I added the 1Meg resistors after the output cap and everything is as it should be. The blue hypno is now connected in my system and making good music. If first listen is anything to go by I'm really going to enjoy owning this buffer; so dynamic and the bass.......
You tell us more with time, some in system pics even. Congrats.
just sell one of your kidneys for duelund silver foil CAST and be done with it
I need to decide which of my caps I want to buy 2 more of to use there if needed; as I have 2 x mundorf SIO, 2 x duelund VSF copper, 2 x VCAP CuTF, 2 x VCAP OIMP. since going balanced I have mostly been totally DC coupled, so have all these pairs of everything sitting around and cant do anything with them unless I buy 2 more. I have even tried dropping CuTF in to decouple the AVCC supplies of my sabre just so they are doing something.
I need to decide which of my caps I want to buy 2 more of to use there if needed; as I have 2 x mundorf SIO, 2 x duelund VSF copper, 2 x VCAP CuTF, 2 x VCAP OIMP. since going balanced I have mostly been totally DC coupled, so have all these pairs of everything sitting around and cant do anything with them unless I buy 2 more. I have even tried dropping CuTF in to decouple the AVCC supplies of my sabre just so they are doing something
.
I bought a few dozen Toshiba 2SK170 BL Jfets.
I've been matching them and there's something I want to discuss with whoever's done this themselves:
Bringing them to saturation, isn't quite as cut and dried as one would hope - some of them never settle, or at least not within 60 seconds. Others do settle, and it is clear what their IDSS should be rated at, but others take a long slow build up over 2 minutes or more, before you feel they are at current saturation.
When I measure one and it reads the same as another I've already done, I go, "whoopee, a match" and then check the first one again to be doubly sure - it quite often now reaches up to .5mA higher!!! Very frustrating that. Why is it?
I have tried to be consistent with my procedure with regards to ambient temperature, voltage applied, method etc.
When we say that a jfet has an IDSS of 6.72mA, for example, it may be a reading taken at 30 seconds when it settled for a bit, but I am sure that prolonged exposure to being run at IDSS in a hot DCB1 buffer for a few hours would extend that to a new rating.
Has anybody ever removed a set of "matched" k170s and measured them to find they have new higher IDSS readings, and no longer matched? I suspect this may be the case quite often.
I'd be interested to hear of your experiences.
I've been matching them and there's something I want to discuss with whoever's done this themselves:
Bringing them to saturation, isn't quite as cut and dried as one would hope - some of them never settle, or at least not within 60 seconds. Others do settle, and it is clear what their IDSS should be rated at, but others take a long slow build up over 2 minutes or more, before you feel they are at current saturation.
When I measure one and it reads the same as another I've already done, I go, "whoopee, a match" and then check the first one again to be doubly sure - it quite often now reaches up to .5mA higher!!! Very frustrating that. Why is it?
I have tried to be consistent with my procedure with regards to ambient temperature, voltage applied, method etc.
When we say that a jfet has an IDSS of 6.72mA, for example, it may be a reading taken at 30 seconds when it settled for a bit, but I am sure that prolonged exposure to being run at IDSS in a hot DCB1 buffer for a few hours would extend that to a new rating.
Has anybody ever removed a set of "matched" k170s and measured them to find they have new higher IDSS readings, and no longer matched? I suspect this may be the case quite often.
I'd be interested to hear of your experiences.
Hi Lucas,
Haven't had this experience , what i have seen is that different batches from different sources are very different.
Some have IDSS which track quite closely a specific average value, other batches vary wildly and it's very dificult to get a match........i would guess that all the matches have been taken out already !!!
But one can always get matches between diff batches.
Haven't had this experience , what i have seen is that different batches from different sources are very different.
Some have IDSS which track quite closely a specific average value, other batches vary wildly and it's very dificult to get a match........i would guess that all the matches have been taken out already !!!
But one can always get matches between diff batches.
I could absolute agree you recommendation
At the moment i use a russian K75-10 1,5µF bypassed by a K72-P6 teflon 0,047µF as output caps on my Tube-I-zator board. The combination is brilliant.
depends on the value? if only 0.01 or 0.1 not amazing value, pretty standard, but a larger one maybe. what is the capacitance of these you mention?
well actually no, not so flash, PCX sells the 1200v version of same for about the same for the 2.2u and almost 20usd cheaper for the 3.3u and if you are lucky you can catch a sale at PCX and get 15% off. in fact I think theres one on at the moment.
they'll be HUGE though!! like 40x60mm or so
I actually prefer the silver/oil and silver/gold/oil versions, I would take the silver/oil over the plain silver/gold anyday
they'll be HUGE though!! like 40x60mm or so
I actually prefer the silver/oil and silver/gold/oil versions, I would take the silver/oil over the plain silver/gold anyday
I've matched more than 300 of 2SK170 and about 100 of 2SJ74, BL grade.
Same process, stable 9v PSU, min 2.5 mn before reading the value and... yes, measures aren't the same, variation from 0.3 to 0.4mA.
IMHO because of component and room T°, batches are mixed too.
The goal is to obtain similar values, best around 7.2mA.
I don't try to desolder matched sets and tests them after...
is 10ma idss too high? i'm ordering some LSK170 to use instead I would like to have decent current output in case of driving headphones; or should I just get the lower 7-8ma parts and parallel if needed. seems would be better to have the lower input capacitance. also may use some in an IV, so the 8ma would be fine there. 10 isnt too hot though is it?
yeah that would be an eventual rework, probably with some kind of follower and only with my 600R cans, like I said just an option I would like to keep. i'm getting both parts, but thought I would ask here. maybe just get them all 8ma and stack them if it comes to that. just trying to stick with getting as many of one part type/grade as possible in the order in case of some kind of discount.
Last edited: