Ken Fischer: cablaggi cavi ed altri snake oil?

[robi]

Alcune considerazioni fatte da Ken Fischer riguardo cablaggi, cavi, ed altro materiale:

You 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.

http://www.ax84.com/bbs/dm.php?thread=360118

[alexradium]

lo avevo letto tempo fa,sicuramente lui è stato un grande però francamente certe affermazioni mi lasciano perplesso...
disse anche di sentire la differenza fra un cavo awg 16 e un 18 in uno speaker,un pò come quelli che sentono la marca delle batterie nei pedali....
ho ricavato tanti buoni consigli dalle sue trainwreck pages,ma alcune cose sono forse più riferite ai suoi ampli che non in senso generale

[robi]

Più un ampli è semplice, meglio si sentono le differenze dei dettagli. Per questo sul trainwreck si sentono.

Analizzando le prima affermazioni del discorso

Un cavo di sezione maggiore ha più corpo di un cavo a sezione minore, ma se usi un ampli da sei stadi di gain su una cassa coi classic lead non riesci a sentirlo.

Il coprivalvole aumenta la capacità fra i due triodi, smussando gli alti, ma i nuovi datasheet non lo riportano più.

Un solid core generoso ha sicuramente la capacità di mantenere uno slew-rate superiore rispetto ad un cavo da elettricista (ho una sezione effettiva superiore).

Riguardo il "suono" dei vari cavetti di colore diverso, me ne parlò un tecnico plexista rimanendo peraltro basito sul fatto che preferisse i cavetti in pvc blu, chiedendomi se potesse trattarsi di suggestione essendo i cap LCR azzurro-blu.

[Fix_Metal]

disse anche di sentire la differenza fra un cavo awg 16 e un 18 in uno speaker,un pò come quelli che sentono la marca delle batterie nei pedali....

[robi]

ragass.. però prima di ridervela goduti qualche prova fatela..

[Fix_Metal]

Solo a me sembra folle mettersi a pensare che il colorante dei cavi modifica la sua capacità trasmissiva?
Alla fine della fiera siamo chitarristi che suonicchiano per locali. Non vedo perchè arrovellarsi il cervello in questioni tanto inutili. Nemmeno i professionisti lo fanno, per un motivo: non impazzire. Semplicemente suonano, ed è quello che si deve fare, dopotutto.
A forza di cercare il pelo nell'uovo si entra in un circolo vizioso deleterio che porta l'elettronica in primo piano rispetto alla musica. Non so minimamente chi sia, ma è da questi articoli che nascono i mojo e le leggende per cui i bumblebee e i tropical fish suonano meglio dei poly odierni..........
Mo' non verrete a dirmi che qualcuno di voi ha SUL SERIO avvertito differenze dopo aver tolto le valvole per manutenzione dell'ampli. E' una cosa tanto ridicola quanto un maiale che si affetta da solo.

[alexradium]

su cavi di segnale specialmente nei primi stadi ci può stare la differenza ad orecchio.
vedi george L per esempio,totalmente diversi dai cavi standard,però a mio parere tagliano le medie e lasciano le alte,che in una chitarra è una bestemmia,imho.
quindi la composizione delle guaine fra anima e calza ed esterno ha la sua valenza in questo caso
qualche prova l'ho fatta sui cavi cassa,anche con cavi surdimensionati da audio hifi,cavi per casse da cinema...
alla fine il risultato era lo stesso che col cavetto standard dell'ampli.ho preferito concentrarmi su altro.
voglio dire su massimo 1 metro di cavo di potenza,se la dimensione minima è sufficiente a portare anche il picco massimo dell'ampli non ci dovrebbero essere problemi di sorta.

[robi]

Alla fine della fiera siamo chitarristi che suonicchiano per locali.

Questo discorso lo puoi fare su accordo, qui siamo su diyitalia e se ci sei vuol dire che hai la passione per l'audiofilia.

Non vedo perchè arrovellarsi il cervello in questioni tanto inutili.

Allora perchè intervieni sul thread denigrandolo, se non ti interessa?

Nemmeno i professionisti lo fanno, per un motivo: non impazzire. Semplicemente suonano, ed è quello che si deve fare, dopotutto.

Allora che ci fai su diyitalia, che è un sito per il DO IT YOURSELF?

A forza di cercare il pelo nell'uovo si entra in un circolo vizioso deleterio che porta l'elettronica in primo piano rispetto alla musica.

No, porta chiunque di noi, con un minimo di grano salis, a capire che il mojo è pienamente spiegabile e si possono ottenere cavi audio spaziali (o suoni inarrivabili) commercializzati a centinaia-migliaia di euro con pochi euro.

Non so minimamente chi sia, ma è da questi articoli che nascono i mojo e le leggende per cui i bumblebee e i tropical fish suonano meglio dei poly odierni..

Ken Fischer è uno dei progettisti più acclamati in ambito di amplificazione per chitarra, i suoi ampli vengono venduti intorno ai 10-15 mila dollari. ..ed è anche bravo a fare marketing, chiaramente. È proprio quella la parte che va epurata per coglierne le utilità.

Mo' non verrete a dirmi che qualcuno di voi ha SUL SERIO avvertito differenze dopo aver tolto le valvole per manutenzione dell'ampli.

Sì, dopo aver tolto le valvole l'ampli non suonava più. A quale punto del discorso ti riferisci di preciso?

E' una cosa tanto ridicola quanto un maiale che si affetta da solo.

..attento a non tagliarti!

[robi]

su cavi di segnale specialmente nei primi stadi ci può stare la differenza ad orecchio.

Sicuramente, lì le differenze sono fortissime perchè è ad inizio catena, e quindi quello che tagli o guadagni si ripercuote sull'intero sistema amplificato più volte.

qualche prova l'ho fatta sui cavi cassa,anche con cavi surdimensionati da audio hifi,cavi per casse da cinema... alla fine il risultato era lo stesso che col cavetto standard dell'ampli.ho preferito concentrarmi su altro.

Se hai fatto qualche prova e non sei impazzito, benvenuto nella banda! =) Prova a farti un cavo cassa con il cavo ethernet (quello con 8 solidcore all'interno), usando due spezzoni. Noterai le differenze anche sul cavo cassa. =)

PS
le differenze si sentono soprattutto su ampli semplici ma che tendono al crunch, tipo le plexi.

[robi]

Se avete tempo e voglia, provate a farvi i cavi cassa dello stereo con il cavo ethernet classico, noterete di avere un tweeter. =)
Il passaggio sulle mie klipsch dal cavo normale all'ethernet ha veramente cambiato al timbrica dell'amplificatore, rendendo i bassi molto più reattivi e pronti. ..è il discorso di ken fisher, se ci pensate. =)

[robi]

Riassumo il discorso iniziale per frasi, spero possa tornare utile a comprendere il senso generale del discorso di Ken:

And a resistor that’s used in a power supply circuit will sound different than when it’s used in a preamp circuit.

Questo lo notai anche io, un intorpidimento delle alte (e quindi un ammorbidimento delle basse) a favore dei medi. Notai però un effetto simile scaldando troppo la resistenza col saldatore. Presumo sia dovuto a qualche micro-pseudo-sinterizzazione della resistenza (spero si capisca cosa intendo), dato che l'effetto scatenante pare essere l'eccessivo calore.

And especially, neatness in wiring counts.

Questo mi pare indiscutibile. Un layout chiaro e definito è la chiave di un buon suono, quantomeno come ripetibilità dello stesso su vari amplificatori.

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.

Questo sui cavi di chitarra l'ho notato molto meno, e dove pareva esserci qualche leggera differenza, era su cavi che non mi piacevano comunque in nessuno dei due versi (troppi alti-medioalti).

Putting tube shields on and off will change the sound of the amp.

Di questo ne ho parlato innumerevoli volte negli anni (avevo anche aperto un thread sull'argomento). L'interelectrode capacitance aumenta di un ordine di grandezza con i coprivalvola, da 0.16pF a 1.4pF: http://ieeexplore.ieee.org/xpl/freeabs_ ... er=1694919

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’

Credo in molti dediti al DIY abbiano provato il solid core "nudo" che vende tube-town. Paragonato a del cavo da elettricista di pari sezione suona molto di più e con più medioalti. Può risultare addirittura "secco" in certe applicazioni.

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, so either they nickel-plate it or silver-plated, which changes the sound again, because silver’s a better conductor than copper.

L'effetto pelle viene enfatizzato dalla minore resistività della superficie del cavo, ottenendo un cavo che sembra enfatizzare la componente "harsh" del suono.

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.

la costante dielettrica del pvc è 4.5, quella del teflon è 2.1 http://physics.info/dielectrics/

I use aluminum chassis because they conduct better. The chassis goes to ground, and all ground currents eventually go back through the aluminum chassis. If you’re going for more fidelity and a faster response, yeah, you want aluminum because it’s a better conductor.

La resistività del ferro è 9.7 x 10-8 ohm metro, quella dell'alluminio è 2.7 x 10-8 ohm metro, quattro volte meno.

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.*’ 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.

Beh, è il classico esempio dei silvermica utilizzati sui cloni Marshall: ti escono gli acuti frizzanti più fastidiosi della storia, ma molti continuano ad usarli al posto dei ceramici classici a 500V.

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.

Altro discorso spesso ripreso da molti produttori HiFi: il materiale della PCB.

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.” 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.

Questo è lo stesso discorso di Dave Petersen per gli AC30 di Bryan May: per suonare articolato deve essere al limite dell'instabilità. Più lo tieni controllato, meno potrà riportare "dettagli aggiunti".

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?

Qui inizia a smontare i vari mojo sulle valvole NOS.

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.

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.

L'amplificatore non fa altro che modulare la corrente elettrica su un altoparlante. Se l'alimentazione non è valida, l'intero ampli non suonerà a dovere.

[franci_pleximaster]

Ciao robi innanzitutto buon natale, in questo periodo te ne esci sempre fuori con della roba maledettamente interessante.
Mi interessa molto la questione carbon comp vs metal film, perchè nelle prime dicono che vengono generate più armoniche pari (perchè?) e specialmente in zone in cui il segnale ha una ddp. molto alta (perchè?) mentre invece le metal film rimangono più "sterili"? è colpa l'induttanza parassita presente in essa?

un saluto a todosss

[robi]

Ciao franci e buon natale.
quello che cerchi è voltage coefficient of resistance: http://www.geofex.com/article_folders/c ... oncomp.htm

[franci_pleximaster]

grazie mille robi questa cosa mi ha turbato un po'...a seconda della ddp applicata ai capi la resistenza cambia valore, interessante!

quindi sono un po' come le valvole, nel senso che se la ddp applicata ai lati è troppa per loro iniziano a smussare l'onda a favore della seconda armonica, un paragone ardito ma si potrebbe parlare sempre di over-drive, nel senso letterale della parola...

mi rimangono ancora delle domande, perchè le metal film non lo fanno?
se metto una resistenza da 1/2w CC rispetto a una 2w CC in un punto in cui è stressata (anodi o slope credo) a rigor di logica quella da 1/2w dovrebbe generare più distorsione?

[Fix_Metal]

Questo discorso lo puoi fare su accordo, qui siamo su diyitalia e se ci sei vuol dire che hai la passione per l'audiofilia.

Lo faccio qui perchè sono un chitarrista e musicista innanzitutto. Mi sembra fortemente stupido intraprendere lo studio dell'elettronica applicata al lo-fi per migliorare il proprio suono per poi smettere di suonare.

Allora che ci fai su diyitalia, che è un sito per il DO IT YOURSELF?

Quello che fai tu, o che fanno il più degli utenti: imparare.

No, porta chiunque di noi, con un minimo di grano salis, a capire che il mojo è pienamente spiegabile e si possono ottenere cavi audio spaziali (o suoni inarrivabili) commercializzati a centinaia-migliaia di euro con pochi euro.

Mi sembra che siamo d'accordo - è un altro motivo per cui sono qui.

Sì, dopo aver tolto le valvole l'ampli non suonava più. A quale punto del discorso ti riferisci di preciso?

Ho letto male una frase del discorso, quella in cui si parlava della schematura delle valvole. Non avevo letto shields e avevo pensato che il semplice mettere e togliere le valvole dall'ampli, durante la manutenzione, a sua detta cambiasse il suono.

Il discorso pvc/teflon non lo capisco e mi suona ridicolo! Anche se il dielettrico dei due materiali è differente, se non c'è una linea/filo/chassis nelle immediate vicinanze dello stesso, non vedo proprio come possa crearsi una capacità. Sbaglio?