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-   -   Salas DCG3 preamp (line & headphone) (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone.html)

Salas 26th November 2016 09:45 PM

Quote:

Originally Posted by Hikari1 (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4898623.html#post4898623)
Got my jfets today. Any reason to be concerned about fakes?

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.

Hikari1 27th November 2016 12:16 AM

I have no reason to believe they are fakes and I haven't tested them for idss yet. Waiting on my boards to get serious about building this thing. I don't have a curve tracer but once I test for idss I will post it.

AndrewT 27th November 2016 08:49 AM

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.

nashbap 27th November 2016 03:33 PM

Salas, can one substitute a different Mosfet for M1? Perhaps the Toshiba 2SJ313?

Thanks. nash

Salas 27th November 2016 03:43 PM

No, its too sensitive for such substitutions regarding performance. It was showing substantially more THD even with Fairchild FQP3P20.

nashbap 27th November 2016 03:47 PM

Quote:

Originally Posted by Salas (https://www.diyaudio.com/forums/analog-line-level/296406-salas-dcg3-preamp-line-headphone-post4899254.html#post4899254)
No, its too sensitive for such substitutions regarding performance. It was showing substantially more THD even with Fairchild FQP3P20.

Ok Thanks.

Theodosis O. 28th November 2016 08:14 PM

Hi Salas,

can one substitute bigger capacitors for C6, C7 ?
i.e. 330 uF

Thanks

Salas 28th November 2016 08:55 PM

Probably but I haven't tested more than 100uF

lykkedk 1st December 2016 05:02 PM

Mambo double Polish donuts, classA big sound this evening folk's
 
4 Attachment(s)
So...

Thread is waiting for people recieving theyr'e pcb and part's i guess :o

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 :D

Jesper.

Salas 1st December 2016 05:21 PM

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?


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