/diy/ - Do It Yourself

So I just built this, I don't have a signal generator, just a phone, tablet and speakers. It is suposed to modulate the sound from the bottom diff pair with a low frequency coming in the upper ones. It *works* but if I put the sound in using a capacitor then there are loud ticks and tocks and screeching but if I bypass the capacitor it "works" but with a distorted low frequency wave (it's a triangle but gets squarier).
My question to you is, what the fuck? Don't cellphone/tablets audio outputs do not like capacitors? The ticks are periodic and of only a couple Hz.
>>1694912
It makes no diference with the exception of when you are designing important things and need to think about ESD paths and optocoupler shit.