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mark evans
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Amp causes speaker "pop"

Maybe someone can help me with this. The amplifier I am currently using is an Adcom GFA 555, 200w/ch amplifier.

When I turn the amp off after listening, a 'pop' occurs through the loudspeakers after the capacitors discharge Im assuming. Adcom amps are known for this, but I have never investigated it.

Will this transient hurt the crossover or drivers in my speakers?

Thanks to all that respond in kind.

Mark Evans

jackfish
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Re: Amp causes speaker "pop"

I lived with the Phase Linear "thump" for years and it never seemed to do any harm to a variety of loudspeakers.

mark evans
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Re: Amp causes speaker "pop"


Quote:
I lived with the Phase Linear "thump" for years and it never seemed to do any harm to a variety of loudspeakers.

Thanks. I have heard differing opinions on this. With my new speakers, I was a little concerned.

Mark

Jan Vigne
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Re: Amp causes speaker "pop"

It's possible the thump will harm your speakers. If not now, in a few years as the capacitors age a bit more. There's not much you can do about it though as the decision was made by Adcom not to engage a muting circuit upon power down. I don't recall, didn't the GFA 555 have a speaker selector switch you could disenage?

mark evans
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Re: Amp causes speaker "pop"


Quote:
It's possible the thump will harm your speakers. If not now, in a few years as the capacitors age a bit more. There's not much you can do about it though as the decision was made by Adcom not to engage a muting circuit upon power down. I don't recall, didn't the GFA 555 have a speaker selector switch you could disenage?

It doesn't Jan. Thats the one thing amongst a few others I don't like about the Adcom.

Personally, I think the JBL's that have been powered by the Adcom for over 20 years may have suffered some damage to a degree. They seem to sound strained for the lack of a better word. Or it could be that my old age ears have suffered damage from having to listen to sirens on the fire truck.

Like you said, and I agree. This pop can not be good over the long term. I hope the 336 will be back soon so I can take the Adcom out of my system. I just don't want to take the chance with the EW Andra's.

Thanks!
Mark

jackfish
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Re: Amp causes speaker "pop"

If such sounds being reproduced by a loudspeaker will harm them then the program material they are being fed on a regular basis is likely to harm them as well. What do you think the SPL and frequencies of the sound are at power down? Compare that to the numerous sounds and volume your speakers are emitting with "regular" use.

From someone who has serviced Phase Linear amplifiers for 30 years, "I don't think that the thump, which is a momentary DC offset will harm anything". Now, the Adcom could be releasing more DC current which at some point which can be bad. I'd consult with Adcom, they have been very responsive to my inquiries.

mark evans
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Re: Amp causes speaker "pop"


Quote:
If such sounds being reproduced by a loudspeaker will harm them then the program material they are being fed on a regular basis is likely to harm them as well. What do you think the SPL and frequencies of the sound are at power down? Compare that to the numerous sounds and volume your speakers are emitting with "regular" use.

From someone who has serviced Phase Linear amplifiers for 30 years, "I don't think that the thump, which is a momentary DC offset will harm anything". Now, the Adcom could be releasing more DC current which at some point which can be bad. I'd consult with Adcom, they have been very responsive to my inquiries.

I will contact Adcom and see if they can mod my amp to stop the transient pop. And your right, I had to replace the off/on switch and Adcom sent me one in record time. Great service.

I think, and you may know if the Adcom GFA 555II or the 5500 and 5800 series amps have a protection circuit to stop the pops. If so, they should be able to mod mine. I have reconed the JBL's twice over the last 20 years, and that would be due to my high volume listening levels over time. That in itself may have been an attributing factor in the speakers sounding a bit dry.

Do you think that could be the answer, even if I have reconed them in the past?

Thanks jackfish,
Mark

Jan Vigne
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Re: Amp causes speaker "pop"

The "protection" circuit doesn't come into play with the power down tansients. Typically, there will be a muting circuit which is switched on to ... well, "mute", the pops. You never can tell why such things are not on an amplifier. Some designers feel anything between the outputs and the speaker makes for a degraded sound. Other times, particularly on higher wattage amplifiers, it's considered a needless expense because such circuits are going to have to deal with the high voltages present. Kind of like that $0.05 muffler bracket on the old Pintos.

The 555 was built when Adcom was a more budget oriented product competing with the likes of B&K and a few of the British lines back when the currency exchanges better favored the USD. While the Adcom isn't "overly engineered" neither is it hairshirt. It's possible they felt the inclusion of a muting circuit was more expense than the competition would allow.

If the pop begins to bother you - and the possibility of even a short burst of DC through the voice coil should, you could add a high wattage potential switch to the speaker line and simply switch the speaker feed out before shutting down the amp.

You've got a 200 watt amp and JBL's, Mark. Just how loud do you play your music?

mark evans
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Re: Amp causes speaker "pop"


Quote:
The "protection" circuit doesn't come into play with the power down tansients. Typically, there will be a muting circuit which is switched on to ... well, "mute", the pops. You never can tell why such things are not on an amplifier. Some designers feel anything between the outputs and the speaker makes for a degraded sound. Other times, particularly on higher wattage amplifiers, it's considered a needless expense because such circuits are going to have to deal with the high voltages present. Kind of like that $0.05 muffler bracket on the old Pintos.

The 555 was built when Adcom was a more budget oriented product competing with the likes of B&K and a few of the British lines back when the currency exchanges better favored the USD. While the Adcom isn't "overly engineered" neither is it hairshirt. It's possible they felt the inclusion of a muting circuit was more expense than the competition would allow.

Absolutely. Even the retail price of $750.00 was a bargin back in 1988. So it was just a very straight forward amp. No frills.

If the pop begins to bother you - and the possibility of even a short burst of DC through the voice coil should, you could add a high wattage potential switch to the speaker line and simply switch the speaker feed out before shutting down the amp.

Noted. I appreciate the info Jan.

You've got a 200 watt amp and JBL's, Mark. Just how loud do you play your music?

LOL! I've toned it down considerably over the last 25 years. I remember when I first got the JBL's, I was amazed at how great Eddie Van Halen's guitar sounded so, I'm sure there may be a 'little' tone deafness has set in from the jamming days

These days volume is much lower, my taste in music has done a 180, for the better I may add .

Mark

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