ZEN V4 without feedback loop

[Selfmade]

I have build a ZEN V4, and I want to eliminate the feedback loop from the output to the input.

Are there any negativ aspects?
Is there an improvement in sound?

regards

Günter

 

[Nelson Pass]

I suggest that you want to retain the "internal" high impedance loop from the output device's Drain to its Gate, as this sets the DC value of the output, otherwise feel free. Be prepared for a lot of gain, tho.

 

[Selfmade]

thank´s for the answer Mr. Pass.
I mean the feedback loop from the output after the caps to the gate of the ZVP3310 with resister 221K and the capacitor 5pF.

regards

Günter

 

[Nelson Pass]

Right. Just remove it and ground the 47K input resistor. Replace
them with an input divider, formed by about 5 K from input to the Gate of the Jfet and the 47K from Gate to ground.

 

[Selfmade]

what negativ aspects are there by doing this?

Less gain?

lower damping factor?

no more linear frequence up to 100 KHz?

Does it sound warmer und more clearly?

regards

Günter

 

[Nelson Pass]

what negativ aspects are there by doing this?

Less gain?

lower damping factor?

no more linear frequence up to 100 KHz?

Does it sound warmer und more clearly?

More gain
What damping factor? It's a current source.
Probably not to 20KHz, but so what.
Maybe warmer at low levels, certainly not more clear at any decent wattage.

Without feedback, I see this as a low power (5 watts or so) mid/top amplifier for horns. For this case, better off to ditch the JFET input and drive the Gate through 221 ohms and bias it with an 8 ohm resistor. If you want a schematic, say pretty please and I'll draw you one.

 

[till]

🙂 please

 

[Selfmade]

please, Mr. Pass

 

[Nelson Pass]

OK, I'll post it Sunday night.

pass/ - likes his glass of wine on sunday nights.