Safe line level for consumer preamp or integrated amp

[mike_k]

Hi.

I use simple USB audio interface (besides connecting guitar and headphones) to output "line-level" audio to the integrated amplifier. I wonder is it safe to turn the volume all the way up on the source if there is no noticeable distortion out of the amp.

Interface (soundcard) is Behringer Euphoria UMC202HD, manual: https://media.music-group.com/media/PLM/data/docs/P0BJZ/UMC404HD_UMC204HD_UMC202HD_UMC22_UM2_QSG_WW.pdf
Amplifier is Onkyo A-9010, manual: http://www.eu.onkyo.com/downloads/2/7/8/9/9/ONKYO_A-9010_datasheet_EN.pdf

Manuals say:
- the interface output is rated as "maximum +3dBu" (~ 1.1V RMS).
- the amplifier input sensivity/impedance is "150 mV/100 kΩ" (~ -14.25dBu).

I don't hear any distortion/clipping briefly trying to maximize the volume on the source and not turning amp attenuator all the way up at the same time. I don't need maximum power out in my room, so I can leave the source knob on 1/3 or 1/2 level and hardly hit the 1/2 mark on the amp. But as I assume there is bit worse SNR in this case, I still want to know how to tell what the safe level is. It might happen that the amp is highly tolerant to the high input levels... but who knows.

P.S.
The other idea I've had was buying just the power amp and connecting the audio interface directly to it (especially if it has so high output level), but that is another topic.

 

[WaynePflughaupt]

There is no “safety” issue with high line level signals. The worst thing that can happen is overloading the inputs of the amplifier, which will cause distortion.

Regards,
Wayne A. Pflughaupt

 

[TLS Guy]

Hi.

I use simple USB audio interface (besides connecting guitar and headphones) to output "line-level" audio to the integrated amplifier. I wonder is it safe to turn the volume all the way up on the source if there is no noticeable distortion out of the amp.

Interface (soundcard) is Behringer Euphoria UMC202HD, manual: https://media.music-group.com/media/PLM/data/docs/P0BJZ/UMC404HD_UMC204HD_UMC202HD_UMC22_UM2_QSG_WW.pdf
Amplifier is Onkyo A-9010, manual: http://www.eu.onkyo.com/downloads/2/7/8/9/9/ONKYO_A-9010_datasheet_EN.pdf

Manuals say:
- the interface output is rated as "maximum +3dBu" (~ 1.1V RMS).
- the amplifier input sensivity/impedance is "150 mV/100 kΩ" (~ -14.25dBu).

I don't hear any distortion/clipping briefly trying to maximize the volume on the source and not turning amp attenuator all the way up at the same time. I don't need maximum power out in my room, so I can leave the source knob on 1/3 or 1/2 level and hardly hit the 1/2 mark on the amp. But as I assume there is bit worse SNR in this case, I still want to know how to tell what the safe level is. It might happen that the amp is highly tolerant to the high input levels... but who knows.

P.S.
The other idea I've had was buying just the power amp and connecting the audio interface directly to it (especially if it has so high output level), but that is another topic.

So 150 mv is -14.5 db. So you can increase voltage 5.3 times before clipping the input is 0.8 volts.

So your Onkyo is slightly more sensitive than a typical line input, which in the range of 1 to 2 volts.

So you need to be careful as your unit has limited head room. Your interface has a maximum output of 2.2 volts. So you need to keep your interface 4 to 5db below maximum, for some wiggle room.

 

[TLS Guy]

There is no “safety” issue with high line level signals. The worst thing that can happen is overloading the inputs of the amplifier, which will cause distortion.

Regards,
Wayne A. Pflughaupt

Overloading OP amp chips can also blow them up.

 

[mike_k]

So 150 mv is -14.5 db. So you can increase voltage 5.3 times before clipping the input is 0.8 volts.

I see that 0.150 * 5.3 = 0.8, but where from those 0.8V came from?

So your Onkyo is slightly more sensitive than a typical line input, which in the range of 1 to 2 volts.

150mv VS 1-2V is rather big difference, isn't it?

So you need to be careful as your unit has limited head room. Your interface has a maximum output of 2.2 volts. So you need to keep your interface 4 to 5db below maximum, for some wiggle room.

You mean, limiting the output voltage of the interface to be ~1.25V? That makes sense, but I'll have to measure this somehow or compare with some different source that is known to be within the reasonable limit.

 

[TLS Guy]

I see that 0.150 * 5.3 = 0.8, but where from those 0.8V came from?

150mv VS 1-2V is rather big difference, isn't it?

You mean, limiting the output voltage of the interface to be ~1.25V? That makes sense, but I'll have to measure this somehow or compare with some different source that is known to be within the reasonable limit.

The 0.8 volts comes from your interface.

According to specs that is the maximum input for your Onkyo.

If you are worried about over load, then purchase to make 4 to 6 db in line attenuators ahead of the Onkyo.