Zen V4 modifications

pro · 31st August 2004, 02:23 PM

Hi averybody.
I have made last year a Zen V4, and it sounds very good.
Now because I connected it on the mid high section of my three way speakers, 700 Hz 12 dB octave crossover, I am planning some modification for the V4.
First one, increase the gain so to reduce feedback. The question is:
Do is it better to decrease input resistor R2 or increase R3 or both.? I am planning about 20-22 dB of gain. any contraindication
for this gain ?
Second mod, is to decrease C2 to 0.5u so I have a light hi pass at the low frequency (-3 dB at 50 Hz) for unload the gain fet.
Last mod, to change C1 (10mF) with two 1mF (panasonic FC) back to back, with a 221K rersistor from +rail to the mid of the two caps for a bit of bias (should work better with reactive load).
Did some one made some things lke this?
Any contraindication.
Tks to averybody.
Ciao.

Nelson Pass · 31st August 2004, 04:57 PM

Probably better to increase input resistor, but try it both ways.

If you want to hi pass filter the amp, do so at with a series capacitor on R2, not the interstage capacitance, which will
affect the loop stability, and then check it for stability anyway.

C1 will already have a bias, so it doesn't need that arrangement.

pro · 31st August 2004, 05:19 PM

Many thanks Mr. Pass.
Ciao.

31st August 2004, 02:23 PM	#1
pro diyAudio Member Join Date: Feb 2004 Location: Milano	Zen V4 modifications Hi averybody. I have made last year a Zen V4, and it sounds very good. Now because I connected it on the mid high section of my three way speakers, 700 Hz 12 dB octave crossover, I am planning some modification for the V4. First one, increase the gain so to reduce feedback. The question is: Do is it better to decrease input resistor R2 or increase R3 or both.? I am planning about 20-22 dB of gain. any contraindication for this gain ? Second mod, is to decrease C2 to 0.5u so I have a light hi pass at the low frequency (-3 dB at 50 Hz) for unload the gain fet. Last mod, to change C1 (10mF) with two 1mF (panasonic FC) back to back, with a 221K rersistor from +rail to the mid of the two caps for a bit of bias (should work better with reactive load). Did some one made some things lke this? Any contraindication. Tks to averybody. Ciao. __________________ Michele

31st August 2004, 05:19 PM	#3
pro diyAudio Member Join Date: Feb 2004 Location: Milano	Many thanks Mr. Pass. Ciao. __________________ Michele

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31st August 2004, 04:57 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	Probably better to increase input resistor, but try it both ways. If you want to hi pass filter the amp, do so at with a series capacitor on R2, not the interstage capacitance, which will affect the loop stability, and then check it for stability anyway. C1 will already have a bias, so it doesn't need that arrangement.

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