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"Pop" when relay closed or open.
"Pop" when relay closed or open.
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Old 31st December 2017, 08:10 AM   #21
Samsara is offline Samsara  France
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Ok. You have to check the delay and try to adjust it, means modify it.
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Old 31st December 2017, 09:49 AM   #22
dotneck335 is offline dotneck335  United States
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Did you try writing to Rod Elliott (the designer of your circuit) and see what he has to say?
Contacting ESP
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Old 31st December 2017, 10:27 AM   #23
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Mooly View Post
Please read ALL the posts.

Thanks
Sometimes one responds to all the posts read from the beginning to where one has reached.
Later posts get read AFTER the reply has been posted.
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Old 31st December 2017, 10:31 AM   #24
AndrewT is offline AndrewT  Scotland
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Flacman.
Is the amplifier single ended, or single polarity supply?

If so then the output must be given time to stabilise.
All the capacitors need time to charge to their fully operational state.
This can take more than 5 times the RC time constants and maybe for some, you may have to wait till 20 times the RC time constant has expired.

When the headphones are not connected, can the various capacitors actually charge to their final voltages?
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Old 31st December 2017, 10:37 AM   #25
AndrewT is offline AndrewT  Scotland
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R5 is quite high in value.

The switching transistor (Q3) should be in saturated mode (hFE~10) when ON, i.e. base current ~ 10% of emitter current.
What current do the relays draw when ON?
Divide by 10.
That's the lowest current that should flow through the base.
You could even go to divide by 8, that would get you to an hFE of ~9

The 1k (R4) will pass 0.8mA when the Vbe is @ 0.8V (which is a typical saturated Vbe)
R5 has to pass the saturated base current PLUS that 0.8mA

If the relays draw 20mA, then the base current of Q3 would be around 2mA.
R5 current will be around 2.8mA
The voltage drop will be around 22k*2.8mA = 61.6Vdrop
What voltage is available to drive Q2 via R4 & R5?
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Last edited by AndrewT; 31st December 2017 at 10:47 AM.
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Old 31st December 2017, 11:03 AM   #26
flacman is offline flacman  Viet Nam
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Quote:
Originally Posted by AndrewT View Post
Flacman.
Is the amplifier single ended, or single polarity supply?

If so then the output must be given time to stabilise.
All the capacitors need time to charge to their fully operational state.
This can take more than 5 times the RC time constants and maybe for some, you may have to wait till 20 times the RC time constant has expired.

When the headphones are not connected, can the various capacitors actually charge to their final voltages?
Thanks you.
My problem is "pop" sound when close/open relay. I have controlled relay manually (when my amplifier was stable).
(I'm testing it before connecting it to DC detection circuit and muting button)

I tried other types of relay, but the result is the same.

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

ps: Sorry for not mentioning from the beginning.

Last edited by flacman; 31st December 2017 at 11:13 AM.
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Old 31st December 2017, 11:14 AM   #27
AndrewT is offline AndrewT  Scotland
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Quote:
my amp is class A .......... dc offset about <5mV
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.
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Last edited by AndrewT; 31st December 2017 at 11:16 AM.
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Old 31st December 2017, 11:18 AM   #28
AndrewT is offline AndrewT  Scotland
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Quote:
I tried other types of relay, but the result is the same.
changing the 24V relays to other 24V types does not help.
You should have measured your relays before fitting to check they were compatible with the switching circuit.
What is your supply voltage?

If your 24V relays draw only 9mA, or less each, then you would find that R5 @ 22k would be suitable.
Did you measure them?
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Old 31st December 2017, 12:38 PM   #29
flacman is offline flacman  Viet Nam
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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.
Yep. But i think 5mV dc offset is low. What is dc offset of other class AB or opamp consumer headamp?

Quote:
If your 24V relays draw only 9mA, or less each, then you would find that R5 @ 22k would be suitable.
Did you measure them?
I use 10v source with 5v Takamisawa relay (165ohm coil). I set 35mA for it's coil.
I used common source and gnd with my amplifier

Last edited by flacman; 31st December 2017 at 12:40 PM.
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Old 31st December 2017, 01:41 PM   #30
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by flacman View Post
.................

I use 10v source with 5v Takamisawa relay (165ohm coil). I set 35mA for it's coil.
I used common source and gnd with my amplifier
Then R5=22k is definitely not suitable.
You would need ~94V at the top of R5 to get sufficient base current to saturate Q3.
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