There wasn't any real demand for those so the fakers to target them, the packaging is unusual to readily have for faking anyway, and the letters look old school in your photo so I would not easily worry. If you can trace them I had posted their curves to compare. What Idss they got? All of my samples show very near Idss between their sections.
the cheap and easy way to test Idss is to use a 9V battery, a 100r resistor and a DMM voltmeter.
Short the Source and Gate leadouts together with a croc clip and lead.
Connect this G+S to battery negative.
Use a second lead to the 100r resistor.
Use a third lead from resistor to Drain leadout.
Measure the voltage drop across the 100r.
BTW,
the different batch codes probably indicate you have genuine devices.
Short the Source and Gate leadouts together with a croc clip and lead.
Connect this G+S to battery negative.
Use a second lead to the 100r resistor.
Use a third lead from resistor to Drain leadout.
Measure the voltage drop across the 100r.
BTW,
the different batch codes probably indicate you have genuine devices.
Mambo double Polish donuts, classA big sound this evening folk's
So...
Thread is waiting for people recieving theyr'e pcb and part's i guess
Meanwhile mine is cooking on hifi...
15-20min. for best sound IMHO, then everything is around 30-35C. hot.
AKG's headphone are addicting, why do i keep my speaker's... Well they sound marvelous too on this combo.
This little big classA preamp. is having only few hours on it, and allready sounding very very good.
Nothing more, just wanna showoff
Jesper.
So...
Thread is waiting for people recieving theyr'e pcb and part's i guess
Meanwhile mine is cooking on hifi...
15-20min. for best sound IMHO, then everything is around 30-35C. hot.
AKG's headphone are addicting, why do i keep my speaker's
... Well they sound marvelous too on this combo.This little big classA preamp. is having only few hours on it, and allready sounding very very good.
Nothing more, just wanna showoff
Jesper.
Attachments
Hardcore DIY boards, great pictures, and a nice forerunner adventure for the industrial boards builders to have seen. Congratulations for your work. You even confirm the pdf guide words "Due to class A operation its not being a cold idling circuit so some warm up time is recommended before critical listening". Nice that you like the AKG K240 recommendation also. Difficult for me to try suggest solutions as subjective as choosing transducers and not disappoint. Do you hear some positive differences now that you run it on proper double mono Tx execution?
Thank you for the very kind word's Salas... It makes me proud
If we start with the cold/warm circuit, as can be seen on older pictures, i removed some Alu' bars for circuit to be a little hotter
... I allway's like a little heat/cooking when running such amp's! Donno if it make's any different to sound, but i like the idea of warmth sounding parts. -And this is excatly what this circuit does; make music warm, well IMHO. I also noticed some recording i allway's hear when judging amps, such as Road to hell part 1+2, Eagles, ZZ-top and some George Michael along with Maria Careys all i want for xmas is you 
(Happy 1. Dec btw.) this amp. are not producing sibilance... this is proberly one of the most perfect things with this amp. i think.Listning to your'e pre. with two torrid's are also great, but it's a little hard to tell excatly how much difference it does compared to my old 650VA unshielded torrid (This torrid is not for such circuit's)... Most noise are gone now, and the rest remaining is from poweramp (LM4780). When listning i can really tell that stereo perspective is very very very good.. Lot's of details flowing around the livingroom.. I love it!
Speaking of detail's. The first word from my wife, when she tried the AKG's was... they are very deep ... What do you mean i asked
... there are so many detail's was her answer! Soo next step is take it all apart and build into my old chassis... See ya'
And again thanks to all for helping me through this build...
Jesper.
Will make its own small greenhouse effect when boxed up for sure. Mine are 38C when directly probing on the Mosfets with the FLUKE thermocouple. Flatter AKG K240 were the 600 Ohm old models but this newer 55 Ohm "Studio" named one is not too bad, especially at its affordable nowadays price, and its much more efficient. Very suitable for you having set to 2x gain only so to can range well on the volume dial both with cans and your sensitive power amp. The K240s have a lively sibilance range response so if there is any in the system you will surely hear it. I don't know if it was engineered in on purpose to highlight microphone technique flaws in radio studios and recording but they can be very picky about that.
Hi Salas, these were measured at 9VDC. Is that what you mean?. I can just increase the source resistors until 5ma is achieve?. I thought we were looking for 6-8mA. TIA.
Quan
I didn't know the AKG 240 Studio were good enough to bother plugging in to this project.
That's why I didn't buy a kit from Tbag, because I don't like the idea of buying more headphones.
I might have to reconside this decision.
Hey
I don't know if they are considered good or bad around the world.
I bought them, because i got a tip here. But i don't have any experiance at all, with headphones.
But i can for sure confirm, that they sound very very good IMHO. But again i have no experiance in
Jesper.
