HELP! line-level crossover design for solar-powered biamped soundsystem - Page 4 - diyAudio
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Old 4th June 2012, 01:21 PM   #31
gfiandy is offline gfiandy  United Kingdom
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Location: Cambridge UK
Hi,

Sorry I as I said I have not used this part and I didn't read the data sheet very carefully. If its not designed to run into large caps then just use the 100uF suggested. (If you want to use your 220uF parts since you have already bought them 2 in series will give you 110uF which is close enough). It won't have such a good transient response but the opamps shouldn't draw that much current so the 100uF will be OK.

It sounds like you have formed an approximate star ground (i.e. all the grounds connected together in one point) if this is working well stick with it, it is one of the easiest grounding schemes to get working.

Results look good, but keep in mind it is very unlikely that your speakers will have a flat response around your crossover point. Whilst this schematic is a good starting point if you want it to sound well integrated you will need to take acoustic measurements and optimise the electronics to match the acoustic roll off of your drive units.

For this you will need a measurement microphone. So long as you have a fairly good sound card a very acceptable measurement microphone cab be made for about 5 euros (much less if you can get the capsule at trade price) using the WM61A mic cartridge from Panasonic and the outside of a plastic biro to hold it. It is flat enough to measure the crossover region and optimise it. See this site for more information (you don't need the pre-amplifier if you are using a PC sound card)

http://www.johncon.com/john/wm61
a/


I use Holm impulse software with mine which is a good free maximum length sequence system analyser that works with most computer sound cards.

HOLM Acoustics

The advantage of this type of measurement is that at above about 400Hz you can modify the impulse response by cutting of the end and remove room reflections so you get an anechoic like measurement in any room so long as you don't need the low frequency information.

Regards,
Andrew

Last edited by gfiandy; 4th June 2012 at 01:23 PM. Reason: correct typo
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Old 4th June 2012, 06:32 PM   #32
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Join Date: Apr 2012
Quote:
Originally Posted by gfiandy View Post
Hi,

Sorry I as I said I have not used this part and I didn't read the data sheet very carefully. If its not designed to run into large caps then just use the 100uF suggested. (If you want to use your 220uF parts since you have already bought them 2 in series will give you 110uF which is close enough). It won't have such a good transient response but the opamps shouldn't draw that much current so the 100uF will be OK.

It sounds like you have formed an approximate star ground (i.e. all the grounds connected together in one point) if this is working well stick with it, it is one of the easiest grounding schemes to get working.

Results look good, but keep in mind it is very unlikely that your speakers will have a flat response around your crossover point. Whilst this schematic is a good starting point if you want it to sound well integrated you will need to take acoustic measurements and optimise the electronics to match the acoustic roll off of your drive units.

For this you will need a measurement microphone. So long as you have a fairly good sound card a very acceptable measurement microphone cab be made for about 5 euros (much less if you can get the capsule at trade price) using the WM61A mic cartridge from Panasonic and the outside of a plastic biro to hold it. It is flat enough to measure the crossover region and optimise it. See this site for more information (you don't need the pre-amplifier if you are using a PC sound card)
[...]
That warning wasn't on murata's datasheet (wich is quite useless), it's referring other's DCDC converter, but i think it's a reasonable advice. According to murata's application hints, there aren't no capacitors except from the 2.2nF of the LC filter. I think that's because it's unregulated, and it's intended to be used before the DC/DC, directly to the regulator.
We have plenty of electrolytics, so we don't care about finding other values like 100uF (or have 10 more 220uF caps in the lab )

With this star ground all seems to work fine with a lab bench supply, ad it will be better with the real application (powered via solar cells or batteries). I'm just worried because eventually we'll get a switching power supply for indoor uses, and this could introduce some noise whith such a ground loop. I'll have care to make connection between grounds only via jumpers, so we can tweak the whole thing later.

Actually, the cutoff frequency is very close to the reccomend one directly from ciare's project. And we simulated the filter with some softwares, and the system sounded pretty fine. HF and LF levels can be regulated indipendently, and frequency tweaks cannot be made without desoldering everything.
I'm looking for a good microphone for other projects, and maybe we'll get it soon (maybe for more than 5$). thanks for the precious infos, but we think that we'll use the crossover in this way. It would be great just if doesn't output distorsion or noises

The real challenge now is the PCB design. I did some little projects before, but this is quite big network. I've always used ExpressPCB. Do you suggest some other software?

Last edited by PinkNoiser; 4th June 2012 at 06:56 PM.
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Old 13th June 2012, 09:12 AM   #33
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We made it! It was hard to fit the whole circuits on a single sided 10x15 cm board. In addition, we had troubles with the old "toner method" used to print the pcb and it ended with half of the traces made by hand, but we did it. The crossover works flawlessly. It's a bit noisy, but it's just a white noise on the backgound, no hums and ripples , and it can't be noticed when playing music, even at low volumes.
Now we'll make a smaller board with digital vu meters and signal splitters to feed the amplifiers (this things didn't fit on the same board in any way I tried).

Now i'm working on the power regulator, i'm looking for the right design. I think I'll cross-post
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