Just a suggestion by Nico to cope with the 25V devices I want to use. I'd rather be without them, hehe
The cascode discussion is for using JFETs other than LSK489 / LSJ689. These have 50V ratings were other JFETs are often around 25V. A cascode mitigates this.
In my Spice experiments, the voltage drop on one of the FETs in above scheme is 95%. With my very limited understanding, I can only imagine, the above usage of multiple JFETs as a diff purpose.
Looking at examples for JFET cascodes, I was able to get a well working circuit, in which the voltage is distributed across both JFETs as desired (well, you need to adjust the resistors building the voltage divider to really get 50/50). Since this is just looking at examples and trial-and-error, I might have gotten something wrong.
In Spice it works fine, though.
I have just used the JFETs of the original design to minimize effort. I expect this works similarly with 2SK146 and 2SJ73.
Thanks! Looks fine, but is it necessary to have separate bias for the cascode FETs? Here are a couple of example using BPs, but that shouldn't matter, I believe.
And another Borbely
I am in doubt about the Borbely variant. It looks like the cascode bias shares current with the FETs, so the some calculation is needed. Not for me.
The first one is similar to what you suggest, if the cap is added. Is that right?
And another Borbely
I am in doubt about the Borbely variant. It looks like the cascode bias shares current with the FETs, so the some calculation is needed. Not for me.
The first one is similar to what you suggest, if the cap is added. Is that right?
If using FET for the cascode has advantages over BP, I will gladly use FETs. In addition it looks rather serious with those vintage aluminium cans! 😎
No, it was just late and LTSpice, while being a really great tool, has a bad UI and I was too lazy to combine after I had it.
Rwan,
build it and test it then you will know if it is any good. Nobody here can look at a schematic and predict what it will sound like, regardless of simulation. Everything that simulates perfectly does not mean it will sound good. Furthermore, layout components placement component quality all makes a difference. The models used in simulations does not mean they are perfect, also if you build it not a single component will be the direct equivalent of the model, unless you measure each transistor, cap and resistor and place them into the simulator that you will use to build the product.
In 2002 I designed and build the RAS-ELD doing exactly that. It took almost one year to complete (almost full time) and cost me about $28000 only buying 1000s high quality components from different manufacturers (no labour costs) used in matching exactly and the yield was very, very low. It took 9 PCB layouts to find the best measured results. Then I did the mechanics of which all machined parts were done in-house at cost. The transformers (one each channel) was wound to specification using silver wire. All internal wiring was silver PTFE coated single core wire, routed for least noise pick up.
When completed, it was demonstrated to my fellow directors (hoping we could enter the high-end market) costings and margins calculated by the financial director personally. The marketing director costed all the advertising marketing fees, literature, printing, exhibitions, and display samples, etc for one year in the future. What happened to it in the end? Well the only sample is sitting on my hi-fi shelf since that meeting and went nowhere commercially, it was just too expensive.
My point is that many high-end manufacturers charges the exorbitant prices for their equipment, simply because it cost exorbitant prices to R&D market and distribute, offering direct sale from the manufacturer just to cut out the profit from dealers so that the product is more affordable to the few that can purchase it.
The moral of the story, an audiophile product cannot simply be accessed by a simulation, it is a good starting point only and represents almost nothing in the real world other that a few graphic representations that you can look at and adjust for hours.
And yes I admire people like Andrew (Bonzai) to dedicate his existence to making high quality audio products. People said I was nuts when purchasing my Wadia6 CD player, it is not worth it. Well, this is not true, once you realize what actually goes into a excellent audio (or any) product and the mechanical engineering of the transport, etc, etc. That is what counts.
So what do I think of your schematic, nothing really, it is what it is, a schematic.
build it and test it then you will know if it is any good. Nobody here can look at a schematic and predict what it will sound like, regardless of simulation. Everything that simulates perfectly does not mean it will sound good. Furthermore, layout components placement component quality all makes a difference. The models used in simulations does not mean they are perfect, also if you build it not a single component will be the direct equivalent of the model, unless you measure each transistor, cap and resistor and place them into the simulator that you will use to build the product.
In 2002 I designed and build the RAS-ELD doing exactly that. It took almost one year to complete (almost full time) and cost me about $28000 only buying 1000s high quality components from different manufacturers (no labour costs) used in matching exactly and the yield was very, very low. It took 9 PCB layouts to find the best measured results. Then I did the mechanics of which all machined parts were done in-house at cost. The transformers (one each channel) was wound to specification using silver wire. All internal wiring was silver PTFE coated single core wire, routed for least noise pick up.
When completed, it was demonstrated to my fellow directors (hoping we could enter the high-end market) costings and margins calculated by the financial director personally. The marketing director costed all the advertising marketing fees, literature, printing, exhibitions, and display samples, etc for one year in the future. What happened to it in the end? Well the only sample is sitting on my hi-fi shelf since that meeting and went nowhere commercially, it was just too expensive.
My point is that many high-end manufacturers charges the exorbitant prices for their equipment, simply because it cost exorbitant prices to R&D market and distribute, offering direct sale from the manufacturer just to cut out the profit from dealers so that the product is more affordable to the few that can purchase it.
The moral of the story, an audiophile product cannot simply be accessed by a simulation, it is a good starting point only and represents almost nothing in the real world other that a few graphic representations that you can look at and adjust for hours.
And yes I admire people like Andrew (Bonzai) to dedicate his existence to making high quality audio products. People said I was nuts when purchasing my Wadia6 CD player, it is not worth it. Well, this is not true, once you realize what actually goes into a excellent audio (or any) product and the mechanical engineering of the transport, etc, etc. That is what counts.
So what do I think of your schematic, nothing really, it is what it is, a schematic.
Many cut and paste schematics and tweak it to work on a simulator, not really understanding what the simulator does other that it is a mathematical approximation only. Yes 30 years ago we did the same with prototypes, real measurements and calculators and took weeks, sometimes months, but the end result was real life stuff, not prediction.
You have a better chance predicting the weather a year from now than predict the sound of a system exactly. Let the simulator be a guidance only.
You have a better chance predicting the weather a year from now than predict the sound of a system exactly. Let the simulator be a guidance only.
Thanks for good advice anyway, all of you!
Yesterday I finished PCB for the IRF version by lineup.
I think I'll go for a PCB for this cascode version.
Yesterday I finished PCB for the IRF version by lineup.
I think I'll go for a PCB for this cascode version.
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A lot of people choose to small an input capacitor, not realizing the the preceding equipment may come with a capacitor in the output. The two caps in series may impair the bass response without even realizing it.
Here is what I have so far. Corrected missing GND on input connector. Added Groundplane for input GND. Added AC/DC select jumper on input.
Made space for screw terminals on MOSFETs in case I want to use TO-3 Exicons. Placed VAS transistors on PCB edge in case someone tells med they need cooling... Don't think cap multipliers need cooling, though.
Any thoughts?
Made space for screw terminals on MOSFETs in case I want to use TO-3 Exicons. Placed VAS transistors on PCB edge in case someone tells med they need cooling... Don't think cap multipliers need cooling, though.
Any thoughts?
About 100 yesra ago my first real job was at NDRE (Norwegian Defense Research Establishment,.. puh!) where I started making PCBs. My supervisor told me that "first it has to be nice, then it has to work". I guess it stuck. But I have no expertise in audio layout, as all my work back then was more or less digital designs. So "star grounds" and and other rule-of-thumbs. I am bad at those. Usually the 2-3 last routes don't make me proud! At least it looks good.
And before anyone asks, Helion Audio does not exist i real life. Only in my head. Many of you audio gurus out there have fancy names and logos on your PCBs, so that's why.
And I don't make PCBs for sale, I'm afraid most of them are not good enough to offer for sale. A few have been tested by me and my audio friend, successfylly, though. And I just love playing with KiCAD... 😎
And I don't make PCBs for sale, I'm afraid most of them are not good enough to offer for sale. A few have been tested by me and my audio friend, successfylly, though. And I just love playing with KiCAD... 😎
I don't understand the question. The terminalblocks will accommodate plasitc FETs the normal way. The blocks are supposed to be place on top side of PCB.
I recently offered my KiCAD libraries to diyaudio.com users in a saparate thread. When I started with KiCAD I would have loved having something ready-made to play with. Have a look. Post #5 is my Dropbox folder, dont't know for how long this will work. Post #11 is the AppBox folder.