Matching line levels for DAC and Amp

[swampfire]

I have an AudioEngine D1 with a maximum rating of 2V on it RCA outputs (volume knob turned all the way up). Tomorrow, I have a Dayton Audio APA150 arriving, and its input sensitivity is 1V. I would like to make my day-to-day volume adjustments on the amplifier, since the DAC will be tucked away on the back of the rack. Should I just set the D1’s volume knob to halfway?

I’m also wondering how to find “halfway”, without an oscilloscope. I was thinking I would just feed a sine wave to the D1, crank the volume knob, and measure the A/C output voltage, then back off the knob until I’m at half that value. Is that a reasonable approach?

 

[staticV3]

I have an AudioEngine D1 with a maximum rating of 2V on it RCA outputs (volume knob turned all the way up). Tomorrow, I have a Dayton Audio APA150 arriving, and its input sensitivity is 1V. I would like to make my day-to-day volume adjustments on the amplifier, since the DAC will be tucked away on the back of the rack. Should I just set the D1’s volume knob to halfway?

I’m also wondering how to find “halfway”, without an oscilloscope. I was thinking I would just feed a sine wave to the D1, crank the volume knob, and measure the A/C output voltage, then back off the knob until I’m at half that value. Is that a reasonable approach?

Just use a multimeter to measure the RMS AC voltage of your D1 playing a sine wave at -0dBFS. Even cheap ones will do the job.
Then turn the volume knob until you have 1Vrms.
Setting the knob to halfway to arrive at half the voltage is not a valid approach unfortunately.

 

[mansr]

Just use a multimeter to measure the RMS AC voltage of your D1 playing a sine wave at -0dBFS. Even cheap ones will do the job.

True, but use a sine wave of no more than 100 Hz. The AC voltage function on most multimeters is only intended for 50/60 Hz mains frequency and loses accuracy quickly at higher frequencies.

 

[DVDdoug]

Setting the knob to halfway to arrive at half the voltage is not a valid approach unfortunately.

Right... Our hearing is logarithmic (or "proportional") so volume control pots are audio tapered rather than linear to work better with human hearing.

For example, going from 10% to 20% is double* but going from the same 10% increase from 90% to 100% is barely noticeable. Audio taper pots make it sound more linear.


* A factor of two is a 6dB change but it doesn't sound "twice as loud" (or half as loud).

 

[swampfire]

Just use a multimeter to measure the RMS AC voltage of your D1 playing a sine wave at -0dBFS. Even cheap ones will do the job.
Then turn the volume knob until you have 1Vrms.
Setting the knob to halfway to arrive at half the voltage is not a valid approach unfortunately.

I played this 60Hz 0dB tone through my Airport Express:
(EDIT: sorry about the huge preview)

With the volume knob maxed out on the D1, my multimeter reads .605V, which is around .85V peak. So I guess as long as I’m using the Airport Express as the source, I can just leave the D1 at max.

 

[staticV3]

I played this 60Hz 0dB tone through my Airport Express:
(EDIT: sorry about the huge preview)

With the volume knob maxed out on the D1, my multimeter reads .605V, which is around .85V peak. So I guess as long as I’m using the Airport Express as the source, I can just leave the D1 at max.

The Audioengine D1 is rated at 2.0Vrms though, so something isn't right here.

 

[swampfire]

The Audioengine D1 is rated at 2.0Vrms though, so something isn't right here.

Yeah. I just switched to my old AppleTV (with optical output), and my meter is now reading a solid 2.0V AC (~RMS).

Should my target voltage be 1V RMS (i.e. what the MM shows), or .707V which would correspond to 1V peak?

As an aside…I went back and forth a few times, making sure that my iPhone’s “volume” was at maximum each time. The Airport Express consistently gave me .6V, and the A1469 AppleTV consistently gave me 2.0V. I think the Airport Express (gen 1) is going into the trash…

 

[swampfire]

Just to tie this all up…I received the Dayton APA-100 amp today. I connected my Airport Express Gen 2, which puts out 2VRMS. With the volume at maximum on my iPhone, I slowly ramped up the volume on the amp. Distortion kicked in when I got to about the 10:00 position, so I backed it off slightly. It was a decently loud and clean 40W, and I probably could have lived with it, especially in an office situation. But I realized that there’s no headroom for loud parties, with arcade games on. I also missed my Yamaha AVR’s tone controls, so it’s going back into duty,

The takeaway is that it’s fine to send a full 2V RMS input signal to the Dayton Audio APA-150, but you’ll hit distortion/clipping once you reach 40W of output.

 

[staticV3]

Just to tie this all up…I received the Dayton APA-100 amp today. I connected my Airport Express Gen 2, which puts out 2VRMS. With the volume at maximum on my iPhone, I slowly ramped up the volume on the amp. Distortion kicked in when I got to about the 10:00 position, so I backed it off slightly. It was a decently loud and clean 40W, and I probably could have lived with it, especially in an office situation. But I realized that there’s no headroom for loud parties, with arcade games on. I also missed my Yamaha AVR’s tone controls, so it’s going back into duty,

The takeaway is that it’s fine to send a full 2V RMS input signal to the Dayton Audio APA-150, but you’ll hit distortion/clipping once you reach 40W of output.

Do you think you could measure the voltage point at which distortion kicks in? Just to see how reliable Dayton's input sensitivity spec is.

 

[swampfire]

Do you think you could measure the voltage point at which distortion kicks in? Just to see how reliable Dayton's input sensitivity spec is.

Good idea, but unfortunately I already packed it up to send it back. I’m going to use the cash to buy my own oscilloscope. I’ll check the site here for recommendations.