@devinplombier I got very useful respons from one user so far. I'm happy with that. The rest are trying to "teach" me that boutique caps are coloured and inferior to Wima caps. That is a very condescending attitude.
Do you think it is sensible to suggest purchasing two more amps to conduct experiments with, seriously??
And no, I am not interested to find out who people are and what they have done if they repeatedly disregard my wish to stick to the topic. This is a very basic skill that anyone who wishes to interact on a forum should possess. But clearly that skill is completely lacking in everyone here but johnss.
I do however agree with you that I should have asked a more general question, these 3 caps used as coupling caps rather than used in Airtight ATM300 specifically.
Now let's get back on track, please.

