Silly idea: Shorten the amp remote sled contact

Every once in a while, I find myself in a situation that requires I pull the player out of the car sled with the ignition still on and the amplifiers still on.

This is very rare. Usually I can turn off the ignition, or put the player into standby mode, before pulling the player out of the sled. But once in a while a software bug (for instance, a third party app, a test app, or even an alpha version of the player software) will lock things up to the point where I can't get the player into standby mode. And in those cases, sometimes even turning off the ignition won't get it to go to standby mode and therefore doesn't shut off the amps.

So we all know what happens when you pull the player out of the sled with the amps still on:

POP!!!!!!

With high end stereo systems, sometimes that "pop" is darn serious.

So I was sitting here wondering if this would work:

Mod the docking connector (not sure if I should do the male or female side) so that the amp-remote pin connector was a bit shorter than the others. Thereby making it disconnect a fraction of a second sooner than the audio and power connectors when you pull the sled. Thereby putting the amps into "mute" mode an instant before the pop reaches them.

Anyone think this is do-able? Or if it wouldn't work even if I could do it and why?

I would say that would work but I my self wouldn't really want to mod the connector, but instead us a normally closed momentary contact switch on the remote amp wire that I could hide but get to fairly easy to push that would turn the amp(s) off so they don't "POP!!!"

Oh just an after thought the mod would only work if the amps shut down quickly otherwise the "POP!!!" will still happen.

Makes me wonder if I could mod some kind of a temporary switch into the back of the sled so that the player closed it when inserted. Adjust its position until it's Juuuuust right...

I think you'd need to be removing the player from the sled fairly slowly to see any difference, but test your theory out by sticking some electrical tape over half of the pin.

Otherwise, affixing a switch in the rear of the sled sounds like it might work.

I think you'd need to be removing the player from the sled fairly slowly to see any difference,

Which would be fine, because in the situations where I know I'm going to get a pop, that's what I'm already doing anyway (wincing and cringing as I do it, you see...).

Maybe you could use a piece of thin Lexan like what is used in remote control car bodies to cover half the pin, then you wouldn't need to permanently alter the pin. The Lexan is durable enough that you wouldn't need to replace it I don't think .

Stu

Yeah an adjustable height switch in the back would work too. It' all depends on how temporary or permanent you wish to make this mod. I'm just going by what I'd do, and I would drill a hole in the back of the sled and adjust the switch so that once I started to pull on the Empeg it would open the circuit and shut off the amp(s).

Just a thought does anyone know if you short to ground just the lead going to the remote turn on of the amp if it will shut them down faster or maybe instantly (or maybe kill the amp). So you'd have a switch that disconnects the Empeg from the amp then connects that lead to ground leaving the lead coming out of the Empeg just hanging so to speak.

What about placing a small capacitor in-line with the remote amp line? This'd make the voltage drop less abrupt & maybe stop the thump.

-Zeke

What about placing a small capacitor in-line with the remote amp line? This'd make the voltage drop less abrupt & maybe stop the thump.

That would accomplish the exact opposite of what I want to do. My amps (like most good amps) are designed to mute the instant the amp.rem line goes low. If you use a capacitor to slow down the amp.rem, then it would keep the amps on LONGER and make the pop MORE likely.

I don't think "in-line" would be the way to do it.. but we all know what you meant!

I always figured the pop was due to extremely sudden voltage loss: a step function. So why does the amp pop then? I figured head units let it down gracefully & hence no pop.

Mark-thanks. IANAEE!

-Zeke

I always figured the pop was due to extremely sudden voltage loss: a step function.

If so, it would be voltage loss on the MAIN POWER or perhaps a voltage loss or spike on the AUDIO CABLES, but not the amp remote line. The amp remote line is there to PREVENT pops. And even on the empeg, it does a really good job of it as long as I'm not doing something goofy to the software (like crashing it) that prevents it from shutting off the amp remote line when it should be.

Got it. What about a small reed switch in series on the amp remote line and a small magnet taped/epoxied to the back of the empeg? This would cut the amp remote line a bit early (if the spacing was correct). Even simpler would be your basic washing machine cover switch. In either case mounting could be a pain, but there's a lot of these type of switches out there.

-Zeke

Even simpler would be your basic washing machine cover switch.

Yeah, that's the sort of thing I'm talking about. A temporary switch whose height I can adjust. I could do this in pretty short order, I even have what I think would be the perfect switch. Now I just have to find the time to rip into my dash again.

A membrane switch and a rubber adhesive bumper on the back of the empeg would be very cool. No drilling, short travel, and a good deal of room for error on axial and side-side positioning. The only tricky bit would be going rom the membrane tail to the copper wire. Lots of litho houses do membrane keypads & supply free samples to boot. Just a thought.

-Zeke

Maybe Mark (or someone) could figure a way to get the software watchdog support in the kernel to cut off the remote amp line, or, hell, go ahead and reboot like it's designed to do in the first place.

Of course, I don't know exactly what's happened when the player won't shut down, so it's easily possible that a software watchdog would provide a false negative.

Can you not do a Hijack reboot in these instances?

Can you not do a Hijack reboot in these instances?

I'm talking specifically about situations where everything has locked and I can't even get to Hijack. Or situations where I'm testing Alpha team software that locks up, and I'm not running Hijack in that instance.

or spike on the AUDIO CABLES, but not the amp remote line. The amp remote line is there to PREVENT pops.

That is correct, to prevent the "POP!!!" i.e. a DC voltage spike to your speakers the amp(s) need to shut off just before your head-unit does, which is why the remote line powers down first (or at least it should) just as the head-unit powers down.

And there should be a way, if the hardware has a watchdog support, to preform a set of instructions if the software is locked up and if so is that something the Empeg/Rio team needs to set it up or is it something we can add, I say hardware only because I build servers and they have the watchdog built-in but it usually just writes a log file if the system locks)

Watchdog processes don't catch everything. For example, there was once a software bug where the front panel input is locked up, and player keeps playing even after you turn off the ignition. This was one of the bugs in Beta 11. Player software is still running, so things aren't completely locked, just the inputs aren't responding (ignition sense is an input). A watchdog process would think things were OK because stuff was still running. But in that case, there was no way to get the player to reboot other than to pull it out of the sled and cause a pop.

Admittedly, that bug got fixed. I'm just using it as an example of a situation where a software bug could possibly manifest itself in such a way that it would cause the pop but a watchdog process wouldn't catch it.

I suspect that by the time you've adjusted the position of the switch so that it is optimal and does what you want it to do, you will have popped your speakers more times than you will if you didn't bother.

I'd second the idea of a hidden dash switch that you physically press. What you need is a push-to-break switch. (as opposed to the push-to-make that you'd want in the sled).

How about positioning the switch to sense handle lift somehow ?

I suspect that by the time you've adjusted the position of the switch so that it is optimal and does what you want it to do, you will have popped your speakers more times than you will if you didn't bother.

You know, you've got a really good point there. I bow to your superior wisdom.

How about positioning the switch to sense handle lift somehow ?

That might be fun. It could be done in the player, internally. The handle mechanism is a bit fiddly, though, not sure if there'd be an easy way to implement that. Worth a look at least.

Maybe position a switch on top of the sled above where the catches poke through? I haven't looked at an uninstalled sled in a while to know if they poke through enough, but it's an idea.

The clips don't protude above the sled - they sit flush. The problem with this method would be that you'd only need the handle to move a few mm and the circuit would get broken. I'm guessing that having the Amps turn off every time you hit a bump wouln't be optimal.
I like the idea of an internal switch based on the handle though. Possible a slim reed switch and a very small magnet would do the trick.

I like the idea of an internal switch based on the handle though. Possible a slim reed switch and a very small magnet would do the trick.

I looked, and on my player at least, there's a spot on either side where the handle hinge assemblies reach the bottom of their travel. It's right next to the motherboard mounting screws. Seems like something clever with a reed switch attached to one of those screws would do it.

I just worry about reed switches... I had an old Sony car CD player that depended on reed switches to know how to mechanically load the CD into the player, and they were always failing and needing to be replaced.

http://www.digikey.com/scripts/us/dksus.dll?Detail?Ref=55690&Row=166260

Unless you have quality amps, won't you also need an 'anti-thump' circuit as well?
can you have a relay which switches in a configuration of caps to slowly turn off the speakers? (at least more slowly than sudden power disconnection)

I thought the whole idea of amps having an on/off input in addition to actual power was so that they could deal with the thump issue themselves. No?

Thats correct, thats why the remote line (the on/off switch) powers down just before the head unit does.