ZEN V4 without feedback loop

Selfmade · 19th February 2003, 07:56 PM

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 · 19th February 2003, 08:34 PM

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 · 19th February 2003, 08:41 PM

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 · 19th February 2003, 08:45 PM

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 · 19th February 2003, 09:00 PM

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 · 19th February 2003, 10:44 PM

Quote:

Originally posted by 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?

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 · 19th February 2003, 10:56 PM

please

Selfmade · 20th February 2003, 06:00 AM

please, Mr. Pass

Nelson Pass · 20th February 2003, 03:38 PM

OK, I'll post it Sunday night.

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

19th February 2003, 07:56 PM	#1
Selfmade diyAudio Member Join Date: Feb 2002 Location: Flensburg	ZEN V4 without feedback loop 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

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19th February 2003, 08:34 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	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.

19th February 2003, 08:41 PM	#3
Selfmade diyAudio Member Join Date: Feb 2002 Location: Flensburg	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

19th February 2003, 08:45 PM	#4
Nelson Pass The one and only Join Date: Mar 2001	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.

19th February 2003, 09:00 PM	#5
Selfmade diyAudio Member Join Date: Feb 2002 Location: Flensburg	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

19th February 2003, 10:56 PM	#7
till Banned Join Date: Apr 2002 Location: Germany, Clausthal	please

20th February 2003, 06:00 AM	#8
Selfmade diyAudio Member Join Date: Feb 2002 Location: Flensburg	please, Mr. Pass

20th February 2003, 03:38 PM	#9
Nelson Pass The one and only Join Date: Mar 2001	OK, I'll post it Sunday night. pass/ - likes his glass of wine on sunday nights.

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