Active filter board GB

[BobEllis]

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.

[mpmarino]

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

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.

[BobEllis]

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.

[mpmarino]

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?

[BobEllis]

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.

[JensRasmussen]

Ok,

Here is the plan so far:

Input -> HP -> gain -> Buffer
|

[JensRasmussen]

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

[BobEllis]

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

[JensRasmussen]

Originally posted by BobEllis
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

Like this?

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

Yes the input is like the mox

\Jens

[BobEllis]

LT should be in the low pass, bypassable.

Thanks