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Active filter board GB

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#887
I've got enough take home work that I won't be able to order anything until Monday. So, I'll leave the buy open until Sunday.

Hey all you latecomers...

I'll order some extras of everything, but don't count on too many. The last buy was two years ago, and it will probably be as long before I do it again, if at all.
 
#891
I'm still showing about 70 more AF4 requested than paid. PSU2.2 matches pretty well. I won't be buying 70 extra boards, probably closer to 30, which will be used to cover shipping losses if any before being offered to the public.

I've acknowledged receipts privately except for some of those that I updated the wiki to reflect paid. If you didn't get an email from me or see that I updated the WIKI that you'd paid, please PM me. I'll be shipping using PayPal's built in label maker, so if you have PayPal receipt then you'll get your order.
 
#892
can it be used in preamp to drive subwoofer

Hi Bob / Jens,

Probably a stupid newbee question.

Can I use this filter in a passive preamp to split high and low frequencies?
I want to create an extra balanced output to drive a subwoofer?

If so, I will pay you for 2 boards + shipping.

Thank you

Peter
 
#893
Hi Peter,

The filter provides high and low pass sections, so you could use it to drive a two way (woofer and tweeter) through independent amps. It also provides a buffered but unfiltered output that could be used to drive a subwoofer. Unless your main speakers roll off at a convenient subwoofer crossover frequency and you sub amp has a high pass filter, you'll want to add another pair of boards to properly cross over the sub(s). One PSU 2.2 will power for boards with ease.

A pair of AF4s would do main to mono or stereo subs.

Of course, you are no longer in the passive preamp realm. The filters are active, although you could use your passive preamp to control the volume by plcing it upstream of the filters.

Download the AF4 manual from my website - not perfect, but it will give you an idea what you can do with the filters.

Hope this helps.
 
#894
Hi Bob,

I have added a simple pic of my idea.

I want to be able to change settings on the filter in the preamp to allow for any speaker combination to be driven, with or without sub. My main intrest is speaker building (lots of wood work 🙂 ) and experimenting is the fun part.

by the way: My Speakers do have a low pass filter and my sub does have a High pass filter.
 

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#895
Peter, the filter boards are single ended. They will accept balanced inputs, but immediately convert back to SE. you can use an inverting bufer to derive the balanced signal, or transformers as shown.

A suggestion - you might consider using your relay attenator AFTER the filters, but before the buffer on the boards (in place of P1 and R18, etc.) to attenuate any noise generated in the filters. Of course this would require a third attenuator and may not be economically feasible. I use fixed resistors to pad the signal down before the buffer.
 
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