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RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → Maximum safe voltage for line inputs?
Obviously the line inputs can handle up to +24dBu before clipping, but I'm curious how much higher voltage they can handle without risk of damage.
The ADI-2 Pro's analog input circuitry has two overload protection stages. The second one protects the ADC from too high voltage when switching between the Ref Levels. The first one is at the input, directly in front of the first opamp, limiting the peak input voltage to +-15.6 V. That means everything above 11.03V rms or +23.07 dBu unbalanced, and +29.07 dBu balanced is clipped at that level.
The protection is designed to work up until 21 Vrms or 60 Vpp or 28.7 dBu unbalanced and 34.7 dBu balanced. Above that expect some smoke signs coming out of the unit...
Obviously the line inputs can handle up to +24dBu before clipping, but I'm curious how much higher voltage they can handle without risk of damage.
May I ask for what use case ? In which scenario you would require more ?
The ADI-2 Pro's analog input circuitry has two overload protection stages. The second one protects the ADC from too high voltage when switching between the Ref Levels. The first one is at the input, directly in front of the first opamp, limiting the peak input voltage to +-15.6 V. That means everything above 11.03V rms or +23.07 dBu unbalanced, and +29.07 dBu balanced is clipped at that level.
The protection is designed to work up until 21 Vrms or 60 Vpp or 28.7 dBu unbalanced and 34.7 dBu balanced. Above that expect some smoke signs coming out of the unit...
Thank you Mathias, much appreciated!
May I ask for what use case ? In which scenario you would require more ?
I want to record the output from various standalone headphone amplifiers for analysis purposes. Most of them won't produce more than +24dBu, but I was curious how much safety margin I had in case of incorrect specs or any other form of error on my part. A safer solution would be to put something like Linear Audio's Autoranger in front of the ADC input, but I don't have access to one at present.
Unfortunately the Autoranger would affect (decrease) noise measurements with the ADI. For your application I would recommend to use a simple, fixed 10 dB attenuator when required. This makes it easy to re-calculate the measured values. It is also very easy to build and use. Passive voltage divider made of two resistors, for example 2.0 k Ohms (serial) and 1 k Ohms (+ input pin to ground), resulting in -10 dB attenuation (including the ADI's input impedance of 10 K Ohms). This would be the unbalanced version, for balanced measurements change 1 kOhms to 2 kOhms and connect it between + and - input pins, with one serial resistor of 2 k Ohm on each input pin.
MC wrote:The ADI-2 Pro's analog input circuitry has two overload protection stages. The second one protects the ADC from too high voltage when switching between the Ref Levels. The first one is at the input, directly in front of the first opamp, limiting the peak input voltage to +-15.6 V. That means everything above 11.03V rms or +23.07 dBu unbalanced, and +29.07 dBu balanced is clipped at that level.
The protection is designed to work up until 21 Vrms or 60 Vpp or 28.7 dBu unbalanced and 34.7 dBu balanced. Above that expect some smoke signs coming out of the unit...
Thank you Mathias, much appreciated!
ramses wrote:May I ask for what use case ? In which scenario you would require more ?
I want to record the output from various standalone headphone amplifiers for analysis purposes. Most of them won't produce more than +24dBu, but I was curious how much safety margin I had in case of incorrect specs or any other form of error on my part. A safer solution would be to put something like Linear Audio's Autoranger in front of the ADC input, but I don't have access to one at present.
Bucknaked: Are you going to publish it for the public? Would love to see the results 
(sorry for off-topic)
Unfortunately the Autoranger would affect (decrease) noise measurements with the ADI. [...]
Hello Matthias,
Sorry to bother you; but is there any update on this regarding the new L|A Autoranger MK II?
Thank you! Your expertise is always much appreciated.
Best regards
I am currently checking it.
That's good news!
I'm sure you must be busy with more important things; but it would be nice to get an update once testing is done, as I'm waiting to get a MK II version built for use with both my ADI-2 Pro ('FS' and non-FS) - if all turns out to be fine.
Have a great weekend!
I checked the AR II and am very happy with the improvements over the first version of the AR. THD+N is near -120 dB at higher levels, so the unit is basically transparent. It is an ideal front-end to measure higher output levels, for example from power amps, with any sound card.
But even at mid and lower levels the AR II delivers. Its signal to noise ratio varies between 110 dB and 126 dB in auto mode with 2V output (Jan made a higher voltage version for testing, max output level with this one is +10 dBu, the ADI would be set to +13 dBu).
Further discussion of this unit should be done in the diy forum, or with Jan directly.
Thank you very much, Matthias, for your continuous support!
I'm glad the 'AR II' is suitable for use with the ADI-2 Pro FS, for example, and I'm already in contact with Jan for a while now.
Have a great Sunday!
To conclude this topic and in case anyone else is interested in using the ADI-2 Pro (FS) series + 'AR II' for amplifier measurements:
The "Measurement Of Amplifiers Rig" (MOAR): Standard Tests, Loopback results, and the AMOAR Score.
What a great opportunity!
RME User Forum → ADI-2 & 2/4 Pro series, ADI-2 DAC series → Maximum safe voltage for line inputs?
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