HELP! line-level crossover design for solar-powered biamped soundsystem - diyAudio
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Old 21st May 2012, 02:21 PM   #1
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Default HELP! line-level crossover design for solar-powered biamped soundsystem

Hi! Yes, i used the forum's search and read tons of topic, but i still need to post for some help. I'll try to be schematic:

My system: solar-powered soundsystem, designed to be louder as possible with the given power.
-This is the speaker project http://www.ciare.com/pdf/Progetti/My...aker/pr020.pdf . We have already built them, all the loudspeakers are replaced with their 4ohm variants.
-they are bi-amped:
4x100W tk2050-based amplifier board for LF (4 channel for 4 woofers)
2x10W ta2024-based amplifier board for HF (2 channels for 2 tweeters)
-Power sources: 30Vdc (for tk250) and 12Vdc (for ta2024) regulated from solar panel sets.

My needings:
From a line-level input (0-800mV, standard for mp3 players, pc, smartphones...) to 2x line-level output LF and 1x line-level output for HF in order to feed the amp boards properly.
Extra: a little more gain (eventually with a preamp stage), in order to use smaller inputs. Eventually it will be a 3-way crossover: the speakers aren't very loud at frequency lower than 60Hz, so it would be nice to cout that out, (we culd also plan to add a subwoofer soon).

I've googled ad looked around for an active crossover design, i've quite a bit knowledge about analog circuits and how to build them.

The main issue is we have just single polarity supplies. I read a lot of papers regarding single-supply operations (benefits, drawbacks, circuit designs), and I found some possible solutions:
Make a dual supply: using 2 regulator (eg: lm317) to make a +/- Vcc. Maybe the easiest solutions, but it costs: not in money (actually, it's free), but in energy dissipation, as it adds 2 more regulator. Also, don't know if it's a good design, since i found no qualified references.
Make a -Vc: eg. from the 12Vdc we already have, with something like MAX1044 / ICL7660. It couldn't be easy to find theese ICs, and, as above, dunno if this is a good idea or not.
Single supply design with dual-supply opamps: I'm scared about all the drawbacks i read about doing this. I found some circuit but still I would like to have some feedback from someone that already build this. For the virtual ground I found infos about the "rail splitter" TLE2426, but it seems to have quite low current (20uA if i remember well). Is this a viable solution?
SINGLE SUPPLY OPAMP: really: if someone knows some single-supply opamps that works well with audio works, it would make my day. I've got some IC from microchip (mcp6004) that i could try (but i think they are a no-no for audio equipments), or eventually I would buy everything you will name if it suits my needings.

And, at last
Commercial products: Like a "crossover" "splitter" "preamp" for car audio use, that uses 12Vdc supply to do something similar. I could cnsider to buy something already made, but only if it's not crap, it suits my needings, and it doesn't costs a lot (just to say, < 60 )
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Old 22nd May 2012, 02:35 PM   #2
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Up?

If i'l choose the rail splitter option, so i would buy a regoular op-amo, which should I get in your opinion? Low noise and distorsion, maybe that works well with non-unitary gain? Supply voltage would not be a problem, as i can take every voltage <30V
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Old 22nd May 2012, 03:32 PM   #3
djQUAN is offline djQUAN  Philippines
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Quote:
Originally Posted by PinkNoiser View Post
Make a -Vc: eg. from the 12Vdc we already have, with something like MAX1044 / ICL7660. It couldn't be easy to find theese ICs, and, as above, dunno if this is a good idea or not.
You can give this a try:
Low Power Negative Supply For Cars
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Old 22nd May 2012, 03:44 PM   #4
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also two transistor batteries
The boxy ones , 9 V , should last long ; also the rechargeable 8.2 V types .
Just connect them in series and the ground ref is the joint between them .
Usually there's a double switch to connect them between themselves and then to ground.
If not satisfied by low voltage , you can use four of them , to get + and - 18 V
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Old 22nd May 2012, 03:58 PM   #5
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Quote:
Originally Posted by djQUAN View Post
You can give this a try:
Low Power Negative Supply For Cars
nice...but would't be the same than using the MAX1044? http://datasheets.maxim-ic.com/en/ds...60-MAX1044.pdf


Quote:
Originally Posted by picowallspeaker View Post
also two transistor batteries
The boxy ones , 9 V , should last long ; also the rechargeable 8.2 V types .
Just connect them in series and the ground ref is the joint between them .
Usually there's a double switch to connect them between themselves and then to ground.
If not satisfied by low voltage , you can use four of them , to get + and - 18 V
Transistor batteries? What does it mean?
BTW, I won't use any batteries for this project
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Old 24th May 2012, 05:53 PM   #6
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any help?
I'm just asking for some opinions!
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Old 24th May 2012, 09:57 PM   #7
gfiandy is offline gfiandy  United Kingdom
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I tried both single supply op amps and a negative rail chip. I found the negative rail chip was by far the best solution. With good filtering you can keep the noise out of the opamp and it allows you to use whatever opamp you like. You don't get the problems of capacitive coupling circuits and the large DC thumps they tend to create at power on and off on single rail circuits.

Regards,
Andrew
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Old 25th May 2012, 09:29 AM   #8
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Quote:
Originally Posted by gfiandy View Post
I tried both single supply op amps and a negative rail chip. I found the negative rail chip was by far the best solution. With good filtering you can keep the noise out of the opamp and it allows you to use whatever opamp you like. You don't get the problems of capacitive coupling circuits and the large DC thumps they tend to create at power on and off on single rail circuits.

Regards,
Andrew
Wow many thanks! that's the kind of feedback i extremely need.

Actually, i was inclined to use the "virtual ground way", but i'm a bit scared of the fine tuning (and DC thumps), but i think i'll try the -Vcc way. Could you tell me what IC did you use? do you think that the MAX1044 is a good choice? What kind of filtering are you telling 'bout? A simple RC low-pass in order to cut out ripple would be enough?

For everyone: could you suggest a good op-amp for that purpose?
obviously: need good "audio" quality (or "excellent", why not ) and quite stable with a standard design. In other words, are you aware of some particular opamps that give troubles in design and tuning?
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Old 25th May 2012, 03:59 PM   #9
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quick update: i'm seriously considering to go "fast food" mode, and get a couple of UAF42, universal active filter. They are continuos time, 3-way 2nd grade crossover. The IC runs on a single supply. Q factor, center frequency, filter tipe are easy selectable. Also, an application bulletin (ab-035) and a software are avaible in order to have a pain-free design stage.
The only issue, is that i'm having troubles with the various sheets to understand if the auxiliary integrated opamp in order to have a non-unitary gain (let's say 4V/V). What do you think about?

Last edited by PinkNoiser; 25th May 2012 at 04:08 PM.
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Old 25th May 2012, 04:17 PM   #10
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The Ic doesn't run on single supply , as it's specified to work with ( max ) + and - 18 V supply . It's a state variable filter.
Don't you know what a 9 volt battery is ?
It's also available as a rechargeable battery , with a little lower voltage , 8,2 V .
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