Aussiedrummer, I'm not the guru, just a fan. Hopefully, you will become a fan as well.
According to Jadis, you can only use EL34 variants in your Orchestra. The Orchestra Reference, with its upgraded transformers, allows use of the larger tubes. I have my own opinion on the matter, but suggest you contact Jadis if you are that interested in using KT88.
One thing about the JOR is that it buys you the better cosmetics, as you mentioned the Orchestra's finish is reflective of a Chinese amp. I'll say that these days, the Chinese put a lot of resources into the casework, using a lot of metal and CNC milling equipment. But, in the effort to come across as distinct, classy, or even edgy, the cosmetics have a short shelf life, and come across as tacky within a few years. In my opinion, many of the Chinese marques would be better served by investing the time in bringing the design and implementation of a circuit to a higher level.
In the simplest terms, think of a tube as a conduit for the travel of electrons. They go from one place (cathode) to the other (anode, also called the plate). That's basically it.
Of course, amplification is a product of going from that one place to the other, which is why tubes are used in amplifiers.
Still keeping things simple and easy, because a tube works so well at the aforementioned task of having electrons go from the cathode to the anode, the tube can burn up quickly. Then, we'd need a new tube well before its time. So, we want to moderate/modulate that process and slow things down to a manageable level. That obviously requires something else to be added into the equation. The third element is called the control grid. Three elements in the tube means we have what's called a triode. Prior that, we had just two elements (cathode and anode/plate), a diode.
As we all know, opposite charges attract each other, which is why the electrons fly toward the plate in the first place. Conversely, like charges repel each other, so two electrons will try to stay away from each other.
The control grid sits between the cathode and the plate, and, again its job is to modulate the electron flow from the cathode to the plate (anode). It does this by having a negative charge, and as we said, like charges repel each other. The electrons now see a negative charge in front of them, and their impetus for the travel from the cathode to the plate has been reduced. That negative charge, which we'll measure in voltage and call bias (yes, that's what we mean when we say bias), can be nothing (ZERO) which would be as if the control grid wasn't even there, or high enough so that no electrons make the jump at all (tube is essentially "off"). Ideally, we'll look for some value that's high enough to allow the electrons flow and make music, and low enough so we're not replacing our tubes more frequently than our socks.
Note, as we said, the bias voltage is negative, which confuses most everyone so we'll take a second pass at it. A MORE negative (-70V is more negative than -40V, as -70V is further from 0 than -40V is) voltage will allow LESS electrons to flow. A LESS negative (closer to 0) voltage will allow MORE electrons to flow. Once we understand things that way, it all actually begins to make sense. Colloquially, people will use the terms "hotter"/"warmer" and "colder" to describe all of this.
Quickly, and keeping things simple there can one or two additional elements in the tube that will make the tube work better (whether or not that is true when it comes to high-end audio will bring us into a lot of, um, "discussion" shall we say). Adding one additional (fourth) element the screen grid, make it a tetrode. Adding another (fifth) on top of that, the suppressor grid, makes it a pentode like the EL34 and KT88 we've been talking about.
Along with going deeper into what the screen and suppressor grids do, there are other more esoteric things to talk about one day like cathode bias and fixed bias, and even making the control grid positive (yes, positive). But for now, just try to first understand how the cathode, control grid, and anode/plate work, and get comfortable with that.
According to Jadis, you can only use EL34 variants in your Orchestra. The Orchestra Reference, with its upgraded transformers, allows use of the larger tubes. I have my own opinion on the matter, but suggest you contact Jadis if you are that interested in using KT88.
One thing about the JOR is that it buys you the better cosmetics, as you mentioned the Orchestra's finish is reflective of a Chinese amp. I'll say that these days, the Chinese put a lot of resources into the casework, using a lot of metal and CNC milling equipment. But, in the effort to come across as distinct, classy, or even edgy, the cosmetics have a short shelf life, and come across as tacky within a few years. In my opinion, many of the Chinese marques would be better served by investing the time in bringing the design and implementation of a circuit to a higher level.
In the simplest terms, think of a tube as a conduit for the travel of electrons. They go from one place (cathode) to the other (anode, also called the plate). That's basically it.
Of course, amplification is a product of going from that one place to the other, which is why tubes are used in amplifiers.
Still keeping things simple and easy, because a tube works so well at the aforementioned task of having electrons go from the cathode to the anode, the tube can burn up quickly. Then, we'd need a new tube well before its time. So, we want to moderate/modulate that process and slow things down to a manageable level. That obviously requires something else to be added into the equation. The third element is called the control grid. Three elements in the tube means we have what's called a triode. Prior that, we had just two elements (cathode and anode/plate), a diode.
As we all know, opposite charges attract each other, which is why the electrons fly toward the plate in the first place. Conversely, like charges repel each other, so two electrons will try to stay away from each other.
The control grid sits between the cathode and the plate, and, again its job is to modulate the electron flow from the cathode to the plate (anode). It does this by having a negative charge, and as we said, like charges repel each other. The electrons now see a negative charge in front of them, and their impetus for the travel from the cathode to the plate has been reduced. That negative charge, which we'll measure in voltage and call bias (yes, that's what we mean when we say bias), can be nothing (ZERO) which would be as if the control grid wasn't even there, or high enough so that no electrons make the jump at all (tube is essentially "off"). Ideally, we'll look for some value that's high enough to allow the electrons flow and make music, and low enough so we're not replacing our tubes more frequently than our socks.
Note, as we said, the bias voltage is negative, which confuses most everyone so we'll take a second pass at it. A MORE negative (-70V is more negative than -40V, as -70V is further from 0 than -40V is) voltage will allow LESS electrons to flow. A LESS negative (closer to 0) voltage will allow MORE electrons to flow. Once we understand things that way, it all actually begins to make sense. Colloquially, people will use the terms "hotter"/"warmer" and "colder" to describe all of this.
Quickly, and keeping things simple there can one or two additional elements in the tube that will make the tube work better (whether or not that is true when it comes to high-end audio will bring us into a lot of, um, "discussion" shall we say). Adding one additional (fourth) element the screen grid, make it a tetrode. Adding another (fifth) on top of that, the suppressor grid, makes it a pentode like the EL34 and KT88 we've been talking about.
Along with going deeper into what the screen and suppressor grids do, there are other more esoteric things to talk about one day like cathode bias and fixed bias, and even making the control grid positive (yes, positive). But for now, just try to first understand how the cathode, control grid, and anode/plate work, and get comfortable with that.