Well I cannot contribute neither a lot of knowledge, nor experience! I just can contribute my ambition 
But you can count on Nelson Pass! He was so kind to point out that the earlier discussed 2SJ109 (with reduced current) input works without a hassle
So the whole business about increased high-frequency distortion due to lower open-loop gain (follows from reduced transconductance of the 2SJ109) and higher output impedance due to JFET input, is - as he says verbatim - spurious.
And that's all we need.
I'm more or less now only collecting further details about the Aleph-X, so that I can make a nice pcb in the future (a couple of other projects want to be finished first!).
Cheers, Hannes
PS: ah and for the 2SJ109BL I don't know any good source here in europe, sorry!
But you can count on Nelson Pass! He was so kind to point out that the earlier discussed 2SJ109 (with reduced current) input works without a hassle
So the whole business about increased high-frequency distortion due to lower open-loop gain (follows from reduced transconductance of the 2SJ109) and higher output impedance due to JFET input, is - as he says verbatim - spurious.
And that's all we need.
I'm more or less now only collecting further details about the Aleph-X, so that I can make a nice pcb in the future (a couple of other projects want to be finished first!).
Cheers, Hannes
PS: ah and for the 2SJ109BL I don't know any good source here in europe, sorry!
jacco vermeulen said:
u sure?
I actually found several places who listed them in this price range ... all where out of stock when I called / mailed. I have one last request running, let's see...
I wonder why everybody is soooooo cryptic when talking about these little beasts ... no clear statements nowhere ... anyways thanks for the clue.
LC
Thanks Jacco,
I love gifts, but already did it myself.
Ordered the LAST pair from here:
01110111 01110111 01110111 00101110 01100101 01101100 01110111 00101101 01110011 01101000 01101111 01110000 00101110 01100100 01100101 00101111
Decrypt It Yourself
I heared HeHo is out of stock, but they are the ones I'm waiting for reply ... Freitag in Biberach.
cheers,
LC
I love gifts, but already did it myself.
Ordered the LAST pair from here:
01110111 01110111 01110111 00101110 01100101 01101100 01110111 00101101 01110011 01101000 01101111 01110000 00101110 01100100 01100101 00101111
Decrypt It Yourself
I heared HeHo is out of stock, but they are the ones I'm waiting for reply ... Freitag in Biberach.
cheers,
LC
The parts availibity question is pretty annoying. The basic problem is that the 2SK389 and 2SJ109 have been discontinued. Access to these parts is spotty and getting worse by the day.
Yes, yes, yes...there's Linear, but they don't have a '109 yet. Hearing people point out that you can match '170s and '74s is getting tiresome, too. They're nearly as hard to get as the duals and you have no control over the grade; all I've ever gotten are GRs and no one will ever tell you what they stock. None of the Japanese JFETs are easy to get in the US. For whatever reason, Toshiba doesn't want to sell in North America--everything is gray market here.
I'm trying to develop alternatives that don't require blackmailing someone at the Toshiba factory. I had hoped that my purchase of hundreds of J271s would convince Mouser to stock the part. Unfortunately, it didn't work.
The whole thing's a bummer.
Grey
Yes, yes, yes...there's Linear, but they don't have a '109 yet. Hearing people point out that you can match '170s and '74s is getting tiresome, too. They're nearly as hard to get as the duals and you have no control over the grade; all I've ever gotten are GRs and no one will ever tell you what they stock. None of the Japanese JFETs are easy to get in the US. For whatever reason, Toshiba doesn't want to sell in North America--everything is gray market here.
I'm trying to develop alternatives that don't require blackmailing someone at the Toshiba factory. I had hoped that my purchase of hundreds of J271s would convince Mouser to stock the part. Unfortunately, it didn't work.
The whole thing's a bummer.
Grey
> The XA100 strikes me as a more interesting case. We're talking, what, two, maybe three output pairs per side?
I have a variant of AlephX-100 with +/-24V, 7.7A bias running for a couple of years using 2SJ109BL frontends without any problems. 6 FETs per channel. If you care to check out the thread posted by William, you will find enough information on how I did it.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=98763&perpage=10&pagenumber=1
If no 2SJ109s then i would suggest to just use 2 pieces of 2SJ74BLs and stick them together with thermal glue. 2SJ109s are not ALWAYS as well matched as people think (3% according to datasheet).
Patrick
I have a variant of AlephX-100 with +/-24V, 7.7A bias running for a couple of years using 2SJ109BL frontends without any problems. 6 FETs per channel. If you care to check out the thread posted by William, you will find enough information on how I did it.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=98763&perpage=10&pagenumber=1
If no 2SJ109s then i would suggest to just use 2 pieces of 2SJ74BLs and stick them together with thermal glue. 2SJ109s are not ALWAYS as well matched as people think (3% according to datasheet).
Patrick
cviller said:
Compare the spec sheets for the Vishay/Siliconix parts vs. the Fairchild and tell me if you notice anything funny.
EUVL said:
Ah...but have you measured distortion, particularly at high frequencies?
At the risk of repeating myself, none of the Japanese JFETs are readily available here in the US. Pointing out alternative Toshiba parts is an exercise in futility. No matter how many times I (and others) say this, folks elsewhere in the world assume that because they can run down the street and pick up a few, that we can too. Sadly, that's not the case.
Grey
> Ah...but have you measured distortion, particularly at high frequencies?
True, I don't have equipment to measure distortion at high frequencies, but I have the same open loop gain as the widely published "standard" 100W version, and an open loop frequency response of over 20kHz at -3dB, so I do not see why I should expect more HF distortion. I have also calculated the fully amplitude response and do not have worst, if not better, linearity than using all MOSFETs.
I respect your dislike of Japanese devices. I like them personally.
And I think it does no harm to let people know that there is more than one road to Rome.
If one looks at Geoff Moss's website dedicated to another classic -- The Linsley Hood Class A, you see a lot of experiments there based on the original circuit. Some works better, some not; for me that is the interesting part. Building a standard circuit from a famous audio designer no longer offers any challenges to me.
> none of the Japanese JFETs are readily available here in the US.
If one looks hard enough, one will find them. Just ask Jacco.
There are many people here on the forum who do not live in the US. They don't seem to have any problems finding Toshiba parts to build F4's and what not .......
Just MHO,
Patrick
True, I don't have equipment to measure distortion at high frequencies, but I have the same open loop gain as the widely published "standard" 100W version, and an open loop frequency response of over 20kHz at -3dB, so I do not see why I should expect more HF distortion. I have also calculated the fully amplitude response and do not have worst, if not better, linearity than using all MOSFETs.
I respect your dislike of Japanese devices. I like them personally.
And I think it does no harm to let people know that there is more than one road to Rome.
If one looks at Geoff Moss's website dedicated to another classic -- The Linsley Hood Class A, you see a lot of experiments there based on the original circuit. Some works better, some not; for me that is the interesting part. Building a standard circuit from a famous audio designer no longer offers any challenges to me.
> none of the Japanese JFETs are readily available here in the US.
If one looks hard enough, one will find them. Just ask Jacco.
There are many people here on the forum who do not live in the US. They don't seem to have any problems finding Toshiba parts to build F4's and what not .......
Just MHO,
Patrick
Anyone who speaks French (and/or enjoys frequent shopping in Lille like me) can still get the 2SJ109 at Electronique Diffusion in France.
Also has an online web shop besides the regular stores: www.electronique-diffusion.fr
Currently lists the 2SJ109 at $8/pc, $12 for a 2SK389.
Requesting BLeu types needs an email.
Green Light means they're in stock, TTC price is sales tax/VAT included, HT without tax.
(mm, have to admit i was the one who totally ransacked both Pacificsemi in Vancouver, Matchaknob in New York, Union Electronics in Chicago, and Audiolab in Georgia)
Also has an online web shop besides the regular stores: www.electronique-diffusion.fr
Currently lists the 2SJ109 at $8/pc, $12 for a 2SK389.
Requesting BLeu types needs an email.
Green Light means they're in stock, TTC price is sales tax/VAT included, HT without tax.
(mm, have to admit i was the one who totally ransacked both Pacificsemi in Vancouver, Matchaknob in New York, Union Electronics in Chicago, and Audiolab in Georgia)
Hi,
just to give you some motivation.
My Aleph-X is now working very, very nice with the J-Fet input (still not in it´s final stage). I don´t think it ever sounded this nice before.
I still must do a few things but after some first problems things seem definitly worth the hassle.
Will report in my original thread.
William
just to give you some motivation.
My Aleph-X is now working very, very nice with the J-Fet input (still not in it´s final stage). I don´t think it ever sounded this nice before.
I still must do a few things but after some first problems things seem definitly worth the hassle.
Will report in my original thread.
William
EUVL said:
Patrick,
As a professional author, I have a horror of not being able to express myself clearly in print. If you can point out a post where I said or implied that I disliked the Japanese JFETs, I'd be appreciate it. I have never, to my knowledge, said that I didn't like the parts.
What I have said, repeatedly, is that the Japanese JFETs:
A) Aren't sold legitimately here in the US. What's available is gray market. Saying that people who don't live in the US can find the parts is like saying to a man living in the desert that you have a lake full of clean water. That's nice, but it doesn't do the man in the desert a bit of good. Yes, people elsewhere in the world can get Japanese JFETs, but that doesn't mean that folks in the US can. And given that the 2SK389 and 2SJ109 are out of production, it's only a matter of time before the rest of the world wakes up some fine morning to discover that, surprise!, they're all gone.
B) Many places say that they have them, including some here in the US, but they don't. Just because it's listed on their website doesn't mean a thing. Just because someone got some two weeks ago doesn't mean a thing. Just because some guy goes so far as to say so on the phone doesn't mean a thing. (Ooops! Sorry! I know I told you I had them, but one of the other salesmen must have sold them while I was still on the phone with you...)
C) If they do have them, quantities are frequently small, meaning five to ten devices. Frequently less. If two people buy the parts, they're out of stock and remain so for months, often a year or more.
D) This one is a biggie...even if you are, by some miracle, able to find some parts, you have absolutely no control over what grade of device you get. For instance, I've ordered 2SK170s and 2SJ74s several times. All I have ever gotten are GRs. Ever. Period. Regardless of what the website (or even a live human being on the phone) said. Usually they just flat out won't tell you, no matter how nicely you ask. There's an expression here in the US about buying a pig in a poke. I'm tired of buying blindly, in hopes that maybe I'll get BL devices this time. It's a waste of my time and money. VI devices? Forgetaboutit!
E) The prices keep climbing. In the near future, the quoted retail price for Japanese JFETs here will surpass Linear Systems' (admittedly fairly high) price. At which point it will become more economical to buy the LSK parts. I just hope they get their P-ch devices going soon. There's a limit to what I (or any reasonable person) will pay for a part. Assuming that parts are available in Europe, for instance, given the exchange rate between Euros and dollars, plus shipping, plus import, etc. it's still cheaper to buy from Linear (something they well know). Again, we're back to the fact that they don't have P-ch parts yet.
F) A more subtle point, but one that I try to keep in mind whether anyone else cares or not. I have, from time to time, posted circuits here. What good does it do to post a circuit that only people in certain parts of the world can build? A circuit that can't be built is useless. At this time, the IRF parts are widely available, but that may change now that their power MOSFETs have been bought by Vishay. (Is there no limit to Vishay's appetite for acquisition?) Lateral MOSFETs are unobtanium here in the US. Likewise Japanese JFETs. The Fairchild MOSFETs are in short supply. Hopefully this is only a temporary shortage as they shift over to lead-free parts. What happens if someone wants to build an Aleph-X and the IRF MOSFETs are no longer available? And Fairchild's kaput? And lateral MOSFETs, regardless of manufacturer, won't work without a complete redesign, given their lower transconductance and higher capacitance--and not even particularly well then...? RIP Aleph-X. Ditto Mini-A. Ditto SOZ with current sources. Etc. As I've said before, I try to worry about these things so others won't have to.
G) I have on hand: 2SK389BL, 2SJ109BL, 2SK170GR, and 2SJ74GR. I also have a solitary pair of '389VIs given to me by another member. They're good parts. I like them. But I know what I went through to get them and I'm reluctant to post a circuit using them if they can't be found by others--no matter how nice the parts themselves might be. Particularly given that five years down the road the '389 and '109 won't be available at any price. And, if my suspicion is correct, the '170 and '74 as well. The Aleph-X project is already five years old and still viable--at least for the time being. But if I were to post a '389 circuit today, half the members of this site wouldn't be able to build it. The other half wouldn't be able to build it in five years. What I build for myself is one thing. What I post here is another. So I'm trying to jumpstart availability of the Siliconix J271. The J310 is available, reasonably priced, and I highly recommend it. The main drawback is fairly low transconductance, but that's a matter of topology. (Single JFETs, true, but low noise and beyond Toshiba VIs in current. I've got J310s on hand with Idss>40mA. Now, that's pretty nifty current capability!).
No matter how many times I say these things, people always come up with two or three obscure websites that 'prove' that the Japanese JFETs are available. Well, yes, they are, in the most limited sense of the word. And so are blue diamonds if you're willing to pay enough and wait long enough and deal with enough charlatans and false leads and so forth. The fact that the Hope Diamond exists does not mean that it's practical for everyday people to buy a blue diamond.
*****
I actually once tried to buy a blue diamond. I had jewelers put it on the wire. And waited. And waited. And waited. At long last one...and only one...became available. In the whole world, mind you. The punchline was that it wasn't truly blue. It was gray.
I gave up.
*****
Oh, regarding using a '109 to drive that many output devices...think of it in terms, not of open loop gain, but of slew rate. Different animal entirely. You'll see the distortion in the high frequencies first because the cumulative Gate capacitance is harder to load and unload at high frequencies.
...I will now pause for those who want to do the math and decide whether or not a '109 can do the job before it exceeds its ratings...
Done?
I acknowledge that there are widely varying opinions as to how much slew rate is enough. My personal feeling--and anyone who happens to remember that I like wide bandwidth may be able to guess where this is going--is that 20kHz is too low a cutoff point for calculating slew rate. Just my two cents worth. But there are limits as to what a '109 can do even if you accept 20kHz as an upper cutoff. Choose whatever slew rate you think is reasonable and run the numbers.
Grey
Nelson Pass said:
The XA100 uses 24 output devices per channel.
Why does the commercial XA100 use so many output devices? Compared to other Aleph's, this one uses far more per channel. Most diy amps comparable to the XA100 in output power and total dissipation per channel use half of that number of output devices.
Is it because of plastic casing or something else?
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