Adcom GFA-555 makes a "pop" sound when changing sources - help

[starflight]

Hi guys,

I have been wanting to purchase a good external amp to power the Polk RTi12's that I have. These are hungry beasts. Anyway, I finally received my Adcom amp yesterday and I hooked it up last night. At first I wasn't able to tell the difference but I recalibrated my setup with YPAO and then set the bass output to the Fronts and all could say was "HOLY SH_T!" These woofers came alive as I expected them too. The bass was soooo good that I had to dial down the bass on the receiver down.

I think I read this somewhere before but now I can't seem to find the threat as to where I read this, but I do notice that when I change sources on the receiver or when I go from menu to menu on my dvd player, I hear a light pop coming from the RTi12's that are connected to the Adcom.

Is this normal? Is there something I can set on the receiver to avoid this? Or is there something else I can do to eliminate this? Thanks for the help!

 

[WmAx]

Hi guys,

I have been wanting to purchase a good external amp to power the Polk RTi12's that I have. These are hungry beasts. Anyway, I finally received my Adcom amp yesterday and I hooked it up last night. At first I wasn't able to tell the difference but I recalibrated my setup with YPAO and then set the bass output to the Fronts and all could say was "HOLY SH_T!" These woofers came alive as I expected them too. The bass was soooo good that I had to dial down the bass on the receiver down.

I think I read this somewhere before but now I can't seem to find the threat as to where I read this, but I do notice that when I change sources on the receiver or when I go from menu to menu on my dvd player, I hear a light pop coming from the RTi12's that are connected to the Adcom.

Is this normal? Is there something I can set on the receiver to avoid this? Or is there something else I can do to eliminate this? Thanks for the help!

What you describe sounds like no fault of the amplifier. You never hear this pop unless you change source or use the menu, right? If it's not a loud noise, and you can ignore it when changing sources, then do so. If not, you may have to change the receiver out for another model to avoid this issue. While it seems unlikely, perhaps this is a grounding issue, or some sort of DC transient? You can try a ground loop isolator connected between the amplifier and receiver as a last resort; the isolator would remove both issues as possible variables.

-Chris

 

[Rickster71]

What happens if the volume is turned all the way down?

 

[starflight]

What happens if the volume is turned all the way down?

I just turned the volume all the way down and when I skipped the track on the DVD/CD player. No pop sound. As soon as I turn it up just a little, and change tracks, I heard it.

 

[starflight]

What you describe sounds like no fault of the amplifier. You never hear this pop unless you change source or use the menu, right? If it's not a loud noise, and you can ignore it when changing sources, then do so. If not, you may have to change the receiver out for another model to avoid this issue. While it seems unlikely, perhaps this is a grounding issue, or some sort of DC transient? You can try a ground loop isolator connected between the amplifier and receiver as a last resort; the isolator would remove both issues as possible variables.

-Chris

Hi Chris,

thanks for your suggestion. I was seeing if I can ignore... at least right now cause I'm not so used to it yet. The pop sound is not very loud, but it's definitely noticeable. Not really sure what a ground loop isolator is or what it looks like or what it would entail to set up one up either. Got any links to what you are referring to? Thanks!

 

[WmAx]

Hi Chris,

thanks for your suggestion. I was seeing if I can ignore... at least right now cause I'm not so used to it yet. The pop sound is not very loud, but it's definitely noticeable. Not really sure what a ground loop isolator is or what it looks like or what it would entail to set up one up either. Got any links to what you are referring to? Thanks!

You should be able to find a RCA plug/jack type ground loop isolator at nearly any car audio shop for $15-$20. Be certain they will give a cash refund if you return the device(many car audio places may only offer in store credit for returns) - you may find that the isolator does not fix your problem. Best Buy or other major local retailer may have one in stock, and a major retailer is usually easier to deal with issues like refunds. So this would be preferred.

http://www.crutchfield.com/S-clyiM7PrEPR/App/Product/Item/Main.aspx?i=127SNI1

http://www.provantage.com/xitel-gli1-x1~7XITL004.htm

-Chris

 

[starflight]

You should be able to find a RCA plug/jack type ground loop isolator at nearly any car audio shop for $15-$20. Be certain they will give a cash refund if you return the device(many car audio places may only offer in store credit for returns) - you may find that the isolator does not fix your problem. Best Buy or other major local retailer may have one in stock, and a major retailer is usually easier to deal with issues like refunds. So this would be preferred.

http://www.crutchfield.com/S-clyiM7PrEPR/App/Product/Item/Main.aspx?i=127SNI1

http://www.provantage.com/xitel-gli1-x1~7XITL004.htm

-Chris

Thanks for the links and suggestions. I didn't have a chance to get one yet, but I plan on going to BB or Fry's tomorrow afterwork to see if they indeed have one. I see them everywhere on ebay. I'll have to give a report on what this does for me.

 

[starflight]

Doing more research on these ground loop isolators shows that they tend to reduce/eliminate the buzz or hum on signals, but I have neither problem. Other research has led me to understand that Adcom are known to have a thump sound when powering off, but in my case it happens each time the CD changes track, or my TV changes channel or even when I change menu while watching DVDs.

 

[Haoleb]

It do not understand why anyone would think you need a ground loop isolator for this problem as I cannot imagine that being a problem here. The only reason I can think is if indeed its sending some sort of DC out like Wmax suggested and you would be using the ground isolator sortof as a coupling capacitor to eliminate any DC.

Are you using digital connections between your source player and your reciever? If so try the analog ones instead and tell us if you still have the problem. Im going to bet the answer is no.

 

[PENG]

Doing more research on these ground loop isolators shows that they tend to reduce/eliminate the buzz or hum on signals, but I have neither problem. Other research has led me to understand that Adcom are known to have a thump sound when powering off, but in my case it happens each time the CD changes track, or my TV changes channel or even when I change menu while watching DVDs.

When powering off the 555 does make a sound when the capacitors discharge. It does not really thump, it sounds more like someone letting some air out............... If it thumps it is not normal.

 

[Ron Temple]

When powering off the 555 does make a sound when the capacitors discharge. It does not really thump, it sounds more like someone letting some air out............... If it thumps it is not normal.

Yup...I've read about the source change pops occurring with with the GFA555, as I recall it's something specific with this amp...just don't remember what.

 

[WmAx]

Doing more research on these ground loop isolators shows that they tend to reduce/eliminate the buzz or hum on signals, but I have neither problem. Other research has led me to understand that Adcom are known to have a thump sound when powering off, but in my case it happens each time the CD changes track, or my TV changes channel or even when I change menu while watching DVDs.

If you have a switching ground issue or a DC current transient, a ground loop isolator is a transformer coupled connection, and can not allow DC through. So if DC transient is the problem, this will remove it.

Turn on/off thump and/or sounds is not related to anything that occurs as a result of your source and/or pre-amp components while the amp is in a constant 'ON' state.

-Chris

 

[starflight]

It do not understand why anyone would think you need a ground loop isolator for this problem as I cannot imagine that being a problem here. The only reason I can think is if indeed its sending some sort of DC out like Wmax suggested and you would be using the ground isolator sortof as a coupling capacitor to eliminate any DC.

Are you using digital connections between your source player and your reciever? If so try the analog ones instead and tell us if you still have the problem. Im going to bet the answer is no.

Yes, most of my connections from the source to the receiver are digital connections. The DVD player using a toslink cable, from the Media Center PC I am using my SoundBlaster's digital out as well. I have my pda which is streaming internet radio wireless hooked up to the front analog connectors and when I change songs or stations, there is no pop.. hmm....

 

[jerelect]

Yes, most of my connections from the source to the receiver are digital connections. The DVD player using a toslink cable, from the Media Center PC I am using my SoundBlaster's digital out as well. I have my pda which is streaming internet radio wireless hooked up to the front analog connectors and when I change songs or stations, there is no pop.. hmm....

Be aware that many of them (the first gen 535, 545, 555, etc ) did not have any DC decoupling caps...which is good from an audiophile perspective that is running pure 2 channel mode, but not necessarily from an HT perspective...the result being that if you have any DC offsets in your system and they are not isolated, the amp will make a small popping sound when changing inputs, etc...HK, parasound, also have amps that are not DC decoupled...it was done intentionally to extend the FR. These days it's not as critical because many people use subs to supplement the low end.
Found this in another forum hope it helps.