chiark

Oh bum

I'm just installing an old but good audiocontrol 4xs back into the car with the intention of running my CD Technologies HD62s actively in the front. I've got the spare amp channels on the Soundstream 604 amp, so "why not?" I thought.

Wired it all up, tested everything. Large turn-off pop whenever the active crossover powers up or goes down. EEK! I tested it with an old set of speakers (just 5.25" woofers) and the things move quite a bit. This would destroy a tweeter! (eek again).

I'm running everything from a common ground, common power... It's definitely the crossover because if I disconnect the input from the HU and manually connect/disconnect the remote power-on for the x-over then I always get the noise.

Any ideas?

nom

At a guess, it's a 'low' pop, so the tweeters shouldn't be affected? Umm, maybe, hopefully...
I've always left the caps in line with active set-up; being a wuss, I'm worried about the same thing

chiark

nom, it's definitely a low pop. If I connected the output of the amp straight to a tweeter, it would wipe out the tweeter.

I don't really want to leave a cap in, as that will change the phasing of the treble, but needs must. What value would you recommend?

Ta,

Nick.

chris12102

xover is powering off before the amp - have you got a cap on the power cable? could try wiring power so that cap only feeds the amp so amp is last to power off

chiark

the x-over needs to be the last thing to power off tho. (Don't have a cap)

nom

It is the amp which needs to turn of first, isn't it? So a big cap for the amp power supply only might delay it enough so that the clunk from the x-over doesn't get through?
I didn't like putting the cap in 'cos of phasing issues either - but having just popped a pair of highly expensive ribbon tweeters doing exactly the same thing I decided - what's wrong with a little phasing? For the cap size, I 'cheated' & just used the one that the, ahem, new tweeters came with.

chiark

The amp's got a built in delay to turn on, so when the x-over powers up it immediately puts out a "thud" which the amp doesn't amplify because it ain't switched on.

Unfortunately, powering down doesn't work.

Are you talking about putting a cap on the remote turn on to the crossover? That might keep it powered up for the amp to shut off before turning off...

Anyhow, could you look at your capacitor on the tweeters and let me know the rating? Also, how have you wired it? In series?

Many thanks!

David_Wallis

does your bass cube have a delayed remote turn on output??? if not wait and use the eq, as that has 4 connectors + - Rem DR

DR being delayed remote out... so daisy chain through this and hey presto...

David

chiark

No, the bass cube doesn't have that unfortunately. But it still doesn't get rid of the turn off pop!

David_Wallis

What about a cap across the remote and ground... fairly large one?? this charges up with system on then discharges slowly(ish) keeping the x-over powered on?

David

chiark

Yes, I did wonder about this too

kryten

I had this years back and cannot remember for certain how I sorted it out.

I _think_ I used a delay for the remote off to the crossover. The remote line was driving a relay anyway (too much power for the head unit to cope) so I think I just added another one for the crossover alone (with a cap, as has been said).

I'll see if I can find the notes tonight.

chiark

I'm running a relay for the remote turn-on already, so adding another's no problem. I did wonder if it was a lack of "cleanness" or even back emf from the relay causing this. Checked that by putting a switch in the remote turn-on line to the x-over and, you guessed it, it bloomin' well still does it. I may try switching the +12 supply to it using a relay and see what happens...

nom

I'd have thought that the simplest would be do put a cap on the remote switch - just enough to hold the x-over for 4-5 seconds or whatever. By simplest I mean cheapest as well, as it should only take a tiddly cap to slow the pd drop 'cos of the minimal current drain.

David_Wallis

I am assuming as you mention back emf you do have a diode across the relay supply??

Relays arent exactly known for their 'quietness'

David

chiark

Yes, there is a reverse biased diode across there

globbits

Chiark - I'm using a dead-clever (own invention) 30 second delay relay, for powering down my stereo, using a courtesy-light extender from Les Smith. I originally made it because my old Peugeot 406 accessory connection went to ground between key positions, so the stereo didn't turn on/off cleanly. But, it's also useful for turning the engine off and listening to the last bit of that favourite tune

Might be that if you put in a time-delay like this (can send you the wiring diagram if you need?) onto the crossover, you could get 'round the problem?

chiark

globbits, cheers. I think I'm going to go for belt-and-braces: cap on the remote on to the crossover, plus a cap on the tweeter to protect it

David_Wallis

Let me know if that doesnt work... Dad will give you a circuit in 2 secs... if you need one!

audio g man

Do you get the pop when you power up the x-over but leaving the rest of the system off?

I've never had this problem b4 but then again I always use an ignition live feed into the remote/power control input on active filters/eq's. I like doing it that way to prevent having to many items hanging off the head units remote out.

You could consider giving the x-over a perm. live feed to both the perm. live and remote/power control inputs, then fitting a toggle switch in the ground wire. Just a thought.

chiark

g, it's active - without the amp being on I hear no pop whatsoever . I've tried with just the crossover and amp on, then powered down the crossover with the remote, and the pop's there.

audio g man

hmmm

[Edited by audio g man - 6/20/2002 1:02:45 PM]

chiark

No, no humming, it's definitely a "pop"

David_Wallis

Have you tried a cap? if not I can dig you one out tonight if you want?

David

chiark

Not tried yet - please do dig one out

kryten

Checked the notes and I definitely used a delay on the turn off of the crossover - remote on as a trigger and a separate relay to each amp/crossover.

I'd even made up a small PCB with an adjustable delay (or rather a mate did!) - if I find it, you can have it but I've been through most of the stuff I've got lying around and its nowhere to be seen

You could also try using the ignition switched supply to switch the amp and the remote on to switch the crossover - the remote on lead normally changes state a bit later than the ignition feed (did on my Mondeo, anyway).

audio g man

Did you fix this little problem Chiark?

David_Wallis

he didnt... but we will when we fit his horns and the eq I gave him!

David

chiark

Funnily enough, I've gone for the belt and braces approach.

I've just bought 2 audiophile grade 10uF polyesther capacitors from Maplins, which give me a 6dB/octave passive x-over on the tweeters at just under 4kHz. I'm using a crossover point of 4.8kHz on the active x-over, so this should do nothing other than give me some protection. (Admittedly, there may be phasing issues...)

I'm taking apart the crossover tonight to see if I can find a reason for the pop. "Dirty earth" is apparently a common cause of this, so I'll trace that through.

Nick.

chiark

re EQ - it works now . They fixed the symptom, not the cause before... d'oh! Cheers again!