24 dB/Octave 2/3-Way Linkwitz DC on output after power cut

[Calebay]

Hello

i build this 24 dB/Octave 2/3-Way Linkwitz from http://sound.westhost.com/project09.htm

i made it 3 way and i have changed all opamp for OPA627
it seems to be working just fine. but then today i acidently pulled the AC plug, from the filter while the amp was still on. 1 sec. later! a Bad sound! and smoke! from my new Neo3PDR



so i disconecntet the amp and mesured no DC on output when power on. but when i turn it off for 1-2 sec. 1-1.5volt DC on all output

How can i cure this??

 

[sajti]

Apply mute circuit on the end, with relay, or muting transistor. Another solution, to use stronger powersupply to keep the circuit up, untill your powermaplifier switch off.
And last but not least: Use coupling capacitor on the output of the filter 😀

sajti

 

[Calebay]

hmm but is it normal this DC after i cut the power?

 

[Jan Dupont]

The DC could be caused by that the pos. and neg. supply fall at different speed 🙄

 

[Calebay]

they drop at the same speed very close on my scope.


its fisrt after the supply voltage has dropped below 2volt. then i get the DC on the output

 

[sajti]

hmm but is it normal this DC after i cut the power?

Unfortunately yes. Most of the manufacturers use muting circuits on the output, to cut the DC during the ON/OFF period.

sajti

 

[sajti]

they drop at the same speed very close on my scope.


its fisrt after the supply voltage has dropped below 2volt. then i get the DC on the output

Just add series capacitor (1-10uF), and parallel resistor (100-200k) to the output, and You will never see this problem any more....

Sajti

 

[Calebay]

okay did not know that

ill better put some capacitors in there then

tnx for the help

 

[Calebay]

Hello

I’m back whit a new problem, worse i think.

My crossover has been working fine for a I think ½ a yeah. But just 5 minutes ago while playing music. A LOUD, VERY LOUD horrible sound, I don’t believe my speakers can get any louder than that. Very nasty sound I believe it was between 60-3000Hz. it was only in the one channel, I ran over and turned it off. When I turned I back on it was gone. What can cause this? A bad solder join? Or a bad cap? Glad the speaker id not blow.

Hope someone can help

 

[Jan Dupont]

Sounds to me like a bad solder joint.......
Maybe a Gnd connection?

 

[sagarverma]

hey calebay

post the pcb layout that u built for the xover
is performance icreased dramatically after filteration???😀

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i have burnt my $6 ic of tda7293 yesterday night while tesing

 

[Calebay]

is performance icreased dramatically after filteration???

what do you mean?


I found the problem today... i was a very small peice of solder, lying between, one of the rails and a leg at one of the OPA627.

 

[sagarverma]

i meant to say ::: is the overall sound output from the amplifiers system improved in terms of quality of sound after the music signal is passed from lr 24db xover??

i have jus completed the circuit on pcb(12db/octave lr from rod elliot's site).but m scared to power it up.reason being that i didnt understand in his article that how to connect the 100nf caps near op amps on power rails.if u know please tell me.
is it like,for each opamp,take a 100nf cap,solder one leg at pin 4 and other leg at pin 8????? if its something else way then how??
hence i asked for pcb layout or pics of the built x-over

any help welcome.

 

[kkchunghk]

driver choice

Hi Calebay,
This may be a bit off subject, so I say sorry first. I have got the parts to build to 2-way versionof the crossover with OPA2134. But I'm hesitating on the cut off frequency. ESP suggests a cut off at 310Hz for a 2-way crossover, and this seems to be an odd choice when finding drivers to match. May I ask if yours is a 2-way or 3-way crossover, the cut off frequencies, and the drivers chosen, and the million-dollar question - is the sound much better with than without the active crossover? Oops, seems a mouthful to ask.

Cheers,
KK

 

[wxn]

i meant to say ::: is the overall sound output from the amplifiers system improved in terms of quality of sound after the music signal is passed from lr 24db xover??

i have jus completed the circuit on pcb(12db/octave lr from rod elliot's site).but m scared to power it up.reason being that i didnt understand in his article that how to connect the 100nf caps near op amps on power rails.if u know please tell me.
is it like,for each opamp,take a 100nf cap,solder one leg at pin 4 and other leg at pin 8????? if its something else way then how??
hence i asked for pcb layout or pics of the built x-over

any help welcome.

Yes, you could solder 100n caps between 4 and 8 pins, you could put them between 4/8 legs and ground. Or you could do both 🙂

 

[sagarverma]

hi WXN

thanks for help.
which is better,two caps per op amp or one cap per opamp?
will there be any danger without these?
thanks in advance

 

[AndrewT]

Hi,
try both caps.
100nF both supply tracks to grnd.
22nF both supply pins to each other.
These decoupling can be ceramic.

 

[sagarverma]

i will try it out today and will post soon

 

[Calebay]

Hi kk

Cut off at 310Hz appears to be the crossover frequency that he suggests for a 3-way. Between a bass unit and a midrange. In a normal 2 way design it will be a lot higher. But it all depends on the drivers you chose to use. What I use in my case is a Eton 11” crossed over at 150hz to a Fostex FX200 crossed over at 6000hz to a Neo3PDR. I’m happy whit the sound. I can’t compare it to passive crossover because I have only tried the active one whit these speakers.

sagarverma
I can’t post my PCB sorry it got deleted last time I reinstalled windows I have a low quality pic. but its 250kb.. how do i post pic bigger than 102400 bytes?

 

[sagarverma]

no need .what i needed i got from others on the forum.thank u for reply.

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http://www.herohonda.com/karizma/
how is it(i have red one)😕
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