a lead guitar amp is SUPPOSED to be distorted! Who the heck wants a hifi guitar amp? When the musicians complained the amp was too clean the engineers thought the solution was to add "fuzz", which of course was even more horrible.
The kind of distortion was the most important factor. Marshal spent years trying to get transistor circuits to sound like a tube amp. Yet today if you pick up a guitar player mag and do some counting you'll find of all the amps in the ads 75% at least will be tube amps and the rest will claim they sound like a tube amp!
I'm not saying it's impossible to make transistors sound like tubes but it still seems to require so much more complicated circuitry that you might wonder why anyone bothers. The reason is simple: MONEY!
It's much cheaper to make transistor amps! Of course, the savings were never to be passed on to the player in the retail price. The money seemed to stay in the manufacturer's pocket! Nowadays the price of electronic components suitable for tube circuits has escalated a lot due to much smaller production volumes than mainstream electronic parts. This pumps up the price of a tube amp. Still, players don't seem to care. Who wants a cheaper amp if it sounds like "ass"?
