It looks likely that I will receive a bulk quantity from Grey . I have asked for untouched chips , I will not buy the left overs of unmatchable chips dont worry. I would imagine it will take three weeks at the least until I recieve the chips. ThenI will take orders etc.
regards
dave
regards
dave
Matching takes longer than I would like, which is why I was reluctant to undertake it in the first place. In my (admittedly prejudiced) view, my time would be better spent getting a circuit together, but I understand the frustration of wanting matched devices and not being able to get them. In for a penny, in for a pound; I decided to do the value-added thing. Just remember me when you win the lottery, fellas.
I still have untouched tubes. Not to worry. My guess is that something like three or four tubes will give you a decent approximation of a Gaussian distribution (i.e. bell curve). I've gone through single tubes that tended towards higher or lower vaules, but for the most part they're fairly random. Values do tend to pile up approximately the way Nelson's curve looked. I'm still getting the sense that my curve might be slightly to the left of Nelson's, but that's not a formal statement. I haven't got the time to sit and count each bunch and crunch the numbers. If someone else wants to do so, please feel free to post. Please be sure to include N (the number of units tested).
Grey
P.S.: You have no idea what torture it is to be handling all these parts and not be able to stop and play. Tantalus and I know a thing or two about temptation.
I still have untouched tubes. Not to worry. My guess is that something like three or four tubes will give you a decent approximation of a Gaussian distribution (i.e. bell curve). I've gone through single tubes that tended towards higher or lower vaules, but for the most part they're fairly random. Values do tend to pile up approximately the way Nelson's curve looked. I'm still getting the sense that my curve might be slightly to the left of Nelson's, but that's not a formal statement. I haven't got the time to sit and count each bunch and crunch the numbers. If someone else wants to do so, please feel free to post. Please be sure to include N (the number of units tested).
Grey
P.S.: You have no idea what torture it is to be handling all these parts and not be able to stop and play. Tantalus and I know a thing or two about temptation.
Ever since I posted requesting that people consider smaller groups of matched devices, I've been deluged with e-mails from people telling me they want untouched tubes.
Guys, I know you want a chance to match your own devices.
I'm the one who brought it up...remember?
Now, everybody take a deep breath. Hold it...hold it...hold it...okay, now exhale slowly and repeat after me:
Grey bought plenty of JFETs
Grey knows that if I order unmatched I want a chance to match my own devices
Grey hasn't even opened 2/3 of the bags that contain the tubes that contain the devices that everybody wants to match.
Jeez, guys, give me some credit.
I've already fended off a couple of offers and/or demands that I felt were not in the best interests of the members at large. I will continue to do so.
I will attempt to honor orders for larger batches of matches made before I wrote post #312. Once I get further along in the matching process, I may revisit the possibility of large batches. At this time, I've made a rough pass through a thousand devices and will go back through and subdivide each Vgs range until I'm satisfied that I've got reasonable groups. If it turns out that it's easy to get groups of 50, then great. If not, then that's the way it goes. I was silly not to realize that people would want large groups. I still tend to think in terms of tubes. People who want matched sets of tubes think in terms of pairs or maybe quads. My old Premier One had six tubes per channel and that's a big amp. So it just doesn't come naturally to me to think in terms of 50 matched devices as a single group. But solid state people are capable of thinking in those quantities.
I didn't write post #312 because I had run out of devices to match. I didn't even write it because I was on the verge of running out. I wrote it because I foresaw that it could become a problem if I let things go on the way they were going.
It's not a problem and I don't intend to let it become one.
Period.
Now, everybody take a deep breath and repeat after me:
Grey says everything's okay. He's watching out for me. It's going to be all right.
There. Do you feel better now?
Grey
P.S.: I really, really wish this Coulomb/Anthony thing hadn't blown up. One, because I thought he was an okay fella and I hope that nothing bad has happened to him. Two, because it's got people feeling edgy about this sort of buy. Unfortunately, whatever happened, happened, and I can't change that. I am where I am now and all I can do is forge ahead and let people decide for themselves whether this whole JFET thing is worthwhile.
Trust me, if there's something wrong, you'll read about it here fairly quickly.
P.P.S.: If you get an oddball Vgs value, don't panic. Use it for a current source. Don't you know that cascoded current sources are all the rage? Got two of them? Great! Set them aside. We'll need them later on for headphone amplifiers. Remember, I'm the guy who whipped up the Mini-A, in part so that I could use single, unmatched MOSFETs. I can't stand to let anything go to waste. It may take a while, but I'll get some ideas out.
Come to think of it, there's this guy called Nelson Pass. I hear that he comes up with a nifty idea every once in a while. You never know what he might decide to post.
Guys, I know you want a chance to match your own devices.
I'm the one who brought it up...remember?
Now, everybody take a deep breath. Hold it...hold it...hold it...okay, now exhale slowly and repeat after me:
Grey bought plenty of JFETs
Grey knows that if I order unmatched I want a chance to match my own devices
Grey hasn't even opened 2/3 of the bags that contain the tubes that contain the devices that everybody wants to match.
Jeez, guys, give me some credit.
I've already fended off a couple of offers and/or demands that I felt were not in the best interests of the members at large. I will continue to do so.
I will attempt to honor orders for larger batches of matches made before I wrote post #312. Once I get further along in the matching process, I may revisit the possibility of large batches. At this time, I've made a rough pass through a thousand devices and will go back through and subdivide each Vgs range until I'm satisfied that I've got reasonable groups. If it turns out that it's easy to get groups of 50, then great. If not, then that's the way it goes. I was silly not to realize that people would want large groups. I still tend to think in terms of tubes. People who want matched sets of tubes think in terms of pairs or maybe quads. My old Premier One had six tubes per channel and that's a big amp. So it just doesn't come naturally to me to think in terms of 50 matched devices as a single group. But solid state people are capable of thinking in those quantities.
I didn't write post #312 because I had run out of devices to match. I didn't even write it because I was on the verge of running out. I wrote it because I foresaw that it could become a problem if I let things go on the way they were going.
It's not a problem and I don't intend to let it become one.
Period.
Now, everybody take a deep breath and repeat after me:
Grey says everything's okay. He's watching out for me. It's going to be all right.
There. Do you feel better now?
Grey
P.S.: I really, really wish this Coulomb/Anthony thing hadn't blown up. One, because I thought he was an okay fella and I hope that nothing bad has happened to him. Two, because it's got people feeling edgy about this sort of buy. Unfortunately, whatever happened, happened, and I can't change that. I am where I am now and all I can do is forge ahead and let people decide for themselves whether this whole JFET thing is worthwhile.
Trust me, if there's something wrong, you'll read about it here fairly quickly.
P.P.S.: If you get an oddball Vgs value, don't panic. Use it for a current source. Don't you know that cascoded current sources are all the rage? Got two of them? Great! Set them aside. We'll need them later on for headphone amplifiers. Remember, I'm the guy who whipped up the Mini-A, in part so that I could use single, unmatched MOSFETs. I can't stand to let anything go to waste. It may take a while, but I'll get some ideas out.
Come to think of it, there's this guy called Nelson Pass. I hear that he comes up with a nifty idea every once in a while. You never know what he might decide to post.
GRollins said:
Yeah, he is unpredictable. He is a master.
By the way, how long the far east guys have to wait for the left over?
Regards
jh
Still waiting for someone to step forward and take up that part of the globe. If no one does so by, say, the end of the month I will look into doing it myself. By then the North American end of things should be fairly tidy.
Grey
Grey
I'm using the circuit Nelson posted...there'd likely be a riot if I didn't.
The test rail voltage is 3V. Tie that to the Drain. Gate to ground. Source goes through a 1 Ohm (Nelson's schematic says 3W, but you're actually only dissipating about 1W, so a 2W will do nicely if you want) resistor to ground. Measure the voltage across the Source resistor. You'll find that the current values will cluster around 1A or so.
Grey
The test rail voltage is 3V. Tie that to the Drain. Gate to ground. Source goes through a 1 Ohm (Nelson's schematic says 3W, but you're actually only dissipating about 1W, so a 2W will do nicely if you want) resistor to ground. Measure the voltage across the Source resistor. You'll find that the current values will cluster around 1A or so.
Grey
Thanks, Dave.
I will transfer the payment to your bank account.
I will inform you of my address and how many I need when you are ready.
It seems time for me to start wandering around to find nice light bulbs.
Regards
jh
I will transfer the payment to your bank account.
I will inform you of my address and how many I need when you are ready.
It seems time for me to start wandering around to find nice light bulbs.
Regards
jh
My circuit ideas
Hi Dave,
Will order when you are ready.
I will not use bulbs, however they may be OK.
I will start to try the schematic below. Basically the bottom part is as Nesons F3 PDF. Have not seen anything more specific from him.
For the load I first thought about the Aleph type but that will have no DC stability, as the JFET does not provide that like the MOSFET will with the DC feedback from the Output.
This simple circuit around Q3 provides a DC stability through the resistors R9 and P2, while the ElCap C4 will give it a Constant Current source for AC. I used this type of circuit often to bias a photodiode.
The DC at the output is set with P2.
The voltage over the JFET is adjusted with P1 as per Nelson.
The current bias point is set with R1 as per Nelson.
For the PS a simple Cap multiplier should be OK.
When the parts arrive I will test this circuit unless the Master or one of the others will shoot it down.
All the mentioned voltages are first guesses, to be tuned in practical life.
Thanks all for the inspiration.
Regards, Rick
Hi Dave,
Will order when you are ready.
I will not use bulbs, however they may be OK.
I will start to try the schematic below. Basically the bottom part is as Nesons F3 PDF. Have not seen anything more specific from him.
For the load I first thought about the Aleph type but that will have no DC stability, as the JFET does not provide that like the MOSFET will with the DC feedback from the Output.
This simple circuit around Q3 provides a DC stability through the resistors R9 and P2, while the ElCap C4 will give it a Constant Current source for AC. I used this type of circuit often to bias a photodiode.
The DC at the output is set with P2.
The voltage over the JFET is adjusted with P1 as per Nelson.
The current bias point is set with R1 as per Nelson.
For the PS a simple Cap multiplier should be OK.
When the parts arrive I will test this circuit unless the Master or one of the others will shoot it down.
All the mentioned voltages are first guesses, to be tuned in practical life.
Thanks all for the inspiration.
Regards, Rick
Attachments
In post #047 of the "Pass JFET Power Amplifier" thread is the question is raised by lohk and answered by Nelson:
So Nelson is using a CCS but it seems not to be the Aleph CCS. May-be because the DC bias setting that is missing. But I would be happy to read his opinion.
Rick
So Nelson is using a CCS but it seems not to be the Aleph CCS. May-be because the DC bias setting that is missing. But I would be happy to read his opinion.
Rick
Mark Stones (mark stones, here on DIY) has offered to take orders for Australia and 'and the odd one or two orders overseas.'
I'm on a short leash at the moment--got to move on.
Thanks, Mark.
Grey
I'm on a short leash at the moment--got to move on.
Thanks, Mark.
Grey
I remember that answer, Rick, but did NP not specify that at a later state? I cannot find that post.
Rick and Lohk this might be what you are looking for ( Quoting NP):
http://www.diyaudio.com/forums/showthread.php?s=&threadid=70902 The answer I quote is in that thread.
Steen🙂
Rick wouldnt it be a good idea with a new thread on this subject, or taking the discussion to this one?
http://www.diyaudio.com/forums/showthread.php?s=&threadid=70902 The answer I quote is in that thread.
Steen🙂
GRollins said:
As Grey has pointed out I will be doing the Australia orders and one or two overseas orders that are around this side of the planet, unlike grey I will be doing this only once so if you are interested Email me your requirement prior to the 5th of February.
The prices will be whatever grey charges + postage + envelopes + tax (if I get charged then so do you) + share of bank transfer fee (for money to pay grey) + paypal if you pay me with that medium.
In short you will pay what it costs me nothing more hopefully nothing less.
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