User's Manual

User’s Guide ADI-2 Pro FS - v 2.5

For the technician:

• In many measurement applications the generator level is intentionally set below 0 dBFS,

when measuring the frequency response and also when measuring THD (-1 or -3 dBFS).

• Test signals with a frequency close to the DAC's filter slope often cause aliasing effects and

other unwanted intermodulation products. For clean measurements at such high frequen-

cies levels are often reduced to -10 dBFS.

• If such high frequencies are used for measurements at all. One typical frequency for stan-

dard measurements is 10 kHz, which is below the digital filter's influence and therefore not

affected, even when applying full 0 dBFS.

For all these reasons usual audio measurements can mostly be done without running into accu-

racy problems caused by the added filter.

But there also is a simple way to completely rule out any possible issue: Just make sure the

digital output level is not higher than -4 dBFS, either by setting the generator software, or the

volume of the ADI-2 Pro accordingly. With this added headroom even the most artificial and

unrealistic test signals pass all possible measurement applications at 384 kHz sample rate.

To compensate the introduced mismatch of output level and input reference level when using

the ADI-2 Pro in a DA/AD loop: raise the input level via I/O - Analog Input - Trim Gain by said 4

dB.

Examples of worst case headrooms:

HpW FFR (multisine): do not exceed -1 dBFS. Measuring up to 20 kHz: do not exceed -0.03 dB.

Up to 36 kHz: -0.1 dB. Up to 69 kHz: -0.5 dB. Up to 84 kHz: -1 dB. Up to 100 kHz: -2 dB.

Please be reminded that all the above only applies to 384 kHz measurement applications. For

all other uses and sample rates these notes are not relevant.

34.19 Operation in the Hi-Fi Environment

The ADI-2 Pro is a gem not only with professional applications but also when using it at home

with the stereo system. While users working in the studio environment know everything about

reference levels and all kinds of connectors, others get confused by the missing RCA sockets

and have doubts that the unit can be used with Hi-Fi at all - and how to connect it then. This

chapter answers these questions

How do I connect the device to my other devices that have only RCA?

By a simple adapter mono 6.35 mm to RCA (also called Phono and

Cinch). The adapters are plugged into the rear inputs and outputs -

done. Now the existing RCA cables can be used with the ADI-2 Pro.

The adapters can stay plugged in all time.

Cables with mono 6.35 mm on one side and RCA on the other also exist, and work perfectly.

The plug-in adapter solution has the advantage that the user can use his preferred RCA cables.