I agree that they look like GR parts. What I was thinking was that if they
are in fact not 2sj74s at all, then we have a pretty impressive imposter
since both Idss and Yfs are within the GR spec.
Given jackinnj's comment in post #46, it would be interesting to see what
the noise is like.
BTW, I neglected to mention that the parts I traced are supposed to be 2sj108V.
Cheers,
Dennis
are in fact not 2sj74s at all, then we have a pretty impressive imposter
since both Idss and Yfs are within the GR spec.
Given jackinnj's comment in post #46, it would be interesting to see what
the noise is like.
BTW, I neglected to mention that the parts I traced are supposed to be 2sj108V.
Cheers,
Dennis
Last edited:
Agreed IMO.
..nice curves
and nice parts
congratulations
Thanks. Now I can see if I can get more and try to match them
for an Aleph J.
Cheers,
Dennis
I am going to build a low noise amp for testing parts like this. It's really the only final way to rule that they are genuine Toshiba process parts. I can almost hear the sellers comeback - "I bought them from a supplier". Actually, these are great compared to total FAKES I got from componentsMAX a couple weeks a go. It was just a sample lot of 10 they agreed to send. Idss of 8mA, with Yfs of 8 to 10. Something not right about that, and not at all Toshiba.
I also bought 8 linear LSJ74GR type. Now these are a bit low for an Aleph-J as they are grouped around 4mA. However, since I'm designing my own PCB's for the amp, I'll design the PCB for 2 in parallel at the input so that GR types can be readily used.
Do these look genuine or fake to you?
Toshiba 2SJ74 2SK170 Matched Quad to 0 03mA 4MV in Temp Controlled Lab | eBay
The seller is not from China but from US, and has 100% positive feedback.
Toshiba 2SJ74 2SK170 Matched Quad to 0 03mA 4MV in Temp Controlled Lab | eBay
The seller is not from China but from US, and has 100% positive feedback.
Also the 2SJ74BL sold by UTSOURCE at the moment are fake low-gain P-channel JFETs. At a cost below 0.5$/pcs I could not help buying a couple out of curiosity.
Thanks for the offer, I've already got a quad from diyaudio store, I was just curious as to whether the ones above in ebay were fakes or not.
But those you got are not Toshiba 2SJ74/2SK170 - they are (genuine) LSJ74/LSK170
Is there any difference in audio quality performance between the LS and Toshiba parts?
The package should say "Diffused in Japan" and may say "Assembled Somewhere
Else" Where it's diffused is the important part.
Well, now it was my turn to get some crap J74/K170 Jfets
I checked them for IDSS when I got them and it was a bit low for a BL. Today I tested Gm the fast way but the results looks like what others have seen.
Gm is very low and it decreases when it warms up and/or with increasing current.
Both N and P's are the same s**t. Some numbers:
J74. Id 7,2mA ~in 148mV out 120mV !?
Genuine J74 Id 6,04mA, in 98mV, out 897mV !
I will check further tomorrow about complains. I got them from a German company some months ago, I hope it's not to late.
Maybe I can use them as *@#$$*@ expensive current sources ?
PS: It may be intresting to others to know where I got them, but is it Ok to tell ?
/Figge
I checked them for IDSS when I got them and it was a bit low for a BL. Today I tested Gm the fast way but the results looks like what others have seen.
Gm is very low and it decreases when it warms up and/or with increasing current.
Both N and P's are the same s**t. Some numbers:
J74. Id 7,2mA ~in 148mV out 120mV !?
Genuine J74 Id 6,04mA, in 98mV, out 897mV !
I will check further tomorrow about complains. I got them from a German company some months ago, I hope it's not to late.
Maybe I can use them as *@#$$*@ expensive current sources ?
PS: It may be intresting to others to know where I got them, but is it Ok to tell ?
/Figge
Photo
Here's a picture of a genuine part, the upper one, and what I belive is a fake, the lower one.
They don't look the same. The cut on top look different to.
I'm no expert in Gm-testing but this is what happened:
With 0.2VAC 1kHz sine wave to the gate, and 10V D-S with 1k in series, it first had higher Gm but when it got warmer and ID got up it fell like a rock. When I tested the genuine parts they behaved totally opposite.
They also had higher IDSS than the bad ones.
I also tested SJ103/SK246 that i got in the same order. They measure a bit better but behaved similar to the others. I wonder if they are ok. One is marked GR and one Y ? It don't seem right
So, as some people point out - there are mostly fakes around
Figge
Here's a picture of a genuine part, the upper one, and what I belive is a fake, the lower one.
They don't look the same. The cut on top look different to.
I'm no expert in Gm-testing but this is what happened:
With 0.2VAC 1kHz sine wave to the gate, and 10V D-S with 1k in series, it first had higher Gm but when it got warmer and ID got up it fell like a rock. When I tested the genuine parts they behaved totally opposite.
They also had higher IDSS than the bad ones.
I also tested SJ103/SK246 that i got in the same order. They measure a bit better but behaved similar to the others. I wonder if they are ok. One is marked GR and one Y ? It don't seem right
So, as some people point out - there are mostly fakes around
Figge
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