Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on February 12, 2009, 12:11:10 pm

Title: Speaker Crackle After Power Down
Post by: plexi50 on February 12, 2009, 12:11:10 pm
What causes a speaker to crackle a little after the amp is shut completely off?
Title: Re: Speaker Crackle After Power Down
Post by: jhadhar65 on February 12, 2009, 01:36:01 pm
Prolly that middle dude from your Rice Crispies.  I hate those guys!  Real trouble makers they are.

 :)
Title: Re: Speaker Crackle After Power Down
Post by: supro66 on February 12, 2009, 01:57:01 pm
Quote from: jhadhar65 on February 12, 2009, 01:36:01 pm
Prolly that middle dude from your Rice Crispies.  I hate those guys!  Real trouble makers they are.

 :)
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AND I THOUGHT YOU PEOPLE WERE PROFESSIONALS

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Title: Re: Speaker Crackle After Power Down
Post by: plexi50 on February 12, 2009, 02:22:44 pm
That was it! Now how did that get in there?
Title: Re: Speaker Crackle After Power Down
Post by: tubesornothing on February 12, 2009, 03:01:53 pm
he he

I ws thinking a few things about this, but it depends upon the design of the amp and what you mean by "crackle"

When I shut off some of my amps, without shutting off standby, any signal degrades and distortion takes over and it sounds a mess as it slowly discharges the caps.  Basically the headroom on the tubes is being reduced causing distortion.

When I shut off standby first, then shut off the power, sometimes there is a noise.  This is a little more interesting to me, because B+ has been turned off, so where is the power coming from that powers the speakers?

Is this more of what you are wondering about?  Or is it really the cereal?
Title: Re: Speaker Crackle After Power Down
Post by: plexi50 on February 12, 2009, 03:11:36 pm
When I shut off standby first, then shut off the power, sometimes there is a noise.  This is a little more interesting to me, because B+ has been turned off, so where is the power coming from that powers the speakers?

Is this more of what you are wondering about?   

Yes thats it exactly. After i shut the standby off and let it sit there is no noise

But after i shut the power switch off then about 5 seconds later i hear this crackling through the speaker as the voltage bleeds down

May be the cure is just to put in some bleeder resistors that will drain the voltage before reaching the speaker / Then maybe not

Im going to take another look at the schematic / It just hit me! There is no choke in this amp

Could that be a factor / Choke vs: Resistor in possable voltage spike?

Could a choke at shut down act as a VDC storage buffer/filter in effect bleeding VDC itself?

This is only the second amp i have heard doing this that is quiet noticable / Not a great selling feature if you know what i mean....
Title: Re: Speaker Crackle After Power Down
Post by: JimH on March 15, 2010, 06:36:52 am
Hey guys,

I wanted to bump this thread since I'm having a similar issue, except it's not crackle as much as actual guitar signal!

Is this anything I should worry about?

My amp is a 2204 clone type that I just built. It works great. I don't think there are bleeder resistors. Would that solve this issue? I should put one in anyway, so Where is the best place to install one?

Any info appreciated,

JimH
Title: Re: Speaker Crackle After Power Down
Post by: Geezer on March 16, 2010, 09:05:18 pm
I usually install a 220k/3W bleeder across the 1st filter cap.

Look at this schem, just to the right of the standby switch>>> http://www.el34world.com/Forum/index.php?action=dlattach;topic=6176.0;attach=10812
Title: Re: Speaker Crackle After Power Down
Post by: plexi50 on March 16, 2010, 09:21:35 pm
WOW! I must be getting Alltimers. I dont remember posting this thread. Febuary wasnt that long ago!
Too many Ampegs i think / Bleeder resistors will be used on my next adventure / Thanks all!
Title: Re: Speaker Crackle After Power Down
Post by: JimH on April 19, 2010, 06:27:41 pm
Man! A month since I bumped this and I'm finally getting to this. Thanks, I'm going to try this tonight.
Title: Re: Speaker Crackle After Power Down
Post by: Rich on April 19, 2010, 07:26:18 pm
I'm getting this crackling on my DR clone.  One of my tubes started making noise and in the course of tracking it down I noticed this crackling - arcing type sound after killing the power switch (standby still on).

With the power off it has to be the caps draining feeding this noise to the speakers.  I do have a choke and this speaker noise is a new experience.

Anyone have another explanation?
Title: Re: Speaker Crackle After Power Down
Post by: JimH on April 19, 2010, 10:09:17 pm
Ok. I just added a 220K 3W resistor at the first cap to ground. No change though. Fully powered on, switch to Standby and all is quiet, power off and the input signal comes through quiet, and fades.

Could it be that 220K is to high a value, so the voltage doesn't leak down quickly enough?

I'm not overly concerned about it, but I would like to get this amp "right", if anyone has any other ideas.