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Old 6th August 2011, 02:30 AM   #261
prakit is offline prakit  Thailand
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Quote:
Originally Posted by juma View Post
A friend of mine ordered a batch of 2sk2013/2sj313 from utsource.com ten days ago. They arrived today and he brought them to me, for genuinity check. I measured the transfer curve (Id vs. Vgs) and they comply to datasheet - with about 10% dispersion (for example, at 0.3A, Vgs varies from 2.8 to 3.1V) which is OK.
This is how they look:
These look exactly the same as the batch I bought and returned them for refund. The faces were obviously shaved off and re-screened. Knocked them up, the chips were smaller than those I bought from ZF and a local source. UTSource said they were the "Chinese" version.
Actually, with this batch I bought a few Renessas K213/K76 at only $0.8 and $1.0 a piece. Too good the price! The finish of the leads were whithish silver as oppose to slightly lustrous silver for those I obtained from reliable sources. However knocking a few up, the chips inside looked exactly the same. The Vgs measured ok too. Still very skeptical but I decided to keep them for non-critical use.
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Old 6th August 2011, 09:44 AM   #262
juma is offline juma  Germany
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Quote:
Originally Posted by prakit View Post
These look exactly the same as the batch I bought and returned them for refund. The faces were obviously shaved off and re-screened. Knocked them up, the chips were smaller than those I bought from ZF and a local source. UTSource said they were the "Chinese" version.
....
It would be nice to compare the measurements - did you do any?
If you look at the Zhou's parts you'll see that they are dated 2000-2002, and these are 2007. Manufacturers tend to change the plants/production processes during the course of time.
Anyway, if parts measure the same, they are the same...
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Old 6th August 2011, 10:26 AM   #263
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Juma, the picture you posted is very similar to the originals, with the 'bat's ears' but gain category is not marked.

My experience with similar Chinese parts, as opposed to complete fakes, is that if the Chinese parts are used with lesser voltage and current, they perform without a problem. Hence, in your amp, if the number of output devices are increased, so that each device is biased at a lower current, they should work. Using thermistors for thermal compensation will help.

However, what I have and some others, may be total fakes, though I can't say for sure without performing some tests.
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Old 6th August 2011, 02:15 PM   #264
Rush is offline Rush  United States
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Default FAKES

They may have stability issues. They may not sound the same. Really need to plop them in a test amp, which is too much trouble.
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Old 6th August 2011, 02:59 PM   #265
massimo is offline massimo  Italy
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Quote:
Originally Posted by juma View Post
If you look at the Zhou's parts you'll see that they are dated 2000-2002, and these are 2007. Manufacturers tend to change the plants/production processes during the course of time.
This might explain the die difference.
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Old 6th August 2011, 04:12 PM   #266
juma is offline juma  Germany
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Guys, not all parts that were delivered by utsource are the same. There are visual differences, which still tells us nothinig without measurements.

Parts don't sound - the way their properties are used does. And properties are measurable.

Parts from Zhou and those from post #260 behaved exactly the same and in compliance with datasheet, electrically and thermally, in Id range from 10mA to 600mA.

Also, when you look the "Marking" picture in the datasheet from 2006 you'll see that it doesn't show Vgs classification.
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Old 7th August 2011, 04:58 AM   #267
crt is offline crt  Indonesia
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This is the PDF File (scale 1:1) direct print to A4 paper.
maybe if someone interest


F5 Juma layout.zip


THis is one sided PCB (Top Copper only), easier to mount those MOSFET.
the only negative effect is you have to bend VR legs to mount them at PCB
here i use 0R27 Resistor (with a little matched MOSFET to +/- 0.01Volt at 500mA)
but you can use 0R33 alike Juma suggestion (without Macthing)

i had not tested result with scope, because i dont have one
but i'm pretty sure no problem with my layout

Quote:
Originally Posted by juma View Post
You are welcome! I'm glad you like it

Nice job, BTW
Again Thank's for your Design (Also to PAPA)


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Originally Posted by CeeVee View Post
Very nice work CRT....congrats
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Originally Posted by Nelson Pass View Post
Oooooooooooo.....

Shiny.

Thank's for a kind words CeeVee and Papa



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Originally Posted by pmchoong View Post
What is the reason for lots of small capacitors instead of just a few bigger ones?
Actually i use them because i already have them
Those are Panasonic FM (2700uF/25Volt) 56 piece ==> Hope that capacitance is enough
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Old 7th August 2011, 02:32 PM   #268
prakit is offline prakit  Thailand
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Quote:
Originally Posted by juma View Post
It would be nice to compare the measurements - did you do any?
If you look at the Zhou's parts you'll see that they are dated 2000-2002, and these are 2007. Manufacturers tend to change the plants/production processes during the course of time.
Anyway, if parts measure the same, they are the same...
Sorry, Juma. I didn't do any measurement with these parts. I have returned them all too.
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Old 8th August 2011, 11:53 AM   #269
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Quote:
Originally Posted by juma View Post
With some minor adjustments (as Jacco mentioned) it would be great. OTOH, when it comes to power-buffer for low Z headphones (but not lower than 25 Ohms) EUVL's DAO is my favourite ...
Juma,
In anticipation of the arrival of my fets, i am trying to decide whether or not they would improve the F4 like they have the F5. I see how the circuit would need adjusting for the most part, but don't understand the change of Rs to 1R vs.47R, as suggested by Jacco. In a common source setup like F5, this throws away more gain and improves performance, but what function does it have in a common drain amp like the F4. It is, in essence, more degeneration or negative feedback, correct?
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Old 8th August 2011, 11:59 AM   #270
Zen Mod is offline Zen Mod  Serbia
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well - I'm not Juma ...... but I'm saying - don't waste them for F4 ;

there will not be any benefits , just drawbacks
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