paulb said:
Hint, hint...
Yeah, yeah, I know. I've just got to get the twins to feed and bathe themselves. I'm getting pretty adept at feeding with one hand and typing with the other, though.
I just need a couple of undisturbed hours at the bench--something that doesn't happen as often as I'd like. I've got two ideas in mind, just need time to try them out--make sure they work as expected.
As for the bipolar power supply, it allows me to dispense with biasing schemes (other than the simple fixed resistor under the Source) and an input cap. Contrary to popular opinion, it's not that I like caps, it's that they allow me to dispense with a lot of other junk. Going bipolar on the power supply seems to me a small price to pay in order to get that pesky input cap and bias circuit out of the way.
With a simple follower circuit like this, you can either direct couple the input or the output, but not both; at least one is going to have to float from ground by Vgs.
Grey
P.S.: I am perpetually astonished that no one has ever done something so obvious as use a bipolar supply for the Zen, for the same reasons outlined above.
carpenter said:
I feel your pain, as the expression goes. I've about had it with unfindable parts. I've been busting my behumpus trying to find a dependable source for any of a dozen parts I've got on a "hit list" taped next to my monitor. No luck. People don't return phone calls, don't return e-mails, don't have them in stock, never heard of them and deny they exist (Toshiba America had never heard of the 2SK389/2SJ109)...the time and energy I've spent trying to locate these parts would have been better spent with a soldering iron in my hand.
Granted, I was able to work out a brute force solution to the Lovoltech JFET availability problem, but trying to talk to some of these people--even about a multi-thousand unit purchase--is an exercise in frustration.
A couple of examples:
I mentioned somewhere, perhaps in this thread, that I'm trying to source the Vishay/Siliconix J271. Supposedly current. Supposedly available. Huh! Vishay corporate doesn't seem to want to talk about it, nor do their distributors. Supposedly there are 2000 units waiting to be bought in Singapore. I'm not sure I can justify buying that many, but they can't even be bothered to talk about the 2K. I'm about--reluctantly-- to call it quits on them. Bummer.
Nelson had mentioned, once upon a time, using Castin solder. Time came that I needed solder, I got in touch with them. Oh, brother! They gave me a semi-comical runaround over a three week period, asking me how many pounds I needed. I'd say a pound or two, and follow that by telling them that I'd be happy to buy at retail, if only they would give me the name of a retail outlet that carried their product. A day or two would pass and I'd get another e-mail from someone else: How many pounds do I want? I'd say one or two, happy to buy at retail. Another day or two, and I'd get another e-mail from yet another place: How many pounds? Then from the company...from the same guy who'd written before, even: How many pounds do I want? Ad infinitum. Ad nauseum. Screw 'em. I bought somebody else's product.
Just two examples. I could cite many more. If I had nothing better to do with my time, I wouldn't mind so much, but time is a precious commodity to me, dammit. Don't waste it! What I need is a purchasing department--people who spend all day fighting to get the ear of someone who will condescend to sell their product. Obviously, that's not realistic. And even if I had such a thing, it wouldn't do you guys any good.
True, I could use 2SK389s or 2SJ109s in some of the things I post here, because I bought 50 of the confounded things the one time I had a chance. But because I know first-hand just how hard these things are to come by, I'd be reluctant to do that to anyone else.
Grey
EDIT: Metalman, I bow to your superior power supply. I used up some 20000uF caps I had lying around, six, I think it was, three per rail. Did a CRCRC filter with bypasses on the last stage.
Excess is good.
unobtainium JFETs
Didn't I remember correctly from somewhere that Meneer Vermeulen claimed to have tons of 2SK389s and 2SJ109s at bargain prices ?
I am sure he is such a generous gentlemen and he would selflessly offer them at Dutch discounts to everyone in the DIY community.
Cheers (Groeten),
Patrick
Didn't I remember correctly from somewhere that Meneer Vermeulen claimed to have tons of 2SK389s and 2SJ109s at bargain prices ?
I am sure he is such a generous gentlemen and he would selflessly offer them at Dutch discounts to everyone in the DIY community.
Cheers (Groeten),
Patrick
Patrick,
for starters, why not try typing in the numbers at BEEP in Nueva York.
Looks like Steven still has both, the 2SK389 is listed without the suffix but all i received were BL's.
(even received the merchandise in non-customs hazard packaging, good for a $200 saving)
Buying 40 or more of each should not be such a big deal for true dual JFET Lovertechs.
How hard can it be.
Ein gruß von der küste.
for starters, why not try typing in the numbers at BEEP in Nueva York.
Looks like Steven still has both, the 2SK389 is listed without the suffix but all i received were BL's.
(even received the merchandise in non-customs hazard packaging, good for a $200 saving)
Buying 40 or more of each should not be such a big deal for true dual JFET Lovertechs.
How hard can it be.
Ein gruß von der küste.
Now, here's a bitter pill. According to Blaine Thomas of Vishay, the J271 has been discontinued. No word yet on the status of the J310.
This is beginning to sound like the same nonsense as the Japanese transistors. The superstitious part of my mind is beginning to think there's a concerted effort to take away all the interesting audio parts. Hell, this is the reason I came over to solid state from tubes--parts were getting too hard to find, and too expensive. Now I find the same thing in solid state.
I think I'll take up bird watching as a hobby.
Oh, wait, that's right...all the birds are going extinct, too.
What's a guy to do?
Grey
This is beginning to sound like the same nonsense as the Japanese transistors. The superstitious part of my mind is beginning to think there's a concerted effort to take away all the interesting audio parts. Hell, this is the reason I came over to solid state from tubes--parts were getting too hard to find, and too expensive. Now I find the same thing in solid state.
I think I'll take up bird watching as a hobby.
Oh, wait, that's right...all the birds are going extinct, too.
What's a guy to do?
Grey
And now it's not discontinued...
Aaargh!
I can't get a straight answer out of the guy. It's possible that he's looking at the lead vs. no-lead part, but I can't pin him down.
It's enough to drive a man to drink.
No, I'm not going to continue with a blow-by-blow narration of this escapade...I'm just frustrated.
Grey
Aaargh!
I can't get a straight answer out of the guy. It's possible that he's looking at the lead vs. no-lead part, but I can't pin him down.
It's enough to drive a man to drink.
No, I'm not going to continue with a blow-by-blow narration of this escapade...I'm just frustrated.
Grey
Grey,
I just checked that Vishay J271 is still available in quantities from at least one industrial retailer in Germany (www.schuricht.de), somewhat expensive at $1.25 per piece due to import tax, but available none the less. So no ground for frustration, yet.
There is also a J271 from fairchild which is still active product.
Or you meant Vishay sounds better ?
Patrick
I just checked that Vishay J271 is still available in quantities from at least one industrial retailer in Germany (www.schuricht.de), somewhat expensive at $1.25 per piece due to import tax, but available none the less. So no ground for frustration, yet.
There is also a J271 from fairchild which is still active product.
Or you meant Vishay sounds better ?
Patrick
I said this earlier, but no one seems to have caught it--the Fairchild part is listed as a switch. The datasheet is pathetic. Few specs. No charts.
The Vishay part is listed as an amplifier and the datasheet is absolutely full of useful information.
I seem to be one of the few people who take a longer view of things. Folks think nothing of buying drivers with foam surrounds. They either do not know or do not care that foam surrounds rot in ten to fifteen years, leaving you with no driver at all. To me that's absolutely unacceptable. Any driver with a foam surround is a non-starter in my book. By the same token, I do not want to put out a schematic that can't be built in five years. People have awfully short attention spans. They don't realize that the Aleph-X has already been out for nearly five years. If I had designed it for a part that was discontinued the day I posted the schematic, that part would be all but unfindable now. How many people could or would build the circuit now, five years later? How would those who built the circuit when it was new find parts for service? I fret over these things so others won't have to.
I will not post a schematic that uses a part (e.g. 2SK389/2SJ109) that has been discontinued. They're already hard to find and will be impossible in five years. Yes, Linear Systems has the LSK389, and I have found no reason to complain about the part, but the promised '109 has yet to materialize--at least it's not on their web site. (My to-do list has an entry for me to contact them and see what their timeframe for that part is.)
Anyway, my point being, it's not that I want to find ten for myself...I want everyone to have reasonable access to a part before I post a circuit that uses it. If it has been discontinued, I absolutely will not post a schematic. It's pointless. No one will be able to build the circuit or service it.
Grey
The Vishay part is listed as an amplifier and the datasheet is absolutely full of useful information.
I seem to be one of the few people who take a longer view of things. Folks think nothing of buying drivers with foam surrounds. They either do not know or do not care that foam surrounds rot in ten to fifteen years, leaving you with no driver at all. To me that's absolutely unacceptable. Any driver with a foam surround is a non-starter in my book. By the same token, I do not want to put out a schematic that can't be built in five years. People have awfully short attention spans. They don't realize that the Aleph-X has already been out for nearly five years. If I had designed it for a part that was discontinued the day I posted the schematic, that part would be all but unfindable now. How many people could or would build the circuit now, five years later? How would those who built the circuit when it was new find parts for service? I fret over these things so others won't have to.
I will not post a schematic that uses a part (e.g. 2SK389/2SJ109) that has been discontinued. They're already hard to find and will be impossible in five years. Yes, Linear Systems has the LSK389, and I have found no reason to complain about the part, but the promised '109 has yet to materialize--at least it's not on their web site. (My to-do list has an entry for me to contact them and see what their timeframe for that part is.)
Anyway, my point being, it's not that I want to find ten for myself...I want everyone to have reasonable access to a part before I post a circuit that uses it. If it has been discontinued, I absolutely will not post a schematic. It's pointless. No one will be able to build the circuit or service it.
Grey
> I will not post a schematic that uses a part (e.g. 2SK389/2SJ109) that has been discontinued.
Then post one with 2x 2SK170 / 2SJ74 matched pairs glue together with Arctic silver. It is no different from using 2x IRF9610s for Aleph-X.
Of course we can speculate that all JFETs will disappear from the market in 10 years because lithography is too expensive, and JFETs in quantities for a few cent is not worth the while for Toshiba and Vishay. But then we might as well speculate that in 10 years it is all MP3 and Class D anyway.
In 10 years, I probably can not hear over 5kHz anymore !
Patrick
Then post one with 2x 2SK170 / 2SJ74 matched pairs glue together with Arctic silver. It is no different from using 2x IRF9610s for Aleph-X.
Of course we can speculate that all JFETs will disappear from the market in 10 years because lithography is too expensive, and JFETs in quantities for a few cent is not worth the while for Toshiba and Vishay. But then we might as well speculate that in 10 years it is all MP3 and Class D anyway.
In 10 years, I probably can not hear over 5kHz anymore !
Patrick
Patrick,
At first glance, your solution seems reasonable. As far as I have been able to determine, the 2SK170 and 2SJ74 are still current.
However, they're nearly as hard to find as the '389/'109 and all I've been able to lay hands on are GR parts. I want VI for what I have in mind, and if I can't even get BL, then others are going to have trouble too.
Tempting as the idea seems at first, I just can't justify it. Access to the Japanese JFETs (MOSFETs too, for that matter) is just too spotty over here. One place will carry them for a while, then run out. Then another will have them for a while, then they, too, will run out. It's a full-time job just to stay on top of the supply problem.
Grey
P.S.: I suspect that the 2SK170 and 2SJ74 are actually discontinued, production-wise and that Toshiba only continues to list the datasheets in order to support product that is in the distribution pipeline. Once inventory gets below a certain level, those parts will be officially "discontinued."
Do I know this? No. It's just a suspicion on my part, based on how business decisions are made.
At first glance, your solution seems reasonable. As far as I have been able to determine, the 2SK170 and 2SJ74 are still current.
However, they're nearly as hard to find as the '389/'109 and all I've been able to lay hands on are GR parts. I want VI for what I have in mind, and if I can't even get BL, then others are going to have trouble too.
Tempting as the idea seems at first, I just can't justify it. Access to the Japanese JFETs (MOSFETs too, for that matter) is just too spotty over here. One place will carry them for a while, then run out. Then another will have them for a while, then they, too, will run out. It's a full-time job just to stay on top of the supply problem.
Grey
P.S.: I suspect that the 2SK170 and 2SJ74 are actually discontinued, production-wise and that Toshiba only continues to list the datasheets in order to support product that is in the distribution pipeline. Once inventory gets below a certain level, those parts will be officially "discontinued."
Do I know this? No. It's just a suspicion on my part, based on how business decisions are made.