Another Aleph-X coming up!

[Taco]

Originally posted by jrsun
What is Ahe ? Thanks !

Ahe is (www.specmail.nl) local electronicshop. And sells matched fets. Don't know if they deliver over the big pond .

[gnomus]

Edwin,

Great write up.

Your ran a test for R12 and R34. What values did you choose?

[Edwin Dorre]

Originally posted by gnomus
Edwin,

Great write up.

Your ran a test for R12 and R34. What values did you choose?

Hi,

I used 2k potmeters to start off, I set the initialially at 1k. After applying a 1khz sinus wave of about 9V RMS into a 8 ohm load, I adjusted these potmeters to get an even gain of 50% of the active current source . After adjusting I measured the 2k potmeters and they were about 780 ohm ! So it is best to go this route as the value is very dependend of amount of mosfet's used and the value of the bias resistors.

Hope this helps,

Edwin

[EUVL]

Edwin,

A stupid question perhaps :

How exactly did you adjust R12 R34?
How do you measure the gain of the active current source to know it is exactly 50%?

Thanks,
Patrick

[minimustangs]

Edwin...Please contact me off board, urgent!
Steve

[macka]

The best way and perhap the only accurate way is to disconnect the trimer, apply 16 volts 100 hertz to an 8 ohm load at full temperature. Measure the a.c volts across the lower source resisters then measure again with the trimmer in circuit until the desired a.c voltage representing 50% current share is obtained.

imac

[Edwin Dorre]

Originally posted by minimustangs
Edwin...Please contact me off board, urgent!
Steve

Edwin reporting for duty, Sir!