Bluetooth Out Level...Estimating Preamp Gain

[Zyman]

Hi, all. I'm designing a [tube] stereo with both analog and bluetooth input. I have zero experience with bluetooth, anything digital, or using ready-made boards/modules.

My problem is I'm trying to estimate how much preamp gain (in my analog circuit) I need to swing my PA to full power. I have no idea what's a reasonable range for output signal level from a bluetooth receiver. Can anybody give me an idea of what signal levels I'm dealing with...or maybe point me to the appropriate part of the spec sheet I should be looking at to better understand this?

I'm thinking of using this receiver module: AudioB Plus Bluetooth Audio Receiver Module(Apt-X)

I'm assuming the transmitted signal comes in digital then goes through the on-board DAC. The ADC and DAC specs for the chipset are here: ADC_DAC Specs CSRA64215.pdf - Google Drive

Full chip datasheet here: CSRA64215 QFN Data Sheet.pdf - Google Drive

Module datasheet here: TS64215 datasheet.pdf - Google Drive

Would really appreciate any help.

Tim

 

[stocktrader200]

it looks like 770mv *2 differential signal output. you will likely be ok at this level
An Iphone puts out roughly 1000mv for reference

if that module has an active / nonactive pin this could be used for automatic switching
you will need a 3.3v to 5v low noise power supply to supply this part.

 

[Zyman]

it looks like 770mv *2 differential signal output. you will likely be ok at this level
An Iphone puts out roughly 1000mv for reference

Thanks. That rms 700mV is what I assumed would be my max. And the Iphone reference is good to know.

But I'm not so worried about max/clipping. I'm mean it may sound terrible, but there's not way a 5V device is going to blow up the front end of my tube amp.

What I'm most concerned about is the volume being anemic. ~700mV max, but I have no idea if a bluetooth signal will really come close to this level when it comes out the other end of this module. I mean, would it be reasonable to assume I can hit 80% of this max output level with most source devices? Is the analog level out more-or-less independent of the RF signal intensity?

 

[Zyman]

if that module has an active / nonactive pin this could be used for automatic switching

That's a good question, and have thought about that...not yet figured it out. I'm hoping it has this feature, or is somehow programmable to detect from one or more of the I/O ports.

you will need a 3.3v to 5v low noise power supply to supply this part.

Yep. Not worried about that. I'll build a quiet linear supply for it.