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Old 17th October 2007, 12:27 PM   #1
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Default Eliminate POP on power off

Hi folks,

When the RCAs are hooked in from the line level converter to the amplifier and I turn the ignition on and off, the amplifier sends a loud pop to the speaker. The speaker has a significant throw on it when this occurs.

I'm annoyed by it as well as I'm concerned about any damage it is doing.

It does not occur when I turn the amplifier on and off with the RCAs not plugged in.

It's hard for me to isolate whether it is the head unit or the amplifier discharging the input signal that is causing the pop.

My questions are:

1. How can I find out whether it is the head unit or the amplifier discharging an input signal that is causing the pop? I have a multimeter that has a bunch of features I don't know how to use but may be helpful.

2. If the problem was from the headunit, I can't just stick a capacitor on there because wouldn't that work as a high pass filter? What can be done if it's due to the head unit?

3. If the problem is within the amplifer, is there anything I can put between the amplifier and speaker to stop this?

I figure a capacitor in function would seem logical as it would absorb the high pulse of voltage and slowly release it however I do not want to alter the sound (especially not apply a high pass filter on my sub!)

Thanks in advance!
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Old 17th October 2007, 02:04 PM   #2
ppia600 is offline ppia600  United States
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Buy a remote turn on delay box on ebay. Most likely the amp is turning on right before the head unit so it is hearing the turn on thump of the deck. If you connect the turn on delay unit between the remote wire, the deck will turn on first and the amp will turn on after the deck thumps so the thump won't be amplified. I can't remember what they are called specifically.
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Old 17th October 2007, 02:13 PM   #3
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http://www.sfxaudio.com/products/dis...p?ProdId=63361

I think something similar could be built with just a cap, resistor, and relay.
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Old 17th October 2007, 02:14 PM   #4
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You say you get pop both when you turn the ignition on, and when you turn it off?

If so, the delay device will only work when turning the amp on. In my experience, the turn off thump is more prevalent, and difficult to address. If the amp's remote turn-on lead is properly connected to your head unit's remote turn-on lead, then this is a more difficult issue to address.

The head unit is supposed to have its preout signals up and ready prior to the amplifier turning on its outputs. This can be done with a delay on the remote lead, as ppia600 mentions. There should also be a small delay internal to the amp, that the power up cycle takes a half second or so after the application of 12V to the remote lead.

The turn off issue, however, is more difficult. When power is cut to the head unit (through the ignition), two things happen: the preouts are powered down, with the subsequent thump, and the remote turn-on lead is taken from 12 to 0V, telling the amp to turn off. What is happening to you is the amplifier is not fully shut down, or muted, prior to the head unit. The head unit is too fast, or the amp is too slow. Difficult to say which.

For starters, are you sure you have the remote leads connected properly?

edit: Sorry, I just noticed you are using a line level converter. So your are using the speaker outputs on the head unit? That is your most likely issue; the speaker outputs are not synchronized in the same way as the preouts. What type of head unit? Does it have any preouts?
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Old 17th October 2007, 04:29 PM   #5
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After further consideration, you may find some improvement by slowing down the head unit. There are a number of threads currently active about adding capacitors on the head unit's power supply, very near the head unit. From a sound quality standpoint, I'm not convinced, as most head units run right into switching power supplies internally, but regardless, adding a cap onto to the ignition lead may be sufficient to slow down the head unit.

Possibly an easy fix to your problem. You could find a suitable cap at Rat Shack for about $2.
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Old 17th October 2007, 04:47 PM   #6
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A common head unit uses a bridged pair of amplifiers for each speaker. These have a DC bias point of ~1/2 of the B+ voltage. When you power up the head unit, the outputs swing from ground (0v) to the output bias voltage (~6v). A high power line output converter has a transformer for each channel. If you use a line converter without the transformers, there will be a significant pop as the outputs switch from 0-6v. With the transformers, there is no pop because BOTH inputs of the transformer are driven from 0-6v at the same time. If you have a pop, you may have the converter improperly installed or have the wrong converter.

If the amp pops on turn on, you probably have the remote turn-on terminal connected to the ignition instead of the power antenna output of the head unit. Most amps have a slight turn on delay. If the amp is turned on by the head unit's power antenna output, the amp won't be able to pop when the head unit is switched on because the amp won't power up for a second or two (due to the turn on delay).
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Old 17th October 2007, 05:08 PM   #7
Flyin11 is offline Flyin11  United States
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By Rat Shack do you mean Radio Shack?

I might have to look into this as mine does the same thing..Always has...It's a PPI 100xi and I would love to get the turn on and off pop out of it. All wires connected properly as well...Remote and so on.
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Old 17th October 2007, 05:19 PM   #8
built is offline built  Malaysia
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you may want to try this...
http://www.stingerelectronics.com/pr....asp?strID=272
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Old 18th October 2007, 12:23 AM   #9
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Where did you connect the remote lead of your amp?

OEM or aftermarket deck?
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Old 18th October 2007, 12:07 PM   #10
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Quote:
Where did you connect the remote lead of your amp?
It is piggy backed off cable that runs to the cradle that the OEM Phillips head unit sits in. This is essentially off the ignition and not controlled by the head unit.

Quote:
If the amp pops on turn on, you probably have the remote turn-on terminal connected to the ignition instead of the power antenna output of the head unit...
This explains the pop on and I will try changing it this weekend.

Quote:
adding a cap onto to the ignition lead may be sufficient to slow down the head unit
What size capacitor do you suggest? Does it need to be a special type? The ignition lead is just low voltage yeah?

The pop off is a major concern to me and I appreciate the suggestions!
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