Amplifier Input Sensitivity (Bluetooth DAC w/ Sansui au-517)

[LakeWyles]

I know this topic has been hashed and rehashed. I still very much a newbie. I recently purchased a Sansui au-517, which has a line level input sensitivity of 150 mV. I also purchased an Ifi Zen Blue (bluetooth DAC), which I was planning to hook to the Aux input of the 517. The Zen Blue has a line output of 2V. From research I discovered that with the max 2V coming from the zen blue i will probably not want to go above -22db on the 517 (clipping). Not great for volume control, though not awful.

I will probably be mostly streaming Tidal or some other streamer from my iPhone (12 mini). If I keep the Bluetooth output volume of the iPhone very low will that help with volume control (and protection) on the 517? Is there a more exact way to control signal output on the iPhone? Would putting attenuators between the zen blue and the 517 be better? Not that big a deal?

 

[mgosdin]

Lowering the volume on your iPhone in order to lower the Zen Blue's output has some potential drawbacks, it can raise the noise floor and negatively impact sound quality of the Zen.

If it was me I would look at using attenuators between the Zen and the Sansui. That would compensate for the Zen Blue's modern higher output vs the Sansui's classic sensitivity.

Mark Gosdin

 

[LakeWyles]

Lowering the volume on your iPhone in order to lower the Zen Blue's output has some potential drawbacks, it can raise the noise floor and negatively impact sound quality of the Zen.

If it was me I would look at using attenuators between the Zen and the Sansui. That would compensate for the Zen Blue's modern higher output vs the Sansui's classic sensitivity.

Mark Gosdin

thanks! I’ll give it a try. Any recommendations on attenuators? Thinking either 10 or 12 dB

 

[LakeWyles]

Lowering the volume on your iPhone in order to lower the Zen Blue's output has some potential drawbacks, it can raise the noise floor and negatively impact sound quality of the Zen.

If it was me I would look at using attenuators between the Zen and the Sansui. That would compensate for the Zen Blue's modern higher output vs the Sansui's classic sensitivity.

Mark Gosdin

What about passive preamps? Would that also raise the noise floor if I put it between the zen blue and the 419 and kept it low?

 

[cpt_paranoia]

What about passive preamps?

A simple attenuator is a 'passive pre-amp', with a fixed 'gain'...

You could knock up your own input pad, relying on the fairly low o/p impedance of the CD player, and likely fairly high input impedance of the amp; a simple potential divider using two resistors, with a value ratio of ~12.

I'd be tempted to get the service manual, and look at doing a modification to the input circuits, considering any capacitance on the input, so as to be sure not to put the frequency response out of whack.