GRollins said:
To get a semi-reasonable answer, this will have to be a three hundred page thread...five hundred once you add all the people who want to throw in their opinions, then argue semantics, then get into flame wars.
People get religious about this stuff and it quickly goes from fact to fantasy if you're not careful.
Note that negative feedback rates, operating class, and parts choice will rear their heads before the thread passes ten pages, guaranteed.
Good luck.
Grey
No kidding on the semantics and flame wars and fanatics and religious... I guess religious is ok if its good design practice...
I always try if possible back up what I say by some kind of proof when I can but in this case since I doubt most of you have a lab or at least a scope to test these things for yourselves when it comes to the comparison of amps the only real proof to be had besides peoples ears which are really subjective and often biased, is what can be mathematically proven such as damping, and the way the cone is controlled... these are measureableand easily calculated by the layman, but as far as the sound well that is all subjective and there is no proof just taste and if you have not listened to several amps most of the posts will boil down to taste and this thread will go literally no where that you would want it to go... unlike wire hearing and taste cannot be proven...
I think the only way to approach this is to keep it rather basic leaving feeback and all the other stumbling blocks out of the picture... Fet as a rule can have better transient response and cleaner than bipolar and bipolar is very close to fet but from my experience leans more toward tube sound when compared to good fet design...
The biggest difference in amps is between transistor and tube/ccs which gives sound similat to a tube (constant current sounce) is damping and coloration or lack of...
Tube and ccs amps have little or no damping and produce lets say a controlled under/overshooting of the driver and has its own unique coloring effects and as a result the driver will exhibit gain and compression nonlineararities when compared to the original source material...
Tube systems are appropiately coined soft and bright sounding and tubes are typically used by a small group of us old timers who remember them typically on horns because people often believe that is the only way to get the raspiness out of a horn and often just plain like the way a tube colors the sound... at the same time from my experience and I really do not have a good way to describe this but a tube driven horn sounds like its in resonance at all the frequencies because much of the 3rd harmonics are rounded thus more subtle... not just the bass hump area hence the bright sound and a reduction in 3rd harmonic content gives the listener the impression of cleaner more pure sounding music... Its a very interesting sound and has certain properties I really like but not as a reproducer... I like a tube amp as a producer there are certain sounds that are very difficult to produce with a transistor amp that a tube just does naturally...
A tube amp on a guitar tends to mellow out the steeliness of them just enough to cut the shrillness and it has a neet kind of almost a ringing tone with its own harmonics mixed in with the fundamental... so many musicians love em.... the only way to come close in a transistor amp would be to find a low damping amp, (preferably under df=15), or put a resistor possibly starting at 8ohm and possibly as high 20 ohm in series with the driver to lower the damping would work too... but make sure you size it correctly for the wattage or you will get a nasty smell in the house as it starts to fry LOL
Unlike transistor amps tube amps and trans amps have very low or very little damping and usually low power so your how well your speaker is controlled is mainly dependant on the box damping because it will get very little additional damping from a tube amp... Tube and ccs amps usually have a df up to 20ish typically and transistor amps can run from 500 in a faily good one to 20,000.
Tube amps tend to like sine waves when driving a speaker and from tests I have done as you approach the rails they tend to compress the peaks of a sinewave...
When hooked up and measured at the driver as a result of the high source impedance tube amps, square waves tend to be rounded off on the edges as a result of back emf and that is what goes on electrically to tame the 3rd harmonics down in a tube system... meanwhile the low z transistor impedance will force the driver to put out a squarewave much more readliy giving a horn a very raspy sound if not properly adjusted with auxilliary sound processing equipment....
I would not recommend a tube amp for any type of reflex or enclosed box design and its best to stick with transistor in those... Tube amps are commonly used in low power horn systems in a home environment...
A little background on damping... Damping is the ability for an amp to push a driver in/out/stop in exact proportion as determined by the dynamics of the program material... then stop the cone and/or reverse it... ie: transistor amps will force a driver to play a squarewave and a tube will tend to round everything and tend to have a square wave with rounded edges that is why the shrillness of the guitar is cut back a bit giving that nice smooth sound, and a transistor amp playing the same note would require 3rd harmonic frequency cut back considerably to play the same chord to reduce the shrillness...
Driver damping factor is calculated/measured at the driver terminals is a quality measurement that help buyers better understand how well any particular system can follow the input signal... and also how much driver compression/overshoot/undershoot to expect with any given amp/wire/crossover/speaker combination and the amount can be caculated using the theile/small model...
Many tube horn experts will adjust the series resistance using this method of calculation to get a sort of extended bass response from single driver horns...
So basically anything with low damping will sound like a tube amp and anything with high damping will sound like a transistor amp... bipolar will drive a speaker more accurately than a tube, (but not necessarily sound better in "all" cases), and good fet designs will drive a speaker as a rule better then a good biploar design.... and there are always exceptions to every rule.... There are more differences but thats another chapter... and I wanted to sort of stick somewhat to the basics...
So there is the results of several tests I have done on various toys...
gulp never mind then. I saw what happened just talking about wire.
