F5 with 2SK2013/2SJ313

prakit · 2011-08-06 2:30 am

juma said:
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.

juma · 2011-08-06 9:44 am

prakit said:
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...

Samuel Jayaraj · 2011-08-06 10:26 am

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.

Rush · 2011-08-06 2:15 pm

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.

massimo · 2011-08-06 2:59 pm

juma said:
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.

juma · 2011-08-06 4:12 pm

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.

crt · 2011-08-07 4:58 am

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

juma said:
You are welcome! I'm glad you like it

Nice job, BTW

Again Thank's for your Design (Also to PAPA)

CeeVee said:
Very nice work CRT....congrats

Nelson Pass said:
Oooooooooooo.....

Shiny.

Thank's for a kind words CeeVee and Papa

pmchoong said:
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

prakit · 2011-08-07 2:32 pm

juma said:
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.

buzzforb · 2011-08-08 11:53 am

juma said:
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?

Zen Mod · 2011-08-08 11:59 am

well - I'm not Juma ...... but I'm saying - don't waste them for F4 ;

there will not be any benefits , just drawbacks

buzzforb · 2011-08-08 12:23 pm

I guess you advice will do

nik_d · 2011-08-09 3:43 pm

Hi everybody. I'm proud owner of new amp that's coming directly from Juma's 'kitchen'

This amp replaced NP F5 clone. The box is new. Due to global crises, PCB's got smaller, output transistors as well

Great amp. Thank you Juma.
:cheers:

buzzforb · 2011-08-09 4:28 pm

Nice!

Nelson Pass · 2011-08-09 6:00 pm

It's always a pleasure to see really clean work.

Not like my prototypes.....

dobrivoje · 2011-08-09 11:25 pm

@nik.d and Yuma
Fugly!

@Nelson Pass
It's always a pleasure to listen Papa's amps.

buzzforb · 2011-09-12 2:41 pm

Question. In looking at pics of completed amps, I notice that the transistors have thermal compound on them, but cannot tell if they have an insulator. Seeing as how they have a plastic case, no insulator is necessary, correct.

ManicP · 2011-09-12 2:43 pm

buzzforb said:
Question. In looking at pics of completed amps, I notice that the transistors have thermal compound on them, but cannot tell if they have an insulator. Seeing as how they have a plastic case, no insulator is necessary, correct.

Yup!

Zen Mod · 2011-09-12 10:47 pm

you can , to decrease current through trimpots

even if I'm not loosing my sleep with issues like that

buzzforb · 2011-09-12 10:58 pm

ZM,
You saw my dumb question before it was deleted. Its funny how you stop thinking sometimes when you are in the middle of doing something that is somewhat foreign or new . Maybe intellectually lazy is the correct term. Thanks anyway.

Zen Mod · 2011-09-12 11:19 pm

ya know that I'm used to dumbness .....

in any case - I'm still asking much dumber questions

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