On A Hippie Trail, Head Full Of Zombie

[2 picoDumbs]

I will look at notch filtering to see if I can find out more.

I have a notch filter design.
Just thinking the best way to make it tunable.
Basically thinking a dual gang pot to tune the notch frequency and then another pot to tune Q.
I think that's how I will make it.

Actually a 4 gang pot might be best.

 

[twitchie]

I only wondered today what that meant and Google'd it (what does head full of zombie mean):

'They open with the singer travelling in a fried-out Kombi, on a hippie trail, head full of zombie. In Australian slang "fried-out" means overheated, "Kombi" refers to the Volkswagen Type 2 combination van, and having "a head full of zombie" refers to the use of a type of marijuana.'

 

[2 picoDumbs]

Hahahahahaha

Excellent work.

Just gotta get you guys eating vegemite now.

 

[Zen Mod]

proper translation is "brain already fried, properly"

 

[wtnh]

Here is something of interest: I just returned from the grocery store to buy some Aussie lamb for dinner and the store was playing "Who Can It Be Now" on the PA system.

 

[2 picoDumbs]

It's Pico with a Jar of vegemite.

 

[2 picoDumbs]

proper translation is "brain already fried, properly"

Yes.
See, you're already Australian.
Hahahaha

 

[wtnh]

It's Pico with a Jar of vegemite.

Couldn't find the vegemite - was not sure which aisle to look in. But the Asian lamb lettuce cups were dynamite.

 

[2 picoDumbs]

Awesome.

 

[wtnh]

Ground Lamb Lettuce Cups recipe - Lava Lake Lamb

 

[2 picoDumbs]

Looks real good.

 

[wtnh]

I have a notch filter design.
Just thinking the best way to make it tunable.
Basically thinking a dual gang pot to tune the notch frequency and then another pot to tune Q.
I think that's how I will make it.

Actually a 4 gang pot might be best.

Was thinking of building a state-variable filter myself. Here is a possible cheapo (non-precision) 4-gang pot:
https://www.mouser.com/ProductDetai...vNq13R5i%2BeXDpWTL8/GmnSX9cmh65sKVzqF1vtdAg==

 

[RobLK]

There are some new models recently posted by IanHegglun for the Exicon 20N20 and 20P20. So I simulated the f7 with them using matched and unmatched jfets. I also simulated a notch filter to see if the distortion waveform phase would change in ltspice. The unmatched pair distortion was 180 degrees out of phase with the matched pair distortion. The Idss of the 2sj74 was 6.4ma and the 2sk170 was 8.4ma. The distortion was 0.04 thd for the matched pair and 0.01 for the unmatched pair.The unmatched pair has a higher loop gain.

 

[2 picoDumbs]

How new?

Try 5.4 and 8.4 with 5 ohms and 15 ohms source respectively.


I generally modify the models so the curves actually match the parts I am using.

Your simulated measurements are very close to the real measurements, I get depending on feedback etc.

 

[2 picoDumbs]

That's 5.4 and 8.4 Idss

 

[RobLK]

Well Pico, I have never tried to modify models myself and I don't have a 5.4ma model. I got the jfet models from circuits Patrick posted. Ian posted the models on 19 july 2020. Here are some transfer curves.

 

[2 picoDumbs]

No worries Rob.
It's close enough for demonstration purposes.

 

[RobLK]

Here is what the distortion looked like in Ltspice. The gain is 14.6db. I had to recalculate the value of Rsen because the output impedance changed when I went to the unmatched pair of jfets.

 

[2 picoDumbs]

That looks good.

 

[RobLK]

With the matched jfets and a voltage gain of 8 ltspice showed a thd of .05.