Just to remind those new to this thread, the 4 quadrant complementary differential j-fet, mosfet topology is what the CTC Blowtorch used to buffer the line pot and to amplify the audio signal.
Perhaps someone from the past can put up a simplified schematic, so we know where to start.
This design is at the heart of the CTC Blowtorch and most of Charles Hansen's Ayre designs. It is particularly useful for open loop designs,
We could also talk about and compare 4 quadrant all j-fet, non-folded cascode designs as well. such as is in the Parasound JC-2 preamp, just released this year. The 4 quadrant differential is not a new topology, as I first used it 40 years ago with bipolar transistors. However, with cascode, it gets even better, especially with j-fets.
Perhaps someone from the past can put up a simplified schematic, so we know where to start.
This design is at the heart of the CTC Blowtorch and most of Charles Hansen's Ayre designs. It is particularly useful for open loop designs,
We could also talk about and compare 4 quadrant all j-fet, non-folded cascode designs as well. such as is in the Parasound JC-2 preamp, just released this year. The 4 quadrant differential is not a new topology, as I first used it 40 years ago with bipolar transistors. However, with cascode, it gets even better, especially with j-fets.
I will ;
you want RtR , or mic ?
so - let's make old geezers tumbling in their graves
Since Zen Mod meant Gu-50 tube, should we put a schematic of a Telefunken microphone that used it?
I still think that a Telefunken schematic would be interesting to discuss.
My only Telefunken schematics are from quality portable radios from the 1960's, including one that Dick Sequerra worked on. However, even though they are very good sounding units, they are made with germanium transistors that are difficult to get today.
In my opinion, we should start somewhere, not changing from A to D, or amps to mikes. It makes it more useful, that way.
My only Telefunken schematics are from quality portable radios from the 1960's, including one that Dick Sequerra worked on. However, even though they are very good sounding units, they are made with germanium transistors that are difficult to get today.
In my opinion, we should start somewhere, not changing from A to D, or amps to mikes. It makes it more useful, that way.
It would be nice to have such a thread, but are you ready for the role?
First of all, you need a plan of the course. No doubt, you have some already, you may start from physics and technology of semiconductors. Then, 24/7 duty, voluntary.
Are you ready?
Hi John,
It was closed for reasons different than what you attempted to pass as a true reason.
Can we call a halt to "putting down" other members, this forum and it's moderators from now on? The same would apply the other way. No personal attacks allowed towards you. In other words, let's keep everything professional. There is no room for egos here.
-Chris
I'm sorry, I can't agree with this post at all.
It was closed for reasons different than what you attempted to pass as a true reason.
Can we call a halt to "putting down" other members, this forum and it's moderators from now on? The same would apply the other way. No personal attacks allowed towards you. In other words, let's keep everything professional. There is no room for egos here.
Yes, they really are compared to what you normally get these days. I am pretty sure it comes down to much better speakers and a more linear part than silicon transistors.
Yes, and expensive! I have some stored in a box, including many JIS numbers. I may be able to help if you need a couple one day. They can get pretty leaky though.
John, I couldn't agree more with you on that. Do you want to start with the BT diagram and go from there? Of course, any other design that illustrates the point you want to make would make an excellent addition as a diagram for discussion.
-Chris
Starting a new thread for discussion on state of the art?
Hi Anatoliy,
I don't think it's up to MJL21193 to plan the course of the thread. That's a bit much to ask. How about simply letting the thread find it's own way, and stay away from directly commenting on John's design in this one.
I know you were joking a bit here Anatoliy, but it is a great idea. Would you like to start it? MJL21193? Anyone? I can, but we should give someone else a chance at the mechanics of it.
-Chris
Hi Anatoliy,
To be honest with you, that's a great idea. There are pleanty of topics that do not fit in this thread. I'm sure John would agree, just as I'm sure you would as well.
I don't think it's up to MJL21193 to plan the course of the thread. That's a bit much to ask. How about simply letting the thread find it's own way, and stay away from directly commenting on John's design in this one.
I know you were joking a bit here Anatoliy, but it is a great idea. Would you like to start it? MJL21193? Anyone? I can, but we should give someone else a chance at the mechanics of it.
-Chris
One of the best examples of the 4 quadrant folded cascode topology was put up on this website, by Justcallmedad, on 5-30-2006. This is a fairly easy to read schematic, and only has a few 'extra' resistors that could be removed without changing the circuit, fundamentally. I do have a copy of it here. However, it should be in the website files as well.
A new thread ? With a more professional atmosphere ?
Amps to mikes ? .. power amps , headphone amps , preamps .. they are all amps. One amp design can be applied to another amp.
To discuss germaniums , the "sound of tubes" , would not be too "offtopic" if it helped others to understand the history and theories behind the designs.
State of the art ? Surely, BJT amps could be "new" , maybe even embracing SMD's (aussieamps) , microprocessor control (syn08) , but SOTA ?... this would be in the realm of mean, green Class D. (I personally do not believe this)
"Design principles" would be good for us "greenies" , we could hear the opinions of those "hardened ones" and ask questions (without being put down). Sounds good in concept !
OS
Amps to mikes ? .. power amps , headphone amps , preamps .. they are all amps. One amp design can be applied to another amp.
To discuss germaniums , the "sound of tubes" , would not be too "offtopic" if it helped others to understand the history and theories behind the designs.
State of the art ? Surely, BJT amps could be "new" , maybe even embracing SMD's (aussieamps) , microprocessor control (syn08) , but SOTA ?... this would be in the realm of mean, green Class D. (I personally do not believe this)
"Design principles" would be good for us "greenies" , we could hear the opinions of those "hardened ones" and ask
questions (without being put down). Sounds good in concept ! OS
No, I'm not joking, I really support Syn08's idea, and am ready to contribute to the thread as soon as he starts it.
How about "Syn08 Lectures on Semiconductors and Best Practices of Their Usage"?
I remember Feynman lectures on physics I used to read when was a kid. They were very strictly written, but at the same time fun to read!
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I would be interested to discuss this design. John, do you know in which thread and/or which post # this was?
jd
I am not quite sure which circuit you mean, John. My "BT-like" circuit analysis shows open loop bandwidth of some 400kHz (without input RC).
It was actually 31/5/2006, and quite predictably the images are gone. Even the server on which they resided is gone.
I can put here the "BT-Like" circuit, but need your permissison, as well as estimation if it should be blind or with component values.
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