Ok, I have done a quick sketch and I would like to hear what you guys think - is this completely insane or something that could end up being really cool?
There is a volume control for each channel - I would probably use double pots for stereo.
The filters are going to have dip switches so that the cross frequency can be set without too much trouble.
The headers J1-J6 are intended to be expansion slots where additional filters can be added (to get more than 12db slopes). I thought I would use jumpers to short them out when not in use.
As you can probably see, I have been very much inspired by B4 and XVR1...
Hi cviller,
I took a look at your schematic and I'm a little confused.
1. I can't see the filter caps and resistors.
2. Jacques' original circuit has one more buffer in each branch of the filters, with volume pot only *after* the filters. This appears quite different from your proposal, which has them before the filters.
3. Can I point out posts #24 and #74 , which have an important adjustment inthe original schematic (and addition of another buffer in the LP section). Does your plan include this and I misunderstood? Or have you found another way around the problem?
4. I like the idea of making the board enough to do a three-way, but how much does the discussion above on the LP section affect the band-pass section in your design?
5. (Dumb question, maybe) What do you mean by a dip switch?
Cheers
Nigel
I would not put a 6channel volume pot after the input buffer when a 2channel volume pot can do the job just as well.
Adjustments in the 6channels to balance out gain and sensitivity variations should be done at the output of the filters, but before the final line driving buffers. Some of this (fixed) adjustment can be built into the power amps if the gain required in one frequency band is much different from all the others.
Adjustments in the 6channels to balance out gain and sensitivity variations should be done at the output of the filters, but before the final line driving buffers. Some of this (fixed) adjustment can be built into the power amps if the gain required in one frequency band is much different from all the others.
I can see that - the blocks of filter sections need to be drawn, but what I have made is just the "conceptual framework".
Thanks for you comments Andrew! I know you don't like too many pots.
I see it this way (for a two way full range with woofer): Normally, I would have higher efficiency on the fullrange, so I'd need to attenuate the highs - ok no need for pot on LP. This would also work if I decide to use an F4 as driver for the woofer. But right now I use a chipamp for the woofer, which has more gain than the power amps I build - in I case I would also need a pot on the woofer. But I can't take the pot away from the HP. I know I can adjust the gain on amps, but I would most likely use this XO on both home-brewed and borrowed amps, so I would lose a lot of friends this way...
Your other point about the placement of the pots is interesting. I expect your rationale is: "why throw away gain before filtering - this will hurt SNR". This is a good point, but I just copied what I saw (and heard) here:
http://www.diyaudio.com/forums/pass-labs/4486-diy-progress-report-208.html#post1921621
But if I did move the pots in the end, I would have to add yet another buffer stage.
I'm using the BF862s, and the buffers that are up and running sound great. YMMV, of course... It may be worth remembering that juma used the BF862's on little adaptor boards, which could be used on a PCB designed for 2SK170 if you wanted to.
Cheers
Nigel
I am not sure how gain stages fit into this. This thread started out as an active crossover. Then we added an attentuation stage (what I refer to as LPAD stage) and a volume control stage. All of which can be achieved through buffers. Can the boost not be achieved through a preamp and then attentuating the rest? My 2c would be to keep it simple.
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