Why is my information "unhelpful"?
Each of my three statements are offering guidance to help avoid expensive errors, expensive in either time and/or money i.e. resources.
Without proper knowledge, it's the best way to make complete mess.
No, they are sometimes wrong. Non-experts are seldom right.
NP did -- but it's way back in the thread -- he also commented on it in the original AudioXpress article.
Vishay purchased the IRF Mosfet biz last year -- the devices are now being shipped with the ST Logo -- they test the same as the IRF devices, but I can't comment on the quality of the listening. One thing I have noticed is that the tubes are not date stamped, nor is the country of origin posted. The Vishay devices occasionally have fingerprints on the back indicating a lot of manual handling.
The Fairchild TO-247 devices seem to be going "unobtanium" -- while both Arrow and Mouser list them as available, none are in stock. This is a bit of casuistric ethics bending going on here with Arrow in particular -- they list an item so that it shows up on the search engines but it is nowhere to be found.
Fairchild TO-220 analogues seem to be in current production -- they handle a bit less current than the TO-247's.
Reading cascode article by NelsonPass
Dont know, but sounds to me its like a ccs, dealing with fluctuating voltage induced distortion
But also, like mentioned, cascode will make life easier on the Jfets
Especially when we want to raise voltage and drive multiple output devices
When suggesting that BCs will be fine fore cascode, are we forgetting the request fore raised voltage and multiple outputs ?
I mean, even if the Jfets will be working less, the first cascode transistor should be able to handle ALL the raised voltage and exstra work, or ?
Dont know, but sounds to me its like a ccs, dealing with fluctuating voltage induced distortion
But also, like mentioned, cascode will make life easier on the Jfets
Especially when we want to raise voltage and drive multiple output devices
When suggesting that BCs will be fine fore cascode, are we forgetting the request fore raised voltage and multiple outputs ?
I mean, even if the Jfets will be working less, the first cascode transistor should be able to handle ALL the raised voltage and exstra work, or ?
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No, driving two pairs of output MOSFETS will be almost equally easy, especially Toshiba'a MOSFETs.
Why ALL, what extra work? In the sch. I drawn the PS voltage (40V) is almost equally split between JFET and BJT (20V each). They share the same current and they will dissipate almost the same power.
Find out what's typical Vgs of k170/j74 with Id=6mA and answer will jump in your face
(E. Borbely wrote about it long time ago)
Depletion mode amp; maybe we can talk about that in a year or two
Doesnt matter
To me its about having fun
And having good amps that work
Better or worse, I dont care
Its a nver ending story
Juma, you have to know that I use PDaniels and Cvillers to see how to orient transistors
And nice help from Thanh
If I had better understanding of this I wouldnt need to ask
Vgs, ids or whatever, I have no idea what it is
I can connect A to B, if it says so, not much else really
But Im learning a bit still
btw
If I manage to do this, I might offer PDs and Cvillers F5 boards fore forum donation
Doesnt matter
To me its about having fun
And having good amps that work
Better or worse, I dont care
Its a nver ending story
Juma, you have to know that I use PDaniels and Cvillers to see how to orient transistors
And nice help from Thanh
If I had better understanding of this I wouldnt need to ask
Vgs, ids or whatever, I have no idea what it is
I can connect A to B, if it says so, not much else really
But Im learning a bit still
btw
If I manage to do this, I might offer PDs and Cvillers F5 boards fore forum donation
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Thank you guys for all of U r help and advise
I want to be clear in one or more fact .
Firs my transformer would give around 36V rail max in class A not 40V or more .
Probably with 2A bias is still will be OK? The main idea to bias the amp into class A mode until the transformer would allow me (1KVA).
I can use 2SK170BL & 2SJ74BL for cascode also if that is OK ! I have nothing against those parts .
You guys right , better to be careful than after to be sorry .
Probably if I do not have the right (clear) picture at the front of me I will create a complete mess and after I would give up as NOT WORKING project.! It happaned with another amp before , I blew up all the amp including some expensive Sanken power transistors . After I gave up .Waste of money and bitter taste .
I do not want to repeat the same mistake again and again just to learn something or almost nothing !
A question if I use 3 pair Toshiba power mosfet do that work with out cascode with 36V rail power ?
The reason I ask these question if I understood well it is easier to drive the Toshiba MOSFET s .
The best way to learn "hands on" that is true , but also true to avoid wasting parts or money to get advise from Experts !
Someone already built the amp with 3 par power mosfet with out cascode but He did it with lower power supp .
Also he use IR type mosfet not Toshiba if I remember well .
Probably I can try if 3 pair Toshiba mosfet work with out cascode ? I'm not into that cascode mode if it would be OK with out .
To hard wire the amp is more difficult to me than to design the layout .
Also I can end up with burned parts using hard wire to .I would like to avoid that.
Greets
I want to be clear in one or more fact .
Firs my transformer would give around 36V rail max in class A not 40V or more .
Probably with 2A bias is still will be OK? The main idea to bias the amp into class A mode until the transformer would allow me (1KVA).
I can use 2SK170BL & 2SJ74BL for cascode also if that is OK ! I have nothing against those parts .
You guys right , better to be careful than after to be sorry .
Probably if I do not have the right (clear) picture at the front of me I will create a complete mess and after I would give up as NOT WORKING project.! It happaned with another amp before , I blew up all the amp including some expensive Sanken power transistors . After I gave up .Waste of money and bitter taste .
I do not want to repeat the same mistake again and again just to learn something or almost nothing !
A question if I use 3 pair Toshiba power mosfet do that work with out cascode with 36V rail power ?
The reason I ask these question if I understood well it is easier to drive the Toshiba MOSFET s .
The best way to learn "hands on" that is true , but also true to avoid wasting parts or money to get advise from Experts !
Someone already built the amp with 3 par power mosfet with out cascode but He did it with lower power supp .
Also he use IR type mosfet not Toshiba if I remember well .
Probably I can try if 3 pair Toshiba mosfet work with out cascode ? I'm not into that cascode mode if it would be OK with out .
To hard wire the amp is more difficult to me than to design the layout .
Also I can end up with burned parts using hard wire to .I would like to avoid that.
Greets
Hi gaborbela!
So, you want someone to design for you 100% safe & tested modified F5 with +/-36V rails (1KVA transformer), three pairs of Toshiba MOSFETs in output stage (per channel) and with cascoded input stage (without cascodes 2sj74 will die quickly).
Sorry, it doesn't work that way
It's not a trivial project and you better save your transformer for the time when you acquire necessary knowledge and skills to use it without having a "bitter taste" in the end.
Right now, it would be best to build standard F5 (use Toshiba MOSFETs freely, even two pairs per channel - you can because their capacitance is lower than IR's).
The most important thing is to read and understand F5's service manual completely (I know that soldering iron wielding is far more interesting than reading such a long text, but it will pay off believe me)
So, you want someone to design for you 100% safe & tested modified F5 with +/-36V rails (1KVA transformer), three pairs of Toshiba MOSFETs in output stage (per channel) and with cascoded input stage (without cascodes 2sj74 will die quickly).
Sorry, it doesn't work that way
It's not a trivial project and you better save your transformer for the time when you acquire necessary knowledge and skills to use it without having a "bitter taste" in the end.
Right now, it would be best to build standard F5 (use Toshiba MOSFETs freely, even two pairs per channel - you can because their capacitance is lower than IR's).
The most important thing is to read and understand F5's service manual completely (I know that soldering iron wielding is far more interesting than reading such a long text, but it will pay off believe me)
Yes there is a balance needed between having adequate knowledge and a hands on approach, in this situation.
However you guys are still wrong.
Where do you think all this information came from.
God didn't write our text books, men and women wrote them. Men and women who were willing to experiment to find the answers.
Before there were transistors, was there a book on cascoding transistors.
So if none of us are willing to experiment we stand still and we all build Douclas Self amps.
However you guys are still wrong.
Where do you think all this information came from.
God didn't write our text books, men and women wrote them. Men and women who were willing to experiment to find the answers.
Before there were transistors, was there a book on cascoding transistors.
So if none of us are willing to experiment we stand still and we all build Douclas Self amps.
Yes there was. Cascoding was known in the world of tubes too. And even before that cascoding as an physical concept was used in different branches of engineering. "Nihil novi sub sole" has been said long time ago, but some people are just lazy to read
It was stated clearly just few posts back, that 30V would work without cascode, and a few exstra outputs, but not higher than 30V(22V trafo)
There are amps around too running healthy on that
But now there seems to be issue with orginal IR outputs as well
And cascode not going well either
Not going well
I think I will give it a rest until things are resolved
Enough other things to do at the moment, so I wont loose my sleep over it
But I still hope someone can work this out so we less skilled can do it safely
There are amps around too running healthy on that
But now there seems to be issue with orginal IR outputs as well
And cascode not going well either
Not going well
I think I will give it a rest until things are resolved
Enough other things to do at the moment, so I wont loose my sleep over it
But I still hope someone can work this out so we less skilled can do it safely
You offer a lot of helpful advice.
But sometimes it can come across as discouraging, rather than encouraging.
It could put people off, before they even start.
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Hi Juma
Ok that was a bad example, but hopefully you are intelligent enough to know what I am trying to say here.
Without the people to do the experimenting in the first place, there would be no source of information to refer to.
And just because one guy has observed some unusual new behaviour, there are quite a few assumptions made in interpreting it's meaning.
If one expert says the world is flat and another expert says the world is round, are they both right?
Ok that was a bad example, but hopefully you are intelligent enough to know what I am trying to say here.
Without the people to do the experimenting in the first place, there would be no source of information to refer to.
And just because one guy has observed some unusual new behaviour, there are quite a few assumptions made in interpreting it's meaning.
If one expert says the world is flat and another expert says the world is round, are they both right?
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