SimontY said:
I would just like to clarify that the 'B' op-amp is the unused one, and that your filter is built around 'A'? If so then I see no problem so far.
SimontY said:
All that sounds fine as well. As I mentioned in an earlier post connecting the output directly to the inverting input feeds back 100% of the signal thus meaning we get unity (1x) gain.
I hope you used an IC socket
You could just drop in a TL072 if you have. Maybe the op-amp you have is not unity gain stable. If you are doing a rebuild then it would be simpler to use a single op-amp. You can get one stage working then simply cascade another identical stage to get a 24dB/oct filter.If you are really stuck I may (if I can find them) be able to dig out an old prototype PCB (or two) of mine, I'd be willing to donate in the name of SimontY audio research
"I would just like to clarify that the 'B' op-amp is the unused one, and that your filter is built around 'A'?"
Yep.
"I hope you used an IC socket"
Nope.
"You can get one stage working then simply cascade another identical stage to get a 24dB/oct filter."
I'm only looking for 12db/oct, which I will connect to my plate amp, whose 12db/oct filter will be in action, and of course variable, giving me 24db/oct or 12db + 12db at antoher fr. Some versatility, which I hope will help combat the 'wodge' of apparent output in the x-over area.
"If you are really stuck I may (if I can find them) be able to dig out an old prototype PCB (or two) of mine, I'd be willing to donate in the name of SimontY audio research"
You're very kind! Let me try again first though. I feel I should be able to crack this little nut!!
edit: I'll go and take a couple of photos, for amusement.
Yep.
"I hope you used an IC socket
"Nope.
"You can get one stage working then simply cascade another identical stage to get a 24dB/oct filter."
I'm only looking for 12db/oct, which I will connect to my plate amp, whose 12db/oct filter will be in action, and of course variable, giving me 24db/oct or 12db + 12db at antoher fr. Some versatility, which I hope will help combat the 'wodge' of apparent output in the x-over area.
"If you are really stuck I may (if I can find them) be able to dig out an old prototype PCB (or two) of mine, I'd be willing to donate in the name of SimontY audio research
"You're very kind! Let me try again first though. I feel I should be able to crack this little nut!!
edit: I'll go and take a couple of photos, for amusement.
On the first pic of the PSU, I assume that bank of 3 caps on the right is two caps deep, i.e. a total of six -- 3 per rail? I assume that you have wired the PSU up like this:
What are the two black electrolytic caps on the stripboard? Chip power decoupling?
An externally hosted image should be here but it was not working when we last tested it.
What are the two black electrolytic caps on the stripboard? Chip power decoupling?
Absolutely correct Rich. I am confident in the PSU, because I very recently knocked up a p-p LM3886 tester the same way, which btw sounds pleasant. (also, the caps don't explode - surely a good sign
The black 'lytics are indeed for decoupling/bypassing (the same thing?)
Do you think it's possible everything is wired correctly, but I've fried or otherwise damaged my op-amp? I did afterall remove it from my cd player, and perhaps with heavy hands
The black 'lytics are indeed for decoupling/bypassing (the same thing?)
Do you think it's possible everything is wired correctly, but I've fried or otherwise damaged my op-amp? I did afterall remove it from my cd player, and perhaps with heavy hands
I am beginning to think that the op-amp was either damaged by desoldering or static, or is not unity gain stable. Get a DIL socket and new chip and see. If it works OK, you can reuse the chip
Bardwell's used to sell some nice red chip sockets made by Cambion. If you can't get those anymore see if they do any other 'turned pin' ones. These kind are much better than the 'wiper' type as it's easier to get the chip in.
Bardwell's used to sell some nice red chip sockets made by Cambion. If you can't get those anymore see if they do any other 'turned pin' ones. These kind are much better than the 'wiper' type as it's easier to get the chip in.
The subtractive high/low pass network in the National Semiconductor app-note (with a second-order roll-off on both the LP and HP outputs) works very well. I use the circuit myself on a 2-way speaker. The HP and LP outputs sum flat in amplitude and phase. (But don't forget that the drivers' own response will affect this).
If you can't find the app-note I'll put the schematic on here.
If you can't find the app-note I'll put the schematic on here.
I once found this app-note accidentally.
In one of John Watkinson's books however I found a statement that subtractive crossovers could be made with almost any desired orders, symmetrial and asymmetrical.
So I did some maths and came to a simpler solution than the NS one.
Good that you like the transient perfect crossover.
Regards
Charles
In one of John Watkinson's books however I found a statement that subtractive crossovers could be made with almost any desired orders, symmetrial and asymmetrical.
So I did some maths and came to a simpler solution than the NS one.
Good that you like the transient perfect crossover.
Regards
Charles
phase_accurate said:
I've the parts piled up ready to be stuffed into the breadboard...
For the ap this version is going into i'll need 2nd/1st or maybe 3rd/1st, but i find subtractive XOs facinating so i would be interested in your 2/2. I have been following all the work you have been doing (don't necessarily grok it all).
dave
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