ODS FET Board 4u7 Voltage Recommendations

[ViperDoc]

What rated DC voltage is recommended for the FET board 4u7 polar capacitors? I can find up to 35V with 50V on back order. Is 35V high enough?

See the 124 schematic here:



Again, the small "blue" 4u7 caps on the FET board are what I mean. Thanks.

[erwin_ve]

On #124 there are blue tantalum caps on the FET board. 35v is ok.
You can use electrolytics. Either one work fine

Erwin

[ViperDoc]

Thank you!

[ViperDoc]

Do the NTE452 leads match up on both the 124 schematic and the NTE452 manufactured orientation?

See the 124 Schematic here: https://ampgarage.com/forum/download/file.php?id=4805

The schematic shows the FET signal inserting into the GATE, connected to the 10K at the DRAIN, and biased at the SOURCE.

See the Layout here:



The orientation of the NTE452 here is a "SOURCE-GATE-DRAIN" orientation.

See the NTE452 datasheet here: https://www.tme.com/Document/86964789c0 ... nte452.pdf

The datasheet shows a "SOURCE-DRAIN-GATE" orientation.

Is it possible to find NTE452 JFETs with either configuration? I can only find the SDG versions. I designed a board with the SGD orientation (like the layout), I'm wondering if SGD versions exist in the wild or if I need to redesign the board. Thanks.

[martin manning]

AFAIK they are all going to be the same, both NTE 452 and 2N4416A. Looking from the bottom, CW from the tab, SDG Case, as shown in the NTE data sheet you linked. The layout drawing shows the same.

[ViperDoc]

“Looking from the bottom”.

That’s likely my problem. Thanks Martin.

[ViperDoc]

I ripped apart my old FET board, added a few small eyelets for the trimmer and rebuilt it with the NTE452 in its proper orientation. I went with Nichicon MUSE electrolytics in place of the tantalum caps. And what do you know:

IT WORKS!

The FET pulls harder on the power supply than I anticipated (I just went from 187 to 140 VDC on my V1 plates), but it sounds quite good. I've got it biased at about 11 VDC. I'll need to change my dropping string a bit to get those plates and the max FET bias back up. It sounds more like a clean boost than the JFET boosts I'm used to running in front of my amps; but if I recall, the ODS FET input was intended for acoustic guitar, so that explains it.