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E19 headphone amplifier board K2381 J407 MOSFET Yuanjing Audio
E19 headphone amplifier board K2381 J407 MOSFET Yuanjing Audio
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Old 25th September 2017, 06:06 PM   #51
nattawa is offline nattawa  Canada
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Then could there be a possibility that the perceived "hysteresis" behavior in threshold was a result of the threshold Vgs being modulated by the die temperature dynamic, which is nothing out of ordinary?
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Old 26th September 2017, 02:56 AM   #52
EUVL is offline EUVL  Europe
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Same measurement for a NOS Sanyo "Switching" NMOS.
Not all FETs are created equal.


Patrick

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File Type: png Sanyo Switching NMOS.png (9.7 KB, 112 views)
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Old 26th September 2017, 03:48 AM   #53
keilau is offline keilau  United States
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Quote:
Originally Posted by EUVL View Post
A few comments, just stumbled into this by accident :

uPC1237 is meant for loudspeaker protection, and has a trigger point at +0.7/-0,2V.
One can decide whether it is high or not, but I guess most over-ear phones should survive 0.7V DC.
In any case some protection is better than none.

On 2SK2381 / 2SJ407, we got curious, bought some, and curve traced them.
They are one of the most horrible curves we have seen.
They were traced with a triangular wave form (linear current ram) at 100Hz.
So it is just normal operating condition.

You can see that the positive and negative swings followed completely different curves, with a huge hysteresis.
So that was end of story for us. The 5 pairs we bought went to the bin straight after.

You always get what you pay for.


Patrick

.
Were you able to compare 2SK2381/2SJ407 pair from US distributor? Were you able to verify that the units you got were NOT line rejects?

The 2SK2381/2SJ407 are good devices and standard units should not behave the way you measured. I am not sure what the source of the problem is, but suspect defective line rejects sold by Ebayer.
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Old 26th September 2017, 04:25 AM   #54
EUVL is offline EUVL  Europe
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> The 2SK2381/2SJ407 are good devices ...

If you say so.


Cheers,
Patrick
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Old 26th September 2017, 01:14 PM   #55
keilau is offline keilau  United States
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Quote:
Originally Posted by EUVL View Post
> The 2SK2381/2SJ407 are good devices ...

If you say so.

Cheers,
Patrick
It doesn't matter what I said. Toshiba has been making MOSFET for a long time. Yes, the 2SK2381/2SJ407 are not the proper pair and they may not be the best choice for audio output devices. But your test result looks very unusual for Toshiba device that I used.

Get some 2SK2381/2SJ407 from Digikey for your test. It is not fair to treat fake products from Ebay as the genius part.

Quote:
Originally Posted by EUVL View Post
You always get what you pay for.
I can't agree more with you on this.

Last edited by keilau; 26th September 2017 at 01:24 PM.
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Old 29th November 2017, 02:47 AM   #56
phase is offline phase  United States
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It looks like the original version of this amp is available once again;
http://diyhifishop.com/new-assembled...diy-p-216.html

The site was pretty dim a year or two ago, with nothing showing available, however it looks like that has changed...
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Old 29th November 2017, 02:20 PM   #57
keilau is offline keilau  United States
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Quote:
Originally Posted by phase View Post
It looks like the original version of this amp is available once again;
http://diyhifishop.com/new-assembled...diy-p-216.html

The site was pretty dim a year or two ago, with nothing showing available, however it looks like that has changed...
How do you know that they are active again?
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Old 29th November 2017, 09:27 PM   #58
phase is offline phase  United States
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A while back there wasnít much showing available, looks better now...

Havenít ordered from them however.
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