Not hijacking but I'd be down to help sourcing the jfets. It makes more sense to centralize the purchase with one guy so one doesn't need to buy 20 jfets to get the 4-8 matched ones.
I can do the legwork but I'd need help though.
I believe we need the LSK170A to get them matched between 3-6.5mA. Unfortunately Pass' paper specify between 3-8mA and there is a risk of getting a few below 3mA as per the attachment.
I plan in matching them like Mr Pass' post.
If there is any interest please send me a private message and we can get this going, hopefully getting the jfets at the same time as the boards!
Of course it depends on how easy it is to get them matched - and I'd appreciate some input from somebody who has experience in doing so - I estimate the cost to be around USD5 per jfet (considering I can match 70% of jfets in the same roll)
I can do the legwork but I'd need help though.
I believe we need the LSK170A to get them matched between 3-6.5mA. Unfortunately Pass' paper specify between 3-8mA and there is a risk of getting a few below 3mA as per the attachment.
I plan in matching them like Mr Pass' post.
If there is any interest please send me a private message and we can get this going, hopefully getting the jfets at the same time as the boards!
Of course it depends on how easy it is to get them matched - and I'd appreciate some input from somebody who has experience in doing so - I estimate the cost to be around USD5 per jfet (considering I can match 70% of jfets in the same roll)
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Good idea. I have my own stock of K170GR, BL and V JFET (bought them years ago...) so I'can do my own. But you guys need an alternate solution.
GASCo take note that LSK part are much more variable from JFET to JFET than Toshiba part used to be. You may need more to be able to do a match. I recommend that you ask someone in the admin section of this forum to get in touch with the Diyaudio Store guys.
Maybe they can recommend a safe approach to this task. Just a thought.
Or we buy the 200 parts stock from the apparently trusty member on ebay, it cost about 535U$, under 2.70US ea, much cheaper than Linear parts...
2SK170 Toshiba J-FET Transistors Qty 200 - 2SK170BL - NEW - Audio Low Noise | eBay
NP himself said that they are genuine parts...
SB
GASCo take note that LSK part are much more variable from JFET to JFET than Toshiba part used to be. You may need more to be able to do a match. I recommend that you ask someone in the admin section of this forum to get in touch with the Diyaudio Store guys.
Maybe they can recommend a safe approach to this task. Just a thought.
Or we buy the 200 parts stock from the apparently trusty member on ebay, it cost about 535U$, under 2.70US ea, much cheaper than Linear parts...
2SK170 Toshiba J-FET Transistors Qty 200 - 2SK170BL - NEW - Audio Low Noise | eBay
NP himself said that they are genuine parts...
SB
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Haha! I just purchased some 2sj74's from this seller for an Aleph J build. They should be here Saturday. I can test them in this setup:
Transistor matching
If they're good I'm willing to purchase the above mentioned lot, match them, and split them up amongst say 10-12 people.
Any interest? 12 people puts the cost to say $50 with shipping for 16 Jfets.
Transistor matching
If they're good I'm willing to purchase the above mentioned lot, match them, and split them up amongst say 10-12 people.
Any interest? 12 people puts the cost to say $50 with shipping for 16 Jfets.
I just ordered an inexpensive bag of 50 2SK170-GR and plan to match a set as Nelson suggested a decade ago:
They were a fair bit cheaper than those listed so it'll be interesting to see if they are the real deal or not....
Get a 5 to 13 volt supply and a DC voltmeter. Connect the +V to the
Drain, connect the Gate and Source together to a 100 ohm resistor,
and connect the other lead of the resistor to ground.
Measure the voltage across the resistor, which gives the Idss. 1 volt
= 10 mA of current.
Try to measure all devices under the same conditions, temperature,
and duration of test.
They were a fair bit cheaper than those listed so it'll be interesting to see if they are the real deal or not....
So essentially the device has a neutral sounding microphonic tube that needs input and output buffering and a wonderful switcher as extras but it uses electrolytic caps for coupling? You could take into account that 10 µF 50V MKT/MKS caps can be used but they need slightly more room/board space. In all the cases where I changed electrolytic caps for MKS/MKT there was a clear improvement but that is from "sound quality is the main goal" point of view. It makes me wonder how it will compare to the DCB1/B1 without the added stuff.
The mains fuse is very close to signal input. It is possible to use solderable 10 mm fuses and so create way more distance between mains voltage and signal input.
that needs input and output buffering and a wonderful switcher as extras but it uses electrolytic caps for coupling? You could take into account that 10 µF 50V MKT/MKS caps can be used but they need slightly more room/board space. In all the cases where I changed electrolytic caps for MKS/MKT there was a clear improvement but that is from "sound quality is the main goal" point of view. It makes me wonder how it will compare to the DCB1/B1 without the added stuff.The mains fuse is very close to signal input. It is possible to use solderable 10 mm fuses and so create way more distance between mains voltage and signal input.
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Then adapting to 10 µF 50V film caps in 5 mm pitch still is possible. They just need a few mm more space than electrolytic caps as they are wider. I really do not understand the design goal when using tubes and precious JFETS together with the worst of the worst in caps.
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I'm with you on the capacitor upgrade. I've been focused on replacing electrolytics with polypropylene since I read Walter G. Jung's and Richard Marsh's article in Audio magazine back in 1980.
However, I was one of the lucky ones to get one of Nelson's Christmas B1 Korg board with JFETs and built it according to the BOM. It's a beautiful sounding preamp and I have absolutely no regrets in using the specified electrotytic coupling caps. Nelson's design plays wonderful music!
I just ordered an inexpensive bag of 50 2SK170-GR and plan to match a set as Nelson suggested a decade ago:
They were a fair bit cheaper than those listed so it'll be interesting to see if they are the real deal or not....
Do you know how to test them for being fake or not?
If you order from the link I posted, it was confirmed by NP that they were the real thing...
Gerber had been sent to the PCB Fab for production...
BTW these small Silmic-II coupling caps are used into a lot of the current PassLabs gears, as into my original INT-150 I have here. I can confirm that the sound of this small cap is excellent...
You can always assemble your preamp into a larger enclosure and install big, fat Film coupling caps outside the pcb. Some of my friends built their B1 point to point, with Duelund coupling caps. But we are not talking about the same kind of project here. Its your project, you can do what you want...
Gerber had been sent to the PCB Fab for production...
BTW these small Silmic-II coupling caps are used into a lot of the current PassLabs gears, as into my original INT-150 I have here. I can confirm that the sound of this small cap is excellent...
You can always assemble your preamp into a larger enclosure and install big, fat Film coupling caps outside the pcb. Some of my friends built their B1 point to point, with Duelund coupling caps. But we are not talking about the same kind of project here. Its your project, you can do what you want...
I have no idea, nor knowledge to understand it. I’m monkey see monkey do regarding electronics.
I just don’t want to pay $60 for a matched 8. Lol
Up to now at least this is my understanding. You need 8 matches parts. I don’t even know if this is correct...
Btw I’ve been talking to a distributor of linear systems and he said he will try to gather what the usual deviation is in the same tape. I don’t know if I will get help since I’m not buying 1000’s though.
Probably a silly question, but are the 50k pots to control the volumes of CH1 and CH2 or to control LH and RH?
And the silk says 'mount volume pot upside down'. Does that mean the pots are connected via flying leads if the PCB is mounted at the bottom of the case?
Also - is this board always live when plugged in or has a jumper been incorporated to allow for a switch?
And the silk says 'mount volume pot upside down'. Does that mean the pots are connected via flying leads if the PCB is mounted at the bottom of the case?
Also - is this board always live when plugged in or has a jumper been incorporated to allow for a switch?
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Two pots, volume, one per channel. See the picture. You can also use just one stereo (2 channels) pot, and connect the wires accordingly...
Always live, but you can easily modified the board to add a switch, just one trace to cut, or use an AC inlet with integrated switch, or don't use an ac inlet pcb mounted, and run the ac wires from the socket to the pcb, while doing so, run the live wire through a power switch.
The PCB is made to accept Stackon tab connectors on the AC inlet location to use an off board ac inlet for this reason... There is a lot of options.
SB
Always live, but you can easily modified the board to add a switch, just one trace to cut, or use an AC inlet with integrated switch, or don't use an ac inlet pcb mounted, and run the ac wires from the socket to the pcb, while doing so, run the live wire through a power switch.
The PCB is made to accept Stackon tab connectors on the AC inlet location to use an off board ac inlet for this reason... There is a lot of options.
SB
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group buy for 2sk170 bl grade Toshiba Jfets
As I posted earlier in the thread I ordered some matched toshiba Jfets from a reputable ebay seller, the very one Sb quoted:
I built the following simple circuit and tested the Jfets for Idss. They tested perfectly matched as described.
Transistor matching
I also received the B1 board with matching fairchild jfets from the diyaudio store. I must admit to being slightly disappointed that half of the transistors are Fairchild labeled 113's and the other half are unbranded. long story short the Q1's and Q'2 are very different Idss values. The Q1's came in around 6.5ma and the Q2'2 are 21ish range- they actually took a 60 seconds or so to settle whereas all the others gave immediate accurate readings. the Q2's came with resistors (r1 on NP's schematic/board) to equalize the pair.
After this I contacted the seller and asked about the 200 piece 2sk170 BL grade lots he has posted on Ebay. He says they are unopened and in his experience the bulk of them, say 70%, run in the 7-9 ma range.
Now I am proposing a group-buy, which I will host, for 8 Toshiba Jfets matched in octets or at least close quads. if I can get 13 buyers, I'm aiming for two for me, the price will be $40 plus shipping. I'll do the matching within the specified .3ma range (hopefully we can do much better. Shipping will be $8 for priority mail in the US. Outside US shipping will be actual cost.
I will post the actual group buy tomorrow when I have a little more time to figure out how to create one. This will be my first. If anyone knows of a tutorial please post a link.
Lastly I hope I'm not breaking any rules by posting this on this group buy on this thread. I'm not trying to take over this thread I will post athe actual group buy as it's own thread tomorrow.
Jeffrey
As I posted earlier in the thread I ordered some matched toshiba Jfets from a reputable ebay seller, the very one Sb quoted:
I built the following simple circuit and tested the Jfets for Idss. They tested perfectly matched as described.
Transistor matching
I also received the B1 board with matching fairchild jfets from the diyaudio store. I must admit to being slightly disappointed that half of the transistors are Fairchild labeled 113's and the other half are unbranded. long story short the Q1's and Q'2 are very different Idss values. The Q1's came in around 6.5ma and the Q2'2 are 21ish range- they actually took a 60 seconds or so to settle whereas all the others gave immediate accurate readings. the Q2's came with resistors (r1 on NP's schematic/board) to equalize the pair.
After this I contacted the seller and asked about the 200 piece 2sk170 BL grade lots he has posted on Ebay. He says they are unopened and in his experience the bulk of them, say 70%, run in the 7-9 ma range.
Now I am proposing a group-buy, which I will host, for 8 Toshiba Jfets matched in octets or at least close quads. if I can get 13 buyers, I'm aiming for two for me, the price will be $40 plus shipping. I'll do the matching within the specified .3ma range (hopefully we can do much better. Shipping will be $8 for priority mail in the US. Outside US shipping will be actual cost.
I will post the actual group buy tomorrow when I have a little more time to figure out how to create one. This will be my first. If anyone knows of a tutorial please post a link.
Lastly I hope I'm not breaking any rules by posting this on this group buy on this thread. I'm not trying to take over this thread I will post athe actual group buy as it's own thread tomorrow.
Jeffrey
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