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Old 17th May 2006, 09:44 PM   #31
EUVL is offline EUVL  Europe
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> Other JFETs should work well, too.

I would have just used 2 matched 2SK170s. Plenty around.
LSK389 is not widely available, expensive, and not really better than the Toshibas, as they claim.

> That's a pretty straight forward Circlotron.

I thought that is the Pass philosophy ? Certainly cannot be simpler than what he has drawn. What are the srawbacks of that circuit ?

Patrick
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Old 17th May 2006, 11:39 PM   #32
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The Pass Philosophy??? Crrently I have a couple prototype line amps that you see below. I think it deffinatly has it's roots in the Pass Philosophy... It is my first answer to the "How to drive the New-Tron" question... I've also been thinking in bridged circles for a while and the topology below will do the job. It simulates pretty good and an unmatched component version measures about 10X the sim data so I'm anctous to measure the second "matched" prototype...
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Old 17th May 2006, 11:42 PM   #33
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As I was saying... Bridged Circles
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Old 19th May 2006, 02:46 AM   #34
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EUVL,
Here in the US, the 2SK170 is not readily available. If you are able to find them, you have no control over whether you're getting GR, BL, or VI. Actually, strike that--I've never even seen a 2SK170 VI. Like the Nonesuch, I've come to doubt that they even exist. The LSK170 is available and you can order the Idss you want. The price is somewhat higher than what we pay for the Toshiba parts, but that may improve if bought in quantity.
Note that although the '170 is available, you still have to buy in quantity and hand match them to simulate a '389. Your cost skyrockets accordingly.
Toshiba parts are not--unfortunately--the kind of thing you can just walk into a store and buy here in the US. They're all black market.
Speaking of which, I'd love to try the Toshiba 2SK2013/2SJ313 (I think I've got those numbers right), but they do not seem to be available anywhere at any price here in the US. If anyone can suggest a source, I'd appreciate it. Yes, I know Borbely lists them, but he has a steep minimum order and I have a feeling that the parts themselves can be had more cheaply...if only I can find the damned things. I am reluctant to sink a lot of money into those parts until I can try them in a circuit I've got going. If they don't work, I don't want to be sitting on a bunch of the silly things.
The circuit referenced earlier is a standard Circlotron. It's essentially the same circuit I've posted, just drawn differently.
Most tube circuits were pretty simple. Solid state adaptations of those topologies tend to remain pretty simple unless someone gets a wild hair and decides to "improve" the circuit. Some improvements work. Most don't. To the extent that it's a simple circuit, I'd say that it's certainly in line with Nelson's KISS circuits.
flg,
The circuit looks good, but I think it needs a couple of power JFETs.
(ahem...)

Grey
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Old 19th May 2006, 03:06 AM   #35
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UHHmmm, Yes, your right. Something like that is in order. I wouldn't want to stretch the thread to far...But, I want to use my JFETs in a variation combining the ZV7T and ZV9. I guess I'm free to call it ZV9T. There has been a little chat about that path already. I beleive there is something working out there that is at least 1/2 of that... I have this real free time crunch going on too... I'm being Dev#$%ed and I have to sell my house etc etc etc... So, I don't have much left thats not in a box but the simulator and the kitchen table... I would also like to develope a good Pspice model for the JFET while I'm winding down things at the homestead... I'm workin on it...
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Old 19th May 2006, 05:19 AM   #36
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Grey,

You can get 2SK170BLs AND Vs from Fibra Brandt Semiconductors (just google) at reasonable price, and the specific type that you want. I actually have more problems getting GR. I have bought enough Vs from him, so they definitely exist.

I have located a possible source in Japan for 2SK2013/2SJ313. They are not expensive, not more than any other Toshiba TO220 MOSFETs. If you are interested, please contact me by private mail. They are also not available in Europe, or anywhere else other than Japan. I actually asked Toshiba here.


Patrick
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Old 19th May 2006, 01:21 PM   #37
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Grey,

The NTE132 is offered as equiv. to 2SK170

Zero–Gate–Voltage Drain Current IDSS VDS = 15V, VGS = 0 2 – 20 mA

But they must be tested for possible BL-GR-V ...

PS: Active.ca sells them for $1.81 CAD pc.

Alain.
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Old 19th May 2006, 02:48 PM   #38
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If I read the datasheet correctly, NTE132 has a forward transconductance of 2.5~7 mS; and 2SK170 has 20mS ??

Also I wonder what capacitance values the NTE132 has ?

Patrick
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Old 19th May 2006, 11:38 PM   #39
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flg,
Just teasing, of course. The circuit will work without power JFETs...just not as well.
(Who, me? I'm not nudging people to use these things...)
EUVL,
I haven't checked the Euro/dollar conversion recently, but the prices Fibra-Brandt quotes seem high to me. Especially with the US dollar falling against other currencies.
Regarding the 2SK2013/2SJ313: Why on Earth would a manufacturer make a product, then make such an effort not to sell it? Mind boggling. You'd think that they would make at least a rudimentary effort to distribute the product so they could sell a few.
Grumble.
Alain,
I had problems with consistency with NTE product--so much so that I quit buying anything they sell. I would buy one or two devices, do some R&D, then go back and buy more, only to discover the the next ones didn't behave the way the first ones did. I've also had problems with parts that weren't good matches for the ones they were supposedly replacing, etc. And the price was usually high. I gave up.
The worst case was a high voltage regulator I built for a tube circuit. It used a MOSFET as a pass device--I don't remember which NTE part number, this was ten years ago. I built three regulators with NTE MOSFETs I had on hand. All worked perfectly. I bought more and they oscillated horribly. Nothing would make them behave. I eventually had to change the regulator circuit. Boy, was I peeved!

Grey
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Old 20th May 2006, 01:01 AM   #40
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Yep, I realize that Grey. but I was already doing Circlotron before the Z9, maybe even before Z8, and before that I was finishing up the "LH". I wasn't willing to complicate things with changing a good looking output device and adding a cascode that may not be necessary???
I really like the Inductor load idea of ZV7 though, especialy with a "triode like" device. I may go on to do the follower thing with the JFETs later... That will be down the road a bit.
How about this for a good reason, speaking of down the road. My Mom & Dad are getting old and I've been in the Phx area since I was 18. Next Sunday I'll be 48. After my Dev$%^*ce, I' want to go live with them back in R.I. and help them out and try to move on myself... My dad was in electronics before me and he's a Ham... I will start the tube like thinking when I can convince him to join me on a project. I've really wanted to try to adapt the Ultra-Linear tube Topology to a cascoded JFET circuit, any ideas on that??? We may actually have been discussing it for months now???
This also means, in a month or so I will dissapear from the forum while me and my doggies drive across the USA in search of greener pastures??? or something... Maybe I'll stop and say hello Grey
It did not seem like I was contributing there...Forgive my mood... O.K. If anyone cares, I got my last 74s &170s from the AmpsLab Guy. Singapore I think??? He has a few other worthwhile components too. Do a dogpile (google for you people without dogs) on ampslab. I wouldn't call it a deal but, I have some...
I work at ON Semi and we don't have any good complementary JFETs either. Do We???
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