JFET follower (Xenover) with MOX like setup? - diyAudio
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Old 5th September 2011, 06:29 PM   #1
NYCOne is offline NYCOne  United States
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Default JFET follower (Xenover) with MOX like setup?

I built a set of MOX like AXOs I like the flexibility of changing the frequency in seconds.

Is it possible to make the same type of layout with a JFET follower (like Xenover)? It seems simple, except for the "Q" In the SK OXs the "Q" hangs off the inverted input of the opamp. Is there a way of achieving the same outcome for a JFET follower?
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Old 9th September 2011, 04:56 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
if you adopt the unity gain version of the opamp filters you can always substitute the jFET buffer in lieu of the opamp.
If the caps are stacked together for each follower/opamp then they can be fitted onto 8pin or 14pin headers.
Then just swap capacitor assemblies on the DIL sockets to change frequencies.
Canging Q requires a bit of arithmetic and although you can change Q by staggering the C values and/or the R values,it is not intuitive.

The equal component value crossover/filter better suits varying Q but this requires gain in the opamp and cannot use jFET followers.
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Old 10th September 2011, 04:04 AM   #3
NYCOne is offline NYCOne  United States
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Quote:
Originally Posted by AndrewT View Post
Hi,
if you adopt the unity gain version of the opamp filters you can always substitute the jFET buffer in lieu of the opamp.
If the caps are stacked together for each follower/opamp then they can be fitted onto 8pin or 14pin headers.
Then just swap capacitor assemblies on the DIL sockets to change frequencies.
Canging Q requires a bit of arithmetic and although you can change Q by staggering the C values and/or the R values,it is not intuitive.

The equal component value crossover/filter better suits varying Q but this requires gain in the opamp and cannot use jFET followers.
I'm new to filters, that's what I was afraid of. I guess I can either build the discrete opamps for the MOX or have a lot of combination for a follower. Since I have my homemade MOX already, I'll likely try the follower to see how it sounds. I have to figure out how many combinations are reasonable to fit on a board.
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