Steve,
There are many ways of implementing a cascode and some, quite frankly, hurt the sound.
To properly discuss the your implementation, a schematic would be helpful.
Too many people have passed judgement on circuit topologies without trying variations of the circuit.
Harry gave an important clue when he said that he used a mosfet as the cascode device and no one caught on. The question of how to bias a cascode should have been brought up but unfortunately that was missed too.
Which brings us to the question do cascodes hurt or help? It depends on the circuit and the implementation. So maybe we can't generalize and must be more open to different ideas.
From what you describe I suspect you are building the Broadhurst design or a varation of it and we would love to hear the results of your experiments.
Jam
There are many ways of implementing a cascode and some, quite frankly, hurt the sound.
To properly discuss the your implementation, a schematic would be helpful.
Too many people have passed judgement on circuit topologies without trying variations of the circuit.
Harry gave an important clue when he said that he used a mosfet as the cascode device and no one caught on. The question of how to bias a cascode should have been brought up but unfortunately that was missed too.
Which brings us to the question do cascodes hurt or help? It depends on the circuit and the implementation. So maybe we can't generalize and must be more open to different ideas.
From what you describe I suspect you are building the Broadhurst design or a varation of it and we would love to hear the results of your experiments.
Jam
You mean the worst......
I guess I can take it from you or anybody else with a sense of humor...... I'm afraid there are few on the forum who actually think I have horns and one that wants to punch me in the face!(where's the moderator on that on that one?) As Oscar Wild said; " There is only one thing worse than be talked about and that is not being talked about." And somehow Jocko seems to get off Scott free! Read any good schematics lately?
"Harry gave an important clue when he said that he used a mosfet as the cascode device and no one caught on." They were too busy Tar and Feathering me for lack of useful content, ironic isn't it.....?
H.H.
I guess I can take it from you or anybody else with a sense of humor...... I'm afraid there are few on the forum who actually think I have horns and one that wants to punch me in the face!(where's the moderator on that on that one?) As Oscar Wild said; " There is only one thing worse than be talked about and that is not being talked about." And somehow Jocko seems to get off Scott free! Read any good schematics lately?
"Harry gave an important clue when he said that he used a mosfet as the cascode device and no one caught on." They were too busy Tar and Feathering me for lack of useful content, ironic isn't it.....?
H.H.
Read any good schematics lately?
You haven't been paying attention, have you? Move to the rear of the class.
Jocko
You haven't been paying attention, have you? Move to the rear of the class.
Jocko
Re: Cascode
Does anybody visit the Borbely site ? He seems to like JFET/MOSFET cascodes also. Check out the all FET line amp, as well as the Ribbon and Millenium power amp schematics.
mlloyd1
who is still unhappy he will never get any V grade JFETs 🙁
Does anybody visit the Borbely site ? He seems to like JFET/MOSFET cascodes also. Check out the all FET line amp, as well as the Ribbon and Millenium power amp schematics.
mlloyd1
who is still unhappy he will never get any V grade JFETs 🙁
HarryHaller said:
Borbely Site
Love it! I have mentioned it several times and put a "gratuitus picture" of a Borbely JFET buffer that I built on the forum. Erno will sell you V bias fets I bet. I am hoarding mine like NOS tubes! Erno favors all fet designs as do I. I won't even suggest the use of the site search engine as that will surely be the last you ever see of my post if I do!
Love it! I have mentioned it several times and put a "gratuitus picture" of a Borbely JFET buffer that I built on the forum. Erno will sell you V bias fets I bet. I am hoarding mine like NOS tubes! Erno favors all fet designs as do I. I won't even suggest the use of the site search engine as that will surely be the last you ever see of my post if I do!
Re: Who is still unhappy he will never get any V grade JFETs
Nothing fancy; just some 2SK170 and 2SJ74. I managed to get some 2SK146 and 2SJ73 in GR grade some years ago. I know I could probably buy some from Borbely. It just seems I should be able to get some a little easier and cheaper. Did he just buy all the V grades on the planet? 😕
mlloyd1
Nothing fancy; just some 2SK170 and 2SJ74. I managed to get some 2SK146 and 2SJ73 in GR grade some years ago. I know I could probably buy some from Borbely. It just seems I should be able to get some a little easier and cheaper. Did he just buy all the V grades on the planet? 😕
mlloyd1
Jocko Homo said:
Jam,
I haven't heard of that circuit. Do you have a link?
My idea was an implementation of the Zen balanced Line stage, only running more bias, and using cascode mosfets and bipolar/led current sources, running at 80mA per mosfet. I want to keep the dual sources so gain can be easily controlled by a resistor. The cascodes will be biased with 5.1V zeners, referenced to ground. I chose to keep the voltage across the lower transistors as low as possible, on a tip from Nelson. I don't know if I will current source the zeners or not, as (if I remember right) you suggested. Supplies will be regulated +60v, -30V to give maximum swing and reduce dissipation on the current source bipolars. I would like to make a high current -30v supply and run both the regulated negative-supply half of the above-mentioned stage and a Ciuffoli power follower for an output stage off of it. I'll see if I can come up with a schematic soon.
steve
I haven't heard of that circuit. Do you have a link?
My idea was an implementation of the Zen balanced Line stage, only running more bias, and using cascode mosfets and bipolar/led current sources, running at 80mA per mosfet. I want to keep the dual sources so gain can be easily controlled by a resistor. The cascodes will be biased with 5.1V zeners, referenced to ground. I chose to keep the voltage across the lower transistors as low as possible, on a tip from Nelson. I don't know if I will current source the zeners or not, as (if I remember right) you suggested. Supplies will be regulated +60v, -30V to give maximum swing and reduce dissipation on the current source bipolars. I would like to make a high current -30v supply and run both the regulated negative-supply half of the above-mentioned stage and a Ciuffoli power follower for an output stage off of it. I'll see if I can come up with a schematic soon.
steve
Mlloyd,
Thanks for posting the link.
Steve,
I would bias the cascodes with a slightly higher voltage maybe 15 to 20 volts. Biasing the Zeners with a current diode usually sounds better than a resistor but whatever you do set the zener corrent at about 4ma. A small cap across the zener ( 1uf ) usually helps.
I would strongly recomend that you replace the bipolars with mosfets.
Regards,
Jam
Thanks for posting the link.
Steve,
I would bias the cascodes with a slightly higher voltage maybe 15 to 20 volts. Biasing the Zeners with a current diode usually sounds better than a resistor but whatever you do set the zener corrent at about 4ma. A small cap across the zener ( 1uf ) usually helps.
I would strongly recomend that you replace the bipolars with mosfets.
Regards,
Jam
Jam,
Nelson Pass suggested in another post that the voltage across the gain transistors should be minimized- he quoted a fairly low figure, if I remember right. I will have to go back and search for it and re-post it. In my simulations, it seems to allow for the most clean voltage swing, which is what I'm looking for in this application (using it for the front end of a power amp to supply all the voltage gain). Is there a reason that you suggest using a higher voltage?
Also, why are mosfet current sources better? I've had a few people tell me that bipolars are superior as current sources... why do you prefer mosfets?
Steve
Nelson Pass suggested in another post that the voltage across the gain transistors should be minimized- he quoted a fairly low figure, if I remember right. I will have to go back and search for it and re-post it. In my simulations, it seems to allow for the most clean voltage swing, which is what I'm looking for in this application (using it for the front end of a power amp to supply all the voltage gain). Is there a reason that you suggest using a higher voltage?
Also, why are mosfet current sources better? I've had a few people tell me that bipolars are superior as current sources... why do you prefer mosfets?
Steve
Steve,
That is true if you want more swing but not necessarly for best sound. I suggest you expermnent with different cascode voltages and compare any sonic differences.
I prefer mosfets in current sources because to me they just sound better, this is something you will have to try for yourself. I doubt you could measure any differences but when listening the differences are readily apparent.
Jam
That is true if you want more swing but not necessarly for best sound. I suggest you expermnent with different cascode voltages and compare any sonic differences.
I prefer mosfets in current sources because to me they just sound better, this is something you will have to try for yourself. I doubt you could measure any differences but when listening the differences are readily apparent.
Jam
Jam,
OK... so a little more voltage for better sound. I'm with you. I will have to try and reach a compromise between voltage swing and best sound.
I will try not to be so easily swayed when it comes to people's ideas of "ideal" devices- like you said about the current sources- sometimes things just sound better a certain way. I can't argue with that. The only problem with using mosfet sources is the increase in the negative rail I'll need. Right now, I am able to use the same supply for both the voltage amp and power amps stages.
What, specifically, do you find happens to the sound with mosfet sources, as compared to bipolar?
Steve
OK... so a little more voltage for better sound. I'm with you. I will have to try and reach a compromise between voltage swing and best sound.
I will try not to be so easily swayed when it comes to people's ideas of "ideal" devices- like you said about the current sources- sometimes things just sound better a certain way. I can't argue with that. The only problem with using mosfet sources is the increase in the negative rail I'll need. Right now, I am able to use the same supply for both the voltage amp and power amps stages.
What, specifically, do you find happens to the sound with mosfet sources, as compared to bipolar?
Steve
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