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There will not be a pre-set level for any sound card. It will depend upon the individual card as the tilt on identical cards can vary and also the transmitter you are connecting to will make a difference as not all transmitters are flat.
This needs an oscilloscope and the ability to modify the card to suit. The “Standard” outout can be viewed on the oscilloscope, but then the circuit needs to be modified, possibly by removing components, changing their values or cutting tracks in the circuitry.
I’ll see if I can find some “tilt correction for dummies” instructions, but it still comes down to trial and error.
I am still trying to find something we can all look to as the definitive guide.
Most manufacturers will produce documentation, but it is always skewed towards their particular product.
I want a instructions which embrace at least most quality sound card providers.I had the opportunity to test several sound cards with BA1. As a reference transmitter I used the RVR link of the PTRL NV series, with very good phase and amplitude response.
The results are as follows:
UMC HD 202
perfect square 60Hz: tilt BA1 = 0
MPX response:
+ 0.3dB at 30Hz; -0.8dB at 57KHz
+/- 0.3dB from 30Hz to 45KHzDisadvantages:
– nasty noise that starts to grow exponentially from 60 + KHz (visible only with an oscilloscope or spectrum analyzer)
-very low main out levelM-Audio Air 192/4
perfect square 60Hz: tilt BA1 = 8
MPX response:
+ 0.5dB at 30Hz; -0.2dB at 57KHz
+/- 0.2dB from 60Hz to 60KHzDisadvantages:
-unstable work with older computers (core2duo). The sound is intermittent.Presonus studio c28
perfect square 60Hz: tilt BA1 = 15
perfest square 60Hz (HP out) = 4
MPX response:
-0.2dB at 30Hz; -1.8dB at 57KHz
+/- 0.5dB from 60Hz to 30KHz
Disadvantages:
-Significant rolloff at 57KHz
-Audible audio echo loop if card input and headphone output are usedscarllett 2i2 3gn
perfect square 60Hz: tilt BA1 = 7
MPX response:
-0.2dB at 30Hz; -1.1dB at 57KHz
+/- 0.5dB from 60Hz to 35KHz
Disadvantages:
-ground loop PC problems (audio interference)
-a nasty noise that starts growing exponentially from 60 + KHz identical to the con Behringer cardMy choice: If you know how to make a sharp low pass damping filter 60KHZ +, a good choice is the Behringer 202 or 404, primarily because of the price. It should be noted that the line in inputs are slightly lighter, so the eq input parameters need to be further adjusted.
Also the output from this card is quite low, so with individual broadcast equipment it may not be possible to achieve 75k deviations without additional preamp. The headphone output can serve as an improvisation for this purpose.Remember to use the Headphone Amp output to feed your transmitter MPX input. on the transmitters i’ve set up the value is always beteen 0 and 10 (tilt adjustment). To calibrate your transmitter you will need a modulation monitor. set the 400hz test tone and adjust until it shows 100% of modulation / 75khz carrier index. Then try the Square Wave test tone. if modulation go over 100% with this, you will need to do more adjustments. First put the sine wave test tone and go put 30hz. withe the PEQ you will need to make the frequency response the same from 30hz to 100hz. then do the square wave calibration another time and play with the Tilt compensation slider until you get 100% of modulation again. If you have a oscilloscope connected to the MPX Output of the modulation monitor it will be extremely easy to calibrate.
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