Dispelling Tube Amp Myths

[Em7]

Guys, I have tried to distill this information down to something the technically minded guitarist can understand. However, one may have to read through the post a couple of times.

There is a lot myth surrounding tube amps. That is mainly because myth is easier for the layman to understand than science. One of the main myths is tube watts are louder than solid-state watts. That is complete nonsense, a watt is a watt. A watt is equivalent to one joule of energy per second. There are couple of reasons for this myth. A big reason is that solid-state amp designers were not always honest about power ratings, preferring to state power in peak power terms instead of RMS power, which led to inflated power ratings.

That being said, the reason why tube amp often sounds louder than solid-state amps of the same RMS rating is because tube amps are poorly damped. Damping is the ratio between speaker impedance and amplifier output impedance. Damping factor determines how well the power stage of an amp can control speaker cone movement. Power tubes have high output impedances. In order to drive a speaker, they require an output transformer that steps the power tube output impedance down to the speaker nominal impedance. In the process, the output transformer converts a high voltage, low current signal to a lower voltage, higher current signal. It also increases that amp's damping factor somewhat. For example, A Fender Vibrolux has an output transformer with a primary impedance of 4,000 (4K) ohms with secondary impedance of 4 ohms. However, an output transformer knows nothing about impedances. It works using impedance ratios, that is, if we plug an 8-ohm speaker into the 4-ohm jack, the power tubes will see primary impedance of 8,000 ohms instead of 4,000 ohms because any change in the load attached to the output transformer's secondary winding (a.k.a. the wind that is attached to the speaker jack) is reflected back to the power tubes. This change is due the fact that output transformers actually have impedance ratios, not fixed impedances. The impedance ratio is the ratio between the primary and secondary impedances. In this case, the impedance ratio is 4000 / 4 = 1000. The impedance ratio is the square of the ratio between the number of turns of wire in the primary and the secondary windings, which is SQRT(1000) ~= 32, where SQRT is the square-root function. What that means in layman’s terms is that there is one turn of wire in the secondary winding for every thirty-two turns in the primary winding.


Now, lets get to the meat of why tubes amp tend to sound lively and whereas solid-state designs often sound flat. That is because impedance is not a synonym for DC resistance. Impedance is an AC measurement that contains reactive components; namely, inductive reactance and capacitive reactance. The formula for computing impedance is:

Z = SQRT(R^2 + (Xl – Xc)^2), where SQRT is the square-root formula, R = DC resistance, Xl = inductive reactance, and Xc = capacitive reactance.

Xl = 2 * 3.14 * f * L, where f = frequency, L = inductance henries

Xc = 1 / (2 * 3.14 * f * C), where f = frequency, C = capacitance in farads

The important takeaway here is that both Xl and Xc change with respect to frequency, which means that impedances changes with respect to frequency. DC resistance does not change with respect to frequency, which is why impedance is not a synonym for DC resistance.

Anyone who has ever measured the DC resistance of a speaker knows that is usually not equal to a speaker’s rated impedance. That is because a speaker’s impedance rating is based on the average of its lowest impedance values. An ohm meter uses DC current for measurement, which is zero hertz; therefore, we are measuring the resistance of speaker with the equivalent a zero hertz signal.

Now, the we know that impedance changes with respect to frequency and an output transformer is merely a set of impedance ratios in which the primary impedance is based on the impedance of the load, we can move on to why tube amps tend to sound more lively and louder than most solid-state designs. That is because the output of a tube amp is a constant current source and voltage (E) equals current (I) times resistance (R). However, in our case, impedance (Z) is substituted for resistance. Now, we are in a position to understand why a tube amp often sounds more lively and louder than the average solid-state amp. The impedance of a speaker generally increases with respect to frequency, which causes the voltage applied to the speaker to increase with frequency because voltage equals current times impedance. This change causes an increase in power to be delivered to the load because the current remains constant and power in watts (w) is equal to voltage times current. This effect is unwanted in hi-fi because hi-fi seeks to have even frequency response. Poor damping is the reason why all but the most expensive tube audio power amps have less detail than the average solid-state power amp. In essence, poor damping is a technological foible that guitarists exploited to their advantage.

Most of the second generation of solid-state music amp designs are highly damped because the amplifier’s output impedance is lower than the speaker impedance. High damping factor allows these amps to have much tighter control over speaker cone movement, which is why bass guitarists embraced solid-state amps. A bass is tuned an octave lower than a guitar and low notes require much larger cone movement than high notes, so a high damping factor is boon to bass guitar. Second generation solid-state amps also operate as constant voltage sources instead of constant current sources. That is why power delivered to the load increases when output impedance decreases. If we hold voltage steady and half the impedance of the load we double the amount of current that is flowing through the load because current (I) is equal to voltage (E) divided by impedance (Z). This way of reacting to speaker load is the exact opposite of what happens in a tube amp, meaning that the current delivered to the load decreases with respect to frequency because impedance increases with respect to frequency. If current delivered to the load decreases, power delivered to the load decreases, which results in higher notes not popping like they do with a tube amp.

Now, there is a way to reduce damping factor and make a solid-state power stage behave much like a tube output stage. That is done by changing the topology such that the speaker forms part of the resistive divider that is the feedback loop. The resistance used to ground, Rg, of the resistive divider used for the feedback loop is less than the nominal impedance of the speaker, which functions as Rf. The feedback loop determines the gain of the output stage. The formula for gain equals Rf divided by Rg plus 1. If Rf goes up, the gain of the circuit goes up; hence, it causes power to increase with increases in load impedance much like a tube amp. Marshall first used this topology with their ValveState amps. The tube in the preamp is about as much for show as it is for sound.

 

[John F]

Insteresting phenomenon, great explanation. For some reason, every modeling solid state amp I try sounds buzzy to me and fake. I never get clean tones like from a stereo or radio, whether adjusted like a clean amp or distorted. They don’t seem as articulate as a tube, and feel over compressed. I have not tried an expensive model like a kemper or fractal, maybe I need to.

 

[11top]

Guys, I have tried to distill this information down to something the technically minded guitarist can understand. However, one may have to read through the post a couple of times.

There is a lot myth surrounding tube amps. That is mainly because myth is easier for the layman to understand than science. One of the main myths is tube watts are louder than solid-state watts. That is complete nonsense, a watt is a watt. A watt is equivalent to one joule of energy per second. There are couple of reasons for this myth. A big reason is that solid-state amp designers were not always honest about power ratings, preferring to state power in peak power terms instead of RMS power, which led to inflated power ratings.

That being said, the reason why tube amp often sounds louder than solid-state amps of the same RMS rating is because tube amps are poorly damped. Damping is the ratio between speaker impedance and amplifier output impedance. Damping factor determines how well the power stage of an amp can control speaker cone movement. Power tubes have high output impedances. In order to drive a speaker, they require an output transformer that steps the power tube output impedance down to the speaker nominal impedance. In the process, the output transformer converts a high voltage, low current signal to a lower voltage, higher current signal. It also increases that amp's damping factor somewhat. For example, A Fender Vibrolux has an output transformer with a primary impedance of 4,000 (4K) ohms with secondary impedance of 4 ohms. However, an output transformer knows nothing about impedances. It works using impedance ratios, that is, if we plug an 8-ohm speaker into the 4-ohm jack, the power tubes will see primary impedance of 8,000 ohms instead of 4,000 ohms because any change in the load attached to the output transformer's secondary winding (a.k.a. the wind that is attached to the speaker jack) is reflected back to the power tubes. This change is due the fact that output transformers actually have impedance ratios, not fixed impedances. The impedance ratio is the ratio between the primary and secondary impedances. In this case, the impedance ratio is 4000 / 4 = 1000. The impedance ratio is the square of the ratio between the number of turns of wire in the primary and the secondary windings, which is SQRT(1000) ~= 32, where SQRT is the square-root function. What that means in layman’s terms is that there is one turn of wire in the secondary winding for every thirty-two turns in the primary winding.


Now, lets get to the meat of why tubes amp tend to sound lively and whereas solid-state designs often sound flat. That is because impedance is not a synonym for DC resistance. Impedance is an AC measurement that contains reactive components; namely, inductive reactance and capacitive reactance. The formula for computing impedance is:

Z = SQRT(R^2 + (Xl – Xc)^2), where SQRT is the square-root formula, R = DC resistance, Xl = inductive reactance, and Xc = capacitive reactance.

Xl = 2 * 3.14 * f * L, where f = frequency, L = inductance henries

Xc = 1 / (2 * 3.14 * f * C), where f = frequency, C = capacitance in farads

The important takeaway here is that both Xl and Xc change with respect to frequency, which means that impedances changes with respect to frequency. DC resistance does not change with respect to frequency, which is why impedance is not a synonym for DC resistance.

Anyone who has ever measured the DC resistance of a speaker knows that is usually not equal to a speaker’s rated impedance. That is because a speaker’s impedance rating is based on the average of its lowest impedance values. An ohm meter uses DC current for measurement, which is zero hertz; therefore, we are measuring the resistance of speaker with the equivalent a zero hertz signal.

Now, the we know that impedance changes with respect to frequency and an output transformer is merely a set of impedance ratios in which the primary impedance is based on the impedance of the load, we can move on to why tube amps tend to sound more lively and louder than most solid-state designs. That is because the output of a tube amp is a constant current source and voltage (E) equals current (I) times resistance (R). However, in our case, impedance (Z) is substituted for resistance. Now, we are in a position to understand why a tube amp often sounds more lively and louder than the average solid-state amp. The impedance of a speaker generally increases with respect to frequency, which causes the voltage applied to the speaker to increase with frequency because voltage equals current times impedance. This change causes an increase in power to be delivered to the load because the current remains constant and power in watts (w) is equal to voltage times current. This effect is unwanted in hi-fi because hi-fi seeks to have even frequency response. Poor damping is the reason why all but the most expensive tube audio power amps have less detail than the average solid-state power amp. In essence, poor damping is a technological foible that guitarists exploited to their advantage.

Most of the second generation of solid-state music amp designs are highly damped because the amplifier’s output impedance is lower than the speaker impedance. High damping factor allows these amps to have much tighter control over speaker cone movement, which is why bass guitarists embraced solid-state amps. A bass is tuned an octave lower than a guitar and low notes require much larger cone movement than high notes, so a high damping factor is boon to bass guitar. Second generation solid-state amps also operate as constant voltage sources instead of constant current sources. That is why power delivered to the load increases when output impedance decreases. If we hold voltage steady and half the impedance of the load we double the amount of current that is flowing through the load because current (I) is equal to voltage (E) divided by impedance (Z). This way of reacting to speaker load is the exact opposite of what happens in a tube amp, meaning that the current delivered to the load decreases with respect to frequency because impedance increases with respect to frequency. If current delivered to the load decreases, power delivered to the load decreases, which results in higher notes not popping like they do with a tube amp.

Now, there is a way to reduce damping factor and make a solid-state power stage behave much like a tube output stage. That is done by changing the topology such that the speaker forms part of the resistive divider that is the feedback loop. The resistance used to ground, Rg, of the resistive divider used for the feedback loop is less than the nominal impedance of the speaker, which functions as Rf. The feedback loop determines the gain of the output stage. The formula for gain equals Rf divided by Rg plus 1. If Rf goes up, the gain of the circuit goes up; hence, it causes power to increase with increases in load impedance much like a tube amp. Marshall first used this topology with their ValveState amps. The tube in the preamp is about as much for show as it is for sound.

I gave that a “like“ even though I have no idea what it means. It sure seemed impressive though.

 

[DreamTheaterRules]

There is a lot myth surrounding tube amps. That is mainly because myth is easier for the layman to understand than science.

I have a question for you. Have you ever plugged any electric guitar into any pretty decent hi-fi stereo system? If you ever have, what did you think of the tone?

 

[veinbuster]

I have a question for you. Have you ever plugged any electric guitar into any pretty decent hi-fi stereo system? If you ever have, what did you think of the tone?

I'm interested in Em7's thoughts, but in the meantime:
I played through a hi-fi stereo from a run of shows, feeding the same signal into both channels. I thought it sounded pretty good, squeaky clean, but that was right for what we were playing.

 

[DreamTheaterRules]

I'm interested in Em7's thoughts, but in the meantime:
I played through a hi-fi stereo from a run of shows, feeding the same signal into both channels. I thought it sounded pretty good, squeaky clean, but that was right for what we were playing.

So am I. My point is way to long to try to write out during work. I tried multiple times, with good stereo systems (Musical Concepts modified Hafler pre-amp and amp, modified Adcom pre-amp and amp), and it was extremely sterile. Without some verb or chorus or something, it didn't really sound good. TOO clean. (And very stiff). The point being, the "flaws" in many tube amp designs are there not because the designer didn't "know better" but because they sound better, feel better, or both. The things you design into an amp to make it better as a high fidelity reproducer of sound, are many time counter productive for use as a guitar amp. The undersized power sections of a Fender Champ for example, are a big part of why people who dig them, dig them. I dropped a 15 watt OT and bigger caps in one of my Valve Jr's and it completely changed it from the vibey, sagging, singing amp, to a much tighter, much clearer and cleaner, much punchier and louder (more headroom) amp. For the Marshall type tones I was going after, it worked well, but many guys who want the Champ vibe wouldn't have liked it at all. Totally changed it. That doesn't mean the champ is designed incorrectly, or just to be made cheaply. It's that way on purpose.

 

[Em7]

I have a question for you. Have you ever plugged any electric guitar into any pretty decent hi-fi stereo system? If you ever have, what did you think of the tone?

That is not because a hi-fi is solid-state. It is because a guitar amp has limited bandwidth. A guitar amp will not do remotely close to 20 hertz to 20K hertz like a good stereo. The bandwidth of a guitar amp limited heavily by guitar speakers, which have limited frequency response. With a tube amp, the output transformers also acts like a bandpass filter in that it limits high and low frequencies. That is mostly because the output transformers that have been used in tube amps have undersized cores. If one plugs a Hiwatt into a full range speaker and then plugs a guitar into it, one will see what I mean. The Partridge output transformers used in old Hiwatts are as close to hi-fi quality as one is going to find in guitar amp.

Another important take away is the pass band of the average tube guitar amp output transformer narrows as the amp is pushed into clipping. That is because most guitar amp transformers are so undersized that bandwidth automatically constricts as one attempts to push more power through them. If one halves the bandwidth, one doubles an output transformer's power rating. Here is another technological foible that guitarists have exploited to their advantage. The narrowing of the pass band filters out higher-order harmonics that are produced during clipping. The top and bottom of a clipped signal are composed of the sum of the fundamental note(s) and the harmonics. In essence, a guitar output transformer acts like a variable high and low pass filter (a.k.a. a variable passband filter) that filters out subharmonics and harsh higher-order harmonics. For example, the magic in the Cinemag transformer is that it has horrible upper frequency response. The transformer basically attenuates, if not outright throws away a lot of higher frequency content. That is why the PRS amps that employ it have a warm, fat overdriven tone. Marshall really cheaped out on the transformers that were installed in the amps that were built when they built Duane Allman's 50W bass head (the amp that was used to blueprint the Cinemag output transformer). I guess that they figured that the amp would be used for bass, so the transformer did not need good upper frequency response.

Finally, people should not conflate digital modeling with analog solid-state. They are completely different animals. Digital models are discrete approximations of continuous systems. Analog solid-state, by its nature, is continuous. What this difference means in layman's terms is that digital models have finite resolution. If one were to plot the the output of a digital model, it would look like a staircase that goes up and down. Noise is superimposed on the stair-stepped signal to smooth it out and make it appear continuous. With analog solid-state, the output is continuous with an infinite number of subdivisions. No smoothing noise is necessary. Another problem with modeling is that it is very difficult to model the entire system accurately because we are dealing nonlinear systems. Tube amps are operating the tubes in their nonlinear regions when they are driven. It is very difficult to model nonlinear systems. In simple terms, the change in output of a nonlinear system is not proportional to the input. I can assure everyone that none of the early guitar amp designers were expecting guitarists to operate their amps with tube operating in their nonlinear regions. They were just try to make a device that would take a small signal and make it proportionally bigger. Leo and company did everything in their power to prevent their tube amps from being pushed into the nonlinear region. They were limited by cost. The scoop in the blackface tonestack is a prime example of an attempt to prevent the amp from going nonlinear. That stack scoops out a lot of a guitar's voice.

I do not know how many people here have backgrounds in computer science, but my undergraduate in concentration in computer science is known as computer engineering today (a.k.a. it was focused on digital logic design, computer organization, computer architecture, microcode, firmware, and operating system design as well as data communications in addition to standard engineering and math courses). What most people do not realize is that computers cannot represent every number due in large part to limited precision, but more importantly because some decimal numbers cannot be represented as binary fractions. For example, the decimal fraction 1/10th cannot be represented as binary fraction because it cannot be represented in a fixed number of bits. A lot of magic occurs in floating point units and floating point math packages to handle these kinds of numerical errors, which means that a discrete approximation like a digital model will never reproduce a continuous system with 100% accuracy.

 

[DreamTheaterRules]

That is not because a hi-fi is solid-state.

Didn't mean that it was. Tried this through Conrad-Johnson system as well.

 

[Em7]

It still the same thing. The passband on a hi-fi system, tube or solid-state, displays a guitar's true voice with no filtering. You may want to try this experiment the next time you build a guitar. Instead of using a guitar output transformer, use a hi-fi output transformer that is rated for hi-fi usage at the guitar amp rated wattage. The transformer should be at least double the size if not greater than double the size of the guitar output transformer. It will also be made with a lot better steel. You can also try the experiment with one of you existing builds if you do not mind drilling new holes. A lot of guys during the early days of the roll your own tube guitar amp amp were using hi-fi-rated Hammond output transformers and blaming the harsh sound on the fact the transformer had ultra-linear taps. The reality is that the output transformers used in tube amps in their day where made to a price point; therefore, they are pretty lousy in terms of fidelity, but that is what makes them good guitar amp transformers. It is also why they often blew up when the amp was dimed.

 

[Simon Says]

Z = SQRT(R^2 + (Xl – Xc)^2), where SQRT is the square-root formula, R = DC resistance, Xl = inductive reactance, and Xc = capacitive reactance.

Xl = 2 * 3.14 * f * L, where f = frequency, L = inductance henries

Xc = 1 / (2 * 3.14 * f * C), where f = frequency, C = capacitance in fafarads

Here's my math:

Me + tube*amp = we-go-way-back

 

[DreamTheaterRules]

It still the same thing. The passband on a hi-fi system, tube or solid-state, displays a guitar's true voice with no filtering.

Yes, I know all this. That's what I was eventually going to get too in this thread. A little at a time, because as you know, there is A LOT you can discuss on this subject. Some of the things you've mentioned in the past about tube amps and a couple things that you mentioned as design "weaknesses" or however you choose to say it, are actually on purpose decisions made for what they want out of the amp. I know you know this of course, but for example, the other day you mentioned an amp that had way too small of a OT and power section to put out the amount of watts it was rated at, and it's an amp famous for saturating early and the "sag" that many like. I'm simply mentioning that it's not a design flaw, it's a design choice.

But the analogy of playing a guitar through a high fi system, is referencing more some of the things you're mentioning now, plus a few you haven't gotten too yet. Limited bandwidth, power supplies that limit and change frequency response, power supplies that let the speaker affect the output frequencies, and all the distortions and limiting (compression) and other things that would be a big no-no on a hi fi amp are what makes the guitar amp world go round.

So, to try not to write a book, all those things matter in tube guitar amps. And, many implement each phase of the amp based on the end goals.

 

[Herr Squid]

Z = SQRT(R^2 + (Xl – Xc)^2), where SQRT is the square-root formula, R = DC resistance, Xl = inductive reactance, and Xc = capacitive reactance.

Xl = 2 * 3.14 * f * L, where f = frequency, L = inductance henries

Xc = 1 / (2 * 3.14 * f * C), where f = frequency, C = capacitance in farads

This was a really excellent post, thank you!

And I'm gonna tip my nerd hand a little bit, because I was amused to see both the pythagorean theorem (or something that looks identical to it) and pi in here. My takeaway: the ancient Greeks knew (because they invented) all that math. Though they could never have guessed it would be applied this way.

 

[McMahon67]

This was a really excellent post, thank you!

Yes! Thank you!
You had me at “ the effects of radiation on the polarized goldfish”

You sir, are a genius.

 

[Em7]

Yes, I know all this. That's what I was eventually going to get too in this thread. A little at a time, because as you know, there is A LOT you can discuss on this subject. Some of the things you've mentioned in the past about tube amps and a couple things that you mentioned as design "weaknesses" or however you choose to say it, are actually on purpose decisions made for what they want out of the amp. I know you know this of course, but for example, the other day you mentioned an amp that had way too small of a OT and power section to put out the amount of watts it was rated at, and it's an amp famous for saturating early and the "sag" that many like. I'm simply mentioning that it's not a design flaw, it's a design choice.

That is where you are wrong. You are looking at tube amps from a twenty-first century lens. When the originals were manufactured, the designers were trying to manufacture amps that people could afford, so they cut corners. They used parts that they could acquire cheaply that were good enough. The highest note on a 21-fret guitar has a frequency of 1109 hertz with the highest note on a 22-fret guitar having a frequency of 1175 hertz (no one was thinking about harmonics). Why pay more for a transformer that has more bandwidth? Quality transformers were expensive and so were components. That is a large part of why the older amps have so little power supply capacitance. Sure, tube rectifiers are limited in how much capacitance they can handle in a capacitor input configuration, but many of the old Fender designs do not come close to what the rectifiers employed can handle. That was done because the amps were built to price points just like solid-state amps are today.

Leo Fender was designing amps for Western Swing guitar, which is very clean and very bright. That goal was evident from the circuit changes that were made during the progression from tweed to brownface/blonde to blackface amps (clean was taken to an extreme with the silverface ultra-linear circuits). He never imagined that people would want to dime his amps. That is why there is so little clean headroom on amps like the Tweed Champ and Deluxe. Back then, distortion was undesired for the music styles of the day and so was sag. Once again, you are looking at these circuits from a twenty-first century lens, which gives a distorted view of why decisions were made. Luckily, I had my father to turn to when I started to get seriously involved in tube amp design. He was the ultimate tube amp myth buster. He was a twenty-something electronics professional in the 50s. He would laugh so hard that I thought he was going to pass out when I told about some of the claims that people were making such as the superiority of carbon composition resistors. The only thing that carbon composition resistors have over other resistor types is that they are non-inductive; however, that is only a problem at RF frequencies. In every other way, they are inferior to carbon film resistors, which are inferior to metal film resistors, but the myth sells well to guitarists.

Leo was not alone in his frugalness. Radio manufacturers of the time did the same kind of thing with the All American Five superheterodyne radio receiver circuit. Those things are death traps because they do not have a power transformer. The 35Z5 (octal)/35W4 (7-pin) rectifier is connected directly to the mains with the filaments on all of the tubes daisy chained off of the mains. I would never use one of these radios without plugging it into an isolation transformer, which is what one had to do to work on them.

Let's look at the frequency response for the Celestion G12M (a.k.a. Greenback).

Now, compare and contrast that with the frequency response of the Celestion F12-X200, which is a full-range speaker.

It is easy to see that the speaker employed in a guitar circuit has pretty lousy response after 5K hertz. When guitar amps were originally created, 5K hertz was more than enough bandwidth for guitar because the highest note on 22-fret guitar is 1175 hertz. What guitar speakers really are are AM radio range speakers. AM radio limits the upper modulating frequency to 5K hertz (I hold an Amateur Extra Class FCC license). Tube guitar amps were little more than adaptations of amplifiers first found in radio receivers (the same thing can be said for early public address systems). Fender circuits were adapted from circuits found the RCA Receiving Tube Manual (Fender was a radio repair shop before it was musical instrument company). No attempt was made to make them special. Leo and other designers were looking for a way to make a small signal much bigger in a linear fashion. He sure as heck was not thinking about distortion or sag being good things. That is a modern embellishment of the flaws in the technology. Back then, these artifacts were unwanted.

 

[DreamTheaterRules]

That is where you are wrong. You are looking at tube amps from a twenty-first century lens.

Sorry, I’m not “wrong” but you’re to applying what I said to one set of amps made 70 years ago, and I’m making the statement about amp design in general… so yes amps made then AND since that time. I even referenced my own mods and taking a “champ type” amp and adding a bigger OT and caps and losing that “champ vibe” but gaining punch and power.

Just don’t get lost in semantics. I didn’t say “Leo designed them on purpose,” I said that choices were made based on what we knew about those particular parts values, and that is true of pretty much anyone building an amp today. I’m a hack, and I can take two champs and with a few parts changes completely change the whole sound and vibe of the amp. So if I was building and selling them, even I know enough to make a 3-4 completely different sounding and feeling versions of the same basic circuit. I’ve done it. That’s what I was referring too.

Carry on. Interesting thread.

 

[Em7]

While amp designers are taking advantage of poor engineering practices today, it is still poor engineering. Today, we have the ability to design amps that Leo would have loved to be able to design. In fact, Leo was making the transition with Music Man amps. Music Man amps are pretty much solid-state amps except for the output tubes, which are configured to operate in class B to achieve maximum clean headroom. Peavey took pretty much the same approach with their Classic, Deuce, and Mace amps in the seventies. The reality is that Leo's original target audience has mostly moved away from tube-type equipment. The only area where tube amps still rule is white boy blues and blues-rock, and even there, people are starting to see the light. A tube amp today is as much a status symbol as it is a piece of music gear. Everything that can be done with tubes can be done more reliably with analog solid-state. It just takes more engineering skill and a market that is open to spending real money on a solid-state amp, good luck with overcoming that bias.

 

[RickP]

What, exactly, are digital modelers modeling?

 

[dmatthews]

What, exactly, are digital modelers modeling?

 

[ScottR]

What, exactly, are digital modelers modeling?

I'm no Em7 but, I think they are modeling models of other models.

I'm from Alabama so that's all I've got.

 

[ScottR]

But does she go to 11?