@ Luke
If this is your preference you need 2 pairs B grade LS jfets 8 mA Idss
for front end of this original Push - pull Part 2 amp see on schematic.
Jfets are out of stock today but they be back just hang around every day for
Attention little more advanced level project if compare with Vfet Part 1 CSX
or others diy Mr Pass amp's designs.
Matched JFET pairs (Grade B) - Parts
Kind regards
Yes I know, but fortunately I bought a few of these already so its not a problem. TO3 package is a bit hard to work with but apart from that I'm looking forward to my next Pass amp.
I received 4x 2SK82 from Aliexpress.com : Buy SONY 2SK82 V FET from Reliable fet transistors suppliers on Eternal HONG's store | Alibaba Group today. I was initially skeptical due to the different packaging however they look genuine and measure less than 2 ohms source to drain. I will build frankentracer to check curves. The only thing is vendors photo shows KE-33 parts but these are JA-33 so i'm not sure whether these will work with SJ KF-33.
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I have a few questions, if 8ma IDSS Jfets are not available, can we use source resistors on them like we did for the F6? I see getting 8ma pairs kind of difficult at this point.
The next question is, for the bipolars in front end, It looks like Nelson may have been using a ZTX 450,550, but I am wondering if 2SA1837 and 2SC4793 like is used in the F5Turbo. Forgive me if this has been discussed previously.
The next question is, for the bipolars in front end, It looks like Nelson may have been using a ZTX 450,550, but I am wondering if 2SA1837 and 2SC4793 like is used in the F5Turbo. Forgive me if this has been discussed previously.
source resistors for input Fets can't do much harm , as long you're not using much different Idss ones , so resistors aren't of highish value
regarding cascodes - bigger ones ...... lesser ΔT/ΔI , so better
regarding cascodes - bigger ones ...... lesser ΔT/ΔI , so better
Hi Fatfreddy, how will deal with any mismatches? Your sample group is quie small so its possible you wont get good matches.
Hi Luke, I already had 6 off (plus 2 in CSX1) SK82's from Acronman, plus did not want to risk too much cash on unknown source.
We're working on getting a lot more. We're brewing up a bigger batch for next month!
@ Luke
If this is your preference you need 2 pairs B grade LS jfets 8 mA Idss
for front end of this original Push - pull Part 2 amp see on schematic.
Jfets are out of stock today but they be back just hang around every day for
Matched JFET pairs (Grade B) - Parts
Kind regards
I'm not knowledgaeble enough to tell if JA-33 is considered OK, but I was helping some brave souls to order a few of these, so I tested them one by one before taking them to the post office and one 2SJ28 happens to be bad.
Something I can tell from the dozens that I measured:
- They do display the triode curves of VFETs, I tend to believe they're genuine Sony VFETs.
- As far as I can tell, the JAs are more linear than the KEs and KFs, but they have lower transconductance at the same time.
- With the lower transconductance, I suspected they might be re-badged 2SK60/SJ18. So I drilled open the bad one, but the chip inside seems to be a 4mm chip, so they're not 2SK60/SJ18 which have 3mm chip.
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Hello all. I had got a lot of curves (KE, KF and KD types) and I have not find difference between them (types). Variability is big.
If JA type show typical curves, I think they will be good (always looking only curves). But until I receive them, measure and compare I could not be sure they are good (sure they are, Tim does a good job, thanks a lot, Tim). I think letters (KE, KF, KD, JA, ...) are batch productions (I can be wrong).
N type are better (curves) than p types, variability is lower. Look curves.
When I did the same with tokins (180, 182, 183 and THF51), we got a bigger variability than sony types.
Regards
If JA type show typical curves, I think they will be good (always looking only curves). But until I receive them, measure and compare I could not be sure they are good (sure they are, Tim does a good job, thanks a lot, Tim). I think letters (KE, KF, KD, JA, ...) are batch productions (I can be wrong).
N type are better (curves) than p types, variability is lower. Look curves.
When I did the same with tokins (180, 182, 183 and THF51), we got a bigger variability than sony types.
Regards
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This post suggests they are dual die - can you see a second die inside the package? AudioKarma.org Home Audio Stereo Discussion Forums - View Single Post - A Brand New v-fet design by Nelson Pass?
I remember to have seen a picture of an open 2SJ28 which had two dies, and Nelson commented something like that they are possibly 2 x 2SJ18 dies in one 2SJ28,
So maybe these are rebatched 2sj18/2sk60?
Somebody have to measure them, and post curves or data to compare with real deal Acronmans.
So maybe these are rebatched 2sj18/2sk60?
Somebody have to measure them, and post curves or data to compare with real deal Acronmans.
From the Sony VFET part 1 thread, I remember, member 'ianc13' had blown a few 2SJ28.
Maybe he can open up a defective VFET to see if they are single or dual die?
Calling 'ianc13'....😀
Maybe he can open up a defective VFET to see if they are single or dual die?
Calling 'ianc13'....😀
@ WalterW & Diyers
I remember this Mr Rothacher post about 2SK82 inside chips with photo :
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-181.html#post3616492
Thanks Michael
@ Cwtim01 hope other chip is just not visible on your photo it need to be cut with saw for metal ?
Greetings 🙂
I remember this Mr Rothacher post about 2SK82 inside chips with photo :
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp-181.html#post3616492
Thanks Michael
@ Cwtim01 hope other chip is just not visible on your photo it need to be cut with saw for metal ?
Greetings 🙂
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All of the parts I got from Acronman are dual die.
See my Lab Hangout here, where we looked at them under a microscope:
https://youtu.be/dTqaR5qsT_0?t=19m30s
Try not to be overly paranoid about counterfeits, guys. Most of the counterfeitts I've gotten are pretty obvious, and no one is going to great lengths to make a part "act" like a triode. It's a SIT, or it isn't. Just be smart about your purchases and don't try to scoop up a bunch of expensive parts from an unproven source.
🙂
See my Lab Hangout here, where we looked at them under a microscope:
https://youtu.be/dTqaR5qsT_0?t=19m30s
Try not to be overly paranoid about counterfeits, guys. Most of the counterfeitts I've gotten are pretty obvious, and no one is going to great lengths to make a part "act" like a triode. It's a SIT, or it isn't. Just be smart about your purchases and don't try to scoop up a bunch of expensive parts from an unproven source.
🙂
When I purchased the JA-33 parts my only basis was Visual Inspection of the marking. Under 30X to 50X microscope,
no signs of rework and marking is still original.
During Version 1, I happened to inquire these parts and it cost about 200RMB per piece.
Now the release of V2, since nobody have interest during the V1 period, I was amazed it was sold at 200RMB a pair.
In a period of 2 weeks, the sales has gone up, upon my purchased, after 5 minutes the price raised to 300RMB per pair
including other V-FETS model (YAMAHA and SONY).
Hopefully somebody can final confirm the authenticity of JA-33 which still have a big volume of stocks existing.
And Im sure Papa will be very happy to see many VFETS amplifier displaying on the Picture Gallery🙂🙂.
Cheers.