Pro Audio Design Forum

Note: back when I spent too much time on my bench messing with phono preamps (1970s) I discovered a phase shift issue caused by a 22uF aluminum electrolytic capacitor's internal inductance (in a gain leg in series with 360 ohms). I expect modern electrolytic capacitors are much better but maybe keep...

Sounds like a handful....

JR

IIRC the IEC proposed a real pole at 20Hz (7950 uSec) back in the 80s (?). The RIAA dismissed that suggestion and left the sub 20Hz response pretty much undefined beyond the three standard RIAA time constants (75uSev, 318uSec, 3180uSec). Back in the 80s when I was trying to escape from the audiophil...

One thing I'm going to change is the gain control of the capacitance multiplier. The pot is too cramped at slow rate settings and most people would want stepped controls anyway. Switching input resistors on the inverting stage to use a 6 position rotary switch with 600, 480, 360, 240, 120 and 60 dB...

Over the years, often working with inferior gain elements, at least part of the effort was to mitigate sudden gain change artifacts. The pan between dry and full gating helped coax out subtle flaws. The problem was flaws heard with complex (music) waveforms that weren't heard with standard test sign...

Back when I was seriously designing dynamics processing circuits a homemade tool that I found useful was a variable tone burst circuit. Sorry if I've shared this before, the drawing was done in 2007 and I designed this back in the 70s/80s. The bottom section generates adjustable on time and off time...

Getting a little esoteric is there any risk of making compression too clean (i.e. having no sound signature)? Back in the 80s when I was tweaking companding NR my goal was to be as transparent as possible. Modern compression customers may have preconceived notions about what compression "should...

Lower distortion should always be good.

Does it impact the waveform distortion caused by fast release on pure low frequency tones?

While it is unclear that this mechanism is an audible problem with real world complex waveforms.

JR

yup... the "boing" is the odd overload artifact I was referring to.

JR

Springs have odd overload characteristics, I'm not sure how much pre-emphasis they would tolerate.

Companding NR has difficulty with the spring reverb tail altering the expansion decode accuracy.

JR