Amek Angela Frequency Response

Why would you want bipolar caps? These are two electrolytics in series. This doubles most parasitics and increases price. If you want to get anal about it then measure DC across all coupling caps under all gain conditions to see if the original orientation is right. If an electrolytic has the wrong orientation then just use it the other direction.

jensenmann said:

... If you want to get anal about it then measure DC across all coupling caps under all gain conditions to see if the original orientation is right. If an electrolytic has the wrong orientation then just use it the other direction.

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I think this is a little bit more time consuming than using bipolars.... and without any DC-(Bias) a "normal" electrolytic will be wrongly polarized every half cycle of an AC-Signal.

Thank you all for your comments, explanations and suggestions.
After reading Ian and John Roberts comments I convinced that there's no actual reason to increase the values of the original design.
Also bipolar caps / MLCC  caps will cost me too much money...
I think I'll stick to the original values and order those capacitors:

https://www.mouser.co.il/ProjectManager/ProjectDetail.aspx?State=EDIT&ProjectGUID=09b67f0f-96c7-4e1b-be4b-f9be36a19a46

I'm using this mixer in a home studio that not working 24/7 so I believe that recapping the board with those capacitors will let it works like it should for a long time in reasonable price.

analogguru said:

I think this is a little bit more time consuming than using bipolars.... and without any DC-(Bias) a "normal" electrolytic will be wrongly polarized every half cycle of an AC-Signal.

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Well, one of the two electrolytics in a non polar electrolytic will always be wrongly biased, no matter which it´s surrounded by.

analogguru said:

I think this is a little bit more time consuming than using bipolars.... and without any DC-(Bias) a "normal" electrolytic will be wrongly polarized every half cycle of an AC-Signal.

Click to expand...

A correctly sized coupling capacitor will have a very small voltage across it at ALL points in the waveform. That's how capacitors work.

Cheers

Ian

I received the new caps from Mouser and finished the first channel, here's comparison between the re-caped card:


To a channel with the old caps:

The frequency response has significantly improved as well as the channel's overall volume.

That looks much better.

Cheers

Ian

for the win.....

JR

analogguru said:

But if lifetime is so important you could also use 100uF MLCC, they should last forever.

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100uF MLCC - would be interested to see source for those ?

But yes - electrolytic specs' are one of the most misunderstood things for people who just take datasheet values at face value.
eg - not realising that at end of lifetime  may be defined as having half of nominal capacitance.

MLCC in high values (10u+) tend to fail short after a while. Don't ask how I know.  :

And they are unsuitable for most audio, as capacitance is heavily voltage dependent - thus distorting at cut-off

/Jakob E.