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An interesting JFET-based active XO design from TNT Audio ...

Posted by andyr (M) on March 30, 2014 at 18:34:24

I've been using using Rod Elliott's opamp-based active XO boards (P09) for my tri-amped 'Frankenpans' (and before them, my IIIas) for 15 years or so. These XOs boards are very flexible - they're nominally for 24dB slopes but I was able to modified them to deliver 18dB bass LP and 12dB slopes elsewhere that are comparable to the stock IIIa slopes. Plus they have gain control on each band.

However, I had been looking around for the last 5 years, for an alternative which used discrete transistors, not opamps - and, late last year, I discovered these articles by Grey Rollins, on TNT Audio:

Part 1: http://www.enjoythemusic.com/diy/1109/xenover_2.htm

and

Part 2: http://www.enjoythemusic.com/diy/0310/xenover_part2.htm

So I am about to replace my Rod Elliott active XOs with these - which I believe offer 2 significant advantages:

1. Using discrete components, they will operate with far less feedback than an opamp design,

and - and far more importantly

2. Output DC offset can be adjusted to zero - which means there don't need to be any caps between the final XO buffer and the following power amp. (Whereas I need a cap on each amp, with the Rod Elliott XOs.)

So I thought I would share these links, in case anyone is interested in building some active XOs.

And yes, I thought about using PLLXOs but adding level controls made this problematical with my preamp.

Regards,

Andy

Edits: 03/30/14 03/30/14

This post is made possible by the generous support of people like you and our sponsors:

Analog Engineering Associates

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