JFET farting out

[g3rmanium]

Hello,

so I was trying to add a JFET preamp stage to my squarer. I can get the J201 biased correctly, but it's only amplifying for a short moment, then the level will drop and it will start to sound buzzy. What could be the problem here? Not enough current?

I have the J201 wired from the IA0515S' + output and to the IA0515S' GND.

Thanks.

[MartyMart]

Describe your setup of the Jfet so we get an idea what's going on, also voltages.

MM.

[g3rmanium]

Describe your setup of the Jfet so we get an idea what's going on, also voltages.

There's about 6.4 to 6.6 V available. Input to gate, 4.7 M resistor to GND (virtual ground of the DC/DC converter), ~10 K resistor from V+ to drain, ~ 1 K resistor to source. Biased to about half the input voltage.

[MartyMart]

1k source resistor to ground yes ? so about 3.2v at drain.
What's the "virtual GND DC/DC converter", is this a +9/-9 v setup ?

MM.

[g3rmanium]

What's the "virtual GND DC/DC converter", is this a +9/-9 v setup ?

Exactly. Without load, the voltage is higher than +-13 V, with the AD633, it drops considerably.

[g3rmanium]

Anyone?

[MartyMart]

What's the Gate and source readings when Drain is 1/2 V ?
Perhaps the 4m7 at gate is high, 1M seems "standard" or take a look at
the Fetzer valve setup ?

MM.

[g3rmanium]

What's the Gate and source readings when Drain is 1/2 V ?

Ok, there's about +- 6.4 V available.

The J201 is biased with 22 K to drain and 2.2 K to source.

Drain is at 3.3 V, source is at 0.3 V, gate is 0 V. All relative to the GND from the DC/DC converter.

Perhaps the 4m7 at gate is high, 1M seems "standard" or take a look at
the Fetzer valve setup ?

I tried 1 M but that didn't change anything.