old question never really answered

leftwinger57

Quite a few months ago I noticed a sound coming from what ever set of speakers I was using at the time when I shut down my Adcom 555. some said and the best description was like a ballon deflating in the speakers during spool down.It happened w/ my Infinitys,Bose 601s,ADC 303ax and the DCM Time Frame 350s. When the Polk 2Bs go down for the night they make no sound whats so ever. Is there a technical reason for this or has no one ever come across this phenomenom?

bored184

If you dont mind I am going to piggy back on this thread because I have a similar issue with my Adcom GFA-555. When I power it down it makes a sound very similar to on old vintage video game character jumping. I figured there is a cap that is leaking voltage somewhere, at some point I plan on having the amp recapped which I hope will solve the problem.

cnh

The only thing you should be hearing when you power down are the storage caps discharging, if you have a source on you'll hear that as a slow degradation of the sound as it gets weaker and weaker till there is silence.

You might perceive that as a balloon deflating, I'm not sure. When I think back to running one, yeah that sounds like a reasonable description. Why you don't hear it on SDAs, I don't know?

Remember, there are no relays on these Adcoms.

Here's how Adcom answers this question on their site:

There's a "thump" when I turn off my system.

There are usually two reasons for this: The amp has a large power supply and it doesn't use output relays. Let's look a bit more closely at both.

First, a power supply's job is to filter and store energy until the amplifier circuitry needs it. Adcom amps have HUGE power supplies. That's part of the reason they sound as good as they do. But when you turn the system off, that energy has to go somewhere. The "thump" you occasionally hear is the power supply capacitors dissipating the energy. It's not dangerous at all. In fact, it's just another sign that the amp won't run out of steam when you really want serious sounds.

Yes, we could have used output relays that would disconnect the speakers as soon as the amp turned off. That way, you would never hear the thump. But relays, as we've already seen, aren't great for real high fidelity sound quality. If we used them, you would never hear how good our circuitry is either. Is that a sensible tradeoff? We sure don't think so.

Look at it this way: The "thump" is the same thing as a high performance automobile's rumbling exhaust. The sound alone tells you there's something serious under the hood, right?

cnh

Faustin

I have a GFA 555 II and when I power down it makes the same sound. Most of the time it is from the right channel. Occasionally it happens to both channels. I am using the Adcom power conditioner to power up and down and it does it with or without the conditioner. Kinda bothers me. Planning to find some place to look at it.

Schurkey

The only time I ever heard an Adcom 555 power-down, the music played for a considerable length of time, got quieter, and then silence.

If Adcom says that a thump is normal...fine.

Whistles, meows, balloons, video games--sounds like TIME FOR SERVICE to me.

Faustin

Time for service is what I am thinking also. When it is powering down and my wife is wrongly accusing me of something I have not done even though we had chili for dinner..... it is time for service,

westmassguy

Faustin wrote: »

Time for service is what I am thinking also. When it is powering down and my wife is wrongly accusing me of something I have not done even though we had chili for dinner..... it is time for service,

LOL too funny

dorokusai

I remember hanging with F1Nut one day and monoblocking(Bridged) 2 Parasound HCA-1500 on my pair of Polk SDA1C....and one amp was bad unknown to us. The amp worked fine in stereo but apparently not in bridged mode....

It made the loudest, scariest noise I've ever heard a speaker make to this day @ 120+db....seriously, scared us BOTH, even Jesse....all the woofers went bug eyed and flipped a wig....whew what a great day. Memories....and I've never moved so fast to hit a power button in my life. It was slow motion, like a movie and I think F1 was airborne at some point, hair intact as usual.

Don't fear the thump, fear the high pitched scream.

leftwinger57

Thankfully I never had the thump on power up or down. I do remember a friend of mine had a Mac 2100 and I was always warned to make sure the volume controls were turned down on powering up to prevent the thump from blowing his speakers it was that bad. Now as for my Adcom 555 it has no issues, does not get warm pushes all sets w/ ease when called on and by the poll taken the last time most folks who had other brands of speakers did hear a sound akin to a deflating balloon as the best description. I do not think this is a bad thing just a thing that the amp does when spooling down.My only concern was, why it does not happen w/ my Polk 2Bs on power down and just wondered if there was a techy reason for that.

Mr. Bubbles

I'm kind of curious about the balloon deflating description. I have heard balloons make several different noises while deflating depending on if you are holding it, holding it by the opening, letting it fly through the air, bursting it, etc. I'm just not sure i can get a good mental image of the sound. I run a 555II and have not heard any abnormal noises in mine with any speakers hooked to it. I do run it through the Adcom AC enhancer.

mhardy6647

sounds like 'dying' oscillation as an amplifier goes unstable.

leftwinger57

Mr. Bubbles looking at your sig I see all Polk products.I didn't even notice the sound until I was in the room while it was going on.Usually I shut it down and leave the room and never heard the sound. Like I said before and other members w/ other brands of speakers this sound happens and NOT w/ the Polk 2Bs .That's my question here.Just picture air running out of a balloon ,it's not like letting it go ,not puncturing just slowly deflating.If you can dig up the original post it was pretty funny how many decriptions of the noise there was and this is the closest to accurately describe it.Also if you find the post all of the amps with multiple makers but mostly Adcoms are fully functional are fine and doing well besides this wacky noise.

TennMan

Have you tried it with the IC cable disconnected to see if it still makes the sound? With the IC cable disconnected the 2B should react the same as other brands of speakers. I have and Adcom amp and preamp and 2Bs. I've never heard any odd noise when I turn the system on or off.

Mr. Bubbles

Leftwinger;

Even though i have never noticed any such sounds with my 555II it makes me curious. I think i will listen much more closely tonight when i get home to see if I can tell anything. The amp is currently hooked up to my SRS's but has been hooked to DCM's, Advent's,VMPS's, and many others and i have not noticed anything to this point. My Carver amps are bad to thump if not run through a sequencer or patiently turn all components on and off in proper sequence/ time.

I only listed my Polk gear in the sig since this is CP. I have a lot of other gear and speakers. Just didn't feel like most others here would really be interested in a list of stuff not related to Polk. I'm a big fan of vintage DCM, Advent, and Realistic speakers (among other gear) and have a decent little collection of those also. Dont' know why i like the realistic stuff. i guess it was kind of like the under dog with some decent stuff affordable to the average working man.

leftwinger57

TennMan,very interesting, no I have not tried that and that would in fact make them obviously not bonded and maybe the exact reason.Mr. B the mkII is a bit different and newer so I'm not sure if it would apply here.Try like you said any brand of speaker but not Polk, no sources on and just let the LED diminish and see what happens. Like I said before I never noticed it because I would shut it down and leave the room.I do like the idea of disconnecting the i/c to see if it does it w/ the 2Bs and then the question will be answered.My sig went away one day and I need to talk to I/T dept to reteive and redo it.

gimpod

I think it's time to get some amps in the shop. I run an Adcom GFA 555 (Not the Mk2) and as long as I turn the volume all the way down (you should be whenever you shut down) when I shut down it quite as a mouse.

leftwinger57

That idea made me so nutty about trying it w/o the cable I did.Result, no sound what so ever. Now I just think there's something in the make up of the Polk x-over that does not induce this sound. When I got my amp from Audio Classics it was certified to be at or above spec on paper. They've been in buiness for a long time and have a great reputation ,there is nothing wrong w/ my 555.Volume control on my Onkyo on the other hand is never touched on shut down so maybe there is another experiment in the works.Back to PTI later dudes....