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Old 31st August 2004, 02:23 PM   #1
pro is offline pro  Italy
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Location: Milano
Default 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.
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Old 31st August 2004, 04:57 PM   #2
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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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Old 31st August 2004, 05:19 PM   #3
pro is offline pro  Italy
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Many thanks Mr. Pass.
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