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Active filter board GB

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#21
Jens,

My preferences: (some comments are there to explain to those interested what my choices mean for flexibility, I know you understand them)

Input buffer - I like the way it was handled on MOX/Active Filter 2 - Can handle balanced or single ended wiht a jumper to ground. Either way, you can just jumper R1 and have a unity gain buffer, make it a fixed gain stage, or shelving low pass for baffle step compensation.

HP/LP two 2nd order sections of each (jumper connectable) Sallen Key equal value topology - it can be changed to unity gain by jumpering one reistor space for stanard L-R topology.

2 EQ sections - topology like your active filter one EQ (buffered notch)

2 first order all pass (http://www.linkwitzlab.com/filters.htm#4)

1 Linkwitz transform

2 output buffers - one variable level, one fixed gain to save space.


Can you fit all this on one board without going SMD? I can handle a few SMD parts like Moxlite, but at my relatively advanced age, I'd rather not do the whole thing SMD. I've got no problem with small form factor leaded reistors, though.

Thanks Jens.
 
#22
6) balanced operation ?

I'm sure it's possible by using more boards but is there a way to keep the board count down for balanced? If not, it's Behringer for me:bawling:

Edit: Bob and I posted together. I see the input buffer can handle balanced, how 'bout the rest of it. Please excuse my 'noviceness', active filter topology is something I truly haven't grasped yet.
 
#23
Balanced in is converted to single ended operation. Going back to balanced out would require another dual op amp space (DRV134?) I think I've run it up to 7 with my wish list. If Jens can fit 8 duals, great.

Staying balanced throughout would require MFB topology (more space) to be practical. If conversion at both ends was good enough for the Pass Labs XVR1, it's good enough for me.
 
#24
Thanks Bob,

Yes..good enuff for Pass is good enough for me too😉

How many boards would I need for 2 ch hi pass, 2 ch band pass, and 2ch/mono sub? all 24dB octave...

(balanced in and out on hp and bp, balanced in and bal+se out on sub)

6?
 
#25
We'll have to see what Jens comes up with, but I'd say 2 per channel, and use a resistive mixer to get Mono sub. you can use the same outputs for balanced or single ended, just leave teh unused phase hanging.

first board would do sub-main xo, second would do mid (bandpass because of first XO) - tweeter.
 
#27
Ok,

Here is the plan so far:

Input -> HP -> gain -> Buffer
|
|--LP -> gain -> All pass -> Buffer

You can select either second or fourth order sections.

2 EQ sections on board, but floating so they can be inserted in either of the HP or LP sections.

The signal can be rerouted via jumpers to generate a BP filter

The all pass can be bypassed

Q of the filters is set via the gain as in the active filter two (MOX)

On board PSU

Let me know

\Jens
 
#28
Thanks Jens,

Can you move the all pass to the HP section or float it, since tweeters are usually ahead of the mids?

Is the input buffer as in MOX? (LP+gain/shelving LP)

Any room for a Linkwitz transform? I know, i want it all 😉
 
#29
BobEllis said:
Thanks Jens,

Can you move the all pass to the HP section or float it, since tweeters are usually ahead of the mids?

Is the input buffer as in MOX? (LP+gain/shelving LP)

Any room for a Linkwitz transform? I know, i want it all 😉
Click to expand...

Like this?

Input -> LT -> HP -> All pass -> gain -> Buffer
|
|--LP -> gain -> Buffer

Yes the input is like the mox

\Jens
 
#33
What is LT?
Click to expand...
Hi NuuK, you are in the same boat as me😀 I would like a couple of those boards as well, if I just knew what those guy's were talking about😕 Well, I know that an active filter is pretty good with several amps to feed your speakers allright. Could anyone please inform us (ignorants) of the basics?? To give you one example; I would like a crossover for a subwoofer I am considering to build! Could I use these boards for that purpose, not wanting to change the excisting cross-over-network?? Lets say I wanted to cross at 80hZ
and feed the rest of the bottomend to the sub, would this be the thing?

Steen🙂
 
#37
Yes, float sounds good to me. Never thought of using a Linkwitz Transform (LT for Nuuk) and High pass shaping.

I'll be amazed to see this all on one board.

As for the potential balanced driver, upon rereading the DRV134 data sheet, I think I'll pass on that. It likes a high Z load, such as the 50K provided by its compliment, the INA134. I'm guessing my ~1500 ohm A75 will load it too heavily. If there is room for normal and inverting output buffers great. If not, maybe put the buffered Notch filter last in the signal chain (if no EQ needed, just leave the rest of the parts out and jumper to make a unity gain buffer.) Then the buffer stage could be unity gain inverting.
 
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