Sony vFET Amplifier Part 2

That magnetic shield band on the AS series is quite interesting and toroidy doesn't have that option. I remember seeing somewhere in the forum a member showing such a band to wrap around an existing transformer, but never found it again.

All the xformers shown in this thread should perform very well. Ordering close to home might be cheapest considering shipping costs. As you might notice Antek does not offer AS series lower voltage output xformers in sizes larger than 400VA. This does not bother me because I like to use 2 xformers in dual mono and stay below 500VA each with less load on bridges, contacts, ect. I also like to put large xformers in a separate PS enclosure away from the amp. Nevertheless, if you want a 500VA or larger with outer shield, email Antek and he will ship you a shield and heat transferring tape (mylar? without adhesive) along with the xformer to "wrap your own." I used some adhesive heat transfer tape on both ends to hold both ends. Be sure to wrap tightly. If you have DC in your AC lines, you might need to deal with that which is another thread.
 
Hi. Can someone explain to me how to measure the Sony VFET to match them?

NP mentionned in his article to match them for Vgs at 0.5A and 20V but no more details.

Is it that for example we connect the VFET to a 20V supply, limited in current at 1A for protection, and then we inscrease the Vgate until we meause 0.5A at the drain?

Let me know
Thanks
SB

Don't forget these are depletion mode devices.
 
Hi. Can someone explain to me how to measure the Sony VFET to match them?

NP mentionned in his article to match them for Vgs at 0.5A and 20V but no more details.

Is it that for example we connect the VFET to a 20V supply, limited in current at 1A for protection, and then we inscrease the Vgate until we meause 0.5A at the drain?

Let me know
Thanks
SB

I had to measure some of my parts for the VFET V1 build. I just measured using a 19V laptop brick, 2 x 9V batteries, a potentiometer and a small value resistor.

Use the 9V batteries in series for the bias with the potentiometer to allow adjustment. Set bias to -15V before main power is connected and then just slowly turn on until 0.5A is detected via a small resistor.

I didn't use any current protection, however that could be useful to make sure that you don't fry any parts.

All my parts biased (in the amp) between -6V and -11.5V so the -15V start bias should be low enough to ensure no current flowing in the part at the start of testing.

The whole rig can be flipped to test the 2SJ28s pretty easily.
 
Hi. Can someone explain to me how to measure the Sony VFET to match them?

NP mentionned in his article to match them for Vgs at 0.5A and 20V but no more details.

Is it that for example we connect the VFET to a 20V supply, limited in current at 1A for protection, and then we inscrease the Vgate until we meause 0.5A at the drain?

Let me know
Thanks
SB

Hi Algar

Other schematic are in case if you don't have two lab psu's.
 

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