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"Pop" when relay closed or open.
"Pop" when relay closed or open.
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Old 21st December 2017, 10:06 AM   #1
flacman is offline flacman  Viet Nam
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Default "Pop" when relay closed or open.

I made a delay circuit for my headamp with this scheme. However, there is "pop" in the headphone when the relay is closed or open. How to fix it?
(My DC offset circuit amplifies only about 5mV)
Thanks a lot.

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Thanks you very much for your comments.

My problem is "pop" sound when close/open relay. I have controlled relay manually (when my amplifier was stable).
I tried other types of relay, but the result is the same.

The "pop" sound loud when the relay is closed (when the headphone is connected to the amplifier) , while the relay is open, the "pop" sound is very small.

My amp is class A puss-pull, 130mA quiet current, dc offset about <5mV

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I thinks it is the reason

Quote:
Originally Posted by AndrewT View Post
are you saying that even some time after stabilising that a maual change of the isolating relays that you still hear the pop?
That would confirm that the 5mV of offset is what you are hearing.
5mV offset for a headphone amplifier is too high.
5mVac is only 36dB below 1mW into 100ohms.
a 5mV step change into 100ohms would be just as loud.
For a 95dB/mW 100ohms headphone you would hear a 5mV pop as ~ 59dB SPL.
That is too loud.
5mV offset will also pull/push the diaphragm well off centre.
Quote:
Originally Posted by HotIce View Post
If the pop is when the relay closes *and* open, then it is definitely a DC offset issue.
--
Sorry for wasting your time. (Im not mentioning from the beginning)
I'm afraid to write a lot, because my English is bad.

I will continue this topic to find more experiences of people using other popular consumer amplifiers.

I heard people say that:
- FiioA5 (psu +-11V) has not any noise when switching relay
- TrasamHa2pro (psu +-10V) has not any noise, too. But when the user replace the opamp with the Burson V5i opamp, the "pop" sound occurred.

Looking forward to your comments and experiences.
Thanks you very much!

Last edited by flacman; 1st January 2018 at 09:33 AM.
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Old 27th December 2017, 10:00 AM   #2
JensH is online now JensH  Denmark
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&quot;Pop&quot; when relay closed or open.
If the amplifier has a DC offset you will get a pop when switching the relays on or off. So you need to eliminate the DC offset of the amplifier at steady state. How this can be done cannot be seen from the schematic you provided here.
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Old 27th December 2017, 11:19 AM   #3
Samsara is offline Samsara  France
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Quote:
Originally Posted by flacman View Post
there is "pop" in the headphone when the relay is closed.
If GND of relay contact and GND of headphone output are same and closed together , this is not possible.
I think you wrong with this schematic.
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Old 27th December 2017, 11:42 AM   #4
Mooly is offline Mooly  United Kingdom
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&quot;Pop&quot; when relay closed or open.
Just to expand on the above... if the headphone amp output is truly shorted to ground (at switch on by the relay) then depending on how the feedback is configured, the amp may not be able to correctly bias to the correct operating point.
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Old 27th December 2017, 05:37 PM   #5
HotIce is offline HotIce  United States
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Hmm, the amp output shorted to ground during the bootstrap phase seems like a recipe for fried output transistors
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Old 27th December 2017, 05:48 PM   #6
globalplayer is offline globalplayer  Germany
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That ground is bad.
Rather leave open.
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Old 27th December 2017, 09:16 PM   #7
JensH is online now JensH  Denmark
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&quot;Pop&quot; when relay closed or open.
I don't see any basic problems with the circuit shown. The amp outputs are not shorted to GND. The circuit comes from this page:

Loudspeaker Protection and Muting

With the component values shown it does require a relatively high supply voltage, which may not be available in a headphone amplifier, but that is easy to change by changing component values.

But if the amplifier has an offset, even after stabilizing the DC operating points, there will still be a pop sound at turn on and off.
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Old 28th December 2017, 07:02 AM   #8
Mooly is offline Mooly  United Kingdom
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&quot;Pop&quot; when relay closed or open.
The amp outputs are shown as grounded in the off state. Post #1, right hand side of diagram.
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Old 28th December 2017, 09:20 AM   #9
JensH is online now JensH  Denmark
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&quot;Pop&quot; when relay closed or open.
As I see it, the speakers are grounded, not the amp outputs.
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Old 28th December 2017, 10:38 AM   #10
Mooly is offline Mooly  United Kingdom
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&quot;Pop&quot; when relay closed or open.
Oh yes, you are correct... my apologies for not looking closer at the earlier comments and my mis-reading the diagram.
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