Pro Audio Design Forum

As a junior (read ignorant) technician I have explosively deconstructed capacitors by plugging a low voltage electrolytic into a mains outlet... Sounded like a .22 going off, if you could hear it over the older techs laughing at me... But on that same job I blew up a few in circuit... one that is et...

The discrete output mute fets could be damaged by simple voltage spikes. If using a N channel mute JFET with gate sitting at minus unregulated (unmuted) it won't take the full +48 added on top of say -24 to exceed its Vgs max and release it's magic smoke, (it's only a technicality that 48v is attach...

Not sure I understand the question... Think of 0V (unity gain) as the starting point or home base for current ratioing VCAs. OV=0dB.. +X mV= +Y dB and -X mV = -Y dB (reversed direction from - EC port). From looking at that chart you posted the VCA gain law is +6 mV/dB, so if you want +10dB of gain y...

In fact when wireless microphones were new, the engineers who designed them didn't account for phantom blocking caps. Since these wireless receivers were actually plugged into mic inputs on purpose, and most value consoles/mixers use global phantom power switches so you can't turn off the phantom on...

I've been taking capacitors apart longer than I can remember.. It used to be normal for axial caps that the - lead was always welded to the metal can, and the positive terminal was attached to an insulated nipple.. In typical radials, the metal can is not physically attached to either lead. I recall...

?? I was talking input and output... In general outputs require diode clamps to rails just like inputs. In fact one pretty common failure mode is output mute FETs if they don't have protection diode clamps. Again probably from static hits... Of course I don't know what THAT have built in. I recall y...

Wayne's paper seems to be focused on the energy stored up in the phantom blocking capacitors. For line level inputs in my experience the common faults come from static hits or mains power (at least in live sound reinforcement). The diode clamps can do a good job absorbing static hits, but 120-240V m...

The effective CV is the total of voltages applied to + and - CV pins simply added together, with the sign of the CV pin factored in. So counting the sign, if we send +18mV to both control pins it becomes 18-18 or 0V for unity gain. OTOH +18mV on the + pin and -18mV on the - pin, is 18 - (-18) or 18 ...

AFAIK studio equipment designers figured out that Absolute Polarity was worth preserving back in the early '80s, so gear made since then should be reliably polarity correct.. DIY or esoteric gear not so much... Prior to that it was so bad I put a polarity switch on one of my phono preamps to correct...

Interesting... in recording studio they should have pretty good handle on polarity... perhaps downstream feeds?

JR