::cracks knuckles, looks around::
Okay, where are we? Good stuff, but not nearly enough geekery in this thread yet! tdn, based on your comments in the Strat thread, it sounds like you can only process so much geekery, so I will try to keep it manageable. As **Crotalus **knows from our back-channel correspondance, I have delved into the arcane world of amps a bit so feel pretty comfortable here. To be clear: I don’t know electronics at all - I can barely make sense of the “electricity is like water” analogies that engineer types invoke to 'splain it. So do NOT be suprised if I blow the underlying Faraday aspects of this stuff - I remain pretty comfortable with the musical take-aways from this…
So - how are tubes and transistors different with regards to a guitar amp?
First, start with the basics: Tubes and Transistors function as valves in an electric circuit - which strangely enough is why Brits call tubes “valves.” Anyway, so within the standard performance spectrum of the device, either component is capable of shunting the juice into the right part of the circuit. So, from that standpoint, your dad is correct - either type can perform up to spec in a circuit.
But your dad probably didn’t play guitar
The biggest issues - the things that make tubes different from transistors - are **efficiency **and threshold.
**Efficiency **- So, yeah, in a perfect world, a valve simply channels stuff one way or another, right? Well, the world isn’t perfect, and each valve type has its own effect on the signal passing through. Here’s the difference: transistors are more efficient. Again, I am not Bill Nye the Science Guy, but old-school tubes are apparently less efficient, both in the % of the signal they pass through and the specific frequency spectrum that they tend to damp as the signal passes through. What’s key is that to human ears, a tube’s inefficiency sounds good. Transistors pass more of the signal and don’t selectively dampen the same parts of the signal that tubes do, so they can sound strident and harsh. When the first Solid State amps came out in the 70’s people just cringed because they sounded so ice-picky and harsh. I remember the various generations of transistors they came up with - FETs! MOSFET’s! HexFETs! (I have no idea what these are; I just remember the names from the amp ads in my old issues of Guitar Player) - all of which attempt to mimic the natural inefficiencies baked into tubes.
**Threshold **- anyone can tell you what happens when a circuit is performing within spec - ah, but what matters is what happens when the circuit is driven out of spec - what happens when the threshold is crossed for how much signal the circuit can process? A tube amp circuit (made up of a pre-amp stage to shape the tone and a power amp stage to amplify that signal to produce bigger volumes) when pushed past its standard threshold, collapses. To my knowledge, that is the electronics term but it is used in amp speak, too - a power amp stage sags, then *collapses *when you drive it.
(important aside) - why does a tube amp circuit collapse - is it supposed to? It wasn’t originally. Because tubes are so freakin’ inefficient, you have to build a circuit with a ton of “clean headroom” - so with a high-end home stereo power amp that is rated at, say, 10 watts a channel? Well, you probably are running tubes with a maximum rating of 100 watts or more - yep, you only tap into a small percentage of the capacity because with a stereo, you want LITTLE TO NO distortion to the signal at all and so never want to tempt the tubes into their redline stage. But with the earliest amps - Fenders included - they build these little suckers with 6v6 tubes rated at a few watts each - and you can bet those old first-time amp users quickly realized that the clean headroom on the amp was only available up to about 5 or so on the Volume dial. Sure, you could push for 11 like Nigel Tufnel in Spinal Tap, but the tube started distorting. So - think about it: back in the day, clean-playing country and swing pickers (Fender’s first customers) groused about how their guitar tone would break up if they dialed the volume much past 5 - so Leo Fender had to keep building bigger and bigger amps to provide more clean headroom.
Ah - but blues players and, soon, rock players - LOVED the pushed sound. Blues players wanted the fuzz to give their simple chords complexity and rock players were trying to sound like the horn section of a jump blues combo anyway (Chuck Berry riffs are direct rip-offs - in a brilliant way - of Louis Jordan’s horn arrangements) and the pushed sound helped make a guitar sound like a horn (another aside: the first fuzzboxes were advertised as a way to make your guitar sound like a solo horn). So - you know those same little 6V6 tubes that couldn’t provide much clean headroom? Well, when you push them, they are LOUD - so a tube amp rated at 18watts like an old Fender Tweed Deluxe (one of my main amps of choice) can just blast over drums and be fine for a club - if you like a thick, distorted signal.
Anyway, when both the pre-amp stage and power amp stage collapse, they kinda “retreat to a fallback position.” They don’t even try to pass the full signal through anymore; they only allow a portion of the signal to get through and the rest is simply lost. BUT - the stuff that passes through is the good stuff! This is called “squaring the sine wave” I believe, or “clipping” - the inefficient, collapsed circuit “clips” the signal in a predictable way. Since a bunch of stuff is clipped, the stuff that remains is emphasized and it turns out that the stuff left over includes the simpler, even-ordered harmonics (I think that is right - I never remember) that sit just-so on top of the main note. So when you combine notes into chords, you only have to worry about whether those main harmonics work well together - when you have all of those higher-order harmonics in a full signal, it is much harder for the notes to sound good together in chords - the harmonics of the individual notes are more likely to clash. Am I doin’ okay here - does this make sense?
So with a transistor - well, for the first ones, dude, if you exceeded the threshold, the circuit didn’t collapse - it shut down. A transistor amp rated at 18watts delivered 18. exact. watts. and. nothing. more (aside: I have had amp techs tell me that an 18 watt tube amp is as loud or louder than a 30 or 40 watt SS amp; I believe it). And the ensuing decades have seen ever-more-innovative engineers figure out ways to get transistors and now full digital circuits to model the organic collapse of tubes.
But here’s the deal - as with artificial intelligence, humans can get digital computers to do somethings well, even better, than the natural counterpart, but seem to be a ways away from 100% mimicry. And while an amp is far simpler than an artifical intelligence, I think the analogy holds - there are subtle things that an SS/Digital amp can’t do yet that make the difference between SS and tube amps. But, these days, with all the innovation, it is not about the “base tone” - meaning, I can argue 'till I am blue in the face that “a tube amp sounds better” but if you just set up two rigs side by side and dial up similar tones and play straightforward chords and riffs, 99.9% of listeners won’t be able to tell the difference or care. That is why it is easy to say you can find solid examples of either circuit type - because you can and they can sound great.
What matters is what happens when, no surprise, you are pushing them. With a tube amp, what you do is dial up “the sweet spot” - that legendary, mojo-like term that everyone tosses around but n00b’s react to like you are naming some arcane sex act - they just kinda nod and hope no one notices that they have no clue. The sweet spot is simply - it is the spot where you dial up the Volume (the other controls have an effect, too, but it is the Volume at the core of it) where the signal is just breaking up. BFDR’s (Fender Deluxe Reverbs from the 60’s and early 70’s with a Black Face panel for the controls) are legendarily known to have their sweet spot at 6 - 7 on the dial - you can find amps where the dial is frozen in place because it has never been moved ;)). Anyway, when you have it right there - well, when you spank down hard on a chord you get full, raging distortion, but when you play with a delicate touch, either picky stuff or light strumming, your sound cleans up (and if you roll down the Volume on board your guitar, it cleans up even more). The point is that you are sitting right on top of your amp’s tube’s threshold and your picking dynamics - playing softly or loudly - determines how much clipping you are forcing the tubes to do.
This is an incredibly powerful, subtle thing. If you are a reasonably-experienced player, this is HUGE, difference-making tool in how you approach your instrument. I will use an analogy I have invoked in the past: SS amps are kinda like Big Bertha drivers and Ping Irons - they represent the latest technology and can help okay players really play great. But the pro’s - even if they use those models - have hand-edged irons and other modifications that render the clubs far more responsive and unforgiving - the pro knows how to work with those subtleties and use their swing technique, etc. to impart spin on the ball in ways that the big high-tech clubs can’t accomplish.
So - will your audience pick out the difference? Nah - if an amateur and Tiger Woods both hit the ball 300 yards, can they tell that the amateur took a big swing with a big club whereas Tiger finessed it? But as a player, the touch responsive feedback loop you get with a tube amp is simply unsurpassed - but only if you are playing a style that requires a lot of subtle technique to your playing. When I am playing a song where I have a low-end string droning and I am using my fingers of my picking hand to get a melodic lick happening, the fact that I can grab the strings with my fingers and kinda pluck them just sounds great - they push the tubes and the snap of the notes just vaults them out in front of the dominating bassier notes - so the responsiveness of the amp enables me to better balance out the sounds and ensure the different notes/frequencies I want heard stand out…
Okay - I gotta get back to work. Does that help?