Ken Fischer: cablaggi cavi ed altri snake oil?
Inviato: 22/12/2011, 16:42
Alcune considerazioni fatte da Ken Fischer riguardo cablaggi, cavi, ed altro materiale:
http://www.ax84.com/bbs/dm.php?thread=360118You put a lot of thought even into wire selection?
Yeah, a lot of thought, and a lot of experimenting. Will the solid core sound better than stranded wire? And if it does, is there a difference between thick-stranded and fine-stranded? Does it sound better with polyvinyl-chloride [PVC] insulation? Does it sound better with irradiated polyvinyl-chloride insulation? Teflon insulation? What brand of potentiometer, carbon-comp resistors, carbon film, metal film – what are their benefits, what are their pitfalls. And a resistor that’s used in a power supply circuit will sound different than when it’s used in a preamp circuit. Stuff like that. And especially, neatness in wiring counts. And wire has a polarity, which most people don’t know. If you take a guitar cable and plug it into the amp one way, then you take it out and plug it in the other way, your guitar will sound different. Putting tube shields on and off will change the sound of the amp. The color of the insulation on the wire, the pigment they add to the covering material of the wire, can change the dielectric absorption of the wire. So these are like the microscopic points that I get into. My friends say, ”Hey, you’re the detail man. You get into all the little points...” And I say, ”Yeah, but that’s what I do.”
And I guess that makes the difference, too. It’s easy enough for a tech to look at a schematic and build an amp, but the difference in qualify must come with the details. Oh, there’s a real classic example I use for that. Get a Clyde McCoy Wah-Wah, an early Vox wah like Hendrix or Clapton would use, and get a new Jim Dunlop CryBaby Wah-Wah. Every component value in the wahs and the schematic is completely identical. So why does the old Clyde McCoy Wah have a much more vocal sound than the new CryBaby? It’s exactly the same schematic. So it’s got to be in the details, in the components. So I can take a schematic from any amp and just change some parts, and make it sound like a completely different amp.
Nfhat has turned out to be your favorite wire. It depends on what I’m doing. Certain stuff works well in certain spots. On the Trainwreck amps it was solid-core with PVC insulation. Solid-core wire’s fast, but non-irradiated PVC is slow. But I’m using such short pieces of wire – because I want to get a certain speed, or what they call ’slew rate,’ and there are a number of ways of getting it, but wire’s part of the sound. But because PVC-coated wire is like coating the wire with American cheese, when you solder it the insulation just falls away – that’s a very very hard wire to work with. The irradiated PVC doesn’t melt so fast, but the non-irradiated – which is the one I liked – most people can’t work with it, because they don’t have the soldering technique to get the wire to solder without melting the insulation.
So when I did the Komet amp for the guys in Baton Rouge, those guys wanted to use Teflon wire because with Teflon you can put a torch to it and it doesn’t burn. But Teflon-coated wire is stranded, and to get the Teflon onto it they extrude it, and extruding Teflon will not work with copper, so either they nickel-plate it – which is very uncommon – or more usually most of your Teflon wire is silver-plated, which changes the sound again, because silver’s a better conductor than copper. And there’s the skin effect – because the silver’s on the outside and high frequencies travel on the outside – with Teflon on top of it, which has a very low dielectric coefficient so it doesn’t absorb stuff from the wire... You can make a very shrill- sounding amp very quickly with Teflon wire, if you’re not careful what you do with the rest of the circuit. So they wanted to use Teflon wire, and I just made the amp so it would sound real good with Teflon wire. So Holger, who is one of the co-owners of Komet amplification, said, ”I’m going to build one and I’m going to use the wire that you use,” so I gave him the brand and the specs and colors I would use and whatever. He went to build one and I said, ”It*s going to sound awful. It’s going to sound dark, it’s not going to sound clear.” He didn’t believe me, because he was thinking of how a Trainwreck sounds clear and so forth. He built it, listened to it, and said, ”Yeah, you’re right. This wire sounds awful on this amp.” I said, ”Yeah, I voiced the Komet amp using Teflon wire. I voiced my Trainwreck amp using the wire I was using.”
I use aluminum chassis because they conduct better. I always see in guitar magazines where guys who aren’t engineers are arguing whether aluminum really conducts better, or whether it’s just myth. And they say, ”Well, Marshall didn’t use aluminum chassis for the JTM45 because it conducted better, they used it because it was easy to work with.” Sure, but people who are using aluminum chassis today and getting them manufactured for them – like Dr Z amps, that are all aluminum chassis, Trainwrecks, and Komet amps – they’re getting them cut on a laser machine, which will cut anything, so they’re not using aluminum because it’s ”easy to work with.” It could be aluminum, stainless steel, titanium, whatever. Doesn’t matter whether it’s ”easy to work with.” The chassis goes to ground, and all ground currents eventually go back through the aluminum chassis. Iron steel or mild steel – as Fender was, and Marshall would be later on – that’s a different chassis. What actually happens is, negative flows to positive, so actually all the currents first flow through the chassis, and they flow out of the chassis through the circuitry – through the power filters and then eventually back into the chassis. But the current actually comes out of the chassis, and the chassis is the main conductor in your amp. Aluminum conducts better than steel. Does that make it a better chassis’? Depends on what you are going for. If you’re going for more fidelity and a faster response, yeah, you want aluminum because it’s a better conductor. If you’re going for a traditional sound, Fender never used aluminum, they always used steel, so if you are going to make yourself an amp and you want it to sound like a Fender, by all means use the steel chassis. It’s not like one’s better than the other in an absolute respect, it’s a matter of whether it’s better for what you want it to do. And there are a lot of things I’ve found that I just don’t think work for anything.
Like metal-film resistors – I’ve never heard an amp with metal-film resistors that didn’t sound harsh. A lot of guys will say, ”But they make the lowest noise.*’ Oh, absolutely, they’re far lower-noise. Carbon film is lower-noise than carbon comp, but metal film is way lower noise than either one of those two. Yeah, you can get less noise, but you won’t get as good a guitar tone. That happens also with a lot of the really high-end audiophile caps. The guy makes himself a guitar amp, and it really sounds like it should be used for acoustic guitar or stereo, rather than electric guitar. And the circuit board you make it on... you could make it out of phenolic like some of the old Marshalls, fiberglass, Alexander Dumble has made a lot of circuit boards out of mood, and he likes the sound he gets out of a piece of, say, rosewood for a circuit board. And that’s valid too. But my amp is, keep it simple. And for the high-gain amps, the one with a really high-gain response, like the Express or the Liverpool, it’s ”keep it near the point of instability.” There’s another analogy I can use here: what makes an F-16 or one of these really high-performance jet fighters able to turn so fast and be able to do all these wacky maneuvers and stuff? They’re basically unstable and if they didn’t have a computer onboard to help, the pilot wouldn’t even be able to fly the plane. It’s the instability that let’s the plane, in a fraction of a second, roll 180 degrees and make a 90-degree turn at the same time. When you go into planes like a 747 where you want stability, because you don’t want some jerky movements there, you make the plane very, very stable. If the pilot has a heart attack, even if it’s not on autopilot, it will fly for miles before anyone realizes it. But if you do want to turn it, it’ll take you two-and-a-half miles to do so.
Your amps are more akin to the hair trigger. The hair trigger on those jet fighters, yeah. And when you start getting complex harmonics, that’s what you need to make an amp sound complex. The more stable an amp becomes, the less complex it is. If you’re actually going by the audiophile definition, the amp should be ’transparent.’ Which means whatever you put into the amp is exactly what should come out, nothing more, nothing less, only louder. But a guitar amplifier not only amplifies, it’s a tone generator. If you want to plug in a guitar and it has this and this harmonic, but you want more harmonics in your sound than the guitar itself has, you’ve got to generate them in the amplifier. Or in some cases, you have harmonics that are coming out of the guitar, but the guitar amplifier isn’t quick enough to capture them and reproduce them. With a guitar amp, you want to capture all those harmonics, plus add to them, and that’s what makes a great sound. Hi-fi guys have a term for that – ’euphonic.’ They say, ”OK, it’s a euphonic amp, but it’s not accurate.” A lot of hi-fi guys would not want the amp to change the tone, so a guitar amp is a completely different type of audio amp; all other audio amplifiers are designed to keep distortion down and just reproduce what’s there.
One of the problems with all of this stuff in modern times is that, with solid-state amps being used most, a lot of the best brands of components – resistors, capacitors, tube sockets, potentiometers and whatever – have gone by the wayside, and you’ve got to use whatever is available and make it work the best you can. And the tubes are the same thing. Everybody knows that if you put ’new old stock’ tubes in the amp it will sound better than with any of these Chinese or Russian-made tubes. Do you have a favorite preamp tube of all time?
That depends on the amp. Telefunken made a great 12AX7, but they made a smooth plate and they made a ridged plate, or waffle plate. Fender amps tend to like the smooth plate. Trainwreck amps really don’t like either one in the first position. The Komet 60 amp that I designed likes the ridged plate, but the Komet 80 likes both the ridged plate and the smooth plate. Then you’ve got Mullard from England, their tubes were always changing. They made a long-plate version early on, then they made a short-plate version. What most people really don’t know is, most of the SAR4s you ever see out of Europe are all the same. If it says Amperex Bugle Boy, Mullard, Telefunken – maroon base, large black base, small black base, brown base – they were all made in the same place. It’s interesting to me because people will come to me and say, ”I want a Telefunken with a metal-banded base, because that’s rare.” And I say, ”OK. you’re going to have to pay me this much for it versus this much...” But it’s the same tube. That base didn’t make the difference, the only difference was on the plates inside: the ones with the straight edge on the side of the plate, the ones with four notches on the side of the plate, and the ones with seven notches. Those were the only three variations they made. The bottoms varied a lot, but for the actual internal guts, there’s only three variations. Where were they made? They were made by Mullard, in Britain. When they have the Mullard codes etched in the glass, that’s how you know who made them.
Are there any components that you hear being talked about in tube amp circles these days that are perhaps over-hyped? Well, people get very hyped up about transformers. They’ll say, ”This transformer’s the sound of this amp, this one’s the sound of that amp...” and whatever. And that is true to an extent, because you have different core materials used in different transformers at different times and different winds, a certain thing that makes a Marshall sound like a Marshall – which was their propriety, they know it and I know it, but I don’t give it out because I don’t want to help people clone other people*s amps, you know – but sometimes people get too twisted up on that. I can take an average-sounding transformer and make a great-sounding amp out of it. The output transformer is more critical, but the power transformer makes a difference, the choke makes a difference, all the iron on the amp makes a difference. Or you can take a really great transformer and use it wrong, and get a bad-sounding amp. There was a magazine article about why, if the JTM45 was copied from the Fender Bassman, did it sound different. And one of the differences was the output transformer. So one guy said, ”I took a Marshall output transformer and put it on my Fender amp, and it still sounded like a Fender amp, so it couldn’t be that.” Of course he was using a blackface Fender, not a tweed Bassman. It’s completely different, though, because if you take the output transformer out of your Fender and put it on a Marshall, it’ll definitely sound different. That’s just not a proper way to judge anything. It’s like, if you can put the same size tire on two cars and say, ”It still feels like the same car.” There’s other things involved, you know? The RS transformer that they used on the original Marshall.