Pro Audio Design Forum

It seems we discussed this before. I've black balled some cap series because of noise only when phantom on. IIRC we speculated that maybe they would form in and quiet down over time. Does your I/'F noise get any better after letting the cap run energized for a while (overnight)? Well, it seems to, ...

Another Smoking Gun I modified the "DC-Coupled Input Capacitorless Preamp" to be a conventional preamp by adding 47 uF/63V coupling capacitors. Otherwise the circuit is identical to the Input Capacitorless version. I turned off the common mode servo: The supplies no longer float since it'...

I made a couple of recordings. I think this thing is pretty quiet. The first is the sound of a 22 pF monolithic ceramic capacitor being dropped from workbench height at 75 dB gain using the phantom-powered AT-3525. Think the Sprint pin drop commercial. Beware that it reaches full-scale. http://www....

I have another mic, a LDC that is bigger than the 2535 that I am going to send Wayne. Don't know if it is SS or xfmr out though. I am sending is as ransom/bribe for the Leader lMV185A Wayne sent me Things have been absolutely nuts here, and I meant to get this out a few weeks ago. Thanks Roger! I'm...

My thinking is that mics that have internal transformers, and thus a low DC resistance between pins 2 and 3, are more likely to show this effect in common mode since the winding equalizes the LF currents between legs. Also, these mics may tap phantom off of their output transformer center tap as wel...

Ironically the ECM8000 doesn't do this. Though it does pull unequal static current the dynamic current looks fairly constant. The Audio Technica AT3525 does have significant CM "wiggles." It has a low DC resistance from pins 2 to 3 and appears to have a transformer-coupled output. I suspec...

I've rebuilt the prototype and have a bunch of updates to provide soon but stumbled upon an interesting thing about microphones while poking around this circuit with the 'scope: Some phantom-powered mics have a significant low frequency common mode component due to internal dynamic signal currents....

"The 555 Timer Was Just The Beginning For Hans Camenzind," EDN Article, November 28, 2012. http://electronicdesign.com/article/analog-and-mixed-signal/555-timer-beginning-hans-camenzind-74715?NL=ED-04&Issue=ED-04_20121203_ED-04_72 http://electronicdesign.com/content/content/74715/7471...

I rebuilt the DC-Coupled Input Capacitorless Preamp with a THAT1570. The output is recovered by the AC-Coupled high impedance line amp followed by a double-balanced differential amp. All I can say is wow. This thing rocks. Here is spectrogram of the noise floor with the circuit built on an open pro...

Audio Circuits Using the NE5532, NE5533 and NE5534, Philips AN142, 1984. Just found a copy of this online and thought it needed to be in documents. There's an interesting discussion on the 5532s input clamp diodes I had forgotten about. https://www.ka-electronics.com/images/pdf/NE5532_NE5534_Audio_...