LND150 SHO (aka LND 'HO!)

[mdcmdcmdc]

Hi all,

This is an extremely simple thing, but I hadn't seen it come up on the forum before and the pun is to good to resist, honestly... LND 'HO, an LND150 SHO.



Saves a few parts over a BS170/2N7000 SHO, sounds good, maybe a little quieter?

In the crackle-ok version, the 2K pot will swing the drain voltage between 4.5V and about 8V. Those values sound fine on the breadboard but in case that seems a touch high, a 1K pot will swing between 4.5V and 7.5V (very close to the original SHO values iirc?).

[mdcmdcmdc]

Oh, and w/ the non-crackle version, the series resistor approach taken w/ the crackle-not-ok circuit doesn't seem to work at all with the LND150. It may just need to be tweaked to a different value? In any case, a 1M voltage divider in front of it works a-ok.

[marcelomd]

Hi,
Looks like the second version changes input impedance along with gain (1M or less in parallel with 10M). Is that intentional?

[mdcmdcmdc]

My understanding is that input impedance in the original SHO varies with the gain range in both the zvex version and the CNO™ version. I'm not sure if the range of variation is the same here, though.

From the original 2009 CNO thread over on FSB:

[bluelagoon]

Can I replace the 5kC Reverse Log potentiometer in this SHO circuit for another type taper pot, that would still give satisfactory results,
and a workable effect?

[mdcmdcmdc]

Any taper will work fine; I've been using linear taper trim pots on the breadboard and there's definitely a big jump bunched up at one end, but it's not the end of the world or anything. 1 or 2K though, a 5K is too high.

[POTL]

take the first stage of a tube preamp as a basis. Set the drain and source resistors for maximum net gain. Find a suitable volume pegistor, 10-50k ohms should be fine. By the way, BS170/2N7000 can also be biased with 1 gate resistor, look at the AMZ mosfet booster diagram, depending on the bias current you can change the shape of the distortion, distorting only half of the signal, the entire signal, or leaving it clean.

[Rob Strand]

sounds good, maybe a little quieter?

I would expect so but I haven't done any measurements.

The symbol and orientation of your LND150 looks wrong.

FYI,  some time back Jonny Reckless put up a project using the LND150 device,
https://postimg.cc/pm06jXKV
https://diystompboxes.com/smfforum/index.php?topic=125775.0
https://ww1.microchip.com/downloads/en/DeviceDoc/LND150%20C041114.pdf

In fact Jonny answers the question of noise:
" I was asked if I could maybe use the LND150 depletion mode MOSFET in a distortion pedal design, as it might be less hissy.
...
There's noticeably less hiss than when using BS170 MOSFETs which is nice. "

In a gain stage the LND150 would have less input capacitance.

[mdcmdcmdc]

The symbol and orientation of your LND150 looks wrong.

oops, yes - corrected the orientation, only one option for n-channel MOSFETs in the little web circuit diagram thing I was using.