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-   -   Sony VFET Amplifier Part 2 (https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a.html)

dady 14th August 2015 08:20 AM

Thanks Mark!

Msr Mojo 14th August 2015 05:51 PM

Quote:

Originally Posted by Tea-Bag (https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-post4418643.html#post4418643)
Here is the concept art for the VFET v2 board dubbed "AL"
I have a couple people besides myself looking for errors on the boards. It looks like based on Botte's work that we will need to widen C1 and C2 a bit.

Comments are welcome.

https://origin.dastatic.com/forums/g.../medium/17.png

Click this link below for a larger pic.

AL Concept - My Photo Gallery

Teabag,
This is my first post (hope I'm doing this properly).
Thank you for your efforts, as I'm wanting to build this amp.
Nice artwork on the pcbs.
Upon tracing/checking some of the paths, the R12 and R16 resistors positions appeared be reversed with respect to the original schematic.
Were the other zener diodes on the original schematic (Z2/Z6 and Z1/Z5) deemed unnecessary?
What value are the resistors RSA and RSB going to Q11 and Q12?
Thanks a lot!
Msr. MOJO

luvdunhill 16th August 2015 12:19 AM

Sony VFET Amplifier Part 2
 
In looking at the TL431 data sheet (TI) it seems the output capacitance could be lowered to 6.8uF, which would be stable even in the worst case, and would allow use of the compact Wima film capacitors. Any reason this wouldn't work, such as the larger caps resulting in safer startup conditions?

anilva 16th August 2015 03:08 AM

Quote:

Originally Posted by Nelson Pass (https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-post4392065.html#post4392065)
Here is an example test setup

I am in the process of measuring my VFETS and the power supply is ready. Can someone help me with the markings of G, D and S on the schematic of the test circuit. I don't want to blow these precious VFETS by connecting them wrong.

Thanks.

anilva 16th August 2015 03:53 AM

Quote:

Originally Posted by anilva (https://www.diyaudio.com/forums/pass-labs/276711-sony-vfet-amplifier-2-a-post4421528.html#post4421528)
I am in the process of measuring my VFETS and the power supply is ready. Can someone help me with the markings of G, D and S on the schematic of the test circuit. I don't want to blow these precious VFETS by connecting them wrong.

Thanks.

My bad. Got it. On the schematic, the arrow pin is gate and the pin closer to the gate is source and the remaining one is drain. Sorry.

2 picoDumbs 16th August 2015 10:35 AM

Thank you Mr Pass.
Best wishes.

2 picoDumbs 17th August 2015 03:37 AM

Hello Mr Pass or Mr BrainMod
Any issues with just building output stage and running like an F4?
I have an application that does not require voltage gain.

Zen Mod 17th August 2015 09:07 AM

no issues

increase R20 to 22K or 47K and that's it

2 picoDumbs 17th August 2015 09:35 AM

Now I just need to go out to the garrage and find the bloody devices.

Botte 17th August 2015 01:30 PM

Golden Ear Shootout CSX1 vs VFET Part II (Al)
 
We had the shoot out this weekend; keep in mind that the new amp is still in break-in.

The first major comment is that that the panel decided that they could live happily with either amplifier and that they were both exceptional.

Both designs shine at detail and ambiance recovery. CSX1 is more ”tube like” and romantic and the new version with the “Nelson mods” is more focused and dynamic. An additional comment was that the new amp made you feel like you were wearing headphones; in that you could hear all the little details that tend to get lost in a room system.

There is something intangible about both of the VFET amps compared to other non-VFET amps, they have an ease about them that is non-fatiguing. Is it the devise or the designer?

Next up; single pair output version, that will take some time as I will need to build some new chassis.


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