Pro Audio Design Forum

... Condenser Microphone Distortion" PREMA IC PR2301 TruePhantom® is a high impedance phantom power supply for condenser microphones with a servo-regulated output voltage of 48V. This decreases the load for your microphone considerably. Compared with standard phantom supply circuits, TruePhantom® ...

... at the article. He is floating the frontend and then uses a 220n cap to avoid the level shifting. The floating frontend is a SSM2017 with a DC servo (470k/470n) sampling the output and then injecting correction ("balanced", by also inverting the servo output) into the input through ...

... higher SPLs is likely high in even-order. I've seen the same effect. For the input-capacitorless preamp I've pretty much decided to pursue a dual servo system the first of which would minimize gross offset at the input from current imbalance. The input itself would be the sample point and the ...

... ranging from 1KΩ to 10KΩ/leg. To permit direct comparison I used the MC preamp's 5.5 mA Ic and 1KΩ (499Ω/leg) bias network. For these test the servo was disabled extending the preamp response to DC. The gain is 61.5 dB. The test circuit is found here: https://proaudiodesignforum.com/images/png/Flat_Balanced_Input_Moving_Coil_Phono_Preamp_ZTX851_FLIP_22_Schematic.png ...

... preamp with high collector current and input transistor Hfe around 130-200. I estimate the current noise density to be about 4pA√Hz. The preamp's servo is turned of to extend response to DC. The Focusrite 2i2 is flat to around 2Hz or so and it has a noise corner around 4-5 Hz. The preamp's noise ...

... mic lines. To keep it simple I would eliminate the inductors both at the input and Rg lines and also use a capacitor in the Rgain line without any servos. Since you're using a pot for gain control having Cg keeps DC out of the wiper better than a servo. C1 in Joe's preamp (180pF) or C25 on the ...

... to an unbalanced TRS output via three different low-cut filters as shown in the diagram below. I've read through Wayne's thread about the improved servo and I prefer this one over the floating version that flies along with phantom power. However, I am not sure why I would need to servo the output ...

It looks like you'd have to servo into the input bases since one emitter has Rg in series.

Yes I looked at the 626x a few times. Most recently I didn't like the low-ish gain, no servo and, worse distortion figures on the preamp than the 1580. Thinking about it now, I could fit 2 470uF 10v cg's on a preamp card since I would only need 2 or 3 cards, 39/34 ...

... sheet says it swings to +-4v. So everything following I was thinking max swing is 8v p/p. Do I need ac coupling - C11 and C12, or does the servo on the 5171 eliminate enough dc at the output of the 1580? Figure 12 does not show any caps. https://statics.cirrus.com/pubs/appNote/an241-1.pdf ...