I've been tinkering with audio gear mods for years. My current modding project (a Sony QS-series SACD player) has two electrolytics in the signal path, one after the DAC I/U-converter stage, and one after the differential opamp stage. I started thinking on the possibility to remove the signal path electrolytics altogether.
So, how much DC offset is too much, so that you would not remove the signal path electrolytic capacitors? 1 mV or what?
So, how much DC offset is too much, so that you would not remove the signal path electrolytic capacitors? 1 mV or what?
I'd estimate 100mV would be tops for a power amp output so that becomes 5mV max at the input assuming a gain of 26dB which is fairly typical for a poweramp.
Correct. But these caps are there for a reason. Removing them is like removing fuses.
In case something goes wrong in the player, you can guess what will happen...
Hugo
Depends on the load - for a headphone amp its a lot less than for speakers, for instance, as the driver in a headphone is more sensitive, and has much less excursion.
Hi, I hade a amplifier from an Norwegian brand. It sound ok, but one day I was seeing the woofer was springing out when I turned on the amp. I talk to the maker of the amp, he made me measure the offset. 1500mV ( 1,5V ) left and 2200mV ( 2,2V ) right. The woofer moved maybe 5mm, did not measure it. Played with it for many weeks. Did not damage the Seas Excels, he tryed to fix it but never got it under 800mV. So I left it with him and got money back. As people say onder 100mV ok but try for less then 50mv.
AC signals like AC coupling.
So pretty easy to ignore capacitor magic theory.
Not interested in DC in the system signal chain.
But the common low noise Fet opamps used for Audio
usually have enough compensation inside for 2 to 3mV
DC offset on the output no matter how poor the circuit is.
Not necessarily poor , but many lack external circuits
that follow basic op amp design and dont include
circuits for DC offset compensation. Because the opamp
used will zing away with normal offset.
Some citations include magical opamp upgrades
and if the upgrade needs offset compensation.
Then wont happen because board doesnt include them.
Ac coupled non inverting not as much of a issue as
Inverting stages, which usually need DC compensation.
But often ignored since common fet opamps for audio
maintain offset internally.
So pretty easy to ignore capacitor magic theory.
Not interested in DC in the system signal chain.
But the common low noise Fet opamps used for Audio
usually have enough compensation inside for 2 to 3mV
DC offset on the output no matter how poor the circuit is.
Not necessarily poor , but many lack external circuits
that follow basic op amp design and dont include
circuits for DC offset compensation. Because the opamp
used will zing away with normal offset.
Some citations include magical opamp upgrades
and if the upgrade needs offset compensation.
Then wont happen because board doesnt include them.
Ac coupled non inverting not as much of a issue as
Inverting stages, which usually need DC compensation.
But often ignored since common fet opamps for audio
maintain offset internally.
Power amplifier 15 to 25 mV is acceaptable.
50 to 100mV likely means a issue or semiconductors
or passive components is drifting.
Of course is debatable if the original circuit has
accepted 100mV.
Utterly basic current mirrors / current sources
or even simple amplifier designs. Should produce
10 to 15mV max. And easily easily can be designed for
3 mV or less.
Matter of opinion, my book over 15mV is garbage.
Because its so so simple to be down to 1 to 3mV for a power amp.
50 to 100mV likely means a issue or semiconductors
or passive components is drifting.
Of course is debatable if the original circuit has
accepted 100mV.
Utterly basic current mirrors / current sources
or even simple amplifier designs. Should produce
10 to 15mV max. And easily easily can be designed for
3 mV or less.
Matter of opinion, my book over 15mV is garbage.
Because its so so simple to be down to 1 to 3mV for a power amp.