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
- Start date
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
It is a life preserver
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
It is a life preserver
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.
rob aylestone
Moderator
I'm smiling a little at the different perspectives folk have. I'm remember tube designs from the mid 1970s-early 80s when I was just qualified and in TV, where I went first, valves were things we wanted to get rid of. The heat, the distortion, the shortish life were negatives, and I was rather pleased when the first solid state designs appeared that didn't suffer from the negatives as we saw them. The degradation in the scope traces from source to destination and the changes that happen during warm up each time and eventually lifespan with gains dropping. Going the other way were guitar amp designs, utilising one industry's problems and turning them into features. We now have the same thing with specific products designed to modify sound in wonderful ways, and very clever they are. One person's negatives turned into another person's positives. I just wish we didn't try to use words like 'better'. It's like decibels. Meaningless without context, plus it suggests a difference. Sound A is better than sound B, for whatever reason. We don't have a specification for better we can use. One person can slam a signal with every compression device they have and consider on their sound, that it's better. Another wants to remove every trace of signal distortion, and that to them is better too. Total harmonic distortion used to be a designator of 'goodness', while now some distortion is considered good, and others bad. In the tape days we hated hiss, got annoyed by what hiss removal systems did to the sound and elimination of it became a focus. Then hiss went away and we started to look for other annoyances.
I suppose we all have our hates and our goals to achieve. The snag seems to be we want to convince other people their viewpoint is the bad one, and ours solid. Tube mics are to me a bit pointless - I appreciate what they do, but that's just not my direction. I do have in the studio a valve combo. I never use it. It's not bad, but the solid state ones do what I need. I'm more interested in the annoying clicks I'm getting and the increase in background noise with no signal that was not there before. Far more important to fix.
I suppose we all have our hates and our goals to achieve. The snag seems to be we want to convince other people their viewpoint is the bad one, and ours solid. Tube mics are to me a bit pointless - I appreciate what they do, but that's just not my direction. I do have in the studio a valve combo. I never use it. It's not bad, but the solid state ones do what I need. I'm more interested in the annoying clicks I'm getting and the increase in background noise with no signal that was not there before. Far more important to fix.
What I find interesting is that some features like the poor dampening effect that some think its some sort of compression or limiting effect, is easily made using any amplifying device (tube, mosfet transistor, opamp) because its the circuit construction chosen for the stage that is the cause of the 'effect'. Even though that effect does nothing positive to the signal its reproducing. In guitar amps, it does alter some primary harmonics, but I can't pick it out in a full mix, but the real game changer in improving or customizing the guitar amp in this area is directly chosen with the speaker. So a lot of guitar amps that are combos that people push away from or was disappointed about it even though it had a popular speaker put into it is not the amp's fault, but the speaker wasn't chosen for the best reveal. So a greenback might sound good with a particular amp, but not all of them. That is why you will hear people at times say if you don't like the sound, change the speaker.
Its hard not to use better in certain context because some things are difficult to explain. But the word 'desirable' might be just as bad. The context of it being a design goal should be the focus rather than a comparisons of a whole design. A lot of specifics are quite technical in nature and I try to break it down into a more simple term but I do have to keep in mind that while the simple term helps explain, it opens up room for misinterpretation.
I think a lot of discourse in discussions comes from assuming one viewpoint is correct and another is not, but I do try to keep opinions out of explaining something technical except when I'm trying to express my feelings and viewpoints about something after I drew conclusions about it in the past. Just like your viewpoint about tube microphones, which I agree, because the other parts and their selection is really where the characteristics or dare I should say, personality really comes from. Some might say or give examples of their 1960s tube mic and their opinion that only a nos tube of that era and certain brand is the only thing that works well. I understand this being correct to a point, but my viewpoint as an electronics tech/engineer knows its just because the mic's circuits are adjusted or dare I say, tuned to the best performance with a certain tube and tube brand. Do I totally discount the guy's viewpoint? No, but explaining mine to them sometimes might lead them think I did.
Seeker of Rock
Let’s Go Brandon!
Jc 120s are gorgeous amps!
Seeker of Rock
Let’s Go Brandon!
I can agree with this ^ ^.
But re: how many watts the OP needs in an amp setup for a live show? Assuming it’s a show that has even a rudimentary PA , not many watts on guitar amp
And in modern digital mix and design, a good modeler b with a quality digital line out to FOH which will have all of the volume you’ll need.
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Seeker of Rock
Let’s Go Brandon!
As a purist I will never ever give up my analog tube amps but I could play a large forum gig with only my pedalboard if needed.
LazerBeakShiek
It is a life preserver
thats not a tube amp..it doesnt sound or play notes right. Try an ADA T100S class B amplifier with some EL-34's.. Tubes are the only way to fly.
My ADA MicroFet is Solid State type..Few components on the board. It's got one hell of a Torriod transformer and not a whole lot else..
Yeah, you gotta tear that shit out..filter caps are good for what??? 8 hours..hah
Don't you know polyester box are BETTER than metal film cannister?
What I was referring to is the Marshall using a car radio audio IC output instead of a discrete transistor amp.
Filter caps should last thousands of hours.
As for box type, I still prefer series wound film and foil instead of parallel stacked construction because over time, the stacked box cap degrades. So it doesn't matter if its in a round package or not, its the same construction. But for repairs you go back with whatever is in it so there is no surprises to anyone.
LazerBeakShiek
It is a life preserver
because when you buy Marshall AVT amps, you are really getting that quality heritage.
youre too serious
Yes, the Box polyester cap owes that back to the grid. Thats the payback. A degradation..a change in value..
The Grid. A digital frontier. I tried to picture clusters of information as they moved through the computer. What did they look like? Ships, motorcycles? Were the circuits like freeways? I kept dreaming of a world I thought I'd never see. And then, one day I got in...”
― Kevin Flynn
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