Pro Audio Design Forum

I lowered the value of Rin to 33K2 to give myself some additional trim range.
It varies slightly between channels but at the wiper I'm measuring about 260 mV (-9.5 dBu) for an input current of about 7.8 uA.

I saw Rt but discounted it. 8.3 uA x 49.5k is down a few dB from typical 0VU (around 0.4V) discounting the parallel junctions. Never mind... JR OK, got it. The normalized "0" is less than 0 dBu because there's a -6dB line receiver in the circuit it was taken from. The trim needs to offer ...

Wouldn't subtracting a reference 0VU current from the common emitters (Sym adj probe node) deliver a + and - voltage relative to 0VU threshold? It may need an offset subtracted to account for two pairs in parallel. JR Not sure I completely follow the question but an existing reference current sink ...

The Uno Compressor spawned an improved THAT2252 replacement which is a "0 Vbe-up" design having a 0V output when the input is at the reference current. The gain of 2 amplifiers, which square the log of the absolute value, are level-shifted down by one Vbe. If not for this level-shift, the ...

I've updated the drawing - which I'll post later - that includes the audio signal path, metering and sidechain on two sheets. For the moment I'll be pulling out all of the component designators in the drawing and reassigning them from the layout. It's a little tedious that way but it makes manual DI...

Latest schematic. I added a low frequency single-order high pass filter to the sidechain. With the values shown, the maximum frequency is about 240 Hz. Added series resistance at the Phoenix connector lowers the frequency. When fully open-circuit Fc is about 7 Hz. Jumpers at the output of the Dome f...

The units Paul and I are talking about (e.g. Neumann BSB74, Maselec MDS2) are specific to vinyl cutting and are typically used when the sibilance - or any excessive HF energy - isn't a problem in other mediums. Inverse RIAA, an acceleration-limited mechanical system, cutterhead power limits and powe...

Updated schematic 4/8/24. I added a simple Sidechain HP filter ahead of the Dome filter. https://proaudiodesignforum.com/images/jpg/Unocomp_Sidechain_Schematic_040824.jpg Though there appear to be a lot of op amps they can all be TL072. No attempt is being made to reduce component count because it's...

I've had an interest in a de-esser/sibilance controller for vinyl and have wanted to wrap my head around the BSB74. It would need to be a dedicated box.. Jakob Erland once described it as S&M engineering. With the inductor based delay line. I have the BSB74 literature. If you need anything let ...

I've had an interest in a de-esser/sibilance controller for vinyl and have wanted to wrap my head around the BSB74. It would need to be a dedicated box. I decided to take a look at using a 10K linear pot, wired in a poteniometric configuration, to control the attack-release time and see if it were s...