How do they do the expensive all tube audiophile power amps??
Having heard a few, there’s zero distortion but it has that very full sound.
Question: Is a 30-watt amp head going into a 2x12 cab good enough for medium-sized gigs?
- Thread starter therevivalsband
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Having heard a few, there’s zero distortion but it has that very full sound.
Well, distortion is far from "zero" even for the best valve hi fi amps, it will be 100 times higher than the very best transistor designs. The V hi fi will still retain some of that thermal compression "busting" capability of rough arse guitar amps so even a nominally 20 W valve amp will have the feeling of much greater headroom plus of course there is no need for any protection circuitry.
There is no doubt that many people LIKE the sound that valves bring to music but for the very strictest accuracy transistor beat them hands down. Yer pays yer money...LOTS of money!
Dave.
I am sure the Kenwood is very good indeed and 2X 120W is easily equivalent to 20W a side valves but think of the lektrik you are saving. MOSFET audio power devices did not quite cause the revolution in hi fi we were promised but I have an Arcam 6 50W pch MOSFET amp and its seems fine. I also have a Maplin "150"W kit mozzy amp (not, about 80W tops) and I have gigged bass guitar with it.
Dave.
After building guitar amps for decades, I know what sounds are caused by and how to manipulate circuits to behave the way I want them to be. Its just cost more to do it in solid state. That is why its not really done and the way other manufacturer's tried failed miserably or had limited success. Most of the guitar amp's sound comes from the line stage. The output stage's dampening (or lack there of) is partly caused by the amp at high level and changes depending on the speakers and how it inter reacts with the negative feedback in the circuit. The output transformer does not play a major role on this other than insertion loss between this interaction with amp and speaker.
LazerBeakShiek
Tell Tony, Eddie an the Cruises IS here
It does? What about hybrid amps with the 12ax7's or little green Nu tubes?
In those instances, they try to build it on the cheap, but concentrate on the line stage that is 90% of an amp's sound and pick a speaker to compliment it. Which is 8%. The tube output stage only adds maybe a 2% difference and a lot of times those differences are not picked up by the mic. Because: 1, the mic technique applied and 2, the speaker and cabinet is the main factors in reproducing that sound.
What I am referring to is high voltage solid state amps when it comes to trying to get them to behave like a tube amp. Its hard to get them to behave with sloppy dampening even with an output transformer. What you see commercially done is basically a guitar front end with an equivalent of a car stereo amp on the back end.
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LazerBeakShiek
Tell Tony, Eddie an the Cruises IS here
right. and thats bad. right?
Its what some settled with. Marshall AVT50 is one of them.
What gets me is that there is nothing gained with running tubes the way they do other than wearing them out quicker with a circuit that might self destruct itself and the flopping dampening effect doesn't record well and most of it gets rolled off so the channel fits better in the mix. But other than that, recording at that level that the dampening effect is predominate changes the harmonic balance, and most of the time, for the worse and not better. One thing I noticed is that certain parts for them are way higher priced than they should be. Like the output transformers. I made transformers in the past and had to rewound a few guitar ones and I will tell you this, they are built more like a cheap power transformer than one used as an output transformer on a Hi-fi. Even the budget hifi transformers from Edcor are constructed better.
The drawbacks for making a solid state amp is parts count as there is a lot more resistors, caps, etc that are in the unit and if its built on the cheap its going to have more insertion loss or a poorer signal to noise ratio due to this. Even though they do get away with putting poor quality parts in guitar tube amps all the time because they are much more forgiving but with about 1/5 of the parts in the circuit. That is why you will see IC output amps budject corporate built amps than descrete designs (which are better). Like that Roland 60+60 amp that was mention earlier that is basically a Randall design with japanese instead of american transistors.
The 12ax7 preamp tube is a great tube to work with, but a lot of people don't understand that many of these tubes have a wide operating range. So you will hear at times people complain of a lower voltage applied to them, but don't understand why. But its all in the function they are serving in the circuit. The tube sound itself is not from the applied voltage, rather, its the shape of the elements and their metal they made out of. A lot of NOS tubes were made with silver alloys they don't duplicate, but the main factors were the shape of the plates and cathode. The reasons why is, the tube sound is a product of harmonic propergation from the electrons leaving the 2D world of wires and traveling through a vaccum. Problem with nos tubes in guitar circuits, is the guitar circuit is more tuned to being a guitar amp, so a lot of harmonics are filtered out and most of the remaining get eq-ed out so it can fit a mix. That is why NOS tubes are a waste in a tube amp. Some people will harp on capacitors as that is one area of insertion loss that can be observed. Changing the brand but not the type probably does render a better signal, but I doubt it is audible. It would have to be something particular in construction from one to another for it to be audible. When you change the capacitor type, like from a polypropolene film to mica or polystyrene, the differences in dielectric have different distortion characteristics. When repairing something like a tube amp and have to change those caps, always go back with the same type so the guitarist don't think you are some sort of butcher that ruined their amp sound.